Specifying Concrete for High Performance

Specifying Concrete for High Performance
This seminar is titled Specifying Concrete for High Performance. © National Ready Mixed Concrete Association All rights reserved

Announcement This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.

Introduction Continuing education for engineers and architects
Length of Presentation: 2 Hours Architects Earn 2 LUs Engineers Earn 2 PDHs NRMCA is an AIA/CES Registered Provider Records kept on file with NRMCA and AIA/CES Records This program is intended to provide continuing professional education for architects and engineers. The length of the presentation is 1 hour. As such, architects earn 1 Learning Unit and engineers will earn 1 Professional Development Hour upon completion of this program. Certificates of Completion will be provided to all attendees that registered for this program identifying the number of Learning Units and/or Professional Development Hours earned for completing this program. Credit earned on completion of this program will be kept on file with NRMCA and reported to AIA/CES Records.

Outline Prescriptive vs Performance Specifications
What is a Prescriptive Specification? What is a Performance Specification? Laboratory Study Demonstrating the Advantages of Performance-based Specifications ACI 318 Requirements for Durability Example Specification – ACI 318 Structures Example Specification – Non-ACI 318 Structures This portion of the seminar will address the following: Prescriptive vs Performance Specifications What is a Prescriptive Specification? What is a Performance Specification? Laboratory Study Demonstrating the Advantages of Performance-based Specifications ACI 318 Requirements for Durability Example Specification – ACI 318 Structures Example Specification – Non-ACI 318 Structures

Prescriptive vs Performance Specifications
Prescriptive Specifications Limit the types and quantities of ingredients Identify mixture proportions Detail construction means and methods Performance Specifications Focus on performance and function Assignment of responsibility Flexibility to adjust mixture ingredients and proportions to achieve consistent performance Measurable and enforceable Many project specifications are prescriptive in nature and stifle innovation by limiting the types and quantities of ingredients, mixture proportions and construction means and methods. Performance-based specifications on the other hand encourages innovation by focusing on performance and function. They assign responsibilities to the different parties involved in the construction process. They provide flexibility to adjust mixture ingredients and proportions to achieve consistent performance. And finally, the performance criteria are measurable and enforceable.

Encourages partnering within construction team: Leads to innovation and satisfied customers
11.3 k 22.0 k 21.1 k 19.9 k 20.5 k 15-0 Contractors Performance-based specifications encourage partnering within the construction team which can lead to innovative products and construction methods resulting in superior projects and satisfied customers. Engineers and Architects Concrete Producers

Engineers and Architects are Experts in Design
Natchez Trace Bridge, Franklin, TN Engineers and architects are experts in design. They understand how to design buildings for function and aesthetics to meet the owner’s needs. Complex structures such as multi-use high-rise construction, bridges, or signature buildings require full attention on end use requirements. NBC Tower, Chicago Milwaukee Art Museum

Contractors are Experts in Construction
Concrete contractors employ the latest forming and placement methods to build faster and more economically than ever before. Concrete construction is now much more complicated, and the expertise that exists with the various parties involved needs to be leveraged to ensure that the owner gets a high quality structure with a long projected service life. Tilt-up Post-tension High-rise

Producers are Experts in Mix Design
Testing Labs Modern ready mixed concrete producers have technical experts that participate in the standards development process and laboratories that incorporate rigorous quality control and product development programs to design concrete mixtures optimized for performance for any application. Product Development Material Handling

Performance-based Specifications: Help Control Construction Cost
Innovative construction means and methods Improved construction schedules More efficient structural designs Simplified specifications and submittal process Optimized mix designs Significant construction cost savings can result from the performance-based specificaitons. Cost savings can result from innovative construction means and methods, more efficient structural designs, simplified specification and submittal process, and optimized mix designs.

Performance-based Specifications: Help Meet Greater Demands
High-Performance Concrete The demands for our products have continued to increase. We’re building higher than ever before. Concrete structures are being designed to last longer in harsh environments. Some of the innovative technologies that could be implemented more quickly through the use of performance specifications include high-strength concrete for tall buildings, high-performance concrete for bridges and parking structures, and self-consolidating concrete for highly congested reinforcement and architectural concrete finishes. High-Strength Concrete Self- Consolidating Concrete

Performance-based Specifications Improves Quality Systems
Testing Procedures Ready mixed concrete producers have significantly improved their quality systems by developing sophisticated laboratories for measuring and controlling quality and developing new products. They’ve also improved material handling procedures resulting in improved consistency. Material Handling Product Development

Performance-based Specifications: Encourages Training and Certifications
Plant and Truck Certification Plant Manager Certification Concrete Technologist Certifications Certified Delivery Professional (drivers) Concrete Certified Sales Professional Under development Concrete technologist responsible for performance mixes Concrete producer certification based on quality system The people involved in developing mix designs, concrete production and delivery, and sales and technical support now have rigorous training and certification programs developed by NRMCA. There are certifications for concrete plants and trucks, plant managers, concrete technologists, truck drivers, and sales professionals. NRMCA is also developing new concrete technologist certification for the person responsible for performance mixes and producer certifications based on a rigorous quality management system.

What is a Prescriptive Specification?
Details mixture proportions and construction means and methods Do not always cover intended performance May conflict with intended performance Example: Low w/c for durability could increase thermal and shrinkage cracking Requirements are generally not directly enforceable Producer held responsible for performance and defects, even though he lacks the freedom to make changes Prevents mixture optimization for performance No incentive for quality control / batch uniformity A prescriptive specification is one that includes clauses for means and methods of concrete mixture proportions and construction techniques rather than defining end product requirements. Many times the intended performance is not clearly indicated in the contract documents and the prescriptive requirements may conflict with the intended performance. For example, a low water-cement ratio could result in a high paste content that will increase the heat of hydration and potential for drying shrinkage thereby increasing the potential for cracking and curling. This might also cause a stiff mix that will adversely affect its placing and finishing. Many of the prescriptive requirements are not enforceable on the jobsite – such as a w/c ratio or minimum cement content. A requirement that is not verifiable or not enforceable is of little value in the specification. While ASTM C 94, Standard Specification for Ready Mixed Concrete, might say that the purchaser takes responsibility for performance of a prescriptive specification, the reality is that the producer is called on when there are problems. Prescriptive specifications provide no challenge to the innovative producer to optimize mixtures for performance. In a competitive bid situation a producer that invests more in quality control is at a disadvantage. The engineer might think he has established a level playing field with a prescriptive mix, but this is not true. The engineer should be challenged to address the desired performance and get the expertise of a concrete producer to deliver an optimized mix.

Prescriptive Specification
Intended Performance Placing/Finishing Strength Min Shrinkage Resistance To: Freeze-Thaw Corrosion Sulfate attack ASR Cracking Abrasion Prescriptive Criteria Slump Max w/cm ratio Min cement content Min/max air Min/Max pozzolans/slag Blended cements Aggregate grading Source Limitations Chloride Limits Typically the specifier has some intended performance of in-place concrete but uses prescriptive criteria to control performance. For example, the ability to place and finish is controlled by slump. Strength is often controlled with the w/cm ratio and minimum cement content. The w/cm ratio, cement content, and aggregate grading affect shrinkage. Freeze-thaw durability is controlled by air content and limits on supplementary cementitious materials.

Prescriptive Specification
Intended Performance Placing/Finishing Strength Min Shrinkage Resistance To: Freeze-Thaw Corrosion Sulfate attack ASR Cracking Abrasion Prescriptive Criteria Slump Max w/cm ratio Min cement content Min/max air Min/Max pozzolans/slag Blended cements Aggregate grading Source Limitations Chloride Limits When you start analyzing all the potential conflicts, you can end up with quite a mess. Some of the prescriptive criteria are in the Building Code and the engineer is required to invoke them in the job specification, however, many are not. One goal of the P2P Initiative is to make changes to the building code to allow performance-based alternatives so the design professional can minimize these conflicts in the project specifications. Some prescriptive criteria are required by code but many are not

Prescriptive Specification Example
w/c ratio = 0.40 Min. cement = 600 pcy Strength = 3500 psi No SCM Aggregate grading 8 – 18% No reactive aggregate Low alkali cement Shrinkage = 0.04% max No cracking No curling Slump 5 ± 1 inch Setting time 4 ± 0.5 hrs Max temp 85° F Impermeable Uniform color This might be considered an example of an “Extreme Specification” though it is more common than rare. Many of these requirements are overkill, many are prescriptive, there are several internal conflicts, both with the prescriptive and performance requirements and as a whole this specification is not physically possible to deliver. Prescriptive requirements Should be specified by contractor Performance requirements

Example: Water Cement Ratio
Air Cement Water Air Paste Let’s use one example of a prescriptive specification requirement, the water-cement ratio, to demonstrate why prescriptive requirements can limit innovation and work against intended performance. Water-cement ratio is easy to incorporate into a specification but difficult to achieve and enforce. The concept of water-cement ratio goes back to the 1920s when it was demonstrated that for a certain set of materials, increasing the water content will decrease strength and permeability. Now-a-days specifications and the building code include limits on water-cement ratio as a surrogate for ensuring durability. The intent is most likely for reducing permeability of the concrete. When designing a concrete mix you start with a water content that is controlled by the aggregates you use divided by the water-cement ratio to get the cement content you need. And if you do nothing else it results in a mixture like the one on the right. If you want to optimize this mixture to reduce the paste you can do it by modifying the aggregate size and grading and using admixtures. The mixture on the left will perform better but it takes a producer with a quality focus and expertise to get there. The two concrete mixtures shown here have the same water-cement ratio. The one on the right has a higher paste content which will probably result in higher heat of hydration and associated problems and higher shrinkage and associated problems. The mixes might have similar permeability and strength or they might be significantly different. Clearly one (or both) of the mixtures may not be optimized for the intended performance.

w/cm alone does not control strength
For each set of materials there is a unique relationship between the strength and water-cement ratio. A different set of materials has a different relationship as illustrated here for three different mixes. At 0.45 water-cement ratio these three mixtures have strengths of approximately 6000, 5000 and 4000 psi respectively. These differences in strength can occur simply by changing the aggregate size and type used in the mix as described in ACI 211. Specifying a w/cm ratio alone does not ensure that a certain strength will be achieved. Source: ACI 211

w/cm alone does not control permeability
For the most part, water-cement ratio is invoked as a requirement to ensure durability, which is generally affected by the permeability of concrete. We clearly know that the cementitious component of the mix can also be varied to affect permeability. As water-cement ratio decreases, permeability decreases. But the four different mixes shown here will have a different permeability value at the same water-cement ratio. Even though the producer furnishes a mix at a 0.45 water-cement ratio, there is no guarantee that the mix will have a low permeability. This is not to say that water-cement ratio is not important. It is a tool that the producer needs to use to design his mix. It should not however be a specification requirement. Further, water-cement ratio cannot be measured or enforced on the jobsite by a reliable measurement and a specification requirement that cannot be enforced is not very useful. The challenge is – for what performance attribute is the water-cement ratio being specified and can we use a different performance measure in the specification? ACI 318 chapter 4 on durability requires limits on water-cementitious materials ratio for sulfate resistance, freeze-thaw resistance, and corrosion. Source: ACI 232, 233, 234

Example Prescriptive Specification
Interior Building Column Maximum w/cm = 0.40 Minimum cementitious content = 640 lbs/yd3 Maximum fly ash = 15% by mass of cementitious f’c = 4,000 psi Slump = 4 in. max. Consider an example of a prescriptive specification for concrete used for interior building columns. The specification requires a 0.40 w/cm ratio, a minimum cement content of 640 lb/yd3, a maximum fly ash content of 15% by mass of cementitious material, a compressive strength of 4,000 psi, and a maximum slump of 4 in. For this structural element the critical performance characteristic is the compressive strength. Since the column is protected from exposure the w/cm ratio limit is not necessary for durability and the requirement for a minimum cementitious content is not needed to meet the strength requirements. Presumably the limit on fly ash is to ensure rapid strength gain for form stripping but this is an issue of means and methods of construction and should therefore be avoided in the specification. The restriction on the w/cm ratio and slump will likely cause placement problems with congested reinforcement and likely result in surface defects due to difficulties with consolidation.

Prescriptive Solution 1
Start with water Estimate 295 lbs/yd3 for target slump with local materials Use 740 lbs/yd3 to meet w/cm requirement Strength is probably over 7,000 psi High paste content leads to High heat of hydration High shrinkage High creep Mix will not be economical One option is to start with water, estimated at 295 lb/yd3 for the target slump with the local materials and use a cementitious content of 740 lb/yd3 to meet the maximum w/cm requirement. The strength of this mixture is more likely to be in the range of 7,000 psi or higher. This mixture also has a high paste content which will cause associated problems such as high heat of hydration, shrinkage, and creep. The mix will not be the most economical one because of the high cementitious materials content.

Prescriptive Solution 2
Start with minimum cement content of 640 lbs/yd3 Use 250 lbs/yd3 to meet maximum w/cm requirement Based on water demand of local materials mix needs High dosage of WR admixture, or HRWR admixture This mix has lower paste content May not have proper consistency for placement Strength is probably 6,500 psi Another option is to start with the minimum cementitious content and establish the maximum water content of the mix at 250 lb/yd3 again to meet the maximum w/cm requirment. Based on the water demand of the local materials, this mixture will require relatively high dosages of water reducing and/or high range water reducing admixtures. This mixture has a lower paste content but may not have the appropriate consistency for proper placement. The strength is likely to be in the range of 6,500 psi.

Performance Solution First requirement (engineer) = 4,000 psi at 28 days Second requirement (contractor) = 2,500 at 3 days Optimize mixture Aggregate grading Minimize paste content Admixtures (possibly self-consolidating concrete) Target average comp. strength = 4,600 psi Use 460 lbs/yd3 cementitious materials 25% fly ash This minimizes heat of hydration, shrinkage, and creep Results in better surface finish If the only requirement was strength, 4,000 psi at 28 days for design requirements and 2,500 psi at 3 days for the contractors form stripping requirments, the producer might choose to optimize the mixture by controlling aggregate quantity and grading, minimizing the paste content and provide the necessary mixture consistency, possibly using self consolidating concrete, and achieve the necessary form stripping and design strength. A concrete mixture targeting an average strength of about 4,600 psi can be designed with a cementitious content of about 460 lb/yd3, with possibly up to 25% fly ash. This mixture will have the lowest paste content and minimize heat of hydration, shrinkage and creep. If designed for proper consistency without the restrictions on the w/cm, cement content, or slump, it will also result in a better surface finish.

What is a Performance Specification?
Performance requirements of concrete Hardened state for Service (meeting owner’s requirements) Plastic state for Constructability (meeting the contractor’s requirements) Focus on performance and function Assignment of responsibility Flexibility to adjust mixture ingredients and proportions to achieve consistent performance Changes in weather conditions Changes in materials Measurable and enforceable Defined test methods and acceptance criteria So what is a performance specification? It is one that outlines the requirements for concrete in measurable terms for proper in-place service to meet the owner’s requirements. In addition, it should have enough flexibility to allow the concrete producer to meet the contractor’s requirements for constructability. The specification provisions should be in terms of performance and functional requirements and should avoid limitations or requirements on the ingredients or proportions of the concrete mixture. It provides the flexibility to the producer who has the expertise to provide a better product if the requirements are clearly understood and defined in the contract documents. When changes occur in weather conditions or materials, the mix design needs to be adjusted to maintain consistency. The requirements must be measurable and enforceable. The specification should also define test methods and acceptance criteria.

How does it work? Qualification requirements would be established for producers Performance criteria would be specified by the A/E Contractor would partner with producer to establish constructability criteria Submittal will demonstrate compliance with specified requirements Compliance through pre-qualification tests and limited jobsite acceptance tests This is a general concept of how a performance-based specification would work: There would be in place a qualification system that establishes the requirements for a quality management system, qualification of personnel and requirements for concrete production facilities. NRMCA is currently working on a quality system manual that will be the basis for a producer certification. The specification will have provisions that are performance-based or clearly defined functional requirements. Producers and contractors will be encouraged to partner to ensure that the right mix is developed and delivered. A submittal would be a certification that the mix will meet the specification requirements with pre-qualification test results. The compliance of mixtures will be through pre-qualification tests for the most part with job-site tests for acceptance.

The P2P Initiative Stands for Prescription-to-Performance
Initiative of the ready mixed industry through the NRMCA Coordinated by P2P Steering Committee under the NRMCA Research, Engineering and Standards Committee Members include technical representatives, product suppliers, contractors, engineers, and architects What is the P2P Initiative? The acronym stands for Prescription to Performance with the intent to move specifications from something that prescribes what constitutes a concrete mixture to how this mixture needs to perform. It is an initiative of the ready mixed concrete industry, through NRMCA. The activities of the P2P Initiative are coordinated by the P2P Steering Committee under the NRMCA Research, Engineering, and Standards Committee. Its members include technical representatives of many NRMCA member companies, both large and small, and other experts who have volunteered to help including product suppliers, contractors, engineers, and architects.

P2P Goals Allow performance specifications as an alternative to current prescriptive specifications Leverage expertise of all parties to improve quality and reliability of concrete construction Assist architects/engineers to address concrete specifications in terms of functional requirements Allow flexibility on the details of concrete mixtures and construction means and methods Better establish roles and responsibilities based on expertise Continue to elevate the performance level of the ready mixed concrete industry Foster innovation and advance new technology at a faster pace Some of the broad goals of the P2P Initiative are: To allow performance specifications as an alternative to current prescriptive specifications. Leverage the expertise of all parties in the concrete construction process and ultimately increase the reliability of concrete construction. To help architects and engineers incorporate functional and performance requirements in job specifications and allow contractors and concrete producers to choose the best and optimized construction methods and mixtures, respectively. We hope to better establish roles and responsibilities based on the expertise of the involved parties and promote improved partnering between engineers, architects, contractors, and producers. An important part of this initiative is to continue to elevate the performance and knowledge level of the ready mixed concrete industry through training and certifications. We also need to use the expertise of the producer and contractor to progress innovation in products and construction methods as these are often constrained by the job specification.

What are the Challenges?
Acceptance of Change Trust / Credibility Knowledge Level (training) Reference Codes and Specifications Prescriptive limitations Measurement and Testing Reliability of existing tests Reliability of jobsite tests Well what are the challenges to the success of P2P? The inertia will clearly be hard to overcome. As we know construction is a conservative industry and change is difficult. There is an issue of trust and credibility of the contractor and producer that will have to be overcome. There has to be an enhanced knowledge level of industry personnel not only on their own business but on the business of the other parties in the construction process and an understanding of the needs of the other parties. We have to significantly increase the number of people who are competent and knowledgeable about the industry standards and practice and the design professional’s knowledge level of concrete technology and abilities and constraints of the contractor and producers. With experience and reputation will come credibility and trust. Our current reference codes and specifications, such as ACI 318 and ACI 301 currently have prescriptive limitations on concrete mixtures, especially for durability requirements. They also define a submittal process that is quite onerous. These will need to be revised and changed with appropriate performance alternatives provided. We also need reliable tests for measuring performance and those that we have are quite variable and not always conducive to jobsite testing.

What Activities are Underway?
Communication Engineers, Architects, Contractors, and Producers Articles and presentations Developing Producer Quality System / Qualifications Developing Model Spec / Code Revisions Look at model codes from other countries (Canada, Europe, Australia) Look at similar initiatives in the US (FHWA and DOTs) Documenting Case Studies Conducting Research Test Methods for Performance Quantifying differences between prescriptive and performance mixes Delivering Training Programs These are some of the activities underway. We have initiated dialogues with all potential stakeholders through industry groups and personal contacts to evaluate support and identify concerns. We have communicated the goals of the P2P Initiative through magazine articles and presentations. We have started the process of defining a quality management system necessary for a producer to comply with and have started developing a certification program that would qualify a person to develop and sign off on performance based mix designs. We are in the process of developing a model performance specification and developing code changes that will revise the current prescriptive limitations in the codes. We have compiled some information on how other countries address performance specifications and similar initiatives in the US. We are documenting case studies of performance-based projects to identify problems and challenges. We are conducting research to identify and improve test methods that could be used for mix pre-qualification and jobsite acceptance and identifying the associated precision of these tests. We are also conducting research to quantify the differences between prescriptive and performance mix designs. The NRMCA has several training programs in place for producer personnel and we are identifying others that could benefit other stakeholders.

Additional Resources Visit www.nrmca.org/P2P
Download Example Specifications Download P2P Articles Download Research Studies If you would like additional information on the P2P Initiative, I suggest you visit You will be able to download the example specification, P2P articles, and research studies on performance-based specifications. Thank you for completing this NRMCA Seminar.

Lab Study Demonstrating Advantages of Performance Specification
Case 1: Real Floor Specification from a Major Owner Case 2: Typical HPC Bridge Deck Specification Case 3: ACI 318 Chapter 4 Code – prescriptive durability provisions Three scenarios where prescriptive specifications were chosen, concrete floor slabs, concrete bridge decks, and ACI 318 durability provisions.

Fresh Concrete Tests Fresh Concrete Properties Slump: ASTM 143
Air Content: ASTM C 231 Density: ASTM C 138 Temperature: ASTM C 1064 Initial Setting Time (Case 1): ASTM C 403 Finishability (Case 1): Subjective rating (5=Excellent to 1=Poor) Segregation (Case 1): Cylinders vibrated, density of top and bottom half compared The following fresh concrete tests were conducted for every experimental batch of concrete: Slump, ASTM C 143 Air Content, ASTM C 231 Density, ASTM C 138, and Temperature, ASTM C 1064 Initial setting time was measured for the floor slab mixtures (Case 1) in accordance with ASTM C 403. A method to evaluate the relative finishability was used. 2 foot by 1 foot by 4 inch thick slabs were cast and finished by hand with a wooden trowel. A “finishability rating” value between 1 and 5 was assigned as a measure of concrete finishability with 5 being excellent and 1 being poor. A test to measure segregation was also developed for Case 1. A 6 inch by 12 inch cylinder was cast after the concrete slump was raised to between 5 and 6 inches. The cylinder was vibrated using an internal vibrator. The cylinder was sawed in two after 7 days of moist curing and the density of the top and bottom halves were determined. The difference in density was presumed to be a result of segregation, i.e. course aggregate particles migrating towards the bottom.

Hardened Concrete Tests
Compressive Strength, ASTM C 39 Length Change, ASTM C 157 Compressive strength tests in accordance with ASTM C 39 were conducted for all cases using 4 inch by 8 inch cylinders. Length change of concrete due to drying shrinkage was tested using ASTM C inch by 3 inch by 11 inches prisms were imbedded with studs and length change was measured using a dial gage at various time intervals. The shrinkage test specimens were moist cured for 7 days and then stored at 70 °F at 50% relative humidity. The length change is the average of two specimens except for the floor slab where 3 specimens were tested.

Durability Tests Rapid Chloride Permeability Test (RCPT), ASTM C 1202
Rapid Migration Test (RMT), AASHTO TP 64 Sorptivity, ASTM C 1585 Bulk Diffusion, ASTM C 1556 Several tests were conducted to measure durability. The rapid indication of chloride ion penetrability, also called the Rapid Chloride Permeability test, was conducted on all specimens in accordance with ASTM C In this test, two 4 inch by 8 inch cylinders are cast and cured in a moist room at 70 °F until the test age. The top 2-inch portion of the test specimen are cut from the cylinder. The charge passed through the 2-inch specimen after 6 hours is measured. The average of two specimens tested at the same age are reported. The Rapid Migration Test (RMT) is a provisional AASHTO standard, AASHTO TP 64. This test is similar to ASTM C 1202 in that the chloride ions are driven into the concrete by an electric current. The RMT has advantages over RCPT test as it is not influenced by strong ionic pore solution or admixtures such as calcium nitrite. In addition, for specimens with higher permeability, say greater than 1500 coulombs, the temperature in the specimen does not increase as typically observed in RCPT which exaggerates the charge passed. For the RMT, the top 2-inches of moist cured cylinders are subjected to a constant voltage for a period of 18 hours. The specimen is then fractured along the diameter and sprayed with silver nitrate solution. The silver nitrate reacts with the chloride ion to provide a visible depth of penetration of the chlorides. The sorptivity test, ASTM C 1585, was performed for all specimens. In this test 2-inch thick concrete slices from a cylinder are placed with the exposed surface immersed in water. The other surfaces are sealed with epoxy. The increase in specimen mass with time due to moisture absorption is measured. Sorptivity is not a direct measure of permeability but measures the rate of flow of fluid due to capillary suction. The bulk diffusion test is a new test, ASTM C In this test, after 28 days of moist curing the top 3 inches of a concrete cylinder are cut, sealed (except for the finished surface) and vacuum saturated in saturated calcium hydroxide solution. The saturated test specimens is immersed in a sodium chloride solution with one unsealed face exposed to the solution until the specimens attained an age of about 180 days. The specimen was then removed and ground in 2 mm thick layers from the exposed surface. The acid soluble chloride content is measured at different depths from which an apparent chloride diffusion coefficient is calculated.

Case 1 - Concrete Floor Specification
Prescriptive Performance Specified = 4000 psi; Average = 5200 psi Average past records Max w/c = 0.52, penalties, rejected - No fly ash or slag SCMs may be used Slump (max) = 4”, Non AE Slump = 4” – 6”, Non AE Combined aggregate gradation 8% - 18% No HRWR Shrinkage < 0.04% at 28 days Setting Time = 5 ± ½ hours Two different specifications were used for the floor slab. The prescriptive specification is one that is used by one of the nation’s largest retailers. The features are: Specified 28-day compressive strength is 4000 psi. The average must be 5200 psi. The maximum water-cement ratio is 0.52 with penalties and possible rejection for exceeding the maximum. No fly ash or slag can be used. The maximum slump is 4 inches and the mix must be non air entrained. The combined aggregate gradation shall be 8-18% retained on each sieve below the top size and above the No. 100 sieve. No high range water reducing admixtures allowed. For the performance specifications, the following criteria were specified: Specified 28-day compressive strength is 4000 psi. Required average strength based on ACI 318 or ACI 301 from past records. Supplementary cementitious materials may be used. Slump was not specified by the designer, but is specified by the contractor. Length change (or drying shrinkage) in accordance with ASTM C 157 shall be less than .04% at 28 days of drying after 7 days of moist curing. Setting time in accordance with ASTM C 403 under laboratory conditions shall be 5 hours plus or minus ½ hour as specified by the contractor. Specified by Contractor

Experimental Program (5 concrete mixtures)
One control (prescriptive) and 4 performance mixtures FS-1: CM = 611, w/cm = 0.49, 8-18% aggregate FS-2: CM = 517, w/cm = 0.57, 8-18% aggregate FS-3: CM = 530, 20% FA, w/cm = 0.57, 8-18% aggregate FS-4: CM = 530, 20% FA with binary aggregates, w/cm = 0.53, #467 stone aggregate FS-5: CM = 530, 20% SL, 15% FA with binary aggregates, w/cm = 0.54, #467 stone aggregate One control (prescriptive) and 4 performance mixtures were designed and cast: FS-1 was designed using the prescriptive spec and FS-2 through 5 were designed using the performance spec. FS-1: CM = 611, w/cm = 0.49, 8-18% aggregate FS-2: CM = 517, w/cm = 0.57, 8-18% aggregate FS-3: CM = 530, 20% FA, w/cm = 0.57, 8-18% aggregate FS-4: CM = 530, 20% FA with binary aggregates, w/cm = 0.53, #467 stone aggregate FS-5: CM = 530, 20% SL, 15% FA with binary aggregates, w/cm = 0.54, #467 stone aggregate

Combined Aggregate Grading of FS Mixtures
This graph shows the combined aggregate grading for the floor slab mixes relative to the 8-18% criteria. FS-1 through 3 were designed with the 8-18% criteria and FS-4 and 5 were not.

Compressive Strength and Setting Time
This graph shows the strength and set time for each of the floor slab mixtures. All the mixes met the compressive strength requirement. FS-5 did not meet the set time requirment.

Segregation & Shrinkage
Segregation Index: Difference in the coarse aggregate content was consistently about 20% except for Mixture FS-5 which was about 15% Shrinkage: All mixtures except FS-5 had 28 day shrinkage < 0.020% For the Segregation Index, the difference in the coarse aggregate content from the top of the cylinder to the bottom was consistently about 20% except for Mixture FS-5 which was about 15% As for shrinkage, FS-1 through 4 had 28 day shrinkage < 0.020% and FS-5 had 28-day shrinkage of .035%; all within specified limits.

Slab Finishability Test
All 5 concrete mixtures had a rating above 4.5 indicating excellent finishability All 5 concrete mixtures had a rating above 4.5 indicating excellent finishability.

Durability Although the floor slab did not require a low permeability, durability tests were conducted. FS-1 and FS-2 had relatively high permeability when measured using the RCPT with ratings of over 3000 coulombs. FS-3 through 5 had RCPT test results of less than 1000 coulombs.

Summary – Floor Slab Mixtures
All performance mixtures met performance requirements except Mixture FS-5 Strength over-design factor, limiting w/cm increased cement contents Use of SCMs was beneficial Continuous aggregate grading mixtures did not impact performance Performance mixtures had substantial material costs savings In summary: All performance mixtures met performance requirements except Mixture FS-5 Strength over-design factor, limiting w/cm increased cement contents Use of SCMs was beneficial Continuous aggregate grading mixtures did not impact performance Performance mixtures had substantial material costs savings

Case 2 - HPC Bridge Deck Specification
Prescriptive Performance Specified 28 d strength=4000 psi; Average past records Max w/cm = 0.39 - Total CM = 705. 15% FA plus 7% to 8% SF SCM required. Maximum amounts per ACI 318 for deicer scaling Air = 4% to 8% RCPT < 1500 coulombs Shrinkage < 0.04% at 28 days Slump = 4” – 6” For the second case, a specification for a bridge deck used by one DOT was used for the prescriptive specification: Specified 28 d strength=4000 psi; The average shall be based on past records The maximum w/cm = 0.39 Total cementitious materials content is 705 pounds per cubic yard. 15% FA plus 7% to 8% SF must be used. Air content shall be between 4% to 8% Results of the RCPT < 1500 coulombs There was no requirement for shrinkage. Slump = 4” – 6” In contrast, the performance specifications had the following requirements: Specified 28 d strength=4000 psi; Average based on past records There is no maximum water to cementitious ratio requirement. SCM required. Maximum amounts per ACI 318 for deicer scaling Air content shall 4% to 8% Maximum RCPT < 1500 coulombs Shrinkage < 0.04% at 28 days Slump = 4” – 6” as specified by the contractor. Specified by Contractor

Experimental Program (4 mixtures)
One control (prescriptive) and 3 performance mixtures BR-1: C = 550, Class F FA = 105, SF = 50; Total = 705 BR-2: C = 426, Class F FA = 150, SF = 24; Total = 600 BR-3: C = 300, SL = 300; Total = 600 BR-4: C = 426, Class F FA = 150, UFFA = 34; Total = 612 w/cm=0.39 for all mixtures except 0.36 for Mix 4 One control mix, BR-1, was designed using the prescriptive spec and and 3 performance mixtures, BR-2 through 4 were designed using the performance spec: BR-1: C = 550, Class F FA = 105, SF = 50; Total = 705 BR-2: C = 426, Class F FA = 150, SF = 24; Total = 600 BR-3: C = 300, SL = 300; Total = 600 BR-4: C = 426, Class F FA = 150, UFFA = 34; Total = 612 w/cm=0.39 for all mixtures except 0.36 for Mix 4

Strength Compressive Strength: 28 day strengths were much higher than specified (6800 to 8970 psi) Water Demand: 15% to 20% lower water demand and 15% to 30% lower HRWR demand for performance mixtures barring the slag mixture; better workability Compressive Strength: 28 day strengths were much higher than specified (6800 to 8970 psi)

RCPT (ASTM C 1202), RMT (AASHTO TP 64)
The specified RCPT value of 1500 coulombs after 45 days of moist curing was achieved by all the mixtures except for the prescriptive mixture which had a slightly higher value of 1563 coulombs. Note that this is still a low value. The 180 day RCPT values were all extremely low ranging from 242 for BR-4 to 375 for BR-3, well within acceptable limits. As a comparison, the 60-day RMT results varies from .018 mm/(v-hr) for BR-2 to .023 mm/(v-hr) for BR-4. The 180-day RMT results varied from for BR-2 to for BR-1.

Rapid Migration Test FHWA Performance Grade (AASHTO TP 64)
Grade 1: RCPT = 2000 to 3000; RMT = to 0.034 Grade 2: RCPT = 800 to 2000; RMT = to 0.024 Grade 3: RCPT < 800; RMT < 0.012 For comparison, FHWA Performance Grades for the RCPT and RMT at are as follows: Grade 1: RCPT = 2000 to 3000; RMT = to 0.034 Grade 2: RCPT = 800 to 2000; RMT = to 0.024 Grade 3: RCPT < 800; RMT < 0.012 It is important to note that the RCPT and RMT correspond well with each other. It is also important to note that all mixtures met the most severe requirements of FHWA, Grade 3, at 180 days.

Drying Shrinkage (ASTM C 157)
The specified length change of .04% at 28 days was achieved for all mixtures. This graph shows the drying shrinkage for all four mixtures at 180 days. As you can see the performance mixtures had lower shrinkage than the prescriptive mixture.

Summary – HPC Bridge Deck Mixtures
All performance mixtures met performance requirements Performance mixtures had similar or better performance than Prescriptive mixtures Drying shrinkage, workability (stickiness), HRWR dosage, strength, RCPT, RMT Performance mixtures had substantial material cost savings In summary, all performance mixtures met performance requirements Performance mixtures had similar or better performance than Prescriptive mixtures for drying shrinkage, workability (stickiness), HRWR dosage, strength, RCPT, RMT Performance mixtures had substantial material cost savings

Case 3 - ACI 318 Chapter 4 Prescriptive durability provisions
Objective: Determine if w/cm is the best measure for durability (permeability). Durability provisions for buildings governed by the adopted local codes are addressed in Chapter 4 of ACI 318 Building Code for Structural Concrete. The Code addresses durability requirements for concrete exposed to freeze-thaw cycles, deicer salt scaling, sulfate resistance, protection from corrosion of reinforcing steel, and conditions needing low permeability. In all cases, the primary requirement of controlling the permeability of concrete is a maximum limit on the water to cementitious materials ratio (w/cm) along with a minimum specified strength. The scope of this part of the study was limited to comparing the performance of concrete mixtures having the same w/cm but with different cementitious materials and content with regards to permeability. Drying shrinkage measurements are also compared even though this is not a limitation in the Code.

Experimental Program (4 mixtures)
One control (prescriptive) and 3 performance mixtures 318-1: 750 lbs Portland cement mixture 318-2: CM = 700; 25% FA (1.16% less paste) 318-3: CM = 564; 25% FA (7.24% less paste) 318-4: Same as #3 but yield adjusted largely by coarse aggregate w/cm = 0.42 Slump = 3.75” – 6.5”; Air = 4.1% to 7.4% One control mix (prescriptive) and 3 performance mixtures were designed and tested. 318-1: 750 lbs Portland cement mixture 318-2: CM = 700; 25% FA (1.16% less paste) 318-3: CM = 564; 25% FA (7.24% less paste) 318-4: Same as #3 but yield adjusted largely by coarse aggregate w/cm = 0.42 Slump = 3.75” – 6.5”; Air = 4.1% to 7.4%

Results At same w/cm=0.42 Mix 318-1 318-2 318-3 318-4
Compressive Strength – 28 days, psi 5,440 5,950 5,670 5,600 Length Change – 180 days, % 0.064% 0.048% 0.037% 0.032% RCPT – 180 days, coulombs 2772 608 533 457 RMT – 180 days, mm/V-hr 0.030 0.0077 0.015 0.0082 The results of the various tests are shown in this table: Compressive strength varied from 5440 psi for mix 1 to 5950 for mix 2. Drying shrinkage varied from a relatively high .064% for mix w to .032% for mix 4. RCPT results at 180 days were relatively high for mix 1 at 2772 coulombs. Mix 2 through 4 had RCPT results less than 1000 coulombs which is extremely low. RMT results at 180 days was relatively high for 318 mix 1 at .030 mm/(V-hr). Mix 2 through 4 had RMT values ranging from to .015, all extremely low meaning these mixes have low permeability.

Summary – ACI 318 Mixtures Code limitations on w/cm are no guarantee for high durability concrete Considerable advances in the use of SCMs and chemical admixtures Code durability provisions should be performance based In summary, Code limitations on w/cm are no guarantee for high durability concrete Considerable advances in the use of SCMs and chemical admixtures Code durability provisions should be performance based

Conclusions Prescriptive specs do not assure performance
Performance mixtures achieved equal or better performance Great opportunity for mixture optimization Producers compete on their knowledge, resources ACI 318 durability provisions needs to change In conclusion: Prescriptive specs do not assure performance Performance mixtures achieved equal or better performance Great opportunity for mixture optimization Producers compete on their knowledge, resources ACI 318 durability provisions needs to change

ACI 318 Requirements for Durability
Structural members not exposed to extreme conditions Most concrete for buildings falls in this category Few limits on materials or quantities Structural members exposed to extreme conditions Follow ACI 318 Chapter 4 Most requirements are prescriptive Slabs on grade (not part of structural system) and exterior flatwork (not part of structural system) do not need to meet requirements of ACI 318. For ACI 318 structures, there are basically two main types of concrete. There are those structural members that are not exposed to extreme conditions and those structural members exposed to extreme conditions. Interior members such as columns, beams, slabs, and walls that are protected from the environment do not generally have durability concerns. There are few limits on materials or quantities of materials. Members exposed to freeze-thaw, deicing chemicals, sulfates and so forth such as exterior members, members in contact with soil or other extreme conditions must meet the requirements of chapter 4 of ACI 318. Most of these requirements are prescriptive in nature. It should be noted that concrete elements such as slabs on grade (not part of structural system) and exterior flatwork (not part of structural system) do not need to meet requirements of ACI 318.

Water-cementitious material ratio
ACI Maximum w/cm of 0.40 to 0.50 may be required for: Freezing and thawing Sulfate soils or waters Corrosion protection To provide low permeability concrete Corresponds to f’c of 5000 to 4000 psi respectively Specify w/cm and matching strength (per chapter 4) w/cm is difficult to verify Strength is easy to verify i.e. don’t specify f’c of 3000 psi and max w/cm of 0.40 Don’t specify w/cm for concrete without durability concerns ACI discusses water-cementitious materials ratio. The commentary explains that maximum w/cm of 0.40 to 0.50 may be required for: Freezing and thawing Sulfate soils or waters Corrosion protection To provide low permeability concrete These values of w/cm correspond to f’c of 5000 to 4000 psi respectively Make sure w/cm and strength match (per chapter 4) since w/cm is difficult to verify Strength is easy to verify i.e. don’t specify f’c of 3000 psi and max w/cm of 0.40 Don’t specify w/cm for concrete without durability concerns

Freeze and Thawing Exposure: Air Content
Concrete exposed to freezing and thawing or deicing chemicals shall be air entrained in accordance with table Tolerance on air content as delivered shall be +/- 1.5 % For f’c > 5000 psi reduce air content by 1.0 percent shall be permitted Tolerance on air content as delivered shall be +/- 1.5 % For f’c > 5000 psi reduce air content by 1.0 percent shall be permitted

Freezing and Thawing Exposure: Low Permeability
As we say earlier, limits on w/cm ratio do not necessarily guarantee low permeability, but this is how the ACI code handles it. For concrete intended to have low permeability when exposed to water, maximum w/cm ratio shall be 0.50 and minimum f’c shall be 4000 psi. Examples of might include basement walls in high water table or plaza slabs over occupied space in southern climates. Next, for concrete exposed to freezing and thawing in a moist condition or to deicing chemicals, maximum w/cm ratio shall be 0.45 and minimum f’c shall be 4500 psi. Examples could include parking garage slabs in moderate climates. Then finally, for corrosion protection of reinforcement in concrete exposed to chlorides from deicing chemicals, salt, salt water, salt water, brackish water, seawater, or spray from these sources, maximum w/cm ration shall be 0.40 and f’c shall be 5000 psi. Examples could include parking garage slabs in northern climates or a high-rise residential building on the coast.

Freezing and Thawing Exposure: Deicer Scaling
In order to protect against deicer scaling, Table limits the amount of fly ash or other pozzolans to 25 percent, the amount of slag to 50 percent, the amount of silica fume to 10 percent, the total of fly ash or other pozzolans, slag, and silica fume to 50 percent, and the total of fly ash or other pozzolans and silica fume to 35%.

Sulfate Exposure Concrete exposed to sulfate-containing solutions or soils shall conform to requirements of Table For negligible exposure as defined in the table, there are no limits on cement type, w/cm ratio, or strength. For moderate exposure, type II or other sulfate resistant blended cements must be used and the maximum w/cm ratio is limited to 0.50 with a corresponding strength of 4000 psi. See water is considered to have moderate sulfate exposure. For severe exposure, type V cement must be used and the maximum w/cm ratio is 0.45 with corresponding strength of 4500 psi. For very severe exposure, type V portland cement and a pozzolan that has been determined by test or service record to improve sulfate resistance shall be used. In addition, maximum w/cm ratio shall be 0.45 and minimum f’c shall be 4500 psi. In addition, calcium chloride containing admixture shall not be used for severe and very severe sulfate exposure. In addition, calcium chloride containing admixture shall not be used for severe and very severe sulfate exposure.

Corrosion Protection Finally, for corrosion protection of reinforcement in concrete, maximum water soluble chloride ion concentrations in hardened concrete at ages from 28 to 42 days contributed from the ingredients shall not exceed the limits in table : Prestressed concrete: 0.06 percent Reinforced concrete exposed to chloride in service: 0.15 percent Reinforced concrete that will be dry or protected from moisture in service: 1.00 percent which includes most concrete. Other reinforced concrete construction: 0.30

Weathering Probability Map for Concrete 2003 IBC
ACI 318 doesn’t provide much guidance on when to use severe, moderate or negligible exposure. This map from the International Building Code Provides some guidance. ACI 362 on parking garages also provides some guidance.

Proposed ACI 318 Exposure Classes
Exposure Category F – Exposure to freezing and thawing cycles Exposure Category S – Exposure to water-soluble sulfates Exposure Category P – Conditions that require low permeability concrete Exposure Category C – Conditions that require additional corrosion protection of reinforcement

Exposure to freezing and thawing cycles
Exposure Category F – Exposure to freezing and thawing cycles Class Description Condition F0 Concrete not exposed to freezing and thawing cycles F1 Moderate Occasional exposure to moisture F2 Severe Continuous contact with moisture F3 Very Severe Continuous contact with moisture and exposed to deicing chemicals

Exposed to water-soluble sulfates
Exposure Category S – Exposure to water-soluble sulfates Class Description Water-soluble sulfate (SO4) in Soil, percent by weight Sulfate (SO4) in Water, ppm S0 Negligible SO4 <0.10 SO4 <150 ppm S1 Moderate 0.10≤ SO4 <0.20 150≤ SO4 <1500 ppm Seawater S2 Severe 0.20≤ SO4 <2.00 1500≤ SO4 <10,000 ppm S3 Very severe SO4 >2.00 SO4 >10,000 ppm

Conditions that require low permeability concrete
Exposure Category P – Conditions that require low permeability concrete Class Condition P0 Low permeability to water not applicable P1 Concrete intended to have low permeability to water

Conditions that require additional corrosion protection of reinforcement
Exposure Category C Conditions that require additional corrosion protection of reinforcement Class Condition C0 Additional corrosion protection not a concern – for concrete that will be dry or protected from moisture in service C1 Exposure to moisture but will not be exposed to external source of chlorides in service C2 Exposure to moisture and an external source of chlorides in service – from deicing chemicals, salt, brackish water, seawater, or spray from these sources

Requirements for Concrete - Exposure Class F
Max w/cm Min f’c psi Additional Minimum Requirements F0 - F1 0.45 4500 Table 4.4.1 F2 F3 Table 4.4.2

TABLE 4.4.1—TOTAL AIR CONTENT FOR CONCRETE EXPOSED TO CYCLES OF FREEZING AND THAWING
Nominal maximum aggregate size, in.* Air content, percent Class F2 and F3 Class F1 3/8 7.5 6 1/2 7 5.5 3/4 5 1 4.5 1-1/2 2† 4 3† 3.5

TABLE 4.4.2—REQUIREMENTS FOR CONCRETE SUBJECT TO DEICING EXPOSURE CLASS F3
Cementitious materials Maximum percent of total cementitious materials by weight* Fly ash or other pozzolans conforming to ASTM C 618 25 Slag conforming to ASTM C 989 50 Silica fume conforming to ASTM C 1240 10 Total of fly ash or other pozzolans, slag, and silica fume 50† Total of fly ash or other pozzolans and silica fume 35†

Requirements for Concrete - Exposure Class S
Max w/cm Min f’c psi Additional Minimum Requirements S0 - S1 0.50 4000 Cement Types II, IP(MS), IS(MS), P(MS), I(PM)(MS), I(SM)(MS) S2 0.45 4500 Cement Type V No calcium chloride admixtures S3 Cement Type V + pozzolan‡

Requirements for Concrete - Exposure Class P
Max w/cm Min f’c psi Additional Minimum Requirements P0 - P1 0.50 4000

Requirements for Concrete - Exposure Class C
Max w/cm Min f’c psi Max water-soluble chloride ion (Cl−) content in concrete, percent by weight of cement Additional Requirement Reinforced Concrete C0 - 1.00 C1 0.30 C2 0.40 5000 0.15 Min. Cover Prestressed Concrete 0.06

Future Specification for Concrete
Concrete for parking garage slabs and beams shall meet the following requirements: Specified compressive strength, f’c = 5,000 psi Maximum aggregate size = ¾” Exposure class F3, S0, P1, C2

Example Specification ACI 318 Structures
Interior slabs and beams Interior columns Footings Parking garage slabs, beams, and columns Parking garage slab-on-grade and foundation walls. Now I would like to go through an example specification for a building designed using ACI 318 requirements. I will cover: Interior slabs and beams Interior columns Footings Parking garage slabs, beams, and columns Parking garage slab-on-grade and foundation walls.

Recommendations Comply with ACI 318
Avoid details of mixture proportions (where durability is not a concern) Avoid details of construction means and methods State the required performance in measurable terms that are enforceable Avoid the use of specific brands of products, especially when reference standards are available. Avoid making acceptance criteria more restrictive than industry practice In summary, when writing concrete specifications, comply with the provisions of ACI 318. You have little choice since it’s the code. Do not place unnecessary limits on materials or proportions of concrete. When concrete is exposed to freeze-thaw, deicing chemicals or sulfates, follow ACI 318 chapter 4, but don’t place more restrictive limits. The specification should avoid outlining details of construction means and methods as the expertise of the contractor is stifled. Often the contractor and concrete supplier can work out the requirements of plastic concrete for construction. State the required performance in measurable terms that are enforceable. For example, “Concrete as discharged from the transportation vehicle shall have entrained air of 5.5% +/- 1.5% when tested in accordance with ASTM C 231.” Requiring the use of specific brands of products or equipment should be avoided, especially when reference standards or alternative equivalents are available. Avoid making acceptance criteria more restrictive than accepted industry practice as that may not be achievable or could cost more for no associated benefit.

Quality Assurance Installer Qualifications:
On-site supervisor of the finishing crew who qualified as ACI Certified Concrete Flatwork Technician for flatwork placing and finishing. Flatwork finisher certification is important for constructing slabs General standard of care of concrete construction is addressed in this certification program Concrete performance is sensitive to how concrete is handled and finished. For flat work finishing require that the on-site supervisor is an ACI Certified Concrete Flatwork Technician. In addition to providing guidance for finishing slabs general standard of care of concrete construction is addressed in this certification program.

Quality Assurance (cont’d)
Manufacturer Qualifications: NRMCA Certified Ready Mixed Concrete Production Facility NRMCA Concrete Technologist Level 2 NRMCA certified concrete production facilities demonstrate compliance with requirements of ASTM C 94 Includes an annual certification of delivery vehicles The NRMCA Concrete Technologist Level 2 Certification validates personnel’s knowledge of fundamentals of concrete technology including mixture proportioning. Certification is obtained by passing a 90 minute exam administered by NRMCA with ACI Grade 1 Field Testing Technician Certification as the prerequisite. Details available at . The Manufacturer Qualifications include both production facility certification and personnel certifications. Concrete should be supplied from concrete plants with a current NRMCA Ready Mixed Concrete Production Facility Certification. This provides some level of assurance that concrete is produced and delivered in accordance with ASTM C 94. The certification includes an annual certification of delivery vehicles. Individuals with responsibility for concrete mixtures should be certified as an NRMCA Concrete Technologist Level 2. The NRMCA Concrete Technologist Level 2 Certification validates a person’s knowledge of the fundamentals of concrete technology including mixture proportioning. The certification is obtained by passing a 90 minute exam administered by NRMCA with ACI Grade 1 Field Testing Technician Certification as the prerequisite. Details of NRMCA certifications can be found at

Testing Agency Qualifications: Meet the requirements of ASTM C 1077. Field testing: ACI Concrete Field Testing Technician Grade I. Lab testing: ACI Concrete Strength Testing Technician or ACI Concrete Laboratory Testing Technician – Grade I. Test results for the purpose of acceptance shall be certified by a registered design professional employed with the Testing Agency. Concrete testing is very sensitive to the way specimens are collected, cured, and tested. Proper field and lab procedures are essential to achieving meaningful results. The testing agency qualifications are extremely important since concrete test results can be greatly influenced by the way concrete is sampled and tested. Personnel conducting field tests for acceptance shall be certified as ACI Concrete Field Testing Technician Grade I. Personnel conducting laboratory tests for acceptance shall be certified as ACI Concrete Strength Testing Technician or ACI Concrete Laboratory Testing Technician – Grade I. Test results for the purpose of acceptance shall be certified by a registered design professional employed with the Testing Agency.

Pre Installation Conference: Require representatives of each entity directly concerned with cast-in-place concrete to attend, including: Architect Structural Engineer Contractor Installer (Concrete Contractor) Pumping Contractor Manufacturer (Ready-mixed concrete producer) Independent testing agency One way to avoid potential problems during concrete construction is to require pre-installation conferences for major placements. The conference should include representatives from the architect, structural engineer, contractor, installer (or concrete contractor), pumping contractor, concrete producer, and testing agency. NRMCA and the American Society of Concrete Contractors has a document titled Checklist for the Concrete Pre-Construction Conference that would be helpful in running the meeting. NRMCA and American Society of Concrete Contractors has a document titled Checklist for the Concrete Pre-Construction Conference that can be used as a guide

Concrete Materials Cementitious Materials:
Use materials meeting the following requirements with limitations specified in Section 2.12. Hydraulic Cement: ASTM C 150 or ASTM C 1157 or ASTM C 595 Fly Ash: ASTM C 618 Slag: ASTM C 989 Silica Fume: ASTM C 1240 Avoid listing brand names for most materials in this section if a standard for the product already exists. Many existing standards are performance-based. Avoid limiting the type or quantities of cementitious materials that can be used unless required for certain performance attributes as listed in Section 2.12 Concrete Mixtures. In this section, list all materials allowed in the project. You should avoid limiting quantities or types of materials that can be used. Section 2.12 Concrete Mixtures will provide limitations for use of the specific materials. In addition, avoid listing brand names for most materials if a standard specification already exists. Simply list the reference standard. Hydraulic cement can include ASTM C 150 (Specification for Portland Cement), ASTM C 1157 (Performance Specification for Hydraulic Cement), and ASTM C 595 (Specification for Blended Hydraulic Cement). Fly ash shall meet the requirements of ASTM C 618. Slag shall meet the requirements of ASTM C 989 and Silica Fume shall meet the requirements of ASTM C 1240.

Concrete Materials (cont’d)
Normalweight Aggregate: ASTM C 33 Water: ASTM C 1602 Fibers: ASTM C 1116 Normalweight aggregate shall meet ASTM C 33. Water shall meet ASTM C 1602 which allows some use of recycled wash water. Fibers shall meet the requirements of ASTM C 1116.

Concrete Materials (cont’d)
Chemical Admixtures: Air Entraining: ASTM C 260 Water reducing, accelerating and retarding: ASTM C 494 Admixtures for flowing concrete: ASTM C 1017 Admixtures with no standard designation shall be used only with the permission of the design professional when its use for specific properties is required. Avoid limiting the type of admixtures that can be used unless there is a specific reason (eg. Chloride based admixtures for corrosion). Consider specifying or allowing the use of admixtures which do not have a specific ASTM designation with appropriate documentation indicating beneficial use to concrete properties. These include colors, viscosity modifying admixtures, hydration stabilizing admixtures, pumping aids, anti-freeze admixtures, etc. Chemical admixtures shall meet the requirements of ASTM C 260 for air entraining; ASTM C 494 for water reducers, accelerators, and retarders; ASTM C 1017 for flowing concrete. Avoid limiting the type of admixtures that can be used unless there is a specific reason. Admixtures with no standard designation shall be used only with the permission of the design professional when its use for specific properties is required. These may include colors, viscosity modifying admixtures, hydration stabilizing admixtures, pumping aids, anti-freeze admixtures, alkali silica reactivity, etc. Documentation should satisfy the professional engineer on the product performance and service history.

Concrete Mixtures (cont’d)
Table 2.12 Concrete Mixtures Application Exposure ƒ΄c Nom. Max. Agg. Size1 Air Content Max. w/cm by weight Cement-itious Materials Admix. Max. water sol. Cl ion in conc., % by wt of cement Interior Slabs and beams None 4,000 psi 3/4” N/A2 N/A See section 2.5 A 2.5 D 1.00 Interior Columns 5,000 psi Footings Sulfate (moderate) 4,500 psi 1-1/2” 0.45 Limits on cement4 No calcium chloride admixtures 0.30 Parking Garage Slabs, Beams, and Columns Freeze/Thaw, Deicing Chemicals 6%3 0.40 Limits on cement4, fly ash, slag, and silica fume5 0.15 Parking Garage Slabs on grade, Foundation walls Deicing Chemicals, 5-1/2 %3 This is table For each class list the application (where it will be used), the exposure (none, freeze-thaw, deicing chemicals, sulfate), and specified compressive strength. Then begin limitations on materials and quantities based on chapter 3 and 4 of ACI 318. Chapter 3 addresses materials and chapter 4 addresses durability requirements. Maximum aggregate size is based on limitations in ACI 318 Chapter 3. Limits on air content, water-cement ratio, cementitious materials, admixtures, and chloride ions are provided in ACI 318 Chapter 4.

Interior Slabs, Beams and Columns No Exposure
Table 2.12 Concrete Mixtures Application Exposure ƒ΄c Nom. Max. Agg. Size1 Air Content Max. w/cm by weight Cement-itious Materials Admix. Max. water sol. Cl ion in conc., % by wt of cement Interior Slabs and beams None 4,000 psi 3/4” N/A2 N/A See section 2.5 A 2.5 D 1.00 Interior Columns 5,000 psi Few limits on materials for class 1 and 2 since durability is not a concern No maximum water-cement ratio or minimum cement content Compressive strength based on structural design requirements Maximum aggregate size controlled by ACI 318 – 3.3 Aggregates 1/5 narrowest dimension of forms 1/3 slab depth 3/4 minimum clear spacing between reinforcement (governs) Maximum chloride ions controlled by ACI 318 – 4.4 for corrosion protection of reinforcement that will be dry or protected from moisture in service There are few limits on materials for class 1 and 2 concrete since durability is not a concern. Compressive strength is based on structural design requirements. Maximum aggregate size is controlled by ACI 318 – 3.3 Aggregates. Maximum aggregate size is limited to 1/5 the narrowest dimension between the sides of forms, 1/3 the depth of slabs, and ¾ the minimum clear spacing between reinforcing. For class 1 and 2 concrete, bar spacing governs. Maximum chloride ions is controlled by ACI 318 – 4.4 for corrosion protection of reinforcement. In this case the reinforced concrete will be dry or protected from moisture in service and the limit on chloride ions in concrete is 1 percent by weight of cement.

Footings Exposed to Sulfates
Table 2.12 Concrete Mixtures Application Exposure ƒ΄c Nom. Max. Agg. Size1 Air Content Max. w/cm by weight Cement-itious Materials Admix. Max. water sol. Cl ion in conc., % by wt of cement Footings Sulfate (moderate) 4,500 psi 3” N/A2 0.50 Limits on cement4 No calcium chloride admixtures 0.30 Compressive strength, cement type, maximum w/cm, and restriction on using calcium chloride admixtures are based on ACI – Sulfate exposure Type II, IP(MS), IS(MS), P(MS), I(PM)(MS), I(SM)(MS) Class 4 concrete is exposed to severe sulfates. Compressive strength, cement type, maximum water-cement ratio, and restriction on using calcium chloride admixtures are based on ACI – Sulfate exposure. Again, Type V cement must be used for severe sulfate exposure. If concrete is not exposed to sulfates there is no need to place limits on materials or proportions.

Parking Garage Slab Exposed to Freeze-Thaw and Deicing Chemicals
Table 2.12 Concrete Mixtures Application Exposure ƒ΄c Nom. Max. Agg. Size1 Air Content Max. w/cm by weight Cement-itious Materials Admix. Max. water sol. Cl ion in conc., % by wt of cement Parking Garage Slabs, Beams, and Columns Freeze/Thaw, Deicing Chemicals 5,000 psi 3/4” 6%3 0.40 Limits on cement4, fly ash, slag, and silica fume5 See section 2.5 D 0.15 Compressive strength, air content, maximum w/cm based on ACI Freezing and thawing exposure. Limits on SCMs based on ACI for concrete exposed to deicing chemicals: Fly ash, 25% max Slag, 50% max Silica fume, 10% max Total of fly ash, slag, and silica fume, 50% max Total of fly ash and silica fume, 35% max The parking garage slab, beams, and columns are exposed to freezing and thawing and deicing chemical. Compressive strength, air content, maximum w/cm based on ACI Freezing and thawing exposure. Limits on SCMs based on ACI for concrete exposed to deicing chemicals: Fly ash, 25% max Slag, 50% max Silica fume, 10% max Total of fly ash, slag, and silica fume, 50% max Total of fly ash and silica fume, 35% max

Exterior Slabs on Grade and Foundation Walls Exposed to Freeze-Thaw and Sulfates
Table 2.12 Concrete Mixtures Application Exposure ƒ΄c Nom. Max. Agg. Size1 Air Content Max. w/cm by weight Cement-itious Materials Admix. Max. water sol. Cl ion in conc., % by wt of cement Parking Garage Slabs on grade, Foundation walls Freeze/Thaw, Deicing Chemicals, Sulfate (moderate) 4,500 psi 1-1/2” 5-1/2 %3 0.45 Limits on cement4, fly ash, slag, and silica fume5 No calcium chloride admixtures 0.30 Compressive strength, air content, maximum w/cm based on ACI Freezing and thawing exposure. Limits on SCMs based on ACI for concrete exposed to deicing chemicals: Fly ash, 25% max Slag, 50% max Silica fume, 10% max Total of fly ash, slag, and silica fume, 50% max Total of fly ash and silica fume, 35% max Limits on cement type, calcium chloride admixtures, strength, and w/cm are based on ACI Sulfate exposure. Type II, IP(MS), IS(MS), P(MS), I(PM)(MS), I(SM)(MS) The parking garage slab on grade and foundation wall is exposed to freeze-thaw, deicing chemicals, and moderate sulfates. Compressive strength, air content, maximum water-cement ratio are based on ACI Freezing and thawing exposure. Limits on supplementary cementitious materials are based on ACI for concrete exposed to deicing chemicals. Fly ash is limited to 25% maximum by weight of total cementitious materials, slag is limited to 50%, silica fume is limited to 10%, total of fly ash, slag, and silica fume is limited to 50% and total of fly ash and silica fume is limited to 35%. Limits on cement type, calcium chloride admixtures, strength, and water-cement ratio are based on ACI Sulfate exposure. Type II cement or other sulfate resistant cement must be used for moderate sulfate exposure. If concrete is not exposed to freezing and thawing, deicing chemicals, and sulfates there is no need to place limitations on materials and proportions. Most concrete in building construction is not exposed to weather or chemical attack and therefore doesn’t need to have these limitations.

Possible additional requirements for parking garage concrete
In addition to the requirements in table 2.12, concrete mixtures proposed for parking garage slabs, beams, and columns shall meet the following criteria: RCPT (ASTM C 1202) 1500 coulombs 28 days (7 days moist plus 21 days in 100°F water) for mixture qualification Criteria for acceptance samples should be more lenient 80% below 1500 coulombs, or 95% below 2000 coulombs Shrinkage (ASTM C 157) 0.06% (7-d moist cure, 28-d drying for mixture qualification For those who are extremely concerned about the validity of using w/cm ratio as a surrogate for chloride ion penetration, then you might consider the following clauses for parking garage concrete: In addition to the requirements in table 2.12, concrete mixtures proposed for parking garage slabs, beams, and columns shall meet the following criteria: RCPT (ASTM C 1202) 1500 coulombs 28 days (7 days moist plus 21 days in 100°F water) for mixture qualification Criteria for acceptance samples should be more lenient 80% below 1500 coulombs, or 95% below 2000 coulombs Shrinkage (ASTM C 157) 0.06% (7-d moist cure, 28-d drying for mixture qualification

Possible additional requirements for parking garage concrete
Determine if the aggregate is reactive: Fails either ASTM C 1260 (14 day exp. < 0.10%) or C 1293 (1 years exp.< 0.04%) Has a history If reactive: Use job materials and have producer demonstrate C 1567 (14 day expansion < 0.10%) Determine if the aggregate is reactive: Fails either ASTM C 1260 (14 day exp. < 0.10%) or C 1293 (1 years exp.< 0.04%) Has a history If reactive: Use job materials and have producer demonstrate C 1567 (14 day expansion < 0.10%)

Concrete Mixtures (cont’d)
The installer and manufacturer shall coordinate to establish properties of the fresh concrete to facilitate placement and finishing with minimal segregation and bleeding. Factors shall include but are not limited to slump or slump flow, set time, method of placement, rate of placement, hot and cold weather placement, curing, and concrete temperature. The installer and manufacturer shall coordinate to establish properties of the fresh concrete to facilitate placement and finishing with minimal segregation and bleeding. Factors shall include but are not limited to slump or slump flow, set time, method of placement, rate of placement, hot and cold weather placement, curing, and concrete temperature.

Bridge Deck Freeze Thaw, Deicing Chemicals, Seawater
Table 2.12 Concrete Mixtures Application Exposure ƒ΄c Nom. Max. Agg. Size1 Air Content Cement-itious Materials Admix. Additional Requirements Bridge Deck Freeze/Thaw, Deicing Chemicals 5,000 psi 3/4” 6 % Limits on fly ash, slag, and silica fume See section 2.5 D testing required Limits on SCMs: Fly ash, 25% max Slag, 50% max Silica fume, 10% max Total of fly ash, slag, and silica fume, 50% max Total of fly ash and silica fume, 35% max We suggest the following specification for a bridge deck subjected to freeze-thaw, deicing chemicals, and seawater. In this case, for structural reasons, f’c is specified at 5000 psi. Air content is specified at 6% for severe freeze-thaw exposure. Provide limits on SCMs similar to ACI 318.

Additional Requirements
In addition to the requirements in table 2.12, concrete mixtures proposed for bridge decks shall meet the following criteria: RCPT (ASTM C 1202) 1500 coulombs 28 days (7 days moist plus 21 days in 100°F water) for mixture qualification Criteria for acceptance samples should be more lenient 80% below 1500 coulombs, or 95% below 2000 coulombs Shrinkage (ASTM C 157) 0.06% (7-d moist cure, 28-d drying for mixture qualification In addition to the requirements in table 2.12, concrete mixtures proposed for parking garage slabs, beams, and columns shall meet the following criteria: RCPT (ASTM C 1202) 1500 coulombs 28 days (7 days moist plus 21 days in 100°F water) for mixture qualification Criteria for acceptance samples should be more lenient 80% below 1500 coulombs, or 95% below 2000 coulombs Shrinkage (ASTM C 157) 0.06% (7-d moist cure, 28-d drying for mixture qualification

Loading Dock Wall (marine)
Mass Concrete Freeze Thaw Deicing Chemicals Seawater Concerns Mass concrete – minimize cement content and maximize SCM to reduce temperatures Marine – maximize SCM and minimize w/cm for corrosion protection Salt scaling – limit SCM dosage Strength – is not an issue Cementitious Material – enough to fill all the spaces around the aggregate, 450 pcy for 1-1/2” aggregate Let’s take another example where we have a loading dock wall in a marine environment. It’s in the Northern East coast USA. It’s in excess of 3 feet thick so it is considered mass concrete, it’s exposed to freezing and thawing, sea water and deicing salts, and it’s heavily reinforced. The concerns: Mass concrete – therefore minimize cement content and maximize SCM to reduce temperatures. Marine – therefore maximize SCM and minimize w/cm for corrosion protection. Note that slag and fly ash only give good RCP results after extended curing. Salt scaling – therefore limit SCM dosage. Strength – is not an issue. Minimum cement – need enough cementitious material to fill all the spaces around the aggregate – 450 pcy for 38-mm aggregate?

Loading Dock Wall - Mass Concrete, Freeze Thaw, Deicing Chemicals, Seawater
Table 2.12 Concrete Mixtures Application Exposure ƒ΄c Nom. Max. Agg. Size1 Air Content Cement-itious Materials Admix. Additional Requirements Loading Dock Wall Mass Concrete, Freeze/Thaw, Deicing Chemicals, Seawater 4,000 psi 1-1/2” 5-1/2 % Limits on Cements See section 2.5 D testing required Limits on hydraulic cement – Portland Cement Type I (although seawater is considered to have moderate sulfates, corrosion is more critical so use Type I with SCMs) No limits on SCMs So using our table again, identify the application and exposure. In this case, the required strength is 4,000 psi. The air content requirement is 5-1/2 percent. Limit hydraulic cement to Portland Cement Type I. Although seawater is considered to have moderate sulfates, corrosion is more critical so use Type I with significant amounts of SCMs. Do not use Type II or Type V cement, the need for a reasonably high C3A for chloride binding supersedes the need for sulfate resistance. Don’t place limits on SCMs. Scaling would push SCM content down, but heat and corrosion would push it up. The compromise is to go with high SCM content, be rigorous on curing requirements and live with some scaling on the surface. Producer should consider 30% Class F fly ash or 50% slag for corrosion and reduced heat.

In addition to the requirements in table 2.12, concrete mixtures proposed for loading dock wall shall meet the following criteria: RCPT (ASTM C 1202) 1500 coulombs 28 days (7 days moist plus 21 days in 100°F water) for mixture qualification Criteria for acceptance samples should be more lenient 80% below 1500 coulombs, or 95% below 2000 coulombs In addition to the requirements in table 2.12, concrete mixtures proposed for loading dock wall shall meet the following criteria: RCPT (ASTM C 1202) 1500 coulombs 28 days (7 days moist plus 21 days in 100°F water) for mixture qualification Criteria for acceptance samples should be more lenient 80% below 1500 coulombs, or 95% below 2000 coulombs

Additional Requirements (cont’d)
During placement of the loading dock wall concrete, the maximum differential temperature between the internal concrete (center of wall) and the surface (2” below surface) shall be 35 °F through the use of insulation blankets, cooling the concrete, or other method. Minimum 7 day insulation blanket curing. Alternatively, the contractor may submit an alternative temperature control plan. During placement of the loading dock wall concrete, the maximum differential temperature between the internal concrete (center of wall) and the surface (2” below surface) shall be 35 °F through the use of insulation blankets, cooling the concrete, or other method. 7 day curing on horizontal surfaces. Alternatively, the contractor may submit an alternative temperature control plan.

Specifying Concrete for High Performance
Questions?

Specifying Concrete for High Performance

Similar presentations

Presentation on theme: "Specifying Concrete for High Performance"— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Specifying Concrete for High Performance

Similar presentations

Presentation on theme: "Specifying Concrete for High Performance"— Presentation transcript:

Similar presentations

About project

Feedback