Presentation on theme: "FUNDAMENTALS OF CONCRETE Presented By: Kevin J. Brigandi Construction Services Department Manager Debra A. Nunes Construction Services."— Presentation transcript:
FUNDAMENTALS OF CONCRETE Presented By: Kevin J. Brigandi Construction Services Department Manager firstname.lastname@example.org Debra A. Nunes Construction Services Department Manager email@example.com
Uses of Concrete: Concrete can be formed in almost any color, shape and texture, while serving as an acoustic and thermal barrier Concrete can be placed in all environments and conditions Concrete is resistant to fire, chemical exposure and weather Concrete is environmentally safe and recyclable Concrete is efficient to construction and can be produced with a variety of durability characteristics and strengths CONCRETE BASICS
How Should Concrete Be Specified? Strength Water / Cement Ratio Air % Minimum Cement Factor Slump / Durability
Water / Cement Ratio Calculations 30 Gal 8.33 lb. 250 lb. ----------- X ------------ = ---------- =.44 W/C 6 Sack 94 lb. 564 lb. 30 Gal 8.33 lb. 250 lb. ----------- X ------------ = ---------- =.44 W/C 6 Sack 94 lb. 564 lb.
Adding Water to Concrete Water added (gal/yd³) Approx. Slump Increase (inches) Strength Reduction (psi) (%) 112007% 2240013% 3360020% 4480027% 55100033% 66120040%
Entraining Air in Concrete 2452 188.8.131.52-1/2 34.561 3.5563/4 45.571/2 4.567.53/8 5 79Less than 3/8 Mild Exposure Moderate Exposure Severe Exposure Nominal max size of aggregate, in.
Concrete Quality Control All Field Technicians should be certified And have a working knowledge of the following ASTM standards: C31 C1064 C143 C172 C173 C231 C138
ASTM C 172: Standard Method for Sampling Freshly Mixed Concrete Sample from middle portion of the batch Sample at two or more regularly spaced intervals, not to exceed 15 min Combine and remix sample thoroughly Cover Sample to protect from drying
ASTM C 143: Standard Test Method for Slump of Portland Cement Concrete
ASTM C 231: Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method
ASTM C 173: Standard Test method for Air Content of Freshly Mixed Concrete by the Volumetric Method
Curing Performed as soon as possible after final finishing is completed Performed to prevent the loss of moisture from concrete Helps in maintaining a favorable concrete temperature for a definite period of time Will make concrete stronger –More impermeable –More resistant to stress –More resistant to abrasion –More resistant to freezing and thawing conditions
Curing Methods and Materials Ponding or immersion Spraying or Fogging Wet Coverings Impervious Paper Plastic Sheets* Membrane-Forming Curing Compounds Steam Insulating Blankets or Covers *discoloration can occur if not used properly
Common Concrete Problems Discoloration Dusting Cracking Plastic shrinkage cracking Crazing Scaling Curling Blisters Delamination Pop Outs
Prevention of Discoloration Do not Use Calcium Chloride Type, kind and condition of formwork can influence color Eliminate “Burning” of concrete Proper curing - Caution with Plastic Uniform sub-grade moisture
Powders under any type of traffic Easily scratched with a nail or even by sweeping Very weak wearing surface What is Dusting?
Finishing operation performed while bleed water is on the surface or before bleeding has finished Insufficient curing Placement of non-absorptive sub grade or polyethylene vapor barrier Floating/Troweling after the condensation of moisture from warm humid air is on cold concrete What Causes Dusting?
Prevention of Dusting Do not place concrete directly on polyethylene vapor barriers or non- absorptive sub grades Proper curing Cold weather concrete practices Vent exhaust to the outside to provide adequate ventilation
Cracking The one thing I can guarantee is that your concrete will crack!
What Is Curling? The distortion of a slab into a curved shape due to temperature gradients throughout the depth of the concrete Slab Curling
Why Do Slabs Curl? Other Factors That Cause Curling: Bleeding / Poor curing / Joint spacing Shrinkage of the top relative to the bottom of the slab Moisture gradients in slab Temperature gradients within the slab
How Do You Prevent Blisters? Delay final finish as long as possible Avoid surface drying Initial float done with flat blades
The top 1/8 inch of the surface is densified and separated from the base slab by a thin layer of air or water Forms during final troweling Most frequent in early spring and late fall Delaminations
What Are Pop Outs? A Conical Fragment that breaks out of the surface
Green Concrete Technology Benefits of Pervious Concrete Environmental Benefits Economic Benefits Structural Benefits
Mix Designs of Pervious Concrete Supplementary cementitious materials (SCMs) Coarse Aggregates Water Admixtures
Testing and Inspection of Pervious Concrete Density Testing (ASTM C29) No Slump No Air
Self Consolidating Concrete The use of self-consolidating concrete (SCC) has grown tremendously since its inception in the 1980s. Because of the material performance in its fresh state, the existing testing methods for conventional concrete are no longer suitable for SCC.
Mix Designs for SCC SCC mixtures can be designed to provide the required hardened concrete properties for an application, similar to regular concrete.
Benefits of Self Consolidating Concrete Improved constructability Virtually flawless finish Homogenous and uniform concrete Better reinforcement bonding Flows easily into complex shapes and through congested reinforcement Superior strength and durability Allows for innovative architectural features
Benefits of SCC Wall with Normal and SCC Concrete
Contributions By: The Portland Cement Association The American Concrete Institute The National Ready-Mix Concrete Association Blue Circle Cement St. Lawrence Cement Connecticut Concrete Promotion Council The Portland Cement Association The American Concrete Institute The National Ready-Mix Concrete Association Blue Circle Cement St. Lawrence Cement Connecticut Concrete Promotion Council