Hershey Lodge Preconference Symposium 17 March 2008 Hershey Lodge Preconference Symposium 17 March 2008 State-of-the-Art Technological Developments in Concrete Developments in Concrete “ Nanotechnology Applied to Bulk Concrete ” Barry E. Scheetz Department of Civil and Environmental Engineering The Pennsylvania State University
Presentation Outline *Who first defined nano-? Where are we using nano-stuff? Why the big deal with nano-?Why the big deal with nano-? What exactly is a nano?What exactly is a nano? *How does this work in bulk concrete? * *The future of nanotechnology and bulk concrete?
The term "nanotechnology" was first defined by Tokyo Science University, Norio Taniguchi in aTokyo Science UniversityNorio Taniguchi 19741974 paper (N. Taniguchi, "On the Basic Concept of 'Nano-Technology'," Who first defined nano-?
Medicine cell imaging cancer therapy --- contact agents drug-delivery vehicles Catalysis fuel cells catalytic converters photocatalytic devices Where are we using nano-stuff?
Cosmetics sunscreens Textiles water and stain repellent wrinkle-fee invisibility coat – military Optics scratch resistant coatings Foods anti-microbial packaging
Vehicle manufacturing hard coatings for wear resistance Electronics quantum dots semiconductors
Why the big deal with nano- ? The nano-materials behave nonlinearly i.e. hard materials become ‘super’ hard At the scale of a cluster of a few unit cells [nanometers], conventional ideas of structure-property relationships no long hold.
What exactly is a nano? 1 grain of sand in 200 lbs A billionth of a meter 10 -9
Nanotechnology and bulk concrete practices In 1974 when Dr. Taniguchi first defined ‘nano-,’ nano-seeding of portland cement concrete was being practiced in Philadelphia for 2 years. In 1974, it was being practiced in Europe for about 30 years. It took almost 20 more year, until 1995, before I was able to recognize the phenomena
Humana Inc. Headquarters Building – Louisville, Kentucky - 1983 Applications of this technology *basement structure had to withstand hydraulic head of 16 feet Philadelphia International Airport Parking Garages -1976 *repeated exposure to salt
Camden Aquarium Penguin Exhibit – Camden, NJ - 1998 * Shotcrete application for fast and easy construction of water channels *water treatment facilities NSF Standard 61 approved
Mineralogical Composition of Hydrated Portland Cement
C 3 S + H 2 O C-S-H + CH 3CaO. SiO 2 + (3+m-n)H 2 O nCaO. SiO 2. mH 2 O + (3-n)Ca(OH) 2 nCaO. SiO 2. mH 2 O + (3-n)Ca(OH) 2
Q t Hydration of C 3 A Induction Period Hydration of C 3 S Hydration of C 2 S Heat of Hydration of Portland Cement
Solubility of C 3 S in Portland Cement Slurry Equilibrium saturation curve supersaturation Point at which nucleation occures in ordinary non-seeded systems On set of nucleation with the use of nano-seeds
Benefits of microstructure control on the nanometer scale *Uniformity of the microsturcture >minimize stress concentrators >homogeneous bonding to filler materials *Reduction in critical flaw size KIC = Y σ ( c)1/2 by the dispersion of portlandite
The primary function of the admixture is for the manufacture of “watertight concrete and reinforcement corrosion protection.” The Material Ref: CIAS Report: 02-1
* compositionally it is an Alkaline Earth Silicate [AES] C-S-H * it is sold in the form of a liquid * dosage rate is 1% by weight of portland cement [equivalent to 400 ppm concrete]
Water Permeability Permeability Performance Performance Raw data PA turnpike 0.2 microdarcys * <1 nanodarcy * sample taken from section that was not compromised by deterioration deterioration
Carbon Dioxide Penetration Penetration After 25 Years After 25 Years 25.4mm
“The Big House” University of Michigan Stadium * 460,000 sq.ft. repair to risers and tread surface area; * depth of replacement: 1/8” to 6” * 1972 to 1979 Repair method: alkaline earth silicate modified repair mortar Ref: Concrete International (Sept 1980)
Repaired surfaces --- 25 + years later. Melting snow 2001 1972 Damage to riser and tread area 2001
* cast the same day at the same pre-cast facility * mix designs ‘identical’ > one had AES > one had corrosion inhibitor
* seven structures in 5 mile stretch; 6 control and 1 with admixture * AES modified placed 1973; 6 control placed 1974 Pennsylvania Turnpike
Wiss, Janney & Elstner Evaluation of PA Turnpike Bridge Deterioration
MIP results of pore size distribution in slag-OPC blended concrete Total porosity 9.2% Total porosity 14.5% 78.9% 91.4% 6 sack concrete mix 50% OPC/50% slag W/C = 0.43 Cured 28 days 6 sack concrete mix 50% OPC/50% slag W/C = 0.43 Cured 28 days With AES
Water flow will follow the path of least resistance. Tortuosity is a ratio of the “actual”length of the flow path, which often is very sinuous and the shortest distances between the end points of the flow. L min L max L intermediate Case #1 - ordinary concrete T = L min Case #2 - mineral admixture concrete T = L intermediate /L min Case #3 AES concrete T = L max /L min
Sheriann Ki Sun Burnham Tortuosity #9 3-3 composite 3D solid matrix and and 3D void structure
Tortuosity D eff. = D int D eff. = effective diffusion coefficient D int = intrinsic diffusion coefficient porosity = porosity tortuosity factor = tortuosity factor
The future of nanotechnology and bulk concrete? > Nano-materials must be incorporated into cementitious systems in an aqueous media. > The result is that small mass loadings of very small seed results in extremely large numbers of individual particles. > At conventional low levels of addition, there is not enough material added to impact the physical properties
Future continued: > Distributing seed uniformly throughout a concrete body therefore controls the ‘entire’ volume of the concrete body > calcium carbonate is reported to enhance the mechanical strength of pastes made with 100,000 to 200,000ppm addition of nano-particles
Future continued: > At concentrations greater than 100,000ppm [ a situation not hitherto examined] these seeds offer a significant potential, when used with a system such as DSP cement, to further enhance densification resulting in enhanced mechanical properties