Economical and crack-free high-performance concrete for pavement and transportation infrastructure construction.
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2017-05-01
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Abstract:The main objective of this research is to develop and validate the behavior of a new class of environmentally friendly and costeffective
high-performance concrete (HPC) referred to herein as Eco-HPC. The proposed project aimed at developing two classes
of Eco-HPC for the following applications: (i) HPC for pavement construction (Eco-Pave-Crete); and (ii) HPC for bridge
infrastructure construction (Eco-Bridge-Crete). The binder contents for these construction materials were limited to 320 kg/m3
(540 lb/yd3) and 350 kg/m3 (590 lb/yd3), respectively, in order to reduce paste content, cost, CO2 emissions, and shrinkage. Both
Eco-HPC types were optimized to develop high resistance to shrinkage cracking as well as to secure high durability. Given the
relatively low binder content, the binder composition and aggregate proportion were optimized based on the packing density
approach to reduce the paste required to the fill the voids among aggregate particles. The optimized concrete mixtures exhibited
low autogenous and drying shrinkage given the low paste content and use of various shrinkage mitigating strategies. Such
strategies included the use of CaO-based expansive agent (EX), saturated lightweight sand (LWS), as well as synthetic or recycled
steel fibers. Proper substitution of cement by supplementary cementitious materials (SCMs) resulted in greater packing density of
solid particles, lower water/superplasticizer demand, and improved rheological and hardened properties of cement-based materials.
A statistical mix design method was proposed and was shown to be effective in optimizing the aggregate proportioning to achieve
maximum packing density. The synergistic effect between EX with LWS resulted in lower autogenous and drying shrinkage. For a
given fiber content, the use of steel fibers recovered from waste tires had twice the flexural toughness of similar mixture with
synthetic fibers. The optimized Eco-HPC mixtures had lower drying shrinkage of 300 μstrain after 250 days. The risk of restrained
shrinkage cracking was found to be low for the optimized concrete mixtures (no cracking even after 55 days of testing). The results
of structural performance of large-scale reinforced concrete beams indicated that the optimized Eco-Bridge-Crete containing
ternary combination of 35% fly ash and 20% slag replacements and recycled steel fibers developed significantly higher flexural
toughness compared to the MoDOT reference mixture used for bridge infrastructure applications.
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