Economical and Crack-Free High-Performance Concrete for Pavement and Transportation Infrastructure Construction

The main objective of this research is to develop and validate the behavior of a new class of environmentally friendly and cost-effective 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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Report number: cmr17-007
Published: May 2017
Project number: TR201503
Author(s): Dr. Kamal H. Khayat (principal investigator) and Iman Mehdipour (PhD Candidate student)
Performing organization: Missouri University of Science and Technology