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
The main objective of this research is to evaluate the
feasibility of using high-volume recycled materials for concrete production in
rigid pavement. The goal was to replace 50% of the solids with recycled
materials and industrial by-products. The performance of concrete mixtures
made with different fine and coarse recycled concrete aggregate (RCA) contents
and binder types was investigated. Both single-layer rigid pavement and
two-lift concrete pavement (2LCP) were considered. The optimized mixtures
developed 91-d compressive strength results from 5,900 to 8,600 psi. Flexural
strength was mostly higher than 600 psi at 28 d. The modulus of elasticity
ranged from 4.7 to 6.7 ksi at 56 d. Using the optimized binder incorporating
35% Class C fly ash and 15% slag reduced the 150-d drying shrinkage to values
less than 350 to 500 με. However, an increase in fine RCA content from 15% to
40% resulted in increased shrinkage values (up to 650 με). The optimized
mixtures exhibited frost durability factor higher than 88%. De-icing salt
scaling ratings were limited to 3 for all mixtures, except the mixture with
15% GP and 35% FA-C. All mixtures exhibited comparable coefficient of thermal
expansion (CTE) values, ranging from 4.8 to 5.2 E-6 in/in/°F. Incorporation of
RCA did not have a significant effect on CTE values. Based on the obtained
data, it was concluded that concrete mixtures incorporating high volume
recycled aggregate and SCMs can present viable choices for sustainable
pavement construction. The following four mixtures exhibited satisfactory
performance and can be used for construction of the single layer pavement: (1)
MoDOT PCCP as the reference concrete; (2) concrete incorporating the optimized
binder (15% slag and 35% Class C fly ash replacements), 0.40 w/cm, without any
RCA; (3) concrete incorporating the optimized binder, 0.40 w/cm, and 30%
coarse RCA (30C); concrete incorporating the optimized binder, 0.37 w/cm, and
50% coarse RCA (50C-37). The following three mixtures can be incorporated for
construction of the top layer of the 2LCP systems: (1) MoDOT PCCP as
reference; (2) concrete incorporating the optimized binder, 0.40 w/cm, without
any RCA; (3) concrete incorporating the optimized binder, 0.40 w/cm, and 30%
coarse RCA (30C). The following two mixtures can be employed for construction
of the bottom layer of the 2LCP systems: (1) concrete incorporating the
optimized binder, 0.37 w/cm, 50% coarse RCA, and 15% fine RCA (50C15F-37); (2)
concrete incorporating the optimized binder, 0.37 w/cm, and 70% coarse RCA
(70C-37).
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Report number: cmr17-006
Published: May 2017
Project number: TR201502
Author(s): Dr. Kamal H. Khayat (principal investigator) and Seyedhamed Sadati (PhD Candidate student)
Performing organization: Missouri University of Science and Technology
