Durability and Mechanical Properties of Ternary Blend Concretes

摘要

The FDOT Structures Design Guidelines required that concrete piles placed in a marine environment must contain ordinary Portland cement (PC), fly ash (FA), and silica fume (SF). This blend of PC and supplementary cementitious materials (SCM) is primarily intended to produce a durable concrete that is highly resistant to the penetration of chlorides. The research project evaluated the durability of concrete made with a ternary blend of cementitious materials that included ordinary Portland cement (PC), fly ash (FA), and blast furnace slag (S) in comparison to the current practice of using silica fume. Thirty-two ternary and binary mixtures (not including duplicate mixtures) containing varying quantities of FA, blast furnace slag (S), and SF were prepared to evaluate their effect on the mechanical and durability attributes. The ternary mixtures included PC+FA+S with FA being varied from 10% to 40% and S from 20% to 60% by weight of total cementitous materials. In addition, control mixtures of 80%PC+20%FA and 73%PC+20%FA+7%SF were prepared as control mixtures. Half of the mixtures were Class IV and half were Class V mixtures. In addition, this research also compared mixtures prepared with PC that met the ASTM C150 standard and to those with PC that met the AASHTO M85 standard prior to harmonization. Mechanical tests were conducted that included compressive strength, modulus of elasticity, compressive creep, split tensile strength, and modulus of rupture. The durability tests conducted were rapid migration test, corrosion of embedded steel, surface resistivity, and bulk diffusion. Finally, X-ray Diffraction (SRD) was used to examine the microstructure of the hydration process of these materials. Mixtures were higher FA (30 to 40% by replacement weight) content had delayed gains in compressive strength. Increasing quantities of S (and associated decrease of PC) produced a slight decrease (