Abstract
Pore structure development in Portland cement, fly ash, or/and ferronickel slag (FNS) was investigated using mercury intrusion porosimetry and X-ray CT tomography. The progress of hydration was observed using X-ray diffraction (XRD) analysis and compressive strength while durability of concrete was monitored by chloride penetration resistance and chloride profiles. Mercury intrusion porosimetry (MIP) results suggested that the blended cement had a higher porosity while lower critical pore size. The major reason to this increased porosity was the formation of meso and micro pores compared to ordinary Portland cement (OPC). In terms of chloride transport, replaced cement, especially ternary-blended cement had higher resistance to chloride transport and exhibited slightly lower development of compressive strength. X-ray CT tomography shows that the influence of pore structure of ternary-blended cement on the ionic transport was strongly related to the pore connectivity of cement matrix.
Highlights
Concrete is a nonhomogeneous and porous construction material that includes pore network of different sizes and shapes
As for the mix of ordinary Portland cement (OPC) with fly ash (FA) (OFN0), hydration products mainly consisted of portlandite, calcite (CaCO3 ), and unreacted particles, while OFN15 was indicative of the presence of identical hydration products except for anhydrate olivine crystalline ((Mg, Fe)2 ·SiO4 ), presumably being originated from raw Ferronickel slag (FNS) powder
It is notable that there was no further formation of hydration products in FNS-mixed ternary-blended cement paste
Summary
Concrete is a nonhomogeneous and porous construction material that includes pore network of different sizes and shapes. Its physical and chemical properties are strongly influenced by this pore structure. Properties such as strength, corrosion resistance, durability, and permeability are closely related to the characteristics of the pore structures for cement-based materials [1]. The use of industrial by-products as cementitious materials may reveal different properties compared to conventional materials [10]. Studies on ternary-blended cement using round granulated blast-furnace slag (GGBS) and FA have been completed over the past decades, and are already used as construction materials [12,13]. In order to study the effect of it as an admixture, OPC with binary and ternary-blended mix designs using OPC, FA, or/and FNS were used. Since no chemical admixture was used to exclude possible reactions, the experiment was conducted with a specimen that had been cured for a longer period, i.e., one year
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