Effect of early CO2 curing on the chloride transport and binding behaviors of fly ash-blended Portland cement

Published on Jun 21, 2021in Construction and Building Materials6.141
· DOI :10.1016/J.CONBUILDMAT.2021.123113
Yahong Ding2
Estimated H-index: 2
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Abstract
Abstract Early CO2 curing has attracted a lot of attentions due to sequestration of carbon dioxide and rapid strength development for cement-based materials. This study investigates the chloride transport and binding properties of fly ash-blended cement-based materials with and without early CO2 curing. A comparison is made between the specimens exposed to early CO2 curing followed by subsequent water curing and those continuously cured in water. Results show that early CO2 curing decreases the water sorption and chloride migration coefficient of cement mortar. The replacement of cement with fly ash decreases the strength and permeability of mortar regardless of the curing regime. CO2 cured cement pastes show lower chloride binding capacity than water cured cement pastes after immersion in 0.1 M, 0.5 M and 1 M sodium chloride solutions due to the consumption of calcium hydroxide, presence of carbonates as well as lower contents of C-S-H gel. The presence of fly ash increases the contents of bound chloride in water cured cement pastes but decreases them in CO2 cured cement pastes.
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Abstract Chloride ingress is one of the main causes for the degradation of reinforced concrete structures. Increasing the chloride binding capacity of concrete is generally thought as a feasible way to restrain the chloride ingress. In our previous study, the γ-phase nano-Al2O3 (NA) was found to be beneficial for improving the chloride binding of plain Portland cement paste as a result of the formation of additional Friedel’s salt. Herewith, the cases of blended cement pastes were further invest...
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Abstract Low-calcium (FA) and high-calcium (HCFA) fly ash and granulated blast furnace slag (GBFS) are the most widely known, standardized and used SCMs in the composition of cement and concrete. In the last 4 years, scientific work has focused on improving binder properties (e.g. long setting time, low early strength etc.) containing large quantities of FA, HCFA and GBFS. The main directions of activity are the introduction of high-level additives to concrete composition, such as nano-materials...
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Abstract In cementitious materials exposed to solutions containing chloride, chloride binding typically results from the chemical reactions between chloride ions and aluminate phases to form Friedel's salt, and the interaction between chloride ions and calcium silicate hydrates (C S H). Calcium oxychloride can also form when Ca(OH)2 in cementitious materials reacts with CaCl2 solutions. This paper examines the chloride binding of hydrated cement pastes containing fly ash exposed to CaCl2 solutio...
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#2Jan Olek (Purdue University)H-Index: 36
Abstract This paper presents a study on the carbonation activated binders prepared from pure calcium silicate phases, which included tricalcium silicate (3CaO.SiO2, [C3S]), β-dicalcium silicate (β-2CaO.SiO2, [β-C2S]), γ-dicalcium silicate (γ-2CaO.SiO2, [γ-C2S]), tricalcium disilicate (rankinite, 3CaO.2SiO2, [C3S2]), and monocalcium silicate (wollastonite, CaO.SiO2, [CS]). The overall study consisted of three experimental parts, with individual focus on the following issues: (i) reaction kinetics...
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Abstract null null Carbonation treatment of fly ash (FA) is proposed as a promising method for stabilization of hazardous residues and CO2 sequestration. This paper aims to investigate the performance of cement mortar incorporating carbonated FA and the synergistic effect with carbonation curing. The results show that the content of free CaO and the hydration heat were reduced apparently by carbonation treatment. The synergy of carbonation treatment and carbonation curing compensated for the str...
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