Title:
Use of High-Alkali Natural Pozzolans (NPs) and Reclaimed Fly Ashes (RFAs) as Alternative Supplementary Cementitious Materials (SCMs) in Concrete
Author(s):
Weiqi Wang
Publication:
Web Session
Volume:
Issue:
Appears on pages(s):
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DOI:
Date:
10/23/2022
Abstract:
Using supplementary cementitious materials (SCMs) with alkali content is generally avoided in concrete because alkalis in SCMs may exacerbate the alkali-silica reaction (ASR). This study investigates the potential of materials with this characteristic used in this concrete industry, the availability of these alkalis to be readily released into the pore solution, and the role of these alkalis in affecting concrete properties. First, this research explored the impact of high alkali SCMs on the concrete ASR by using standard test methods such as ASTM C1567, C1293, and AASHTO T380. Further, the available alkali that can release from SCMs into concrete pore solution was investigated and analyzed by ASTM C311. In addition, the pozzolanic reactivity of high-alkali SCMs was evaluated by using the R3 test (ASTM C1897) in combination with thermal gravimetric analysis (TGA). ASTM C596 drying shrinkage test, ASTM C 1012 sulfate resistance test, and ASTM C1202 rapid chloride ions penetration test were also conducted to evaluate how the high-alkaline SCMs affect concrete and other durable properties. In the next stage, we plan to determine how the SCM's available alkalis and total alkalis influence the concrete pore solution through evaluating the concrete pore solution's pH and compositions like alkalis ions concentration. Results to date indicate that all the SCMs are effective in improving concrete performance on ASR mitigation, sulfate resistance, and chloride ions penetration. The results are not proportionate to the SCM's total alkali content, which indicates the total alkali of SCMs is not the determining factor to rule on SCMs' performance.