Role of an amorphous silica in portland cement concrete

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An amorphous silica (AS) replacing up to 10% of the portland cement by mass in concrete behaved partly as a traditional pozzolan, partly crystallized to quartz and the rest underwent some (crystal) structural reorganization without morphological changes. The pozzolanic behavior was evident from a reduction in the calcium hydroxide content of AS-cement paste with time. A new crystalline phase was observed in the scanning electron microscope only when AS was present, and energy dispersive X-ray microanalysis coupled with X-ray absorption near edge structure spectroscopy confirmed that it was the most stable form of silica, quartz. The presence of AS changed the concrete's microstructure, aggregate-paste interface, and pore size distribution. © 2006 ASCE.

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Journal of Materials in Civil Engineering

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