Influence of light radiation on performance-structure of tricalcium silicate (C3S) hydration products

In this work, high-power Xenon radiation is used to simulate real sunlight radiation and calcium silicate hydrate is prepared by hydration of tricalcium silicate (C3S) with two water-to-solids (w/s) ratios of 0.5 and 10. The absorbance, compositions, silicate chain structure, pore structure and micromorphology of C3S hydration products (C3S-H) after exposure to Xenon radiation were determined using XRD, TG, FITR, Si-29 solid-stated NMR, BET and SEM. First of all, fibrous and needle-like calcium silicate hydrate is observed in C3S-H/10 while flaky and honeycomb-like shape is observed in C3S-H/0.5. Although there are remarkable differences in the micro-morphology of calcium silicate hydrate in C3S-H with different w/s ratios, Xenon radiation reduces the amount of bound water, increases the polymerization of silicate chain and refines the nanopore structure of calcium silicate hydrate. The underlying mechanism for the re-organization of chemical structure is attributed to improved polymerization of silicate chains. In addition, the refinement on the nanopore structure is due to the coupling actions of shrinking and polymerization of calcium silicate hydrate sheets. The findings could provide basic knowledge regarding the durability of cement-based materials serviced in atmospheric environments especially with strong solar radiation.