Understanding the aging mechanism of calcium silicate hydrates under the action of solar radiation

This work examines the influencing mechanism of light radiation on performances and structures of calcium silicate hydrates (C-S-H) through exposing synthetic C-S-H samples to high-power Xenon radiation. The compositions, chemical structures and nanomorphology of C-S-H were investigated using XRD, TG, 29Si NMR, Ca XANES, Si XANES and TEM. Xenon radiation reduces the chemically bound water content in C-S-H and the drying effect induced by Xenon radiation is more pronounced in C-S-H with lower Ca/Si ratio. Xenon radiation increases the polymerization of C-S-H and elongates the silicate chain by driving separated Si–O tetrahedron to connect with each other without changing its Ca/Si ratio. Furthermore, Xenon radiation reduces the coordination numbers of Ca–O and causes the self-organization of chemical structure at molecular and atomic scales. The existence of portlandite improves the resistance of C-S-H to compositional and structural changes induced by Xenon radiation. These findings pave the way for understanding aging mechanism of cement-based materials under the action of solar radiation.