In situ chemical modification of C–S–H induced by CO2 laser irradiation

Abstract

Fire-induced compositional changes lead to strength loss and even failure in cement and concrete. Calcium silicate hydrate (C-S-H) gel, the main product of cement hydration, dehydrates at 25 C to 200 C, while temperatures of 850 C to 900 C alter its structure. A Raman spectroscopic study of the amorphous and crystalline phases forming after CO 2 laser radiation of cement mortar showed that C-S-H dehydration yielded tricalcium silicate at higher, and dicalcium silicate at lower, temperatures. Post-radiation variations were identified in the position of the band generated by Si-O bond stretching vibrations.

Biomineralization in saxicolous lichens: Raman spectroscopic study supported with XRF and SEM-EDX analyses

“…Construction materials exposed to diverse environmental conditions suffer changes in their physical, mechanical, chemical and mineralogical characteristics and properties, above all when they belong to facades of buildings located in areas with high concentrations of acid gases (CO 2 , NO x and SO x ) or particulate matter. [1][2][3] Frequently, the chemical weathering of the stones takes place together with physical and mechanical weathering related to changes in temperature, humidity-dryness cycles, solar radiation and freeze-thaw actions. [1] Apart from the widely studied chemical and physical weathering factors, the action of micro-organisms till superior biological organisms (plants and birds) is being currently taken into consideration.…”