Morphological effect of C–S–H gel on the elastic behaviour of early-age cement-based materials

Abstract

The morphological effect of calcium silicate hydrates (C–S–H) on the elastic behaviour of early-age cement-based materials is studied based on a refined multi-scale elasticity prediction model. The model demonstrates that the growth morphology of low-density (LD) C–S–H has a significant effect on the solid percolation threshold and the elastic behaviour of early-age cement-based materials, especially in the cases of higher water–cement (w/c) ratios or lower hydration degrees. Using the refined model, the growth morphology of LD C–S–H is quantitatively determined and verified by comparing the predicted results with previous experimental data. It is revealed that LD C–S–H grows in a lengthened manner when w/c is above 0·40, and the aspect ratio of LD C–S–H varies according to the availability of free growth space. When the w/c ratio is at the level of 0·50, the realistic growth morphology of LD C–S–H is close to that of a prolate, with an aspect ratio of the order of 10. The elongated growth of LD C–S–H is the key factor enabling cement-based materials with high w/c to set and have a rapid development of elasticity within the first few hours.