A Step-by-Step Analytical Solution for Predicting Elastic Modulus of Leached Cement Paste

Abstract

Abstract: The leaching of calcium ions from the interior of concrete in a low alkalinity environment is an important factor causing a significant increase in the internal porosity of concrete, leading to a deterioration in its mechanical properties. In order to investigate the degradation law of the elastic modulus of cement paste after calcium leaching, this paper establishes a step-by-step analytical solution for predicting elastic modulus of leached cement paste. Firstly, the hydrated cement particles are regarded as a three-phase composite sphere composed of unhydrated cement particles (UC), high-density hydrated gel (H-HL), and low-density hydrated gel (L-HL). By introducing an equivalent inclusion phase (EQ) composed of UC and H-HL, the three-phase composite sphere model can be simplified into an equivalent hydrated cement particle model composed of the inclusion phase and L-HL. Finally, the elastic modulus of the two-phase composite sphere composed of the equivalent hydrated cement particles and the porosity of partially leached cement paste is solved using elasticity theory. The effectiveness of the step-by-step analytical solution is verified by comparing with third-party numerical results. Based on the analytical method established in this paper, the effects of hydration degree, volume ratio of calcium hydroxide (CH) to hydrated calcium silicate (C-S-H), and volume ratio of high-density hydrated calcium silicate (C-S-H_a) to low-density hydrated calcium silicate (C-S-H_b) on the elastic modulus of leached cement paste were analyzed. The results show that among the three influencing parameters, the hydration degree has the greatest impact on the elastic modulus of eroded cement paste. This study provides an analytical method for predicting the regression of the elastic modulus of cement paste after calcium leaching, which can provide some reference for the durability design of concrete after calcium leaching.

Key words: cement paste, calcium leaching, elasticity theory, composite sphere model, step-by-step analytical solution

CLC Number:

TU528

QI Fengyan, ZHANG Jian, SONG Wenbing, WANG Hailong, GAO Yun. A Step-by-Step Analytical Solution for Predicting Elastic Modulus of Leached Cement Paste[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2024, 43(8): 2758-2767.

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