In-situ curing mechanism of Portland cement

Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk, Russia

^* Corresponding author: abzaev2010@yandex.ru

Published online: 30 October 2019

Abstract

The paper presents the results of predictive modelling of the curing mechanism of the type CEM I 42.5B Portland cement using the VCCTL tool. The curing lasts during 28 days at 20 оС and the water-cement (W/C) ratio of 0.26, 0.30, 0.35 and 0.40. It is shown that the degree of Portland cement hydration is ~0.70 after 28-day curing. The growth in the W/C ratio significantly intensifies the hydration rate and the dissolution of clinker minerals. The amount of the main hydration products calcium silicate hydrate (C-S-H) and portlandite considerably increases with the W/C ratio. In Portland cement, the fraction of hydrated cement achieves 0.60 of the solid phase and the pore space. It is found that the effective elastic moduli rapidly increase during 400 hours, and then monotonely lower down to 16.79 GPa for the bulk modulus, 8.90 GPa for the shear modulus and 22.69 GPa for Young’s modulus. Relatively high values of the effective elastic moduli are explained by the higher content of the clinker phases and, probably, the higher degree of C-S-H crystallinity. The dependence between the yield stress and Young’s modulus is in good agreement with the VCCTL microstructural model of Portland cement curing.