Modeling of internal relative humidity evolution in cement pastes at early-ages

Author(s): Hui Chen, M. Wyrzykowski, K. Scrivener and P. Lura
Paper category: Conference
Book title: 2nd International Conference on Microstructural-related Durability of Cementitious Composites
Editor(s): Guang Ye, K. van Breugel, Wei Sun and Changwen Miao
Print ISBN: 978-2-35158-129-2
e-ISBN: 978-2-35158-123-0
Publisher: RILEM Publications SARL
Pages: 342 – 349
Total Pages: 8
Language: English

Abstract: High-performance concrete has shown to be more sensitive to early-age cracking than traditional concrete. Such cracks constitute a serious problem with regard to strength and especially to durability. Autogenous deformation is one of the main factors to cause early age cracking in high-performance concrete and needs therefore to be predicted and controlled.
As cement hydration proceeds in low water-to-binder ratio concrete, the water becomes bound into hydration products and adsorbed on their surfaces. The capillary pores are emptied and the air-water menisci become progressively smaller. As a consequence, the internal relative humidity drops (self-desiccation) and an increasing capillary tension is produced in the pore fluid, which may reach several tens of MPa. The capillary stress exerts a compressive stress on the whole porous body, resulting in bulk shrinkage (self-desiccation shrinkage).
In this paper, the chemical shrinkage and the pore size distribution of cement paste (measured by mercury intrusion porosity) are used as input data for the calculation of relative humidity (RH) of Portland cement paste with different water to cement ratio (0.30, 0.35, 0.40). These calculated RH curves are then compared to measured curves, finding satisfactory agreement at early ages but a growing divergence at later ages.

Online publication: 2012
Publication Type: full_text
Public price (Euros): 0.00