Abstract
Cement paste is the basic but most complex component in cement composites, which are the dominant construction material in the world. Understanding and predicting elastic properties and fracture of hydrating cement paste are challenging tasks due to its complex microstructure, but important for durability assessments and life extension decisions. A recently proposed microstructure-informed site-bond model with elastic-brittle spring bundles is developed further to predict the evolution of elastic properties and fracture behaviour of cement paste. It is based on microstructural characteristics of hydrating cement paste obtained from X-ray computed microtomography (micro-CT) with a spatial resolution of 0.5μm/voxel. Volume fraction and size distribution of anhydrous cement grains are used to determine the model length scale and pore-less elasticity. Porosity and pore size distribution are used for tuning elastic and failure properties of individual bonds. The fracture process is simulated by consecutive removal of bonds subjected to surface energy based failure criterion. The stress–strain response and elastic properties of hardened cement pastes with curing ages of 1, 7 and 28 days are obtained. The simulated Young's modulus and deformation response prior to peak stress agree very well with the experimental data. The proposed model provides an effective tool to evaluate time evolution of elastic properties and to simulate the initiation, propagation, coalescence and localisation of micro-cracks.
Highlights
Cement composites are the most popular and widely used construction material in the world
The understanding and prediction of elastic properties and fracture behaviour of such material are of significant technological importance and scientific interest, as they play a crucial role in the durability assessments and life extension decisions of reinforced concrete structures
The time evolution of elastic properties and fracture of such material are complicated since they strongly depend on its heterogeneous and multiphase microstructure, which generally ranges over several length scales from nanometres to metres and develops over time as a result of continued hydration of the cement [1]
Summary
Cement composites are the most popular and widely used construction material in the world. The time evolution of elastic properties and fracture of such material are complicated since they strongly depend on its heterogeneous and multiphase microstructure, which generally ranges over several length scales from nanometres to metres and develops over time as a result of continued hydration of the cement [1]. At meso-scale, concrete can be considered as a three-phase composite consisting of aggregate, bulk cement matrix and interfacial transition zone (ITZ) between them. ITZ is a “special” cement paste with higher porosity and larger pores relative to the bulk cement matrix [1,2]. As the most complicated and basic component in cement-based materials, the mechanical properties and fracture of cement paste accounting for microstructure should be studied in detail firstly
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