Microstructure-informed modelling of damage evolution in cement paste

Abstract

h i g h l i g h t sMacroscopic behaviour from microstructure features and meso-scale principles. Derivation of microstructure features from high-resolution micro-CT images. Construction of site-bond model with microstructure information. Demonstration of agreement between calculated responses and experimental data. Quantitative assessment of microstructure effects on macroscopic behaviour. a b s t r a c tCement paste is a binder for cementitious materials and plays a critical role in their engineering-scale properties. Understanding fracture processes in such materials requires knowledge of damage evolution in cement paste. A site-bond model with elastic-brittle spring bundles is developed here for analysis of the mechanical behaviour of cement paste. It incorporates key microstructure information obtained from high resolution micro-CT. Volume fraction and size distribution of anhydrous cement grains are used for calculating model length scale and elasticity. Porosity and pore size distribution are used to allocate local failure energies. Macroscopic damage emerges from the generation of micro-crack population represented by bond removals. Effects of spatial distribution, porosity and sizes of pores on tensile strength and damage are investigated quantitatively. Results show a good agreement with experiment data, demonstrating that the proposed technology can predict mechanical and fracture behaviour of cementitious materials based exclusively on microstructure information.

Microscale Testing and Modelling of Cement Paste as Basis for Multi-Scale Modelling

“…For saving the calculation time of mechanical model, the original resolution of reconstructed slices was reduced to 2 µm 3 /voxel. Image segmentation was performed using a so-called global threshold approach [ 7 , 9 , 13 , 35 ]. In this method, phases were isolated from the original grey-scale map by choosing the corresponding threshold step by step as shown in Figure 6 .…”

“…Three phases can be isolated: pore, anhydrous cement and hydration product. More details about this approach can be found in previous work [ 13 , 35 ]. However, it is well known that at least three types of hydration product with different mechanical properties [ 14 , 15 , 16 , 17 ] exist: inner product C-S-H LD , outer product C-S-H HD and C-H.…”

Combined experimental and numerical study on micro-cube indentation splitting test of cement paste

“…This prism was scanned with a CT-scanner to obtain the high resolution (2 µm 3 /voxel) greyscale images. Then, a so-called global threshold method [19,20,29,30] was chosen to segment the greyscale images into four phases, namely, anhydrous cement grains (A), inner (I) and outer (O) hydration products and pores (P). The total porosity and hydration degree were regarded as 11.84% and 74.99% respectively according to the segmented images.…”

Towards understanding stochastic fracture performance of cement paste at micro length scale based on numerical simulation

“…Based on the same principles, peak-force tapping atomic force microscopy (AFM) can be applied as an alternative tool to quantify the local elastic properties [7]. These techniques provide a meaningful experimental input for analytical and numerical models used to calculate the global micromechanical properties of cement paste [8][9][10][11][12][13] which can be further used as input within a multi-scale framework to simulate the macroscopic mechanical performance of concrete [14][15][16].…”