Abstract
Silicon carbide whiskers (SiCw) have many excellent properties such as high strength, high elastic modulus, and high temperature resistance. In this paper, by using water reducer as dispersant, a stable SiCw dispersion was obtained, and SiCw-modified cement-based composites were prepared. Tensile strength tests for 8-shaped specimens were carried out on the materials. The fracture properties of the materials were measured using a three-point bending test with pre-cracks based on the digital image correlation method. The microstructure of the SiCw-modified mortar was observed by SEM. The results showed that the SiCw improved the tensile strength of the cement-based materials, and the addition of SiCw effectively improved the fracture toughness of mortar. The SiCw caused crack deflection during crack propagation, accompanied by whisker pull-out and bridging phenomena. The SiCw bridging effect and pull-out mechanism effectively controlled the crack propagation and played a toughening role, thus enhancing the crack resistance of mortar.
Highlights
Silicon carbide whiskers (SiCw) are a kind of material with high strength, a high elastic modulus, high temperature resistance, and good corrosion resistance (Becher et al, 2005; Peng et al, 2012)
Previous studies showing that the improvement of compressive strength with the addition of SiCw was not as great as that observed for the flexural strength, and hydration of the cement was accelerated by SiCw due to the higher number of nucleation sites, which results in a greater amount of nucleus formation
As the loading process continued, the crack development in the blank group was basically stable at P = 0.8Pmax, but at this moment, the height of the unfractured zone of the specimen doped with SiCw was still very large, and the crack almost ran through the specimen until P = 0.2Pmax. These results indicated that the addition of SiCw obviously improved the brittleness of cement-based materials
Summary
Silicon carbide whiskers (SiCw) are a kind of material with high strength, a high elastic modulus, high temperature resistance, and good corrosion resistance (Becher et al, 2005; Peng et al, 2012). They are mostly used to modify ceramic-based (Silvestroni et al, 2010; Zhang et al, 2008) and metal-based (Zhang et al, 2006) materials, but have seldom been used in cement-based materials. Cement-based materials are quasi-brittle materials, and their compressive strength is higher than their tensile strength (Bentur & Mindess, 2006) For such materials, a common shortcoming is brittle cracking. Calcium carbonate whiskers (Cao et al, 2016; Saulat et al, 2020) and calcium sulfate whiskers (Li et al, 2017; Pan et al, 2019) are common whiskers used to improve the mechanical properties of cement-based materials
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