High-temperature mechanical properties of calcium sulfate whisker-reinforced high-alumina cement

Abstract

Brittleness and low flexural or tensile strength limit the applications of calcium aluminate cement (CAC)-based composites in high-temperature oil or gas well cementing. The reinforcement of the CAC with whiskers substantially enhances its strength and toughness and is a sophisticated approach to overcome the mechanical limitations of the CAC. In this study, the effect of calcium sulfate whiskers (CSWs) on the mechanical properties of the CAC-based composites was investigated; six cement specimens, with whisker contents of 0–5%, were prepared and tested. The results exhibited an improvement in the compressive and tensile strengths and the toughness of the whisker-reinforced samples over the control samples. The compressive strength of the samples cured at 50°C and then subjected to high temperature (500°C) increased by 25·93% at 14 d and the tensile strength increased by 93·63% with the addition of 4% CSW to the cement. The cement slurry properties were stable when 0–5% of CSWs was added. Finally, X-ray diffraction and scanning electron microscopy were used to determine the phase compositions and micromorphology of the cement composites. The results indicated that the CSWs improved the toughness of the cement binders by forming a stable phase and deflecting cracks in the cement matrix.

Effect of Calcium Carbonate Whisker and Fly Ash on Mechanical Properties of Cement Mortar under High Temperatures

“…Before exposure to high temperatures, both the compressive strength and exural strength of CaCO 3 whiskerbased specimen were improved rapidly with the increase in CaCO 3 whisker content until this content was up to 10 wt.%; thereafter, the strength enhancement was negatively correlated with the increase in CaCO 3 whisker content, as shown in Figures 3(a) and 4(a). e reason why the strength decreased when the CaCO 3 whisker content was over 10 wt.% may be related to the aggregation of CaCO 3 whisker, which leads to the generation of a heterogeneous microstructure, thereby lowering the overall strength of CaCO 3 whisker-based specimen [13]. In addition, the increase in CaCO 3 whisker content may result in a relatively weak bond between cement paste and CaCO 3 whisker, and thus reducing the strength of CaCO 3 whisker-based specimen.…”

“…Whiskers can be categorized as organic and inorganic whiskers, and organic whisker such as cellulosic whisker is frequently used for reinforcing the polymer materials [6,7]. With respect to inorganic whisker, calcium carbonate whisker [8][9][10][11][12], calcium sulphate whisker [13], zinc oxide whisker [14], silicon carbide whisker [15], and potassium titanate whisker [16] are commonly used, and among which, CaCO 3 whisker has the most extensive application in the reinforcement of cementitious materials. Previous studies have shown that CaCO 3 whisker has the capacity to improve the mechanical strength and enhance the flexural toughness of cementitious materials.…”

Mechanical Properties and Microstructure of Calcium Sulfate Whisker-Reinforced Cement-Based Composites

“…Thus, it is necessary to find out if there is a chemical interaction between the whisker and cement paste. Third, Cheng et al [ 25 ] investigated the effect of CSW on the high-temperature mechanical properties of calcium aluminate cement-based composites. They found that CSW formed a stable phase and deflected cracks to improve the toughness of the cement binders.…”

Preparation of CSHW with Flue Gas Desulfurization Gypsum

“…Additionally, CSHW has a strong market competitiveness as its price is only 1/200–1/300 of SiC, and it is easy for surface treatment. Therefore, CSHW have been widely used in papermaking, plastic, resin, rubber, friction materials, lightweight building materials and other fields [ 5 , 6 ]. The most important parameters of CSHW are the diameter and the aspect ratio, which have significant influence on the comprehensive performance of CSHW.…”