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

Abstract

This study aims to investigate the effect of calcium sulfate whisker (CSW) on the properties and microstructure of cement-based composites. Further, nanosilica (NS) was used as a comparison. The results show that the compressive strength and fracture toughness of cement-based composites increased by 10.3% and 10.2%, respectively, with 2% CSW. The flexural strength, splitting tensile strength, and fracture energy increased by 79.7%, 34.8%, and 28.7%, respectively, with 1% CSW. With the addition of CSW, shrinkage deformation was aggravated, and the capillary water absorption coefficients were clearly reduced. Compared with NS, CSW-reinforced cement-based composites show better tensile, flexural, and fracture properties and smaller shrinkage deformations and capillary water absorption coefficients. The residual mechanical properties of all groups improve when the treating temperature is lower than 400 °C and decline rapidly when the temperature goes over 600 °C. When treated at 900 °C, the residual mechanical properties are 40% less than those at ambient temperature, with the NS group showing the best performance, followed by the control group and the CSW group. X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests show that the addition of CSW improves the microstructure of the matrix. CSW can reinforce and toughen composites by generating ettringite and whisker pullout, whisker breakage, crack bridging, and crack deflection at the microstructure level.

Application of Calcium Sulfate Whiskers to Cement-Based Materials: A Review

“…This contributes to an increase in the compressive strength of the concrete, enhancing its durability under stress. Cao et al [ 10 ] demonstrated a 10.3% increase in compressive strength and a 10.2% improvement in the fracture toughness in cement-based composites with the addition of 2% of CSWs. When the CSWs content was 1%, the flexural strength and fracture toughness increased by 10.3% and 10.2%, respectively.…”

“…Additionally, compared to calcium carbonate whiskers, CSWs had a more significant effect on the strength of Portland cement. Cao et al [ 10 ] investigated the impact of CSWs on the properties and microstructure of cement-based composite materials and compared them with nano-silica. The results showed that the optimum effect was achieved with a 1% addition of CSWs, leading to increases in flexural strength, split tensile strength, and fracture toughness of 79.7%, 34.8%, and 28.7%, respectively.…”

Preparation of a High‐Performance Anti‐Aging Polypropylene Composite with Titanium Oxide and Calcium Sulfate Shielding Agents

“…By environmental protection, low cost, high strength, high modulus, and high toughness, calcium sulfate whiskers (CSW) have strong market competitiveness, [22][23][24] Calcium sulfate whiskers have large mechanical strength, so they can optimize their performance as an enhanced component in synthetic materials. [25][26][27] Because of the small size and large strength of calcium sulfate whisker can play a skeleton role when added to polymer materials, and the mechanical properties of CSW often significantly improve. [28][29][30] At the same time, calcium sulfate whiskers have good compatibility and good interface binding strength, the advantages of ultra-fine inorganic filler and enhanced fiber can be used as efficient functional materials, based on non-toxic characteristics as additives added to PP will not aggravate the harm caused by white pollution.…”

“…Due to the disadvantages of high surface energy and easy agglomeration, the anti‐aging effect will also lead to the reduction of the mechanical properties of PP, which cannot meet the demand for high‐performance polypropylene in many engineering fields. By environmental protection, low cost, high strength, high modulus, and high toughness, calcium sulfate whiskers (CSW) have strong market competitiveness, [22–24] Calcium sulfate whiskers have large mechanical strength, so they can optimize their performance as an enhanced component in synthetic materials [25–27] . Because of the small size and large strength of calcium sulfate whisker can play a skeleton role when added to polymer materials, and the mechanical properties of CSW often significantly improve [28–30] .…”

PMMA-Grafted Calcium Sulfate Whiskers for Applications as Fillers in PVC

“…Calcium sulfate whiskers (CSWs) are single crystals with a large aspect ratio that have excellent properties such as good shape integrity, high strength, high temperature resistance, chemical resistance, and high toughness [ 1 , 2 , 3 ]. When used as reinforcing fillers, CSWs significantly improve the impact resistance, modulus, and heat resistance of polyvinyl chloride (PVC) composites [ 4 , 5 ].…”