In the contemporary modern mining sector, rubber conveyor belts are extensively and frequently utilized. Exceptional tear resistance and high elongation of the top cover rubber of the belt are imperative. In this investigation, a portion of natural rubber (NR) underwent partial vulcanization in advance. Subsequently, this pre-vulcanized NR (PNR) was mixed with the NR matrix via mechanical blending. Due to the increased viscosity resulting from pre-vulcanization, the PNR may disperse in the NR matrix, maintaining a specific microstructure without complete dissolution. During subsequent vulcanization, the PNR could co-vulcanize with the NR matrix, forming a well-bonded interface and ultimately yielding self-reinforced NR (SNR) composites. The influences of the mass ratio of PNR to the NR matrix, sulfur content in PNR and pre-vulcanization time on the mechanical properties of the SNR composites were thoroughly investigated. The results indicated that adding PNR effectively improved the tear strength of NR. When the PNR replaced 20 wt% of NR, sulfur content in PNR was 2.4 phr and pre-vulcanization time was 2 min, the tear strength, stress at 300% elongation and wear resistance of SNR composites increased by 34.1%, 16.6%, and 10.2% compared to NR control sample, while elongation at break remained at 898%. These findings suggest that it is possible to enhance the tear strength of rubber without compromising elongation at break.

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.

The present paper studied the effects of calcination temperatures (200–800 °C) on the appearance, mineral composition, and active SiO2 content in attapulgite and investigated the effects of attapulgite before and after calcination on the chemically bonded water content, the degree of reaction of cement paste, and the mechanical properties such as the flexural strength, compressive strength, and splitting-tensile strength of cement mortar. The results indicate that the calcination temperature changes the mineral composition of attapulgite, thereby affecting the hydration activity of cement-based materials. The attapulgite calcined at 500 °C (AT500) has the best enhancement on the hydration activity of cement-based materials. The calcination at 500 °C is most beneficial to the dissolution of SiO2, and the content of SiO2 reaches 20.96%. The contents of chemically bonded water in the samples incorporated with calcined attapulgite reduced and that of the samples incorporated with AT500 at 28 d is the same as that of the control group. The reaction degree of AT500 is 78.61% at 28 days. Calcined attapulgite clay can reduce the energy consumption of the cement industry and promote the sustainable development of attapulgite clay.

Many scholars are concerned about the effect of nano-MgO as an expansion agent on the performance of cement-based materials at an early age, but over a long period less attention is paid to expansion stability and mechanical properties. This article examines the influence of nano-MgO on the long-term consistency, fluidity, expansion stability, hydration, and mechanical properties of 30% fly ash cement-based materials and improves research into nano-MgO as an expansion agent. Expansion performance, flexural and compressive strength, and stability after boiling and autoclave treatment were tested for specimens mixed with a 2, 4, 6, 8 and 10% cementitious material mass of nano-MgO. X-ray diffraction (XRD) and scanning electronic microscopy (SEM) were employed to study their hydration process and microstructure. The results showed that nano-MgO had an obvious effect on the consistency, fluidity and expansion performance of cement paste. After curing in water for 365 days and autoclaving thereafter, the hydration of nano-MgO was relatively complete. The volumetric expansion pressure of the magnesium hydroxide (Mg(OH)2) crystals and the crystallization pressure generated after their continuous precipitation were the main reasons for the expansion of the slurry. Nano-MgO improved the microstructure of cement paste and significantly enhanced its long-term flexural strength and compressive strength. When the content of nano-MgO was less than 10%, the cement with 30% fly ash had good long-term stability with the potential to compensate for the shrinkage of large-volume concrete.