Mechanical Performance of Hybrid Fibre Reinforced Magnesium Oxychloride Cement-Based Composites at Ambient and Elevated Temperature

Abstract

Magnesium oxychloride cement (MOC) is often recognized as an eco-friendly cement and has found widespread application in various sectors. However, research on its resistance against elevated temperatures including fire is very limited. This paper thoroughly investigated the mechanical performance of fibre reinforced MOC-based cementitious composite (FRMOCC) at ambient and elevated temperatures. A recently developed water-resistant MOC was used as the base matrix which was further reinforced using hybrid basalt and polypropylene fibres at various proportions, and a systematic study on the effect of fibre dosage on compressive and tensile strength of FRMOCC was conducted. The specimens were exposed to elevated temperatures ranging from 200 to 800 °C; mechanical performance and phase composition from a microscale study were analysed. The findings revealed that compressive strength, with the increase in temperature, substantially decreased, with values of 30–87% at 400 °C and over 95% at 800 °C. Specimens with 1.5% basalt and 0.5% PP fibre showed the least reduction possibly due to the vacant channels created as a result of the melting effect of PP fibres. Tensile strength was also completely lost at 600 °C and the specimens suffered substantial mass loss exceeding 30% at this temperature, indicating significant matrix decomposition. Additional analysis using X-ray diffraction (XRD) and scanning electron microscope (SEM) revealed the decomposition stages of the matrix and highlighted the instability of the main hydration phases of FRMOCC at elevated temperatures.

Magnesium Oxychloride Cement: Development, Opportunities and Challenges

“…In general, the literature regarding FRMOC containing 2% PE fiber showed a significant improvement in the ductility of the composites (as shown in Figure 4) with out compromising the overall mechanical performance. In a recent investigation by Rawat et al [35], the influence of 2% basalt fiber on the mechanical properties of MOC was explored, revealing enhancements in compressive and tensile strengths alongside a notable reduction in strain capacity. In a subsequent study aiming to optimize both tensile strength and strain capacity, Ahmad et al [1] delved into the effects of hybrid fibers, specifically PE fiber and basalt fiber, on MOC behavior.…”

“…In a subsequent study aiming to optimize both tensile strength and strain capacity, Ahmad et al [1] delved into the effects of hybrid fibers, specifically PE fiber and basalt fiber, on MOC behavior. They observed that all FRMOC composites exhibited strain hardening behavior, with those containing 2% PE fiber demonstrating the highest tensile strength (10.95 MPa) and strain capacity (4.41%), potentially attributed to multiple cracking mechanisms illustrated in In a recent investigation by Rawat et al [35], the influence of 2% basalt fiber on the mechanical properties of MOC was explored, revealing enhancements in compressive and tensile strengths alongside a notable reduction in strain capacity. In a subsequent study aiming to optimize both tensile strength and strain capacity, Ahmad et al [1] delved into the effects of hybrid fibers, specifically PE fiber and basalt fiber, on MOC behavior.…”

“…Regarding the fire-resisting mechanism of MOC, there is very limited literature available, and the complete understanding of its mechanism is still uncertain and needs further investigation. Chang et al [110] conducted a study on the elevated temperature behavior of pure MOC mixes, noting a complete loss in compressive and flexural strength as temperatures rose from 100 to 500 • C. To enhance the elevated temperature performance of MOC, Rawat et al [35] investigated the incorporation of hybrid fibers (basalt fiber and polypropylene fiber) into MOC. Results showed a substantial deterioration in compressive strength, ranging from approximately 30% to 87% at 400 • C and over 95% at 800 • C (Figure 12), with no observed cracks or spalling.…”

“…Despite the above-mentioned challenges, MOC has been regarded as intrinsically fire-resistant [11,34] attracting practical implementation in fire-resisting infrastructural applications like cladding and façade. However, the research efforts in this area are minimal, and to date, the systematic research work conducted to evaluate the mechanical performance of MOC-based composites at elevated temperatures is very scarce [35]. Nonetheless, some past studies have shown that MOC has the potential to be used as a fireproof coating material and can resist high temperatures without deteriorating the interior substrate [11,34,36].…”