To improve the utilization rate of phosphate tailings (PTs) and widen the sources of subgrade filler, the PTs is employed to modify clay, forming a PTs modified clay, applied in the subgrade. Accordingly, the environmental friendliness of PTs was investigated. Subsequently, an optimal proportion was determined through compaction and California Bearing Ratio (CBR) experiments. Afterward, the stability of mixture with the optimal proportion was further evaluated through the water stability and dry-wet stability experiments. Finally, via the gradation and microstructure experiments, the strength mechanism of PTs modified clay was analyzed. The results show that the PTs were classified in the non-hazardous solid wastes, belonging to Class A building materials. With the increase of PTs content and the decrease of clay content, the optimum water content and the swelling degree gradually decrease, while the maximum dry density and CBR first increase and then decrease, reaching their peak value at 50% PTs content, which is the optimal proportion. The resilient modulus of PTs modified clay at the optimal proportion reaches 110.2 MPa. The water stability coefficient becomes stable after soaking for 4 days, while the dry-wet stability coefficient decreases with the increase of cycles and tends to be stable after 8 cycles. Under the long-term action, the dry-wet change has a greater adverse impact than continuous soaking. The analysis demonstrates that the better strength mainly comes from the skeleton role of PTs and the cementation of clay. The systematic laboratory test results and economic analysis collectively provide data evidence for the advantages of PTs modified clay as a subgrade filler.

This research aims to develop an environment-friendly composite material that possesses enhanced fire retardant (FR), thermal, as well as mechanical characteristics. The aim has been accomplished with the development of a jute/thermoplastic starch (TPS) based bio-composite. The fire retardancy and thermal stability of the jute/TPS composite were enhanced by the incorporation of magnesium carbonate hydroxide pentahydrate (MCHPH). Upon exposure to heat or fire, the MCHPH particles decompose in a two-stage process to yield water vapors and a char layer of MgO and CO2, which restrict access to oxygen and result in flame suppression. Moreover, the main contribution of the article is the improvement of mechanical properties simultaneously with the enhancement in the fire retardant and thermal properties, which have rarely been reported in the literature. The enhancement of mechanical properties is supported by the compatibility of MCHPH particles with jute/TPS. All the composites were developed with a constant 40 % jute fiber content, while the MCHPH concentration varied from 0 % to 9 % by weight. The tensile strength of TPS was enhanced by 595 % with the reinforcement of jute fiber and MCHPH nano-filler. Compatibility between TPS, jute, and MCHPH was discovered through Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) was used to study the fractured surfaces of the composites. Thermo-gravimetric analysis (TGA) revealed a decrease in the weight loss of the MCHPH-filled jute/ TPS composites at high temperatures. The vertical burning test also revealed that the composites met the re-quirements for a V-0 rating. The heat release rate of the composites was reduced by 36 % after the addition of MCHPH, as measured by cone calorimetry test. The biodegradability test confirmed the eco-friendly nature of the composites by demonstrating significant weight loss in soil over a 4-weeks period. Thus, the present study provided the basis for the development of a novel green composite with commendable gains in flame resistance, thermal stability, and mechanical robustness.