Properties of polyoxymethylene fibre-reinforced seawater sea sand concrete exposed to high temperatures

Using seawater and sea sand to prepare concrete can reduce the adverse effects from the resource shortage and environmental pollution caused by the exploitation of freshwater and river sand. In addition, polyoxymethylene (POM) fibres have excellent alkali resistance and durability, which may considerably improve the mechanical properties of seawater sea sand concrete (SWSSC). Fires are a common structural disaster. Thus, the post-fire mechanical properties of POM fibre-reinforced SWSSC (POM-SWSSC) were experimentally studied herein to evaluate the residual bearing capacity of the POM-SWSSC structure after a fire. After the heating and cooling procedures, the apparent morphology and mass loss of POM-SWSSC were recorded, and the compressive and tensile properties of the POM-SWSSC were investigated. The test results indicate that the colour of the SWSSC changed from cyan to yellow with an increase in exposure temperature. When the temperature exceeded 400 degrees C, the mechanical properties of the POM-SWSSC deteriorated sharply. Compared with compressive strength, high temperature had a more significant effect on the tensile strength of SWSSC. The addition of POM fibres could alleviate this issue. Compared with other fibre-reinforced concretes, POM-SWSSC had a higher cube compressive strength and splitting tensile strength after exposure to 400 degrees C. A prediction model was proposed to quantify the effect of different high temperatures on the mechanical properties of NF-SWSSC and POM-SWSSC.