Experimental evaluation of fire resistance performance of cement mortar with PCM/Mg(OH)2-based composite fine aggregate

Abstract

When concrete structures are exposed to fire and high temperatures for an extended period of time, they become significantly less durable due to the decomposition of major hydration products and the evaporation of capillary water. A change in internal properties does not guarantee the stability of concrete structures and may reduce their life cycle. To preserve the durability and stability of concrete structures upon exposure to fire and high temperatures, fire-resistant mortar for exterior walls was developed in this work using zeolite, a phase change material (PCM), and magnesium hydroxide (MH). Zeolite was first coated with paraffin wax. Primary coated aggregates were then coated with MH, which was mixed with dissolved polyvinyl acetate to enhance adhesion on the surface of pre-coated aggregates. The physical and chemical properties of mortar mixed with different percentages of coated aggregates as a replacement for normal aggregates were evaluated by compressive strength tests, X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Fire-resistant properties were investigated by residual compressive strength measurement tests, mass loss calculations, and mock-up tests to compare the internal temperature of mortar covered with normal and coated aggregate when heated in an electric furnace at 1000 degrees C. The residual compressive strength results showed a decrease in strength with a larger percentage of coated aggregates in the mortar. However, according to the mock-up test, control mortar covered with plain mortar took 5430 s (90.5 min) to reach a maximum temperature of 842 degrees C, while the mortar covered with 100% coated aggregate took 7170 s (119.5 min) to reach a maximum temperature of 735 degrees C. The obtained results indicate that the coated aggregate is a proper replacement for conventional aggregate in the development of fire-resistant mortar.