Crack behavior of expanded polystyrene foam-ceramsite composite thermal insulation mortar

Abstract

To compensate for the deficiencies of thermal insulation, fire and crack resistances of traditional thermal insulation mortars, this paper prepares expanded polystyrene foam (EPSF)-ceramsites composite thermal insulation mortar (ECTIM) with ceramsite and EPSF particles as insulation aggregates. The effects of fiber content (i.e., P = 0.3%, 0.6%, 0.9%), fiber length (i.e., l = 3 mm, 6 mm, 9 mm) and fiber types (i.e., polypropylene fiber (PF), steel fiber (SF), alkali resistant glass fiber (ARGF)) on crack resistance of the ECTIM were analyzed. The test results demonstrated that the incorporation of fibers could significantly improve crack resistance and delay the cracking of mortar. With the increase of fiber content P, the water loss rate and cracking index decreased to 43.70% and 79.17% of the specimen without fiber. As the fiber length l increased from 0 mm to 9 mm, the water loss rate and cracking index decreased by 41.50% and 77.08%, respectively. Comparatively, the PF could obviously improve the crack resistance of the ECTIM. Based on the experimental research, the microscopic stress mechanism of mortar cracking, as well as the early and late anti-cracking mechanism of the ECTIM were revealed. In addition, considering the effects of fiber content and fiber length, a comprehensive influence coefficient ϖ was introduced, and a formula for conveniently calculating the maximum crack width Wmax of the ECTIM was proposed. The predicted results agreed well with the test data. The thermal insulation mortar prepared in this study could considerably overcome the deficiencies of traditional organic and inorganic thermal insulation mortars, and had excellent thermal insulation, fire and crack resistances. The resource utilization of iron tailings and the introduction of ceramsite reduced the materials cost. The prepared thermal insulation mortar could be used for wall substrate, geothermal heat insulation layer, external wall, internal wall and roof insulation.