Effect of temperature on the internal components including portlandite, weight loss, and compression stress-strain behavior of lime-based roof and screed paste

Abstract

Conventional lime-based roof and screed pastes (LRP) are multilayer complicated systems composed of various ingredients and binders; their physical properties define the function of LRPs: interact connection, underlayer contact, and external variables. Lime pastes sets as a durable and generally flexible solid mass. It is breathable and permits the transfer and evaporation of moisture. Pastes made of hydrated lime are less brittle and breakable. Hence expansion joints are unnecessary. Various pastes, including cement, lime, mud, stucco, and gypsum, have been used in the building industry. Traditionally, lime pastes often included horse hair for reinforcing and pozzolanic ingredients to decrease application time. As building insulation materials (Bims), a lime-based paste is used against environmental concerns. Microstructure tests, thermal analysis, and compressive strength was used to identify, characterize, and evaluate the LRP. The thermogravimetric analysis (TGA) findings demonstrated that the material exhibited high thermal stability up to 200 °C and 11.4% weight loss at 975 °C, demonstrating the high heat resistance of the LRP. At 28 days of curing, the compressive strength of the LRP with water binder ratio (w/b) of 0.75 and 0.60 was 718.76 and 1190.58 kPa, respectively. Heat treatment at three temperatures of 40, 60, and 80° Celsius for 7 h was applied to the samples immediately after demolding. The compressive strength of all the samples, especially the samples with w/b = 0.60, in 3 days increased significantly when the temperature increased. However, this change was less than 28 days of curing time. The final effect of heat treatment temperatures (40, 60, and 80 °C) on 28-day samples with w/b = 0.60 was 116, 106, and 109%, respectively. The maximum quantity of Portlandite that improved the compressive strength of LRP occurred at 40 °C. The analysis of)SEM(images and observing the percentage of Portlandite development at the fracture surface of the samples also confirmed the order of the above changes.