Temperature-induced Chemical Changes in Soundless Chemical Demolition Agents

This paper explored the relationship between ambient temperature, calcium oxide (CaO) hydration, and calcium carbonate (CaCO3CaCO3) generation in cold and moderate ambient temperatures (2°C–19°C). A total of 22 samples from 2 commercial soundless chemical demolition agents (SCDAs) were tested in 36-mm-diameter×170-mm-long36-mm-diameter×170-mm-long steel pipes. The raw powder and materials resulting from hydration were subjected to X-ray diffraction analysis, derivative thermogravimetric analysis, and thermogravimetry analysis. Raw and hydrated specimens proved chemically distinctive. Experimental results showed that (1) the unconfined portions of hydrated specimens contained more CaCO3CaCO3 due to carbonation of Ca(OH)2Ca(OH)2, and confined portions had higher Ca(OH)2Ca(OH)2concentrations; (2) all materials tested at 19°C ambient temperature had Ca(OH)2Ca(OH)2concentrations nearly 10% greater than those tested at 2°C; and (3) the higher Ca(OH)2Ca(OH)2 concentrations formed at 19°C generated 350% greater expansive pressure than did those that formed at 2°C.