Improvement effect of a double-level phase change material on compressive strengths of Portland cementitious materials after elevated temperatures

Abstract

In this investigation, a specially prepared double-level phase change material (DL-PCM) was introduced to ordinary Portland cement(OPC) to improve compressive strengths after elevated temperatures. Solid-liquid phase transition characteristics of DL-PCM and changes in compressive strength, water absorption, mass, as well as meso structures and mineral compositions of OPC after elevated temperatures were determined to clarify improvement mechanisms of DL-PCM on compressive strengths of OPC after elevated temperatures. Results show after 500 °C and 600 °C exposures, compressive strengths of OPC added with DL-PCM were basically equal to or a little higher than those at room temperatures. Cracks in DL-PCM introduced OPC matrix and water absorptions were significantly reduced. During the heating and cooling process, DL-PCM experienced solid-liquid-solid phase transitions, forming hard densifed solids to fill cracks and pores, significantly improving integrity of OPC matrix. Consequently, compressive strengths of DL-PCM introduced OPC were significantly increased compared to those without DL-PCM after elevated temperatures.