超高性能混凝土的火灾高温性能研究综述

Research on Fire Resistance of Ultra-high-performance Concrete:a Review

超高性能混凝土(Ultra-high-performance concrete,UHPC),以其突出的优点如超高强度与超高耐久性等,符合可持续发展战略,是混凝土科技发展的主要方向之一。近年来,UHPC的火灾高温性能吸引了广泛关注。由文献综述可知,高温会引发UHPC的爆裂和力学强度变化。爆裂主要由蒸汽压机理控制,蒸汽来源于内部游离水,高的内部湿含量往往导致剧烈的高温爆裂,有效的抑制措施是掺加聚合物纤维如聚丙烯(Polypropylene,PP)纤维。关于钢纤维对UHPC抗高温爆裂性的影响,还存在争议。高温作用后UHPC的残余强度在常温至300℃或400℃范围内有所增长,而在更高的温度下则为单调下降。残余强度增长是高温促进混凝土内部的一系列化学变化所引起。最新研究发现,组合养护是有效改善UHPC火灾高温性能的新方法,可避免爆裂发生。

Ultra-high-performance concrete(UHPC)which exhibits superb properties with respect to strength and durability,within the scope of the sustainable development strategy of China,has become one of the major development directions of concrete science and technology.In recent years,fire resistance of UHPC has provoked extensive research attention.Based on a literature review,it can be found that high temperature can cause explosive spalling and mechanical strength variation of UHPC,in which the former is mainly governed by a vapor pressure mechanism.The vapor pressure is induced by internal free water,as high moisture content can lead to severe spalling.Adding polymer fiber,such as polypropylene(PP)fiber,is an effective approach to prevent spalling.However,the influence of steel fiber on UHPC’s resistance to explosive spalling is still under active controversy.Moreover,residual strength of UHPC exposed to high temperature will increase within the range from room temperature to 300℃or 400℃due to a series of high-temperature-activated chemical changes in UHPC,but will decrease monotonically at higher temperature.As a new research finding,combined curing has demonstrated a favorable efficiency to enhancing the resistance of UHPC to explosive spalling under high temperature,which displays a potential as a novel approach to prohibiting the occurrence of spalling.