基于抗冻性的负温混凝土受冻临界强度研究

采用快速冻融循环的试验方法,研究了经过0 h、12 h、24 h、36 h、48 h、72 h、96 h等不同早期预养后,转入恒-20 ℃的负温条件下养护至7 d,再转标准条件下养护至56 d龄期的混凝土试件经历不同冻融循环次数后的相对动弹性模量损失,并以未受冻的正温混凝土标准养护28 d强度和抗冻性为基准,得出了基于抗冻性的负温混凝土受冻临界强度值及其预养时间值。结果表明,未掺加防冻剂C30、C40、C50和C60混凝土达到F300次冻融所需受冻临界强度分别为24.6 MPa、33.6 MPa、40.4 MPa和49.5 MPa,其预养大于等于96 h;掺加防冻剂C30、C40、C50和C60混凝土达到F300次冻融所需受冻临界强度分别为19.6 MPa、27.5 MPa、31.7 MPa和40.5 MPa,其预养时间大于等于48 h。

Research on Critical Freezing Strength of Subzero-temperature Concrete Based on Frost Resistance

The rapid freeze-thaw test method is used to study the loss of relative dynamic elastic modulus of concrete specimens after different freeze-thaw cycles.The concrete specimens are pre-cured at different pre-curing time which are 0 h,12 h,24 h,36 h,48 h,72 h and 96 h,then transferred to the negative temperature of -20 °C for 7 d,and then transferred to standard-curing condition for 56 d.It comes to the conclusion that the values of critical freezing strengths and pre-curing time of subzero-temperature concrete based on frost resistance which use the strength and frost resistance of unfrozen normal-temperature concrete,that are standard-cured for 28 d,as the benchmark.The results show that the critical freezing strengths of the C30,C40,C50 and C60 concrete required to reach 300 freeze-thaw cycles without antifreeze are 24.6 MPa,33.6 MPa,40.4 MPa and 49.5 MPa respectively and the concrete need to be pre-cured for greater than or equal to 96 h;and that with antifreeze are 19.6 MPa,27.5 MPa,31.7 MPa and 40.5 MPa respectively and the concrete need to be pre-cured for greater than or equal to 48 h.