外加剂对低温条件混凝土抗冻临界强度的影响

Influence of Admixture on the Resistant Freezing Critical Strength of Low-temperature Concrete

目的为了防止冬期施工中混凝土早期受冻及由于掺入大量防冻剂对混凝土耐久性带来的不利影响.方法采用恒低温一次冻结法和自然变低温多次冻结法,研究了掺加以早强、减水、引气为主要组分的复合外加剂辅以矿物掺合料混凝土在低温条件下的强度发展情况,及其对抗冻临界强度的影响,以及不同组分混凝土的强度发展情况、抗冻临界强度和达到抗冻临界强度的时间,并对试验结果进行对比分析.结果试验结果表明,以减水、引气、早强为主的复合外加剂并复掺矿物掺合料的混凝土,在低温条件下强度发展好,双掺粉煤灰10%和硅灰4%取代水泥,在恒低温条件下28 h达到抗冻临界强度3.5 MPa,变低温条件下34 h达到抗冻临界强度4.1 MPa.结论以减水、引气、早强为主的复合外加剂并复掺矿物掺合料的混凝土,能够防止早期受冻,强度发展及抗冻临界强度均能满足冬季施工要求.

In order to find out the effects of admixture on the resistant freezing critical strength of concrete under low-temperature, the once-through artificial freezing and repetitious natural freezing methods are used to compare with concrete mixed with traditional antifreeze. The strength development and resistant freezing critical strength of concrete mixed with compound chemical and mineral admixture are studied. The results show that the strength of concrete mixed with compound chemical and mineral admixture develops well, especially for fly ash which is 10 % and silica fume which is 4 %. Under the temperature of - 10℃, 28 h can reach the resistant freezing critical strength of 3.5 MPa; under the temperature of 5～-15℃, 34h can reach the resistant freezing critical strength of 4.1 MPa.