低温条件下不同类型早强组分早强性能研究

Study on early-strength properties of different types of early-strength components under low temperature environment

低温环境下,混凝土强度发展缓慢,严重影响工程施工进度。在低温(5℃)条件下,分类研究了掺入常见早强组分对砂浆1,3,7,28 d抗压强度的影响规律,并明确了早强组分的作用时间范围。结果表明:5℃养护条件下,不同早强组分对砂浆各龄期下强度提高幅度各不相同;适量无机盐类早强组分可使砂浆各龄期强度明显提高,其中NaSCN和LiNO_(3)组分的低温早强效果优异,且后期28 d强度仍有较大幅度提高;晶核类早强组分强度提高作用时间主要在3 d后,掺入0.2%~0.5%纳米SiO_(2)的砂浆3 d后强度提高显著,28 d强度提高幅度可近20%;多数有机类早强组分强度提高作用时间在3 d前,甚至1 d前,三异丙醇胺的作用时间则主要在3 d后,可使砂浆3 d后强度发展接近对比样在20℃养护条件下的强度发展。

Under low temperature environment,the development of concrete strength is slow and can seriously hinder construction progress.In this paper,the effects of different types of common early-strength components on the 1,3,7 and 28 d compressive strength of mortars were studied under temperature of 5℃,and the action time range of each early-strength component was clarified.The results showed that,under curing temperature of 5℃,different early-strength components had different degrees of improvement in the mortar strength at different ages.Appropriate amount of early-strength components of inorganic salts could significantly improve the strength of mortar at all ages.NaSCN or LiNO_(3)component had an excellent low-temperature early-strength effect,which could also increase the 28 d strength dramatically.The action time of the early-strength components of crystal nucleus to improve the strength was mainly after 3 d.The strength of mortar mixed with 0.2%to 0.5%nano-SiO_(2)could be significantly improved after 3d,and the 28 d strength could even be increased by nearly 20%.The action time of most organic early-strength components to improve the strength was mainly before 3 d or even 1 d,while the action time of triisopropanolamine was mainly after 3 d,which could make the strength development of mortars after 3 d close to that of the contrast sample cured in 20℃.