不同养护温度下引气剂对混凝土性能的影响研究

Influence of Curing Temperature and Air Entrained Agent on the Performance of Concrete

通过试验,研究了混凝土含气量的经时损失规律及其影响因素,以及养护温度和引气剂对混凝土强度、抗氯离子渗透性和微观孔结构等性能的影响。结果表明:新拌混凝土的含气量损失与混凝土的初始含气量有关,初始含气量越大,损失也会更大,且处于动态过程的新拌混凝土的含气量损失较静态过程更大;与标准养护条件相比,负温养护条件一方面会使混凝土内部的水化反应变慢,水化程度变低,另一方面水结冰也会引起体积膨胀,破坏混凝土内部的晶体结构,对混凝土内部孔结构造成了一定程度的损伤,使得混凝土抗压强度降低,电通量、气孔间距系数等参数增大;掺入引气剂会引入了大量的微小气泡,使混凝土内部小孔径的孔含量增多,在一定程度上会提高孔的连通性,从而相对减小混凝土受力面积,造成混凝土抗压强度降低,电通量增大,孔径分布也会朝着小孔径方向移动。

By experiment, the gradual-loss law and influencing factors of the air content of concrete and the effects of curing temperature and air entraining agent on concrete compressive strength, chloride ion permeability and micro pore structure were studied. Results show：The air content of fresh concrete is related to the initial gas content of concrete, the greater initial gas content, the greater loss. In the dynamic process, the fresh concrete containing gas loss is greater than the static process. Compared with standard curing condition, the negative temperature curing on the one hand makes hydration reaction of concrete more slowly and hydration degree lower, on the other hand, water turns into ice can also cause the expansion of the volume, destroy the inside crystal structure of concrete and damage the internal pore structure of concrete （ the damage is not recoverable to a certain extent）, this is why the compressive strength of concrete decreases, the chloride ion permeability and the bubble spacing factor increase. Air entraining agent can introduce a large amount of tiny bubbles, as a result, the pore content of small aperture in concrete will increase. To a certain extent, air entraining agent improves the connectivity of pores, reduces the relative stress area of concrete, thereby, the compressive strength of concrete decreases, the electric flux increases and the pore size distribution will shift towards the direction of small aperture.