对比研究了减缩剂单掺及与减水剂复掺对砂浆收缩、抗压强度及抗折强度的影响,并采用扫描电子显微镜(SEM)对掺有减缩剂的水泥石水化产物的微观形貌进行了研究.结果表明:减缩剂内掺对砂浆试件有明显的减缩效果,单掺和复掺下的28 d减缩率分别达到了50％和35％,早期减缩效果尤为明显,且早期出现微膨胀现象,膨胀量达到了总收缩的20％,这些膨胀有效补偿了试件的自收缩;减缩剂的掺入对不同龄期的砂浆抗压强度及抗折强度都有不同程度的不利影响,复掺减缩剂和减水剂可降低这种不利影响,使其控制在10％以内;掺有减缩剂的水化速度减慢,减缩剂不仅具有降低孔溶液表面张力的物理作用,还具有参与水泥水化反应的化学作用,从而影响水泥的水化产物及浆体的力学性能.%The effect of mixing with shrinkage reducing admixtures (SRA) only and compounding with superplasticizer (SP) on shrinkage, compressive strength and flexural strength of mortar were comparatively investigated. The mierostrueture of the cement was determined by scanning electron microscopy (SEM), and the effects of SRA on the mierostrueture of cement hydration production products were studied. Results show that SRA can obviously reduce the shrinkage of mortar. The addition of SRA results in a reduction in shrinkage of 50% and 35% (compounding with SP) at 28 d, as compared to the control mixture. The shrinkage reducing effect of SRA is particularly evident at early age. Mortar containing SRA have indicated an expansion at early age, it's about 20% of total shrinkage, and these expansion effectively compensate the specimen shrinkage. SRA has a certain negative effect on the compressive strength and flexural strength of mortar. Compounding with SRA and SP can reduce the negative effect within 10%. SRA retards hydration of cement pastes and has physical and chemical effects in cement paste. SRA has physical effects to reduce the surface tension of pore solution, also has chemical effects of the hydration of cement to affect cement hydration products and mechanical properties of cement pastes.
展开▼
