新拌水泥浆体自由水定量表征方法及作用机理

Quantitative Characterization Methods of Free Water in Fresh Cement Paste and Its Action Mechanism

将(新拌)水泥浆体流变性能与水泥颗粒堆积密实度相关联,研究了水泥浆体中自由水的定量表征方法及作用机理.结果表明:利用塑限和液限可以对浆体中自由水分进行分类.第1类自由水,即超过塑限的水分,主要使水泥颗粒产生物理分离.第2类自由水,即超过液限的水分,可使水泥浆体在重力作用下产生流动.减水剂提高水泥浆体流动性不仅是由于其对水泥颗粒具有分散作用,更主要是因为其能降低水泥颗粒对水分的吸附作用,降低水泥颗料弱结合水量,提高浆体自由水量.将水泥浆体流动性能与自由水量进行关联,就能够准确有效地调控水泥浆体的流动性能.

The quantitative characterization methods of free water and its action mechanism were studied by relating rheological properties of fresh cement paste to the packing density of cement partials.The results show that free water in cement paste can be classified by the plastic limit and liquid limit.Type 1free water that is the water exceeding plastic limit can separate cement particles.Type 2free water that is the water exceeding liquid limit will cause the flow of cement paste under gravity.The improvement of flowability by adding superplasticizer is not only due to the increase of dispersion of cement particles,but also mainly because of lower adsorption force of cement particles to water,lower loose bound water amount of cement particles,and higher free water amount of cement paste.The flowability of cement paste can be accurately and effectively controlled when it is associated with the free water amount.