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本文从表面张力、动电电位、吸附三方面论述了混凝土减水剂的作用机理。笔者用滴重法测定了六种不同减水剂对表面张力的影响;用电渗法测定了两种高效减水剂对动电电位(ζ电位)的影响;用751紫外光谱仪测定了普通水泥等对高效减水剂的吸附规律。结果表明:①高效减水剂并不降低水的表面张力,它不是一般意义上的表面活性剂,而是一种有较高分子量的电解质。②普通型引气减水剂—微沫剂对表面张力有显著影响,属于较为典型的表面活性剂。③高效减水剂具有强烈分散、减水效应的本质性因素是它被水泥等吸附后,以根本上改变了双电层的结构,引起ζ电位增大的结果。④水泥等对高效减水剂的吸附等温线为兰米尔等温线,极限吸附量与其在混凝土中的最佳掺量基本相符。
In this paper, the mechanism of concrete water-reducing agent is discussed in terms of surface tension, electrokinetic potential and adsorption. The effect of six different water-reducing agents on the surface tension was determined by the dropping weight method; the effect of two types of superplasticizers on the electrokinetic potential (ζ potential) was determined by electroosmosis; the cement was measured by a 751 ultraviolet spectrometer. Such as the adsorption of superplasticizers. The results show that: 1 high-efficiency water-reducing agent does not reduce the surface tension of water, it is not a general sense of the surfactant, but an electrolyte with higher molecular weight. 2 ordinary type air-entraining water-reducing agent - micro-foam agent has a significant effect on the surface tension, is a more typical surfactant. 3 The essential factor of the high-efficiency water-reducing agent with strong dispersion and water-reducing effect is that it is fundamentally changed the structure of the electric double layer after being adsorbed by cement and the like, resulting in the increase of the zeta potential. 4 The adsorption isotherm of cement and other high-efficiency water-reducing agent is the Lanmiler isotherm, and the limit adsorption capacity is basically consistent with the optimal amount in the concrete.