碱金属盐对萘系减水剂吸附分散性能的影响

通过调整Na2SO4,K2SO4,Na2CO3及K2CO3溶液浓度来改变水泥浆体中可溶性碱含量,研究可溶性碱对萘系减水剂吸附-分散性的影响.结果表明:碱金属盐对萘系减水剂分散性的影响存在最佳掺量区间,这一掺量区间与萘系减水剂掺量及碱金属盐种类相关.当萘系减水剂掺量较小时,较低掺量的碱金属盐即可调整水泥浆体表面张力,改善浆体流变性;当萘系减水剂掺量较大时,较高掺量的碱金属盐才可调整水泥浆体表面张力,改善浆体流变性.碱金属盐掺量过高时,水泥浆体流变性下降,表观黏度增加.碱金属硫酸盐除了存在碱金属离子对萘系减水剂双电层的压缩和破坏作用,还存在硫酸根离子对萘系减水剂的竞争吸附作用,因而使萘系减水剂在水泥颗粒表面的平衡吸附量下降程度更大.

Effect of Alkali Salt on Adsorption and Dispersion of Naphthalene Based Water Reducer

The influence of soluble alkali on the adsorption and disersion of FDN(polynaphthalene sulphonate) was investigated through modifying the concentration of Na2SO4, K2SO4, Na2CO3 and K2CO3 respectively. The results show that there exists the optimum content range which contributes to higher dispersion of FDN. The optimum content range is well related to the FDN content and the entrapped anion. When FDN content is low, a bit of alkali can adjust surface tension in cement paste with FDN water reducer added, and the fluidity of cement paste will be considerably improved. When FDN content is high, it is necessary to add more alkali in order to adjust surface tension and improve the dispersion of FDN water reducer. When superfluous alkali is added into cement paste, the paste fluidity will descend radically and the paste viscosity will increase sharply. Different from alkali carbonates, alkali sulphates not only make a contribution to the compression and destruction of double electrode layer through alkali ions, but also cause competitive adsorption between sulfate anion and FDN water reducer, which jointly results in the sharp decrease in adsorption of FDN water reducer.