小分子羧酸聚合物对聚羧酸减水剂在水泥表面吸附机制的影响

Influence of Small Molecular Carboxylic Acid Polymer on Adsorption Mechanism of Polycarboxylate Superplasticizer

通过净浆流动度、有机碳吸附(TOC)、Zeta电位以及电导率等试验方法,研究了小分子羧酸聚合物水解聚马来酸(HPMA)与聚羧酸减水剂(PCE)在水泥表面的相互作用机制。净浆流动度试验表明:单掺HPMA能够提高水泥浆体的流动度;但当HPMA、PCE复掺时,净浆流动度随HPMA掺量的提高先增加后降低。TOC、Zeta电位以及电导率试验表明:HPMA、PCE能够吸附在水泥表面,且HPMA吸附能力大于PCE。结果说明:HPMA对水泥浆体具有一定增塑效果,但对PCE分散能力产生双重影响。HPMA能够接枝在PCE的侧链上,增加其侧链长度,从而提高PCE侧链空间位阻效应;HPMA与PCE存在竞争吸附,能够降低PCE的有效吸附量。由此可知,侧链接枝效应和竞争吸附作用是影响净浆流动度的主要因素,HPMA掺量为0.0%~0.025%时,侧链接枝效应起主导作用,HPMA掺量为0.025%~0.20%时,竞争吸附起主导作用。

The interaction mechanisms between hydrolyzed polymaleic anhydride（ HPMA） and polycarboxylate superplasticizer（ PCE） on the surface of cement were discussed with fluidity,TOC,Zeta potential and conductivity. The result of fluidity shows that HPMA can improve the fluidity of cement paste. However,with the increasing of HPMA,the fluidity of cement paste plasticized by PCE increased firstly and then declined. The results of TOC,Zeta potential and conductivity show that both HPMA and PCE can adsorb onto the surface of cement. By contrast,HPMA has stronger adsorption capacity than PCE. These results show that HPMA has a certain plasticizing effect on cement paste,but has a dual effect on the dispersion efficiency of PCE. HPMA can be grafted on the side chain of PCE to increase the length of side chain,thereby improving the steric hindrance effect of PCE. The competitive adsorption between HPMA and PCE can reduce the adsorption amount of PCE. Therefore,the grafting effect of side chain and the competitive adsorption are the main factors affecting the fluidity of cement paste. When the dosage of HPMA is from 0. 0% to 0. 025%,the grafting effect of side chain dominates,when the dosage of HPMA is from 0. 025% to 0. 20%,the competitive adsorption dominates.