两性型聚羧酸减水剂与粉煤灰的相容性研究

Compatibility of Fly Ash with Amphoteric Polycarboxylic Acid-based Superplasticizer

采用不同粉煤灰掺混凝土，分别掺入两种减水剂一阴离子型聚羧酸减水剂（PCan）和两性型聚羧酸减水剂（PCam），粉煤灰取代水泥总量为10％～50％，设计坍落度在（200±20）mm，测试混凝土塑性阶段和硬化阶段性能，以及通过总有机碳（TOC）实验，探讨两性型聚羧酸减水剂PCam与粉煤灰的相容性。结果表明：掺入减水剂，能有效降低混凝土用水量，PCam作用效果甚于PCan，减水率超过30％，能有效改善因粉煤灰掺入而导致早期强度的不足，提高20％以上强度。TOC吸附量表明硅酸盐水泥颗粒表面的吸附规律不同于水泥颗粒，由于粉煤灰颗粒较为光滑并且表面动电位为负值，因此对高效减水剂的吸附能力较弱。PCam阳离子基团的引入，使得其饱和吸附量大于普通阴离子型聚羧酸减水剂（PCan），相同掺量下具有更高坍落度及较低坍落度损失。因此，PCam阳离子基团的引入，增大了减水剂对粉煤灰颗粒的吸附量，与粉煤灰具有更好的相容性。

Two kinds of superplasticizer, anionic polycarboxylate superplasticizer （PCan） and amphoteric polycarboxylate superplasticizer（PCam） were applied to different dosage of fly ash concrete. Cement clinker was mixed with fly ash by weight at the percentage of 0%, 10%, 30% and 50%. Slump is designed in （200±10） mm, the concrete stage and hardening stage performance were tested and the compatibility of PCam with fly ash was discussed by total organic carbon（TOC）. The results show that the superplasticizer can reduce the water consumption of concrete effectively, the water reducing rate of PCam is more than 30%, and the PCam can effectively improve the early strength of the concrete to 120% when fly ash is mixed into the concrete. TOC adsorption indicated that the pattern of surface adsorption of fly ash particles is different from the cement particles. The reason why fiy ash has a weaker adsorption ability to superplasticizer is that the surface of fly ash particles is relatively smooth and the potential is negative, and the introduction of cationic groups（PCam） makes that the saturated adsorption amount is more than the ordinary anionic superplasticizer（PCan）,which leads to the smaller slump loss under the same content of fly ash. Therefore, the superplasticizer increases the adsorption of fly ash particles and has a better compatibility to fly ash with the introduction of PCam cation radical.