聚羧酸减水剂对改性生土材料性能的影响

Effect of Polycarboxylate Water Reducing Agent on Performance of Modified Adobe

在石膏粉煤灰改性生土材料中掺加聚羧酸减水剂,研究聚羧酸减水剂对改性生土材料工作性能、力学性能、耐水性能以及体积稳定性的影响.结果表明:聚羧酸减水剂能显著改善石膏粉煤灰改性生土浆体的流动度,当聚羧酸减水剂掺量为0.80%时,改性生土材料在浆体水固比性低于生土液限的条件下也可浇筑成型;在一定范围内,改性生土材料的抗压强度和抗折强度随聚羧酸减水剂掺量的提高而增大;当改性生土材料掺15%石膏、5%粉煤灰和1%氧化钙时,加入0.80%的聚羧酸减水剂后,其28d抗压强度可达8.30MPa,抗折强度可达2.98MPa,相较于未加聚羧酸减水剂的改性生土材料,两者分别提高了4.5和2.1倍.采用耐水指数评价了改性生土材料的耐水性能,结果表明:聚羧酸减水剂不仅能显著提高改性生土材料的耐水性能,还能显著降低改性生土材料的干燥收缩率,当其掺量为0.80%时,改性生土材料的干燥收缩率稳定在0.06%左右.扫描电子显微镜(SEM)和X射线衍射(XRD)结果显示,聚羧酸减水剂对改性生土材料水化产物影响较小,但能使改性生土材料结构更加密实.

Polycarboxylate water reducing agent was added to the gypsum fly ash modified adobe,and its effect on working performances,mechanical properties,water resistance and volume stability of modified adobe were experimentally studied. It can be found that the polycarboxylate water reducing agent can significantly improve the fluidity of the modified adobe slurry. When the content of water reducing agent is 0.80%,the slurry can be poured forming under the water-solid ratio which is lower than the liquid limit of the adobe;within a certain range,the compressive strength and flexural strength of modified adobe increase with the polycarboxylate water reducing agent content. When mix proportion of modified adobe is 15% gypsum,5% fly ash,1% calcium oxide,by adding 0.80% polycarboxylate water reducing agent,the 28 d compressive strength of modified adobe can reach 8.30 MPa,and the flexural strength can reach 2.98 MPa . Compared to the modified adobe without water reducing agent ,the compressive strength and the flexural strength are increased by 4.5 times and 2.1 times respectively. The water resistance index is used to evaluate the water resistance of the modified adobe. It can be found that the polycarboxylate water reducing agent can significantly improve the water resistance and reduce the shrinkage rate of the modified adobe. When the content of water reducing agent is 0.80%,the shrinkage rate can be as low as 0.06%. SEM and XRD results show that the polycarboxylate water reducing agent can make the internal structure of modified adobe more compact,and it has little effect on the hydration products of the modified adobe.