Abstract: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 080%, 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 080% polycarboxylate water reducing agent, the 28d compressive strength of modified adobe can reach 830MPa, and the flexural strength can reach 298MPa. Compared to the modified adobe without water reducing agent, the compressive strength and the flexural strength are increased by 45 times and 21 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 080%, the shrinkage rate can be as low as 006%. 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.