COMPATIBILITY OF POLYCARBOXYLATE SUPERPLASTICIZER WITH RAW MATERIALS OF CONCRETE

Polycarboxylate superplasticizer (PCE) with higher water reduction ability is more sensitive to the variation of concrete raw materials. The fluidity and fluidity retention of cement pastes with four PCEs were studied to examine the compatibility between PCEs and raw materials in concrete. The influences of clay, fly ash and fine powders (mineral, stone and sand) on the properties of fresh mortar with PCEs were systematically investigated. The adsorption behaviors of PCEs on different solid particles were measured to explain the compatibility problems between PCE and raw materials of concrete. The results showed that, both the content and type of clay had a significant impact on the fluidity of mortar with PCE. Bentonite had a stronger influence than kaolin on the fluidity of mortar. The adsorption test results showed that the adsorption amount of kaolin was 10 times, but bentonite was 50 times of that of cement. The stone powders in aggregate exhibited equivalent adsorption on PCE. Fly ash and mineral powder can increase the fluidity of fresh mortar as well as improve the workability of concrete. A low molecular carboxylic acid polymer was synthesized and then incorporated with PCE, and accordingly a remarkable improvement effect was achieved.