Absorption behavior of polycarboxylate superplasticizer with different molecular structures on montmorillonite

Abstract

Polycarboxylate (PCE) is a high performance superplasticizer for modern concrete. With the high quality sand becoming precious, more and more low quality sands are used in concrete. However, low quality sands generally contain a relatively high content of montmorillonite (MMT), which could seriously reduce the efficiency of PCE. In order to develop PCE suitable for concrete with low quality sands, the absorption behavior on MMT of PCE with different side chains and acid/ether ratio was investigated. In order to explore the effect of MMT on PCE, two macromonomers were selected, isoprene glycol ether 400(TPEG400) and isoprene glycol ether 2400 (TPEG2400), to synthesize six long and short side chain comb-type PCEs with acid-ether ratios of 1.5:1, 2.5:1 and 3.5:1, respectively. The MMT tolerance mechanism of comb-type PCE in MMT-containing cement slurry was examined by FT-IR, DLS, TOC and other analysis. The PCE with long side chain is much easier to be inserted into the layered structure of MMT, resulting in intercalation absorption. The absorption amount of two kinds of side chain PCE on the MMT particles decreased as the acid ether ratio increases. PCE with long side chains showed shear-thickening properties in MMT-containing cement slurry, on the contrary, short side chains showed shear-thinning properties.