Effect of a novel shrinkage-reducing polycarboxylate superplasticiser on plastic shrinkage cracking of mortars

Abstract

Plastic shrinkage cracking propagating at early ages inevitably impairs the performance of concrete structures. To mitigate this, using a recently developed shrinkage-reducing polycarboxylate superplasticiser (SR-PCA) with outstanding shrinkage-reducing and water-reducing effectiveness can be a promising approach. The present work aims to investigate the effect of SR-PCA on plastic shrinkage cracking and to clarify the underlying mechanisms. For comparison, a traditional polyether type shrinkage reducing admixture (SRA) and a polycarboxylate superplasticiser (PCA) were also used. Based on the investigations on horizontal shrinkage, settlement, bleeding, evaporation mass loss, cement hydration, surface tension of pore fluid and capillary pressure, the underlying working mechanisms of SR-PCA were identified. The results indicate that SR-PCA is able to reduce the crack area, maximum crack width and average crack width by up to 55%, 48% and 50%, respectively. Furthermore, prolonging the bleeding duration and initial time of capillary pressure build-up caused by retarding the cement hydration, lowering the evaporation mass loss, and a lower development rate of capillary stresses and capillary pressure peak value induced by decreasing the surface tension of pore fluid are responsible for preventing the plastic shrinkage cracking of mortars containing SR-PCA.

Influence of novel shrinkage‐reducing polycarboxylate superplasticizer on the nature of calcium–silicate–hydrates

“…18,19 In recent studies, shrinkage-reducing polycarboxylate superplasticizers (SR-PCAs), as novel and multifunction superplasticizers that possess shrinkage-reducing, have been designed and investigated. [20][21][22][23] Generally, SR-PCAs are produced by grafting the shrinkage-reducing groups onto the main chain with the carboxylic group, in turn maintaining its water reduction and shrinkage reduction functions. Compared with the conventional PCEs, SR-PCAs have a similar carboxylate main chain and distinctly different side chains.…”