The influence of plasticising admixtures on drying shrinkage of cementitious composites

Abstract

This article presents a research into the impact of plasticising admixtures on drying shrinkage of cementitious composites by evaluating the effectiveness of plasticising. Materials used in the study: Portland cement CEM I 42.5 R, plasticiser LS (modified lignosulphonates based), superplasticiser PCE (synthetic polycarboxylate esters based), superplasticiser MAP (modified acrylic polymers based), sand and water. The percentage change of plastic viscosity of cement paste indicates the effectiveness of plasticising of cementitious composites. The change of plastic viscosity has been tested by adding a specific amount of plasticising admixtures. The effectiveness of plasticising of pastes were tested using rotational viscometer. Chemical admixtures content in pastes varied from 0 to 1.2%. Drying shrinkage was tested based on length change of the specimens with fine aggregates. The method to minimise drying shrinkage of composites was established through use of plasticising admixtures. It has been found that by increasing plasticising admixture dosage from 0 to 1.2% the following changes occur: LS plasticising effectiveness increases by 35% while drying shrinkage decreases by 8%; MAP plasticising effectiveness increases by 70% while drying shrinkage decreases by 16%; PCE plasticising effectiveness increases by 80% while drying shrinkage decreases by 20%.