Effects of Superplasticizer Types and Mixing Methods of Nanoparticles on Compressive Strengths of Cement Pastes

This paper presents the effects of five different types of superplasticizers on workability and compressive strengths of cement pastes containing nanosilica (NS) and nanocalcium carbonate (NC) particles each at 2% by weight as partial replacement of cement. The NS and NC are dispersed in water containing 1% superplasticizer (by weight of cement) of five different types for 30 min in an ultrasonic mixer at maximum amplitude. Comparison is also made with conventional mechanical dry mixing of NS and NC with cement and ultrasonic mixing of NS and NC in water. Results show that the addition of NS adversely affects the workability of cement pastes more than those containing NC, regardless of superplasticizer types and mixing methods. The measured compressive strengths of cement pastes containing NS and NC dispersed in polycarboxylate ether-based superplasticizer solution are the highest among all five superplasticizer types considered in this study. X-ray diffraction (XRD) analysis results also agree well with the measured compressive strengths. (C) 2015 American Society of Civil Engineers.