Effect of Cement Type and Water-to-Cement Ratio on Fresh Properties of Superabsorbent Polymer-Modified Cement Paste

Abstract

Superabsorbent polymer (SAP) is a material with the ability to absorb liquid and desorb liquid from and to the environment, and it can ensure the internal curing of cementitious composites. Although the fresh state properties of SAP-modified mixtures (SAPCP) are affected and have been investigated nowadays, the rheological properties of SAPCP are still a virgin field and they are worth studying. Hence, the current study was aimed and conducted to observe what occurred if cements with different chemical compositions, various ratios of water/cement (w/c) and SAP were used together. Accordingly, CEM I 42.5R, CEM II/A-LL 42.5R and CEM IV/B (P) 32.5R were selected as binders in the mixtures, and w/c ratios were 0.40 and 0.50 for SAPCPs. In total, 24 mixtures were designed, produced and tested in the laboratory and spreading table tests, Vicate tests, viscosity tests and shear tests were conducted on the fresh state of the mixtures to observe the fresh behavior of SAPCPs. As a result, it was determined that the SAP, cement and w/c combinations considered in the article were effective on SAPCP fresh properties and rheology. However, it was determined that the use of high amounts of SAP in the mixture, high cement fineness and high oxide ratios in the cement (ratios of silicon dioxide/calcium oxide and aluminum oxide/calcium oxide) negatively affected not only the fresh state properties, but also the rheology. Moreover, the coexistence of the aforementioned negative conditions was the most unfavorable situation: high SAP ratio + high cement fineness + high oxide ratio in SAPCP. For these reasons, it was concluded that cement fineness and chemical composition should be taken into account in the rheology/workability-based design of SAPCPs. Then, the SAP content can be regulated for design purposes.