Effect of absorption determining methods of superabsorbent polymers in cementitious environments on the fresh properties

Abstract

Autogenous shrinkage can be mitigated by the use of superabsorbent polymers (SAP) as internal curing agents. SAP are a competitive alternative to lightweight aggregates since SAP could absorb water 20–30 times by its mass in cementitious environments. There is no general agreement on determining the absorption capacity of SAP in cementitious environments. In this study, the absorbency of SAP was determined with the teabag, flow table, and point-count (ASTM C 457) methods. Two SAP with different particle sizes (D50: 215 µm and D50: 725 µm) were used in the mixtures to examine the effect of particle size on fresh properties. Also, two concrete types (slurry infiltrated fiber concrete’s matrix and ordinary mortar) to examine the usability of the methods in different rheological characteristic concretes. This study aimed to use optimal additional water without compromising workability and w/c ratio. Absorption capacities were found to be lower for the point-count method since the flow table method are not taking into account the filler effect of SAP in the mixtures. Using the absorption values obtained from the point-count method, affected slurry infiltrated fiber concrete’s fresh properties negatively. On the other hand, it has been found that this effect was limited for ordinary mortars. Results indicated that even though the point-count method could be more accurate, concrete type is also important when choosing a method to determine the absorption capacity of SAP.