X-Ray Micro Tomography of Water Absorption by Superabsorbent Polymers in Mortar
Superabsorbent Polymers (SAP) have been recently subject of investigation as smart admixtures for cement-based materials. The properties of these polymers enable their use for internal curing, increasing freeze/thaw resistance, boosting autogenous self-healing and providing a crack self-sealing effect in cementitious composites. Except for the earliest application, the functioning of these beneficial effects invloves the absorption by the polymers of ingress water in the hardened cementitious matrix and later release, as well as their capacity to complete multiple absorption/desorption cycles. In this work, the absorption of water in mortar with superabsorbent polymers is monitored during the first 60 min of absorption through micro-CT. The experimental series included the presence of cracks. The registration and differentiation of sub-minute (18 s) scans enabled the individuation of bulk water content distribution in the mortar with a resolution of 55 μm. The swollen volume of SAP could also be quantified and studied in time. The results point out that although embedded SAP absorb water from the matrix, this absorption is slow and reduced with respect to water absorption during mixing for the used SAP. Same effect is observed for SAP in the cracks.
KeywordsSAP Mortar X-ray micro computed tomography Concrete durability
C. Romero Rodriguez acknowledges the financial support from the Construction Technology Research Program funded by the Ministry of Land, Infrastructure and Transport of the Korean Government under the grant 17SCIP-B103706-03 and also the financial aid of the Cost Action 15202 under the Short Scientific Mission with reference number 39002, in the realization of the experiments. The authors gratefully acknowledge UGCT for the use of micro-CT scanner facilities and the Ghent University Special Research Fund (BOF-UGent) for the financial support to the Centre of Expertise UGCT (BOF.EXP.2017.007). FWO is acknowledged for funding Maxim Deprez (project 3.G.0041.15). The authors wish to thank Dr. Didier Snoeck for providing a generous quantity of SAP F for the experiments and to Iván Josipovic and Dr. Tim de Kock for their highly appreciated feedback.
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