Estudo da influência da adição de polímero superabsorvente e metacaulim na retração autógena, resistência à compressão e microestrutura de microconcretos

Abstract

The use of superabsorbent polymers (SAP) in high-strength concrete helps mitigate autogenous shrinkage but may compromise mechanical properties due to pore formation or improper water-to-cement ratio (w/c) determination. Metakaolin (MK) emerges as an alternative to enhance the performance of these cementitious mixtures. This study investigates the combined effects of SAP addition and the replacement of 10% of cement with MK in high-strength microconcretes, considering autogenous shrinkage, compressive strength, hydration kinetics, composition, and microstructure. The results show that SAP reduced autogenous shrinkage by up to 63.5% with a dosage of 0.15% by cement mass and completely eliminated it at 0.30%. The combination of SAP and MK increased compressive strength by up to 59.8% at 28 days. SAP significantly influenced hydration kinetics, promoting greater hydrate production, as evidenced by calorimetry, thermogravimetry, and low-field nuclear magnetic resonance tests. Meanwhile, MK refined the cementitious matrix, acting as a nucleation site for hydrate formation.