Exploring aspartic acid as a chelator to regulate the performance of alkali-activated slag

Abstract

This study proposes to utilize L-aspartic acid (L-Asp) as a Ca^2 + chelator to regulate the performance of alkali-activated slag (AAS). The experimental results revealed that L-Asp can effectively retard the hydration of AAS through Ca²⁺ chelation, thereby prolonging the setting time and enhancing the fluidity of AAS. Moreover, the presence of L-Asp∼Ca chelates has a nucleation effect, which can improve the hydration of AAS at later stages. Consequently, the pore structure of AAS was optimized and the compressive strength was enhanced. More importantly, the autogenous shrinkage was effectively reduced. The mixture with 0.3 % L-Asp exhibited the highest compressive strength, the largest elastic modulus of hydration products, and the greatest cumulative heat of hydration within 72 h, it enhanced the fluidity and reduced the autogenous shrinkage of AAS. Consequently, 0.3 % L-Asp was the optimal mixture based on a systematic comparison of key performance indicators of AAS. Specifically, the addition of 0.3 % L-Asp extended the setting time of AAS by 45.5 %, improved the 28d compressive strength by 6.7 %, and decreased the autogenous shrinkage by 29.7 %.