Understanding the porous aggregates carrier effect on reducing autogenous shrinkage of Ultra-High Performance Concrete (UHPC) based on response surface method

Abstract

In this study, the porous aggregates carrier effect on reducing autogenous shrinkage and optimizing microstructure of Ultra-High Performance Concrete (UHPC) is investigated, including experimental study and mechanism analysis. Based on the modified dense particle packing model (Andreasen & Andersen model), the UHPC skeleton is designed. Then, the shrinkage reducing admixture (SRA) is absorbed by porous aggregates (PA), and the pretreated PA is used to replace the fine aggregates in UHPC. After that, a series of experiments are executed for the developed UHPC, including flowability, setting times, mechanical properties, autogenous shrinkage and microstructure development. Accordingly, based on the obtained experimental results, the Response Surface Methods (RSM) is utilized to get the optimized PA content and SRA solution concentration. The obtained results show that PA acting as carrier is beneficial to reduce the adverse effect of direct addition of SRA. Moreover, when the added PA content is 25% and the SRA solution concentration is 70%, the developed UHPC has advanced properties. Therefore, on the basis of on the method proposed in this study, it is possible to effectively reduce the UHPC autogenous shrinkage without sacrificing its fresh behavior, mechanical properties and dense microstructure.