RETRACTED: Effect of Crushed Granite, Superabsorbent Polymer, and Expansive Agent on the Workability, Compressive Properties, and Autogenous Shrinkage of Ultrahigh-Performance Concrete (Retracted Article)

This study proposed to introduce a combination of crushed granite (CG), superabsorbent polymer (SAP), and expansive agent (EA) into ultrahigh-performance concrete (UHPC) to mitigate the early autogenous shrinkage of UHPC without causing deterioration of its workability and mechanical performance. To this end, the effects of CG, SAP, and EA individually and their combinations on the workability, compressive strength, and autogenous shrinkage of UHPC were investigated. The results showed that CG, EA, and SAP all reduced the autogenous shrinkage of UHPC. However, the addition of CG and EA deteriorated the workability of UHPC, while the introduction of SAP decreased the compressive strength of UHPC. When CG (14.7% vol.), 1% EA, and 0.15% SAP were combined (CG+EA-1+SAP-0.15), UHPC showed the best overall performance. Specifically, the 7-day autogenous shrinkage of the CG+EA-1+SAP-0.15 group was 296.1 mu epsilon, which was 68% lower than the reference group (without CG, EA, and SAP); the 28-day compressive strength was slightly improved; and the slump flow was only 1.6% lower than that of the reference group, which was negligible. The results of thermogravimetry analysis showed that SAP could enhance the hydration of portland cement and EA, and could also promote the pozzolanic reaction of ground granulated blast furnace slag and silica fume. The results of mercury intrusion porosimetry demonstrated that the microstructure of UHPC was refined due to the enhancement of hydration by internal curing of SAP. Besides, when CG, EA, and SAP were combined, the total porosity of UHPCs first decreased and then increased when the dosage of SAP increased. Specifically, the total porosities of the reference, CG+EA-1+SAP-0.1, CG+EA-1+SAP-0.15, and CG+EA-1+SAP-0.2 groups were 9.6%, 9.2%, 5.5%, and 9.4%, respectively. The CG+EA-1+SAP-0.15 group had minimum porosity, which was 42.87% lower than reference group. The above results demonstrated that the combined use of CG, SAP, and EA can effectively mitigate the early autogenous shrinkage of UHPC, but the optimal ratio between EA and SAP should be further studied.