Study on early hydration and mechanical properties of ferrite-rich calcium sulfoaluminate cement-based grouting materials

Abstract

Grouting materials play a very important role in the performance of anchor structures. In this study, a new grouting material (FCSA-1) consisting of ferrite-rich calcium sulfoaluminate cement (FCSA) clinker, ordinary Portland cement (OPC), limestone, and anhydrite was prepared. The objective of this study is to examine how the hydration process of the novel grouting material affects its physical and mechanical properties through laboratory tests. This investigation will particularly focus on parameters such as setting time, fluidity, hydration product formation, microstructure, expansion rate, and strength development within a 28-day timeframe. Additionally, 2D numerical simulations of pull-out tests and field pull-out tests were conducted to validate the anchorage performance of FCSA-1. The laboratory tests results showed that the initial setting time was 25 min and final setting time was 40 min. Additionally, the fluidity of the new grouting material measured at 282 mm. The free expansion rate exhibited a non-linear growth trend, with an average growth rate of 4.51‰/d within 14 days. The expansion was attributed to the increased presence of the expansive product ettringite during the early stages, while the expansion was mainly due to the volume growth of ettringite during the later stages. The uniaxial compressive strength reached 40.35 MPa within 1 day and increased to 61.75 MPa within 7 days, remaining stable thereafter. The primary hydration products of the FCSA-1 identified in the quaternary blend were ettringite and hydroxide aluminum (AH3), with a stable phase content after 1 day of curing, indicating rapid hydration reaction. Due to the rapid increase in hydration products and crystal volume growth, the pore structure of the FCSA-1 became more compact. In addition, numerical simulation results showed that using FCSA-1 as a grouting material improved the anchorage performance of the structure compared to OPC. This indicated that the early high-strength properties of the grouting material improve its anchorage performance significantly. Field pull-out tests showed that the combination of resin and FCSA-1 grouting material increased pull-out force by 34.21% compared with that of using resin alone. According to the results, the novel grouting material exhibits early high-strength and slight expansion performance during the early stages of hydration, making it a suitable grouting material for engineering applications.