Utilization of natural sisal fibers to manufacture eco-friendly ultra-high performance concrete with low autogenous shrinkage

Abstract

This study aims to explore a new method to reduce autogenous shrinkage of ultra-high performance concrete (UHPC) by incorporating natural sisal fibers. The water absorption and desorption behavior of sisal fibers were firstly determined. Then, flowability, setting time, hydration heat, autogenous shrinkage, internal relative humidity, mechanical properties, fiber distribution, hydration performance, and microstructure of UHPC mixtures incorporating various volume content of sisal fibers were evaluated. The results show that sisal fibers can release the absorbed water with decreasing relative humidity in UHPC specimens. The addition of sisal fibers can restraint the cement hydration process and delay the setting times. The 7 days autogenous shrinkage of UHPC was reduced by 71.4% by adding 1.5 vol% sisal fiber due to the internal curing and reinforcing effect induced by sisal fibers. Incorporating sisal fibers can promote late hydration of UHPC, so the 28 days compressive strength was reduced by only 7.7%∼8.2%. Moreover, the obvious gap between sisal fiber and concrete can be observed from the backscattered electron images, which is caused by the contraction of sisal fiber after releasing water. Finally, the environmental and cost evaluation shows that the use of renewable sisal fiber as a shrinkage-reducing material can reduce the production cost and carbon footprint of UHPC, so it is of great significance to the sustainable production of UHPC.