Characterisation of the effects of hemp shives for internal curing of concrete

The effectiveness of hemp shives for the internal curing of concrete has been experimentally investigated in the current study. The effect of internal water embedded through pre-saturated hemp shives on concrete curing was assessed by comparing the strength and shrinkage response of a hemp-concrete composite to those of a traditional concrete mix. Three different hemp shive sizes and two different curing conditions (sealed and unsealed) were considered to replicate typical curing conditions at construction sites. Strength results were compared to a Control Mix subjected to standard laboratory curing conditions. It was observed that the compressive strength of the hemp-concrete composite increased with the reduction of particle size and dosage of hemp shives. The mix that included 1 % shives in the size range 1 to 2 mm was identified as the optimum mix achieving a strength up to 83 % to that of the Control Mix. Importantly, a reduction in unrestrained shrinkage was observed for this mix compared to the control samples. Microstructural analysis of the hemp-concrete composite confirmed that continued hydration took place due to the presence of internal water supplied by the hemp shives. As a result, with the inclusion of saturated hemp shives the process of cement hydration and strength gain continued for a longer period even in the absence of external curing water compared to that of traditional hydration.