173 / 2022-04-30 14:03:53

Mitigating shrinkage of alkali-activated slag pastes by cellulose fibre

Alkali-activated slag,Internal curing,Cellulose fibre,Shrinkage,Compressive strength

Alkali-activated slag (AAS) has been recognized as a green binder to replace the ordinary Portland cement (OPC). As compared to the OPC, it can considerably reduce the embodied carbon of construction material. However, AAS material exhibits large shrinkage, which subsequently increases the cracking tendency of components made by AAS. In this study, cellulose fibres are adopted as internal curing agents to mitigate the shrinkage of AAS paste. The liquid released from the cellulose fibres can achieve internal curing, while the fibres can also reinforce the AAS paste against the shrinkage. The influences of cellulose fibre dosage and length on the properties of the AAS pastes are investigated.

The results indicate that the autogenous shrinkage of the AAS paste is mainly affected by the cellulose fibre dosage, and increasing the fibre dosage can reduce the autogenous shrinkage of the AAS paste by up to 33%. Increasing the fibre length can slightly reduce the autogenous shrinkage of the AAS pastes due to the fibre reinforcement effect. Moreover, adding 5% fibres can decrease the drying shrinkage of the AAS paste due to their reinforcement effect. However, the drying shrinkage of AAS pastes increases with the cellulose fibre dosage, resulting from the accelerated moisture loss through the paths created by the fibres. Additionally, the compressive strengths of the AAS pastes decrease as the cellulose fibre dosage increases, which is mainly caused by larger pores left by the fibres and the weak bonding between the fibre and paste.