Characterization and resistance against the combined effect of chloride erosion and freeze–thaw cycling of sticky rice lime paste enhanced by cellulose fiber and fly ash

The primary objective of this paper is to research the characterization and durability enhancement of traditional sticky rice air lime paste mixed with cellulose fiber and fly ash. The changes in the physical and mechanical properties, pore structure and microstructure and the deterioration mechanism of the durability under the combined action of chloride erosion and freeze–thaw cycling of modified sticky rice air lime paste are studied by means of macro test, NMR, XRD, FTIR and SEM. The results show that cellulose fibers can effectively reduce the drying shrinkage, improve the compressive and flexural strength, and resist the expansion of cracks caused by freeze–thaw cycles. However, when the fiber is added alone, the water absorption of the fiber will delay the carbonization rate and adversely affect the frost resistance of the paste. The mixture of fly ash and fiber can be used to fill the pores, solidify chloride ions, reduce the adverse effects on frost resistance caused by the fiber's water absorption, and enhance the strength and durability of the paste. The modified paste mixed with 1% fiber and 25% fly ash has favorable strength and resistance to the combined effect of chloride erosion and freeze–thaw cycling, which has a certain reference significance for the design and application of ancient masonry building repair materials in complex environments.