Influence of Anti-cracking Fiber on Properties of Traditional Sticky Rice-lime Mortar

ABSTRACT Traditional sticky rice-lime mortar plays an important role in the restoration of Chinese historical buildings. However, its application in ancient building restoration is restricted due to some shortcomings of lime-based materials such as high shrinkage, low hardness in the early phase, cracking during carbonation, etc. In order to make better use of sticky rice-lime mortar, the research presented in this article evaluates the influence of admixtures (flax fiber, polypropylene fiber, and paper fiber) on the properties of traditional sticky rice-lime mortar by testing compressive and flexural strengths, surface hardness, drying shrinkage, water absorption, freezing-thawing cycles, carbonation degree, and through performing X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). Results revealed that three types of fibers ameliorated the mechanical strength, anti-shrinkage performance, durability, and microstructure of traditional sticky rice-lime mortar. 1.5% paper fiber was the most effective admixture to increase the mechanical properties and reduce the water absorption rates, and it improved the freeze–thaw cycles by more than 10 times; the incorporation of polypropylene fiber significantly reduced the drying shrinkage rates. In the practice of brick-stone cultural heritage conservation, it is recommended to consider adding paper fibers to improve the comprehensive performance of traditional sticky rice-lime mortar and adding polypropylene fibers to improve shrinkage resistance.