Mortar modification of traditional Chinese ancient building masonry

Most ancient city walls in China are severely damaged mainly because of the destruction of traditional pure white mortar in the walls. Traditional mortar and cement paste are typically used for restoring ancient city walls; however, traditional mortar exhibits low strength, excessive shrinkage, poor durability, and poor compatibility between the cement paste and the original mortar. Therefore, there is an urgent need to develop new repair materials for ancient building masonry. A new type of modified pure white mortar was developed in this study. Hydroxypropyl methylcellulose and calcium stearate were added to pure white mortar, and the working performance, basic mechanical properties, and shrinkage of the modified pure white mortar were investigated. The microstructures of the modified mortar were analysed using X-ray diffraction and scanning electron microscopy techniques. A 0.4% HPMC or 0.1% CS content can significantly improve the performance of the traditional mortar, and the modified mortar is suitable for ancient masonry repairs.