What effect does HPMC have on mortar?

The addition of hydroxypropyl methylcellulose (HPMC) can significantly improve the durability of mortar, primarily through the following factors:

HPMC significantly enhances the mortar's water retention, ensuring sufficient cement hydration, thereby improving the mortar's subsequent strength and durability. It also optimizes the mortar's workability, imparting excellent thixotropy: excellent fluidity under low shear, facilitating smoothing during application; and increased viscosity under high shear, effectively preventing sagging.

In terms of mechanical properties, HPMC significantly improves crack resistance and reduces shrinkage cracking by enhancing the mortar's elastic modulus and toughness. It also strengthens the bond between the mortar matrix and particles, thereby increasing flexural and tensile bond strengths, enhancing adhesion to the substrate, and improving structural stability.

Furthermore, HPMC improves the mortar's impermeability and water resistance, making it suitable for humid environments and extending its service life. The microporous structure it introduces also helps improve thermal insulation and enhances thermal resistance. In harsh environments such as freeze-thaw cycles, HPMC effectively safeguards the long-term durability and functional integrity of mortars through its excellent water retention and crack resistance.

In summary, HPMC, as a highly effective additive, significantly enhances the mortar's durability and engineering suitability by comprehensively improving its physical, mechanical properties and microstructure.