Effect of HPMC on Mortar Properties

HPMC (hydroxypropyl methylcellulose) is a commonly used additive that has a significant impact on various properties of mortar.

1. Improve water retention

HPMC can significantly improve the water retention of mortar, which is crucial for the construction and final performance of mortar. The better the water retention, the free water in the mortar can remain inside the mortar for a longer period of time, allowing cement and other cementitious materials to have more time to undergo hydration reactions, thus improving the strength and durability of the mortar.

2. Improve constructability

The addition of HPMC can improve the workability of the mortar, making it easier to apply and operate. It can improve the cohesion and uniformity of mortar, reduce segregation, prolong the opening time of mortar, reduce slippage, and optimize construction effects.

3. Increase bonding strength

Research shows that HPMC can significantly improve the compressive shear bond strength of mortar. For example, when 0.2% HPMC is incorporated, the bonding strength of mortar can be increased from 0.72MPa to 1.16MPa1.

4. Affects flexural and compressive strength

Although HPMC has a certain negative impact on the flexural strength and compressive strength of mortar, this impact is usually acceptable within a reasonable dosage range. As the HPMC content increases, the flexural strength and compressive strength of the mortar will gradually decrease.

5. Inhibit plastic cracks

HPMC can effectively inhibit the formation of plastic cracks in mortar and significantly reduce plastic cracks. When the HPMC content is 0.1% and 0.2%, the relative crack index of the mortar is 63% and 50% respectively. When the HPMC content exceeds 0.2%, the plastic cracks of the mortar no longer decrease significantly.

6. Improve sag resistance

HPMC can also improve the sag resistance of mortar, which means that the mortar will not sag or flow downward during thick layer construction, thereby improving construction quality and efficiency.

7. Introduce uniform and fine bubbles

HPMC has air-entraining properties and can introduce uniform and fine bubbles. These bubbles can improve the workability of the mortar and reduce the probability of cracking.

HPMC has many positive effects on the performance of mortar, including improving water retention, improving workability, increasing bond strength, inhibiting plastic cracks and improving sag resistance. However, it should be noted that the dosage of HPMC should be controlled within a reasonable range to avoid adverse effects on its flexural and compressive strength. In practical applications, HPMC with appropriate viscosity and dosage should be selected according to the specific mortar type and construction requirements to achieve the best overall performance.