The Role of Hydroxypropyl Methylcellulose (HPMC) in Dry-Powder Mortar
Hydroxypropyl methylcellulose (HPMC) is typically required in all dry-powder mortar products. Its main function is to improve the mortar’s water retention, fluidity, and workability, increase the initial strength of cement mortar, and prevent cracking, especially noticeable in highly absorbent substrates and high-temperature construction.
This study investigated the effects of HPMC on the flexural, compressive, and tensile bond strength of cement mortar, given the addition of a certain amount to the dispersible latex powder. The pore structure was tested using mercury intrusion porosimetry to analyze the influence of HPMC introduction on the porosity and pore size distribution of cement mortar.
The results showed that the tensile bond strength of cement mortar with added cellulose ether was improved. However, the addition of methylcellulose ether significantly reduced the flexural and compressive strength of the cement mortar. Higher dosages resulted in lower strength. With increasing dosage, the flexural strength of the cement mortar initially increased and then decreased, while the compressive strength gradually decreased. The dosage should be controlled between 0.1% and 0.3%. After adding HPMC to cement mortar, the pore distribution area increases, the number of small pores increases, the number of large pores decreases, and the average pore diameter decreases.
