Effect of HPMC on the properties of wet-mix mortar

HPMC greatly improves the performance of wet mix mortar. Wet mix mortar is a mortar made of cement, fine aggregate, mineral admixture, admixture, additives and water mixed in a certain proportion, measured and mixed by the mixing station, transported to the place of use, and used within a specified time. . The raw materials used in wet mortar do not need to be dried, and there is no need to set up storage tanks, mixers and other equipment on site. It has the advantages of low cost, centralized mixing, stable quality and green manufacturing.

In the current construction situation where manual operation is still dominant, the one-time supply of wet-mixed mortar must be larger than the one-time construction, which determines that the wet-mixed mortar must be used for a long time and still has a certain service life. Good water retention and consistency. Therefore, the two technical indexes of water retention and setting time of wet-mixed mortar mixture become the key to its popularization and application.

1, HPMC can improve the bonding and water retention of wet mortar mixtures, but excessive mixing will reduce the consistency of wet mortar mixtures.

Water retention is an important performance index of wet mortar. Although mortar and concrete have some of the same components, they function differently. Typically, concrete is poured in concrete and wood forms that retain most of the water. Mortars are typically used on absorbent surfaces, and the water in the mortar can easily dissipate or evaporate into the atmosphere, so the water retention of the mortar becomes more important than that of the concrete.

HPMC enhances the consistency of wet-mixed mortar because of water retention, which improves the bonding of mortar and reduces the water secretion rate of mortar to a certain extent, but improves the fluidity of wet-mixed mortar in a specific dosage range; however, the content of hydroxypropyl methylcellulose is too high, which makes the wet-mixed mortar bonding too large, reduces the fluidity of mortar, and increases the difficulty of the construction of mortar.

2, HPMC will reduce the compressive strength of wet-mixed mortar specimens, and the reduction is more significant, but HPMC can improve the tensile bond strength of wet-mixed mortar.

For plastering mortar, bond strength is an important index. Generally speaking, plastering mortar requires a good ease and compatibility. so as to form a uniform mortar layer on the construction surface. Strong bonding strength of the mortar can make the mortar firmly bonded with the grassroots, so that cracking and peeling will not occur in long-term use.

Cellulose ether Forms a thin polymer film with hydrated particles, which has a sealing effect and prevents water loss, and has good water retention, so that it has enough water to ensure the hydration and strength development of the cement, and improve the bonding strength of the paste. On the other hand, hydroxypropyl methyl cellulose enhances the bonding of the wet-mixed mortar, ensures its good plasticity and flexibility, reduces the slip stress between the interface of the wet-mixed mortar and the substrate specimen, and further improves the interfacial bonding capacity of the mortar.

3、During the preparation process, it is recommended that HPMC be mixed into the wet-mixed mortar in the form of solution rather than directly fused in the form of powder.

The former has a better effect on improving the water retention, bonding and mechanical properties of wet mortar. When the converted content of hydroxypropyl methylcellulose was in the range of 0.01% to 0.04%, the water retention of HPMC in solution form in wet-mixed mortar was higher than that of HPMC in powder form by 1.4% to 3.0%. Therefore, HPMC mixed in solution form has a better effect on improving the water retention of wet-mixed mortar.

4、HPMC can also positively impact the aesthetic quality of wet-mixed mortar. By providing smoother application and better surface finishes, it helps achieve cleaner and more uniform results. Additionally, the improved consistency and workability contribute to a more polished appearance, enhancing the overall visual appeal of finished structures.