- June 30, 2021
- Posted by: admin
- Category: News
Masons typically use a mixture of sand, binder, and water to create mortar. Lime, lime mortar and plaster in the form of cooked gypsum are particularly used to restore and reposition historic buildings and structures so that the restoration material resembles the original material in performance and appearance. Several types of cement mortars and additives exist.
The opening time of building mortar refers to the ability of the mortar to maintain its initial workability for a certain period of time after mixing, even if it is applied to a porous (high water absorption) base surface. Products with good water retention lose very little water, and this small part of the water is also absorbed by the base surface.
Construction mortars include plastering mortar, masonry mortar, tile adhesive, grout, and floor mortar. When applied to the base surface with high water absorption, good water retention is very important for building mortar.
Water retention mechanism
HPMC cellulose ether is currently the most common additive used to improve water retention in commercial mortars, but the mechanism of action of such additives is not fully understood. At present, the role of cellulose ether can only be inferred; on the one hand, it is thickened, so that To some extent, the amount of water absorbed by the porous substrate is reduced.
On the other hand, the three-dimensional structure formed by hydroxypropyl methylcellulose HPMC provides water retention. Hydroxypropyl methylcellulose HPMC has high polarity and high demand. Water characteristics keep water in the system well. But starch only forms a helical structure, which does not affect the water retention of the mortar much.
Water retention and its mechanism
The main factors affecting the water retention of construction mortar are:
(1) Viscosity of interstitial water (the higher the viscosity, the lower the mobility of water)
(2) The surface tension of the water phase and the capillary phenomenon of the filter cake/interface (that is, the part where the mortar is in close contact with the water-absorbing base surface)
(3) Water permeability of filter cake/interface (contact interface between mortar and base surface)
The water permeability of the filter cake/interface can be adjusted by the particle size ratio, and low permeability can be obtained by filling the pores at the filter cake interface.
Drymix mortar application guide
EIFS adhesive mortar
• Bond strength: Choose the right HPMC could provide the greatest bond strength of mortar.
• Good workability: HPMC have good consistency, non-sagging property could make the work easier during using of distribution method.
• Water retention: HPMC have good water retention, make sure all other additives can also reach the best performance.
EIFS surface mortar
• Bigger scrape area: The good film property and the suitable viscosity, choose right grade HPMC make the wet mortar more smooth and easy to scrape on the surface, same weight of wet mortar can cover bigger area.
• Anti-cracking: Choose the right specification of HPMC, The excellent property can make sure all other additives in mortar could reach the best performance, reduce the crack on surface.
• Stability: HPMC have good stability in hot environment, keep good water retention even in high temperature.
The above information is provided by the HPMC manufacturer.