The role of redispersible latex powder in mortar

1. The mechanism of action of dispersible latex powder in mortar

The amount of emulsion polymer that can be formed by dissolving the dispersed latex powder in water changes the pore structure of the mortar, and its air-entraining effect reduces the density of the mortar, accompanied by a significant pore reduction and uniform distribution in the whole . The polymer introduces a large number of uniform tiny closed air bubbles into the cement mortar, which greatly improves the workability of the freshly mixed mortar. At the same time, these air bubbles can block the capillary inside the hardened mortar, and the hydrophobic layer on the surface of the capillary is closed. Closed cells; more importantly, when the cement is hydrated, the polymer also forms a film and adheres to the cement hydrate to form a uniform network structure, and the polymer and the hydrate penetrate each other to form a continuous phase . This composite structure forms the polymer-modified cement mortar, and the aggregate is also bonded to the hardened mortar by the composite material. Due to the low elastic modulus of the polymer, the internal stress state of the cement mortar is improved, which can withstand deformation and reduce the stress, and the possibility of micro-cracks is also small; moreover, the polymer fiber crosses the micro-cracks and acts as a bridge and filling The effect limits the spread of cracks and makes micro cracks disappear in places where there are more polymers. The reduction of micro-cracks inside the slurry reduces the water absorption capacity of the capillary inside the mortar, and the anti-water absorption capacity of the mortar is simultaneously improved.

2. Freeze-thaw resistance

The freeze-thaw mass loss rate of the cement mortar test block with latex powder is significantly lower than that of the sample without adding latex powder, and with the increase of latex powder addition, the smaller the mass loss rate is, the better the freeze-thaw resistance of the test piece is. , when the content of latex powder exceeds 1.5%, the rate of freeze-thaw mass loss changes little.

3. Effect of latex powder on the mechanical properties of mortar

The compressive strength of mortar decreases with the increase of the latex powder content, and if mixed with cellulose ether, the compressive strength can be effectively reduced; the flexural strength and bond strength increase with the increase of the latex powder content; When the amount of latex powder is less than 2%, the bond strength of the mortar increases greatly, and then the increase slows down; the latex powder can greatly improve the comprehensive performance of the mortar, and the suitable amount is 2%-3% of the cementitious material.

4. Market value and prospect of latex powder modified commercial mortar

Using latex powder to modify cement mortar can produce dry powder mortar with different functions, which provides a broader market prospect for the commercialization of mortar. Like commercial concrete, commercial mortar has the characteristics of centralized production and unified supply, which can create favorable conditions for adopting new technologies and materials, implementing strict quality control, improving construction methods, and ensuring project quality. The superiority of commercial mortar in terms of quality, efficiency, economy and environmental protection has been increasingly revealed along with research and development and popularization and application, and is being gradually recognized. It can be summed up in eight words: one is more, two is fast, three is good, and four provinces (one is more, there are many varieties; Labor-saving, material-saving, money-saving, worry-free). In addition, the use of commercial mortar can achieve civilized construction, reduce material stacking sites, and avoid dust flying, thereby reducing environmental pollution and protecting city appearance.