The Role of Redispersible Latex Powder in Mortar
Release Time:
2021-09-09
Source:
Latex powder
The performance of redispersible latex powder in mortar is governed by two processes: cement hydration and polymer film formation. The combined system of cement hydration and polymer film formation unfolds in four distinct steps:
(1) After being mixed with cement mortar, the redispersible latex powder is uniformly dispersed throughout the system;
(2) Polymer particles deposit on the surface of the gel formed by cement hydration products mixed with unhydrated cement particles;
(3) Polymer particles form a continuous, tightly packed packing layer;
(4) During cement hydration, the closely packed polymer particles aggregate into a continuous film, binding the hydration products together to form a complete network structure.
The redispersible latex powder forms an insoluble, continuous film (a polymer network) upon drying; this low-modulus polymer network enhances the performance of cement. Meanwhile, certain polar functional groups in the polymer molecules undergo chemical reactions with cement hydration products, forming unique bridging bonds that improve the physical microstructure of the hydration products, thereby mitigating and reducing crack formation. The incorporation of redispersible latex powder slows the initial rate of cement hydration, as the polymer film can partially or fully encapsulate cement particles, ensuring more complete hydration and consequently improving various mechanical and durability properties of the cement.
