Modified Cement Coatings
Cement render generally has good durability against weathering.
The high compressive strength gives cement render its extensive use in buildings. When cement mortar is used in thin layers, as in resurfacing or patching old concrete unless the best of techniques and materials are employed the patch or resurfacing tends to crack and erode away after a short period of time. This failure results from low flexural strength and inadequate adhesion to the substrate. Acrylic modifiers are specifically designed to overcome some shortcomings of cement render, particularly poor adhesion, low impact strength, low flexural strength and thin-section fragility.
By overcoming these deficiencies, acrylic modifiers improve the properties of the mortar and thereby add to the potential uses. These improved properties are especially apparent in thin-section uses. The acrylic polymer cement the cement in adhering tenaciously to old concrete and brick—also to wood, metal, and other substrates once considered off limits to cement mortar. The degree of this adhesion is seen in laboratory shear tests. When sufficient force is applied to break a modified patch from the unmodified concrete to which it has been applied the rupture consistently occurs in the substrate rather than in the stronger bond between the cement render and the substrate.