Gusev N. I., Kochetkova M. V.

Departament of Quality Management and Technology of Building Production

«Penza State University of Architecture and Construction»,

Russia

ADHESION STRENGTH OF POLYMER COMPOSITES FOR EXTERIOR WALLS OF HEATED BUILDINGS

In practice, the creation of protective and decorative coatings for walls of lightweight concrete is widely used foamed solution. It had a compressive strength of 7.5 MPa, and the strength of the lightweight concrete has 5.2-5.8 MPa, a bulk density of 730 kg / m³.

In order to improve traction of the protective layer with foam concrete was added to a solution of the polymer composite. Was added polyvinyl acetate dispersion and synthetic rubber butadiene latex SKS-65РP, which improve the adhesive properties of the composites produced.

Samples were made of foam concrete covered with a protective layer of 20 mm with the ratio of the polymer solution P: C, equal to 0.07; 0.10 and 0.15. Samples were prepared on the basis of polyvinyl acetate and latex dispersions.

Adhesion strength protective topcoat with foam concrete is one of the main conditions that determine the possibility of using this material as a protective coating.

Previous studies had established the relation between shear strength and crushing strength, using the relation R shear = 1,6 R split. In the future, all data are displayed, depending on the R shear .

Samples were tested after drying to constant weight, except special tests in a saturated water condition. The test was conducted in 7; 28 and 60 days of age. Contact strength of cement mortar and lightweight concrete is largely determined by the properties of the polymer additive and its positive impact on the ability to retain moisture.

The polymer solution improves adhesion foam concrete and prevents extraction of moisture from the solution, promotes normal hydration of the cement in the contact zone and the full manifestation of its adhesion properties. High adhesive properties of polyvinyl acetate are well known. Fresh concrete using PVA are glued together with old ones. and achieves a peel adhesion up to 0.1 MPa. Prism concrete has a shear strength of 0.8 MPa, with the proviso that stored in air-dry conditions. In our case protective solutions for PVA dispersion and latex showed almost the same adhesive properties in air-dry conditions (Figure 1).

Premature coagulation of latex has the strength of adhesion is very adverse consequences. Adding latex in this case, improves adhesion compared to an unmodified composition.

It can be concluded that the adhesion of the solution increases slightly faster than its strength. At the age of seven days, the separation occurs on a polymer solution and not on the surface of the concrete. Tests show good adhesion P: C = 0,1. A further increase in PVA dispersion or latex SKS-65PP hardly advisable, since adhesion is achieved already exceeds the strength of the foam.

To study the effect of moisture on the strength of coupling carried out two series of experiments. Samples are dried to constant weight, and then saturated with water. Samples with a textured layer of 18 mm were immersed in water at a depth of 13 mm. In the second series of experiments, samples completely submerged. Bond strength was determined in the first case after 24 and 48 hours, in the second - after 12 and 24 hours after removal from the water. Effect of moisture on adhesion strength shown in the table.

First, the adhesive strength is reduced without the addition of polymer samples. Adhesion strength in the second series of experiments was higher than in the first. With the destruction of the contact layer, especially at high P:C, foam concrete remained dry. Formulations with PVA dispersion and latex SKS-65 PP, even a two-day water saturation showed satisfactory adhesion to foam concrete. Failure occurs, usually on foam (at P: C = 0.1-0.2) and the solution (at P: C = 0.07). A slight increase in the bond strength of the unmodified after water saturation, explained further hydration of cement, dehydrated in the initial phase of hardening.

Figure 1. Adhesion strength penopolimertsementnyh
solutions with foam concrete

Table. Influence of moisture on bond strength polymer-solution with foam concrete

Poly -mer	P:C	Adhesion strength in shear polymer-solution with foam concrete (MPa)
		saturation of water samples with capillary leak				water saturation with full immersion
		24 hours		48 hours		12 hours		24 hours
		R shear	softening coef ficient.	R shear	. softe ning coef ficient	R shear	Softe ning coef ficient.	R shear	softening coefficient.
	0	0,08	0,33	0,09	0,38	0,16	0,65	0,18	0,74
PVA disper sion	0,07	0,41	0,59	0,29	0,42	0,48	0,69	0,23	0,33
	0,10	0,57	0,76	0,56	0,75	0,52	0,70	0,51	0,68
	0,15	0,73	0,67	0,66	0,61	0,66	0,61	0,72	0,66
SCS- 65PP	0,07	0,14	0,49	0,13	0,45	0,17	0,59	0,23	0,80
	0,10	0,16	0,55	0,13	0,44	0,23	0,78	0,17	0,58
	0,15	0,17	0,50	0,13	0,38	0,18	0,53	0,15	0,44

Adhesion strength of polymer-based PVA dispersion and latex can be considered satisfactory.