In this article, we will examine the results of research on binding agents intended for the production of autoclaved aerated concrete. A primary issue with binders based on Portland cement is their significant shrinkage. It was found that adding unslaked lime and colloidal gypsum helps form a strong cement stone with an expansion effect. The optimal composition of additives was determined using mathematical planning methods. The most favorable conditions for minimizing shrinkage in non-autoclaved aerated concrete are achieved under high humidity. The main hydrate phases in the cement stone include ettringite, portlandite, and various origin hydrosilicates.
Application of Aerated Concrete in Construction
Aerated concretes are widely used in modern construction as a material with thermal insulation and structural properties, suitable for erecting buildings of various purposes. Besides the autoclaved method of production, technologies for producing non-autoclaved foam and aerated concrete are gaining popularity. These technologies are economically beneficial, especially in the context of scarce and expensive energy resources.
Shrinkage Issues and Solutions
One of the main problems with aerated concrete is the shrinkage of inter-pore materials, which reduces the crack resistance of products and leads to the formation of cracks and the deterioration of the adhesion of plaster coatings. In the production of foam concrete, the primary issue of shrinkage is related to high water consumption and the low degree of crystallization of the primary hydration products of clinker minerals. Using fillers only partially solves the problem of shrinkage, not eliminating the coagulation of the cement gel. Several methods can address this problem: using non-autoclaved aerated concrete obtained by vibro-impact forming, employing expanding cement, and introducing a maximum amount of microdispersed filler and fibrous component.
Recent studies and publications in the field of construction materials show that the main negative manifestation of shrinkage deformations is increased crack formation in aerated concretes. However, modern developments are increasingly minimizing this negative factor.