PROCESSES OF CARBONIZING SHRINKAGE OF CONSTRUCTION MATERIALS

Abstract

Relevance: This paper studies the durability of structures made of various building materials and the effect of carbon dioxide on building materials with a view to reduce its aggressive and destructive effects. Purpose: The aim of the paper is to identify and eliminate the causes of the building material destruction during their carbonization. Materials/Methods: Silicate brick, cement stone and concrete. Research findings: Research is carried out into the destruction of wall structures made of calcium silicate brick and carbon dioxide corrosion of hydration products in calcium silicate brick and cement brick in concrete. It is found that carbonization in hydration products results in their transfer to a denser state which is accompanied by the reduction in the volume of shrinking deformations which cause sometimes the breach and fracture of material. When considering the water/cement system, it is shown that more credible and visible results on shrinkage processes can be obtained through parameters of its volume phase composition which allow controlling the parameters of the structure rearrangement from the initial to final states of the system, i.e. from cement paste to cement brick hardened at different time intervals. It is shown that after 28 days of hardening, the degree of filling the initial pore space with hydration products reaches 67%, while the porosity of cement brick in the final state is 16.5% at the initial composition of the solid phase Fs1 = 0.5; 13.5% at Fs1 = 0.55; 12.8% at Fs1 = 0.6; 11.2% at Fs1 = 0.65 and 0.7-9.0% at Fs1 = 0.7. It follows that shrinkage processes intensify in cement paste with the initial porosity over 40-50 %. It is possible to reduce the negative effect from shrinkage processes via the addition of carbonate-containing mineral additives such as lime rock or dolomite to the cement or lime and sand composition.