The introduction of low-waste and waste-free processes promotes a healthier environment. The least recyclable steel plants emissions are dust and sludge, cleaning systems and technological pylegazovybrosovaspiration. Due to the physico-chemical composition of metallurgical sludge, they are valuable raw materials for the building industry, particularly in the manufacture of silica bricks. An important part of the technological process in the manufacture of sand-lime brick is a heat treatment to a large extent determines the construction and mechanical properties of the finished products. This paper considers the relationship start chemical reactions on the surface of the workpiece on its geometrical dimensions. By increasing the size of the workpiece the time required for the occurrence period of the start of the chemical reactions at the surface increases.