Influence of barium and lithium compounds on silica autoclaved materials properties and on the microstructure

The silicates materials are autoclaved material, which leads to its substantial fire resistance (class A). This kind of material sometimes is underestimated, despite their beneficial qualities (compressive strength 15-20 MPa, bulk density 1,73 kg/dm(3), little water absorbability), have recently returned on the market with stronger position. The study focused on compressive strength, bulk density, impregnability and water absorbability and microstructural qualities of the modified silicates autoclaved materials. For the purposes of the experiments laboratory samples of traditional and modified products were prepared. Under laboratory conditions samples with dimensions of 40 x 40 x 160 mm were made. After the laboratory tests solid silicate bricks with dimensions 180 x 220 x 250 mm were prepared. The study aimed at determination of optimal ingredients of silicate mass with addition of barium aggregate graining 0-2 mm and liquid lithium silicate in form of solution. Physical and mechanical features of silicates were marked, using compressive strength of samples. To perform experiments, orthogonal compositional plan type 3k (with k=2) was established, thus full experiment with two factors. For every correlation of factors, six parallel experiments were carried out. Analysis and tests of volumetric density were carried out in similar way. Modified silicate mass was precisely mixed, then pressed, and in the last stage placed in autoclaves. Inoculants were: barium aggregate with graining 0-2 mm in amount up to 20% (favorably 20%) and liquid lithium silicate in amount of up to 5% (favorably 4%). The article presents the effect of modification of autoclaved calcium-sand materials with barite aggregate (BaSO4) and lithium silicate on their application parameters. Production process of the modified silicate products has been left without change. Modification proves beneficial impact on silicate's porosity (limits its free space) and value of compressive strength, which was established on the level of 43,1 MPa with 5% of lithium silicate and 30% of barium aggregate in silicate mass (traditional samples have around 20 MPa). Favorably improved the phase microstructure of silicate products. In the microstructure of modified products, large clusters of xonotlite appeared with C-S-H phase and tobermorite. (C) 2019 Elsevier Ltd. All rights reserved.