Analysis of Porous Structure in Autoclaved Materials Modified by Glass Sand

Abstract

This paper describes the use of glass sand in the production of autoclaved bricks. Traditional autoclaved materials consist of SiO2, CaO, and H2O. The purpose of the tests is to analyze the possibility of using glass sand in autoclaved materials and to determine their properties and durability. Depending on the structure, building materials can have porosities ranging from 0% (glass, metals) to over 90% (thermal insulation materials such as aerated concrete). Porosity of materials is directly related to the strength of materials and their density, and further to the thermal and acoustic insulation properties of products used especially for external wall construction, i.e., bricks, concrete, and aerated concrete. This type of silicate brick is formed at a temperature of 203 °C, therefore the dominant phase forming the microstructure is tobermorite, in contrast to the C-S-H phase, which dominates in concretes and which is characterized by a larger specific surface. The nature of pores, their number, appearance and arrangement in the material can be studied using computer techniques (SEM, XRD, computed tomography, porosimetry). Computed tomography (micro-CT analysis) showed that the number of voids in the material modified by glass sand is about 20% in relation to the weight of the product. The density of the product with glass sand was determined to be 2.2 kg/dm3.

Application of the Computed Tomography Method for the Evaluation of Porosity of Autoclaved Materials

“…This difference may be associated with the fact that quartz sand is less reactive because it has a higher Mosh hardness (7) and can scratch glass [ 53 ]. The material strength was in the range of 10–20 MPa (the compressive strength test was the subject of the previous article [ 2 , 3 ]); therefore, it was similar to the reference brick, but the glass-modified material was more compact and uniform. The analysis of voids in the traditional silicate brick sample treated as the reference value showed that the pore content below 300 µm represented 0.02%, i.e., 0.06 mm 3 , while in the sample modified with recycled glass sand, it represented 0.8%, i.e., 2.5 mm 3 .…”

“…At this point, however, the possibility of injecting mercury into the bottle pores should be considered without drastically destroying the structure of the material. The maximum pressure of 420 MPa is necessary to force mercury into pores with a diameter of 0.006 µm [ 3 ]. Assuming that the destructive pressure is close to the tensile strength of the tested material, with mercury penetration into the pores with radius dimensions ≤ 0.02 µm, the damage process will begin, changing the image of the actual pore distribution in the tested material.…”

“…This article deals with the topic of sustainable construction in the context of ecology and material deficits. This work is a continuation of considerations on the possibility of using glass sand from glass recycling in materials resulting from hydrothermal treatment, i.e., subjected to conditions of increased pressure and temperature [ 1 , 2 , 3 ] (a technology which is popular largely in Western Europe and Central and Eastern Europe) in which the main substrate is quartz sand. In order to relieve the environment, alternatives to the use of quartz sand are being searched and tested.…”

“…The functional properties, on the other hand, reflect the structure of the materials, i.e., porosity or appropriate bonds and phase transitions. The sand-lime products referred to in this article belong to the group of porous materials [ 3 ]. In nature, porous substances occur naturally, including various building materials, including concrete and bricks.…”

Influence of Waste Basalt Powder Addition on the Microstructure and Mechanical Properties of Autoclave Brick

“…An example of such a solution is the use of ground chalcedonite [ 24 , 25 ], ground limestone [ 26 ], dolomite powder [ 27 ], metakaolinite [ 28 ], barium [ 29 ], bentonite [ 30 ], thermally activated Carboniferous shale [ 31 ] and silica fume [ 32 ]. In recent years, the impact of waste glass in silicates has been extensively studied [ 33 , 34 , 35 , 36 , 37 ].…”