CZ33182U1 - Mixture for preparing hydrosilicate bricks - Google Patents

Description

Technical field

The technical solution concerns the preparation of the raw material mixture, which is used for the production of masonry elements. Waste from the production of acetylene bottle fillings, sand and ground lime was used to prepare the raw material mixture. The mixture was compacted and then autoclaved. The product can be used as a structural element for various purposes, where it can replace commonly used lime-sand masonry elements.

BACKGROUND OF THE INVENTION

Acetylene is a gas that, due to its reactive triple bond, decomposes instantaneously and bursts as pressure rises. For this reason, acetylene is stored and transported dissolved in acetone, which for safety reasons is saturated in a gas bottle into a porous mass. The basic components for the preparation of porous fillings are lime, sand, fiber and water. The reaction between lime and sand takes place at an elevated temperature and pressure in the autoclave directly in a closed cylinder. Upon completion of the hydrothermal reaction, the excess water evaporates to form a porous material based on tobermorite (Ca5Si6O16 (OH) 2-2H2O) and axonotlite ((ΑΜβΟπύΟΗρ). After the acetylene is consumed, the gas cylinders are recycled. The resulting waste from bottle cleaning has no further application and is placed in landfills, the material is characterized by high humidity and porosity.

The essence of the technical solution

The technical solution uses waste material from recycling of acetylene cylinders based on tobermorite and xonotlit in combination with lime and sand for the production of masonry elements.

Lime sand products are artificial lump building materials made by pressing the wet production mixture. The mixture consists of fine quartz sand and lime. The products are cured in autoclaves under water vapor pressure at temperatures of about 200 ° C for about 5 hours. This process produces hydrated calcium silicate. The surface of the grains of quartz sand reacts with lime, so that the finished product consists predominantly of unchanged sand bonded with a hydrated tobermorite binder.

Waste raw material, which in addition to the hydrosilicate components also contains lime and silica components, participates in the formation of hydrosilicates in two ways during the hydrothermal process. On the one hand, quartz, due to its fineness, dissolves very easily and reacts with the lime component to form C-S-H phases. On the other hand, the hydrosilicate component positively affects the rate of reaction in the autoclave and the formation and quality of tobermorite, thereby achieving high product strengths. In view of the composition and thus the behavior of the waste used during autoclaving, it is possible to use it in the preparation of hydrosilicate products in an amount of 20 to 30% by weight, while preserving the properties of the resulting product.

Example of technical solution implementation

Mixtures were mixed from the feedstocks in a defined ratio (see Table 1) and homogenized. Subsequently, water was added so that the moisture of the resulting mixtures was 4 to 6% and the lime components were completely extinguished and lime hydrate was formed. The mixture was then dosed into molds and pressed at 15 MPa. The bodies prepared in this way were autoclaved at a temperature of about 195 ° C and a water vapor pressure of 14 10 ⁵ Pa with a holding time of 5 h.

- 1 GB 33182 U1

Table 1: Formulation of formulas

VPC 0% cal VPC 20% cal VPC 30% cal Sand 88.89 71.15 62.22 Lime 11.11 8.85 7.78 Hydrosilicate waste 0 20,00 30,00

Technological tests of fired products

Laboratory technological tests were performed on prepared samples for verification of use in the area of sand-lime masonry elements - ČSN EN 771-2.

The following analyzes were carried out on finished products:

• Determination of compressive strength • Determination of dry bulk density • Determination of water absorption • Determination of frost resistance (25 cycles) • Thermal conductivity

The results in Table 2 show that the addition of waste raw material does not have a major effect on the compressive strength, which in all the monitored samples was about 30 MPa. Due to the need to use more water during processing, the products have higher humidity. Waste bodies have increased water absorption, which can be related to a 17% decrease in compressive strength after 25 cycles. Waste, on the other hand, has a positive impact on reducing thermal conductivity.

Table 2: Test results

VPC standard VPC 20% cal VPC 30% cal Humidity after autoclaving (%) 3.3 6.2 6.4 Water absorption (%) 10.7 15.8 16.9 Density 1991 1851 1798 Compressive strength (MPa) 30.35 29.53 29.62 Reduction of compressive strength Rc according to EN 772-18 (%) after 25 cycles 15.15 17.10 17.24 Thermal conductivity λ (W.mkK ¹ ) 0.85 0.42 0.43

Claims (1)

Raw material mixture for the preparation of autoclaved products, comprising sand and lime, characterized in that it consists of 20 to 30 wt. wastes from the production of tobermorite and xonotlite acetylene bottle fillers, the remainder being up to 100 wt. forms sand and lime in a suitable combination.