Evaluation of the Influence of Specific Surface Treatments of RBA on a Set of Properties of Concrete

High water absorption of recycled brick aggregate (RBA) is one of the most discussed parameters in terms of its application in the production of concrete—its influence on the amount of mixing water and, hence, the quality of the concrete, is usually considered negative. In this paper, different methods of decreasing the absorption of RBA and, consequently, the impact on the properties of concrete, are described. The RBA has been treated to decrease the water absorption capacity by impregnation approach using specific impregnators. Afterwards, the RBA samples have been dried at two different temperatures in the laboratory oven—20 and 90 °C. Concretes using 4/8 fraction of the treated RBA instead of natural aggregate (NA) have been mixed and tested. The effectiveness of the RBA treatments have been evaluated on the basis of their influence on the properties of the hardened concrete; by means of the following tests: flexural strength, compressive strength, capillarity, total water absorption capacity, depth of water penetration under pressure, and frost resistance. The method of ranking by ordinal scale has been used as it is suitable for the comparison of a large set of results, while results have been analyzed in terms of the most important technological parameter that influences the quality of the concrete-effective water content. Out of all the tested surface-treatments of RBA, treatment by sodium water glass has the best potential for reduction of the water/cement (w/c) ratio. When the effective w/c ratio is kept within standard limits, concretes containing treated RBA are possible to be specified for various exposure classes and manufacturing in practice. The experiment confirms that at a constant amount of mixing water, with decreasing water absorption of RBA, the effective amount of water in the concrete increases and, hence, the final properties of the concrete decrease (get worse). As the water absorption of the RBA declines, there is a potential for the reduction of the w/c ratio and improvement in the quality of the concrete

Concrete samples prepared with different types of wastes

This paper is focused on utilization of coal fly ash, steelmaking slag and glass bottle fragment in concrete production. Each of these wastes was mixed into concrete, and compressive strength was tested.The first part of this paper is focused on Portland cement replacement by mechanochemical activated coal fly ash and the second part is aimed to natural aggregate replacement by steelmaking slag and glass bottle fragment in concrete mixture. The results showed that coal fly ash has a positive influence on compressive strength development, and steelmaking slag and glass waste can be successfully used as a natural aggregate replacement

The study of concrete properties prepared with a proportion of fly ash

The current annual worldwide production of by-products is estimated about 700 million tons of which 70 % is fly ash at least. Large quantities of fly ash are available at low costs around the world and its use in concrete seems to offer the best solution to reduce its consumption. With regard to these facts and Slovak needs, the chemical and mechanical properties of hardened concrete composites with various share of fly ash were studied. Other focus of this study is the investigation of the influence of different chemical admixtures on development of the concrete properties, their environmental and economic impacts

Examination of Bearing Walls Regarding Their Environmental Performance

A comprehensive understanding of the environmental impacts of buildings is not possible without knowledge of the technical and environmental properties of the materials that are used for their construction. This paper evaluates the environmental impacts of 156 material variations of conventional compositions of external bearing walls, which represent a significant part of a building’s envelope. Environmental (embodied energy, global warming potential, effects to human health, damage to ecosystems, and resources availability) and technical (surface temperature, number of layers, thickness, and weight) parameters are investigated for structures with similar heat transfer coefficients (U = 0.21–0.22 W/(m2·K)). Based on a multi-criteria analysis, an optimal material composition, consisting of aerated concrete with graphite polystyrene, was identified. By analyzing the costs of the best material compositions, it is observed that constructions with environmental benefits do not result in an increase in the cost of the construction. On the contrary, at present, they represent an approximately 10% cheaper solution