Abstract
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.
Highlights
The rapid growth in population has given rise to problems in terms of urban planning
When the effective w/c ratio is kept within standard limits, concretes containing treated Recycled Brick Aggregate (RBA) are possible to be specified for various exposure classes and manufacturing in practice
The experiment is based on the hypothesis, that lower absorption of the RBA and, the higher effective w/c ratio should result in worse properties of hardened concrete, in accordance with general knowledge about negative influence of high amount of water on the properties of hardened cement stone
Summary
The rapid growth in population has given rise to problems in terms of urban planning. Due to modern requirements for living quarters and the developed construction industries, old buildings are being demolished and replaced with new and modern ones [1]. Depending on the recycled aggregate’s (RA) physical properties, it can be used in a variety of construction applications, reducing the environmental impact of the new construction [2,3]. The advantage of this method is that a significant amount of natural resources can be saved if the demolished materials of old buildings are recycled for use in new constructions [4]
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