Abstract
Concrete is a building material commonly used for ages. Therefore, in the result of repairs or demolition of building structures, large amounts of concrete rubble are created, which requires appropriate management. The aim of the realized research was to determine the influence of heat and mechanical treatment of concrete rubble on the properties of recycled aggregate concrete. The research experiment included 12 series, with three variables: X1—roasting temperature (300, 600, 900 °C), X2—time of mechanical treatment (5, 10, 15 min), X3—content of coarse recycled aggregates (20, 40, 60% by volume). Two additional series containing recycled aggregate without treatment and natural aggregate were also prepared. Established properties of individual aggregates have confirmed a positive effect of thermo-mechanical treatment. Then, based on the results of compressive strength, flexural strength, Young’s modulus, volumetric density, water absorption, water permeability and capillarity, the most favourable parameters of heat and mechanical treatment of concrete were determined. The test results showed that appropriate treatment of concrete rubble allows to obtain high-quality coarse aggregate and valuable fine fraction. This was also confirmed by the macro- and microscopic observations of the aggregate and separated cement paste. Works realized on the concrete recycling method resulted in obtaining a patent PAT.229887.
Highlights
Concrete is the single most widely used construction material in the world and one of the most environmentally unfriendly
The above results indicate that recycled aggregates roasted at a temperature of 600 ◦ C were characterized by bulk density which was closest to natural aggregate, both in dry and saturated state
It was due because at the temperature of about 600 ◦ C, calcium hydroxide mainly located in the contact zone between the aggregate grain and the cement paste was dehydrated, making it easier to remove the mortar during mechanical treatments
Summary
Concrete is the single most widely used construction material in the world and one of the most environmentally unfriendly. Its manufacture consumes a large amount of non-renewable natural resources (aggregates: 80%), Portland cement (10%), supplementary cementitious materials (3%), and water (7%). Its production is responsible for 5% of anthropogenic worldwide CO2 emissions [1]. Natural aggregates (NAs) used in the manufacture of concrete are inert granular materials such as sand, gravel or crushed stone. Natural gravel and sand are usually dug or dredged from a pit, river, lake or seabed. Crushed aggregate is produced by crushing quarry rock, boulders or large-size gravel
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