Abstract
The main aim of this study was to investigate the suitability of using demolished construction waste (crushed concrete, ceramic tiles and cement blocks) as raw materials in the production of concrete and mortar. Initially, the physical properties of the aggregates made of demolished and crushed concrete, cement blocks and ceramic tiles were tested and the results obtained were compared with the properties of natural aggregates. Secondly, their optimum mix proportions were obtained by conducting a series of tests on the concrete and mortar samples that were produced by partially replacing the natural aggregates in them with demolished aggregates in the proportions of 30%, 60% and 100% and the results obtained were compared with the results of similar tests carried out on control samples made using only natural aggregates. The results revealed that the physical properties of processed demolished construction materials are almost similar to those of natural aggregates and that the results correlated well with the previous research findings. The results related to the engineering properties indicated that demolished concrete aggregates and crushed coarse tile aggregates can replace natural aggregates up to 30% and 60% respectively in the production of Grade 25 concrete. Furthermore, the study revealed that demolished concrete and demolished blocks in the form of fine aggregates can replace sand up to 30 % in proportion in the production of mortar. The direct cost analysis revealed that the use of demolished construction waste material to replace natural aggregates in the production of both concrete and mortar will be profitable only marginally.
Highlights
The global demand for construction aggregates exceeds 26.8 billion tons per year [2]
The results have shown that when making mortar with the recycled fine aggregates, the particle size has to be kept below 0.6 mm if they are to have an influence on the properties of the mortar
Increased amounts of Demolished Concrete Fine Aggregate (DCFA) tend to reduce the compressive strength of mortar, whilst the compressive strength of Demolished Block Fine Aggregate (DBFA) based mortar shows an increase up to 30% replacement and a slight decrease at 100% replacement
Summary
The global demand for construction aggregates exceeds 26.8 billion tons per year [2]. In Sri Lanka, there has been a significant increase recently in the use of natural aggregates because of the increased number of infrastructure development projects that are being undertaken. The annual amount of construction and demolished waste produced in Sri Lanka is about 4.0 million tons and the management of that waste has already become an environmental problem [22]. The heaviest materials found among construction and demolished waste in Sri Lanka are concrete, blocks (cement and brick), mortar and tile residues of which concrete represents about half of the total waste weight. The use of mineral aggregates such as broken natural rocks (coarse aggregates) for concrete and river sand (fine aggregate) for both concrete and mortar poses a severe threat to the environment
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