Production of Pumice-Based Lightweight Material using Coal Bottom Ashes from Two Industrial Factories in Niğde (Turkey)
Abstract
The production of lightweight material using bottom ash (BA) generated from industrial factories has received further attention because of the economical use of naturally existing raw materials, reuse of waste material, and energy saving approach. In order prevent disposal of waste BAs and turn these wastes into usable construction materials, the study consists of two steps. The pumice-based lightweight materials were produced using the BAs supplied from Bor Sugar Factory and Göknur Foodstuff Co. Nigde Factory sieved through 0.5 mm square mesh sieves in the first and the second steps, respectively. Considering CC-40 and CC-80 concrete classes, mixing that depends on volume basis was applied to the samples since specific bulk densities of the coal BAs and pumices were different from each other. Fine aggregates of the BAs in the volume ranges of 0-25-50-75-100% were displaced with those of the pumice. ÇİMSA CEM I type Portland cement was used. 28 day-axial compressive strengths, specific bulk densities, water absorption percentages, porosities and axial compressive strengths loss percentage after the freezing of the samples that were applied to cure conditions at different mixing ratios were measured from 4.1 to 5.2 MPa for CC-40 and 8.5 to 11.7 MPa for CC-80; from 0.89 to 1.05 g/cm3 for CC-40 and 0.92 to 1.05 g/cm3 for CC-80; from 42.5 to 46.9 for CC-40 and 34.1 to 45.1 for CC-80; from 40.1 to 43.0 for CC40 and 33.2 to 40.7 for CC-80 and from 10 to 25 for CC-40 and 15 to 20 for CC-80, respectively
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Introduction
Recycling and reusing of waste materials has become an increasingly important research area in recent years, and it is widely recognized as an effective method for promoting sustainability [1, 2]. Solid waste management in industrialized countries increasingly aims to reduce the amount of waste requiring landfill, by developing viable reuse applications so that wastes are beneficially used as resources [3-5]. The use of various types of waste materials as additives in the production of lightweight material that is intensively used in building construction due to its low thermal conductivity, shrinkage, density and haulage cost [6] and high heat resistance has received substantial attention during recent years [7].
In recent studies, various types of materials such as coal BA have been investigated as Portland cement replacement materials [8-11]. Their substitution in Portland cement has been an interesting subject for research due to environmental and technical reasons. Clearly, different substitution materials will have different effects on the properties of the cement due to their chemical, physical and mineralogical characteristics [12, 13]. Physical properties of lightweight aggregate concrete produced from lightweight aggregate materials such as tuff, pumice and expanded perlite have also been studied [6, 14-17].
It has been well established that the utilization potential of BA from the burning process is mainly determined by its physical characteristic such as grain size distribution, staining potential, and color [9, 18]. The most important properties of BA are the size and shape of the particles and the porosity. Such properties depend on the burning efficiency, the method in which the BA is obtained and the type of combustion [19]. It is necessary to pay due attention mainly to the dosage parameters, for example, to the water/cement ratio [20]. This parameter is directly influenced by the hygroscopic characteristic of the BA and is difficult to control, since it is dependent on the raw material and the burning process, on the dimension of the particles and on the residue being extracted through a process involving a humid system. BA is often used as a low-cost replacement for more expensive sand for concrete production and as a fine aggregate in high-performance lightweight concrete [21] due to its porous structure and particle size distribution is closed to natural sand size.
Conclusion
In this study, fine aggregates of the BAs that are nondeposit waste in the volume ranges of 0-25-50-75-100% were displaced with those of the pumice used in construction technology very effectively. Following results were obtained from the study:
1. Durable building material was obtained from the study in which the BAs (BA1 and BA2) sieved with 0.5 mm sieves, the pumice in 0-8 mm grain size and the CEM I 42.5 R Portland cement was used in different mixing ratios.
2. In the visual inspection, any deformation or cracks wasn’t encountered in the obtained products.
3. Maximum axial compressive strength value was obtained in the samples produced of 100% ratio of pumice. 28 days’ axial compressive strength values reached the targeted values for the mixtures of CC-40 and CC-80. At the same time, all BA1 to BA2 additived products reached the targeted axial compressive strength values.
4. Different fine BA amounts that were added for pumice based samples led to losses in axial compressive strength. These losses reached to maximum value in 100% ratio of BA fine material. They were obtained as 21.1 and 27.3% in BA1 additived CC-40 and CC-80, respectively. On the other hand, they were also obtained as 13.5 and 28.2 in BA2 additived CC-40 and CC-80, respectively. This situation led to the conclusion that the BAs were effective on the compressive strength values.
5. Maximum bulk density values were measured in the samples that were produced from 100 % pumice in all mixtures. Bulk density value decreases resulted from different ratios of fine BAs. These decreases were obtained as minimum, 7 and 5% in the samples of 100% ratio of BA, BA1 additived CC-40 and CC-80, respectively. On the other hand, they were also obtained as 12.3 and 7% in BA2 additived CC-40 and CC-80, respectively.
6. The measurements of water absorption percentage and porosity values were similar to each other. This is an expected result.
7. After freezing test, 20% of axial compressive strength loss was obtained on average. However, any deformation due to frost effects was not observed in naked eye.
Consequently, in case of evaluating BAs in the world and in Turkey, it was possible not only to produce energy saving building envelop material and cheaper, high quality and durable lightweight construction materials but also to support national economy by reusing of waste material and to protect the environment.