Utilization of Industrial Waste Casting Sands as Sustainable Building Material in Autoclaved Aerated Concrete Products

Autoclaved aerated concrete (AAC) is a building material with low density compared to traditional and structurally lightweight concrete. In addition to being very light, it is frequently preferred in many different areas, especially in external walls, floor slabs, lintels, roof slabs and panel elements of buildings, since it offers good heat and sound insulation. When the AAC production process is evaluated in terms of energy requirement, it has high environmental sensitivity compared to traditional concrete and brick processes. Since environmental sensitivity has become more important today, it was desired to evaluate the waste casting sands (WCS) generated in metal casting companies within the scope of the study. In this study, the usability of WCS as an alternative instead of silica sand used in AAC production was investigated. For this purpose, WCS was provided by 3 different casting companies. The usability potential of WCSs at 30% was examined and the quality of AAC was compared with reference castings. The fineness potentials of WCSs were compared by grinding in a disc mill. First of all, X-ray fluorescence spectrometry (XRF) and grain size analyses were performed on WCSs. 150x150x150 mm3 sized AAC laboratory samples were produced. The produced AAC samples were kept in the oven at 60°C until they set and then cured in an autoclave for approximately 10 hours. After the curing process in the autoclave, analyses such as compressive strength analyses and dry unit weight measurements were performed on the samples, and in addition to these analyses, they were subjected to visual examinations. Mechanical analyses were performed by replacing the WCS, from which positive results were obtained, at 5 different substitution ratios of 5, 10, 15, 20, and 30% by weight. From scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses, it was determined that tobermorite structures were formed. From thermal analyses, it was observed that the thermal stability of the samples produced with WCS was better. When the results were evaluated in general, it was found that up to 30% WCS could be included in the AAC production system. In addition, an increase in compressive strength values occurred. The improvement in compressive strength also showed that WCS could be a good alternative source to silica sand.