본 연구는 정수슬러지를 친환경적인 자원으로 재활용하기 위한 방안으로서 유해성이 없는 점토벽돌 및 보도블록 등으로 재활용하기 위하여 진행되었다. 정수슬러지를 점토벽돌 원료로 대체할 수 있는지에 대한 연구를 수행함에 있어 각각의 원료의 성상을 분석하고 일축압축강도, 흡수율, 중량 및 용출특성을 비교 검토하였다. 그 결과 규사를 20% 고정시킨 후 정수슬러지 5~10%, 점토 70~75% 주입하였을 때 점토벽돌 한국산업규격 품질 1종(압축강도 210.1 $kg_f/cm^2$, 흡수율 10% 이하)에 가장 적합한 결과를 보였으며, 중금속 용출 실험에서도 모든 항목의 농도가 법적 유해물질 용출기준치 이하로 나타났다. 정수슬러지를 이용하여 점토벽돌 제작시 슬러지 5~10%를 주입하여도 시중에서 판매되는 점토벽돌의 품질에 떨어지지 않는다고 사료된다.
This study was conducted to search possibilities of the use of sludge from waterworks industry in the manufacturing of red clay bricks. Different compositions of the sludge were added into the raw materials of the bricks and required engineering characteristics of the manufactured bricks were examined. Compressive strength, plasticity, and surface absorption of the recycled bricks were analyzed and were compared with the bricks quality standard rules and regulation for quality assurance of the product. Compressive strength of the bricks made in a ratio 75% clay, 5% sludge and 20% silica was found 261.3 $kg_f/cm^3$ and that was comparable with first grade bricks standard. Compressive strength of the bricks made in a ratio 70% clay, 10% sludge, and 20% silica was found 249.9 $kg_f/cm^3$ while it was decreased to 217.3 $kg_f/cm^3$ when bricks were made in a ratio 65% clay, 15% sludge and 20% silica. However, these values of compressive strength were in agreement with the bricks quality standard. Surface absorption of the bricks made by the mixing of 20% silica with varying amount of sludge, i.e., 5%, 10%, and 20% was found 10%, 9.65% and 10.92% respectively. These values satisfied the quality standard of bricks of grade 1 and 2. Recycling of proper amount of sludge in bricks making could produce bricks of high engineering characteristics.
