The life expectancy of a water reservoir will decrease due to sediment accumulation year by year. Because the sediment is fine-grained and exhibits high moisture content, it is difficult to process for further application. Studies about alternative research studies regarding alternate reuse of the sediment have caught more attention. One of the reusing strategies is to produce ceramsite through the ceramic sintering process. This strategy has certain advantages over other reuse methods. Process wise, it can be done while having high moisture content in the sediment, and can use up to 100% of the sediment as a reusable material. As a material ceramsite exhibits engineering properties that are advantageous, such as light weight and porosity. These properties endows the sediment certain potential for application.
This main resource for this study is the ceramsite made from the sediment in the Shi-men Reservoir, which is sintered in a large-scale and industrial rotary kiln. Ceramsite with diameter greater than 10mm are composed of three different density: grade-300, grade-500 and grade-700. Among the three grades, grade-300 reveals to be irregular shaped while the other two are round and smooth. The ceramsite is formed into bricks, by the means of three production techniques, i.e. compression-plus-vibration molding, manual compaction molding (mold removed after 2 hours), manual compaction molding (mold removed after 24 hours). The concrete mixture of the brick is modified based on three factors, i.e. density of the ceramsite, the amount of cement and the am amount of ceramsite sand. With 3 production techniques. Each factor consists of three variables or hierarchies. The tested bricks comprise of 9 mixture ratios which are planned according to experimental design and integrate the three factors. Each type of bricks is composed of 3 specimens. Therefore, the compressive test comprises 81 specimens. The test is carried out based on CNS 1232 in a universal testing system in National Cheng Kung University Compressive tests.
This study are to evaluate the influence of the chosen factors upon the compressive behavior of the lightweight aggregate concrete (LWAC) bricks that the production method immensely affects the formation of the bricks. Bricks molded by using the compression-plus-vibration molding techniques reveals the most variation in terms of size. Subsequently, the production technique and quality affect the compressive strength. The bricks made of manual compaction exhibit approximately 50% higher compressive strength than the specimens from compression-plus-vibration technique. Then, particle’s shape of the ceramsite affects the formation quality of bricks by compression-plus-vibration molding. The irregular shape of grade-300 ceramsite leads to better reliability in terms of formation quality compared to grade 500 and grade 700, whose shape and smooth surface result in worse bonding effect and mechanical properties.
The factors of mixture ratio in this study include ceramsite’s density, the amount of cement and the amount of ceramsite sand. Among them, ceramsite’s density is the most influential for compressive behavior. The higher the density is, the greater compressive strength can be achieved. In such tendency, however, bricks made of grade 500 ceramsite show certain discrepancy. Due to round texture, grade-500 cause the brick to poorly form and inevitably lower capacity in compression. The amount of cement used affects the compressive strength as well. The compressive strength of the brick has positive correlation with the amount of cement. Bricks produced by the three techniques reveal convergent tendency. As the amount of cement increases, the compressive strength and ratio of strength to weight also enhances. However, during mixing the trial batch, the study found that excessive cement slurry results in a viscous mixture. This may arise the difficulty to demold the bricks, cause poor formation and debase the compressive strength of the brick. Regarding the amount of ceramsite sand applied, the specimen does not reveal a significant impact on compressive strength. During the mixing trial batch, however, it should be noted that a certain amount of ceramsite sand is necessary to robustly bond the aggerates.