Investigate the use of sintered water treatment sludge as an internal curing fine aggregate for internal curing concrete

Abstract

The thesis reports the investigation carried out in developing an internal curing fine aggregate using water treatment sludge, and studying the changes of concrete properties in using developed fine aggregates in internal curing concrete. The water treatment sludge is converted to burnt clay chips through the process of clay mixing, sintering and crushing. Initially, Thermogravimetric analysis was carried out to identify the thermal behavior of sludge. Also, an X-ray fluorescence test was conducted to identify the chemical composition of the sludge. The firing temperature was made to range from 8000C to 13000C at 1000C intervals. Water absorption, Water desorption, and Relative density tests were conducted on the developed fine aggregates which were heated to different temperatures to observe the physical properties and requirements in order to satisfy the internal curing property. Furthermore, Scanning Electron Micrographs (SEM) analysis was followed to observe the microstructure of the fine aggregates. To carry out the above experiments, the temperature range which had to be maintained in the sintering process was between 9750C and 12000C. The water absorption of the developed ICFA ranged from 15%-25% for the optimum temperature range, while water desorption rate was recorded to be 90%-95% under the 94% relative humidity at 250C room temperature. The relative density of the selected ICFA was recorded to range between 1.7 and 2.0, while the bloating coefficient ranged between 0.8-0.9 for the optimum heating temperature. The latter part of the research was focused on studying the improved properties of ICC using developed ICFA. The mix design was done for grade 30 concrete by referring to BS8110-1983 and ASTM-C1761M codes. Workability, compressive strength and drying shrinkage was compared with normal concrete. Workability and the compressive strength of ICC displayed higher values than that of ECC. Moreover, a significant value deviation was observed in the drying shrinkage of ICC: a 50% reduction in 28 days. Initial studies on water treatment sludge and improved properties of developed ICC confirmed that the sludge can be used to develop an ICFA and that it can be utilized in the construction industry.