Investigation Of The Pyroprocessing And The Optimum Mix Ratio Of Rice Husks, Broken Bricks And Spent Bleaching Earth To Make Pozzolanic Cement

ABSTRACT

This thesis reports the results of a study aimed at optimizing pozzolanic activity of a blend of Rice Husks (RH), Spent Bleaching Earth (SBE) and Broken Bricks (BB) to form pozzolana that would have pozzolanic activity comparable to natural pozzolanas. Four ratios of RH, BB, and SBE were burnt in the Fixed Bed Kiln (FBK). The starting ratio had 20 kg of RH, 0 kg of BB and 4 kg of SBE. The amount of BB was increased by 2 kg each to a maximum of 6 kg as the mass of SBE was kept constant. The effect of varying the particle size of BB in the blended mix was also examined in two samples with equal amounts of RH, BB, and SBE. The resultant ashes were subjected to various pozzolanic tests. This included; change in conductivity by use of a saturated solution of calcium hydroxide, the standard pozzolanicity curve (ISO, 1990) and compressive strength using the ASTM C 593. The samples with variable fineness of BB before calcinations had no effect on the pozzolanicity of the whole calcined blended pozzolana. The calcined blend with 10: 1: 2 mix of RH: BB: SBE exhibited the highest pozzolanic activity. This sample was mixed with acetylene lime sludge (ALS) in the ratio of 2:1 pozzolana: ALS. The resultant mixture was then blended with OPC in various ratios at percent weights of 46 %, 48%, 50% and 52% to make Portland pozzolana cements. These cements were tested for their compressive strength tests in accordance to the KS EAS 18 part 1 equivalent to EN 197-1 standard. Up to 50 % replacement of OPC met the standard requirements.