Spent Bleaching Earth as a Pozzolanic Material

This paper proposes a cementing material from spent bleaching earth (SBE). SBE consists mainly of residual oil and bleaching clay. The SBE reported in this case is the waste material from vegetable oil processing industries. One of the SBE samples tested had a calorific value of 15.8 J/g. The ash content was 52.3 to 58.6 %. When calcined at 550 C for four hours, the resulting ash met the Kenya Standard 02 1263 chemical composition requirements for pozzolanas. When calcined in small quantities in a muffle furnace and tested with commercial hydrated lime (CHL), the material met the ASTM 593 part C requirements for use of pozzolana with lime. The pozzolanic activity of the ashed SBE vis a vis commercial volcanic tuff was investigated. A 1: 2 ratio of the lime to the ash gave the highest compressive strength. At the 28th day of curing, the compressive strength was 10.9 Mpa while that of the volcanic tuff-lime was 8.99 Mpa. The setting time of a workable paste of the ashed SBE-lime material was well within the Kenya standard 02 1263 requirements for Portland pozzolana cements. Key words: Cement, pozzolana, Spent bleaching earth, volcanic tuff, hydrated lime, compressive strengths, setting time