Pyroprocessing and the optimum mix ratio of rice husks, broken bricks and spent bleaching earth to make pozzolanic cement

Protus Nalobile; Jackson Muthengia Wachira; Joseph Karanja Thiong'o; Joseph Mwiti Marangu

doi:10.1016/j.heliyon.2019.e02443

Pyroprocessing and the optimum mix ratio of rice husks, broken bricks and spent bleaching earth to make pozzolanic cement

Heliyon. 2019 Sep 9;5(9):e02443. doi: 10.1016/j.heliyon.2019.e02443. eCollection 2019 Sep.

Authors

Protus Nalobile¹, Jackson Muthengia Wachira², Joseph Karanja Thiong'o¹, Joseph Mwiti Marangu³

Affiliations

¹ Department of Chemistry, Kenyatta University, Nairobi, Kenya.
² Department of Physical Sciences, University of Embu, Embu, Kenya.
³ Department of Physical Sciences, Meru University of Science & Technology, Meru, Kenya.

Abstract

This paper presents the findings of an experimental investigation on 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 resultant ashes were subjected to various pozzolanic tests. This included; saturated lime test and compressive strength analysis. It was observed that 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 compressive strengths for these cements were tested at 2 and 28 days of curing. The compressive strengths of this cement met the required EN standards for Portland pozzolana cement.

Keywords: Blended cement; Broken bricks; Calcium carbide residue; Civil engineering; Materials science; Pozzolana; Pyroprocessing; Rice husks; Spent bleaching earth.