Cement kiln dust in CIMENCAM Figuil (North Cameroon): characteristics and recycling as additives for blended cement production

Abstract

This work presents the manufacture of CKD-blended cement from raw materials such as clinker, gypsum, marble and cement kiln dust (CKD) obtained from CIMENCAM Figuil, North Region of Cameroon. The raw materials were first characterized through XRF chemical analyses. Chemical tests (proportion of free lime, loss on ignition, sulfate, and insoluble residues), physical tests (fineness, consistency, setting time, and expansion), and compressive strength tests were carried out on manufactured CKD-blended cements and mortars. Clinker is composed of CaO (65.30%) and SiO2 (21.13%), with significant MgO (2.71%), Na2O + K2O (1.29%), SO3 (0.81%) and lime saturation factor of (97.9); which make this clinker good for cement production. Gypsum is composed of SO3 (36.32%) and CaO (33.92%) but contains very low proportion of impurities; it is therefore classified as low-impurities gypsum suitable for cement productions. The marble is dominantly composed of CaO (37.09%) with significant SiO2 (7.26%), SO3(2.40%), (2.36%), Fe2O3 (1.82%) and MgO (0.18%); it is classified as low-CaO calcitic-aluminosilicate and ferrosilicate bearing marble. The CKD is dominantly made up of CaO (46.0%) and SiO2 (11.62%) with significantly low Na2O + K2O (1.02%), and SO3(2.16%); this classifies it as low alkalies-sulfate cement kiln dust. The proportion of free lime, SO3, loss on ignition, and insoluble residues in the manufactured CKD-blended cements increase with an increase in the proportion of CKD. The blaine specific surface area (BSSA) (4797–6346 cm2/g) and the sieved residues (26.14–30.36%) show an increase with the proportion of used CKD. The compressive strength tests carried out on the prepared brick-shape hardened CKD-cement mortars (at 2, 7, and 28 days) show that, the resistance depends on the proportion of the used CKD (0% control, 5%, 10%, 15%, 20%… up to 50%). Pressures of 17.5 to 11.6 MPa was obtained in 2 days, 28.9 to 20.0 MPa in 7 days, and 35.5–23.3 MPa in 28 days.