Marbles and meta-schists from Bidzar (North Region of Cameroon) : characteristics and the use of meta-schists as additives in experimenting blended cements production

Abstract

Abstract This work presents the petrography and major element composition of marbles and meta-schists found in the Bidzar CIMENCAM marble quarry (North Region, Cameroon). Some of the studied rocks were selected and combined with other characterized raw materials to process schist-blended cements. Marbles are pure (white) or impure (pink, light to dark-grey, or dull yellow…) calcitic, dolomitic, or transitional type, and composed of CaO (32 -57 wt.%), MgO (0.49-24 wt.%), and SiO2 (0.09-8.4 wt.%). Meta-schists are bluish-green chlorite meta-schist, chlorite-bearing dark-grey meta-schist, and yellowish-green sericite meta-schist with SiO2 (26-47.3 wt.%), Al2O3 (11-16 wt.%), Fe2O3 (8-15 wt.%), CaO (3-26 wt.%), and MgO (4-15 wt.%). The used cement raw materials include: clinker, gypsum, marble additive, low CaO bluish-green chlorite meta-schist and low CaO chlorite-bearing dark-grey meta-schist. The two groups of manufactured blended cements mainly composed of CaO (64.2-64.6 wt.%), SiO2 (18.0-18.5 wt.%), are within the range in ASTM standard, and of some reference cements. The LSF (1.11-1.15), HM (2.6-2.8), SAR (4.6-5.1), SR (2.8-3.1), and AR (1.5-1.7), are within the range of some reference OPC. The proportion of free lime (0.92-1.25 %) is within the range 0.8-2.25 % for reference cement Multi X (CEMIX32.5R). The proportion of SO3 (1.6-2.3 %,), LOI (8.9-13.8 %), and IR (1.3-10.6 %), are partly close to those of reference cement and other OPC. The BSSA (4794 to 5794 cm2/g) and proportion of retained sieved fractions (4.13 to 11.1 %) place the processed cements within high fineness type. The setting time (130-245 min) seem to satify cement standards. The compressive strength tests show a decrease in strength with the increase in proportion of meta-schist; which could be due to the mineralogical composition of the used cements and their high IR.