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 (CEMIX32.5 R). 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 are 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.