Abstract:
Owing to the depletion rates of coastal limestone, the characterization of cementitious
materials occurring on the dry land is important in order to assess their potential as alternative materials for the manufacture of cement. In this study, a naturally occurring
terrestrial rock herein referred to as “Matisaa gray rock” has been studied to determine
its potential for the manufacture of cement. Matisaa gray rock is found in Matisaa village, Kitui County, Kenya, and it covers an approximate area of 7 acres.
These cementitious properties were studied using X-ray fluorescence, X-ray diffraction, vibrational spectroscopy, scanning electron microscopy, micro-sieve, and Blaine
techniques. Matisaa gray rock was found to contain all the oxides of cement in the following percentage abundances: 39.03 – 42.73 wt.% for CaO, 15.68 – 16.79 wt.% for
SiO2, 0.47 – 4.81 wt.% for Al2O3, 0.55 – 1.04 wt.% for Fe2O3, 1.56 – 3.56 wt.% for
MgO, 3.30 – 6.06 wt.% for SO3, 0.11 – 0.21 wt.% for Na2O, and 0.59 – 2.64 wt.% for
K2O. Except for SO3, the proportions of the remaining oxides were found to be within
the recommended thresholds.
The minerals that dominate Matisaa gray rock are dolomite (CaMg[CO3]2) and kutnohorite (Ca[Mn2+, Mg, Fe2+][CO3]2) with trace mineral phases of quartz (SiO2) and
periclase (MgO). The morphology of Matisaa gray rock powder comprises of irregularly shaped particles that are compact with rough superficial texture. 69.65% of the
particle size composition of Matisaa gray rock was found to be <90 µm. Out of this
composition, 71.60% of the particle sizes were <45 µm, contributing to a specific surface area of 292.5 m2
/kg. The high proportion of CaO and SiO2 indicates that Matisaa
gray rock is a silicious limestone. Its general comparison with cement properties of
established raw materials of cement like Konza kunkur suggests that Matisaa gray rock
has potential for utilization in the manufacture of cement.
