Petrographic, Mineralogical and Geo-mechanical Characteristics of Marble from Mohmand District, Pakistan: Implications for its Use in Construction Industry

Abstract

This study aims to evaluate the suitability of marble deposits from Mohmand district for use in the
construction industry. By employing an integrated approach that combines petrographic analysis, chemical
assessments, and physico-mechanical testing, the study seeks to provide a comprehensive understanding of the
marble's properties. Although, megascopically indistinguishable, the petrographic analysis identifies two
varieties of carbonate rocks: Calcitic-marble and dolomitic-marble. The marble from the Sapari quarry is
petrographically fine to medium grained and dominantly composed of subhedral to anhedral calcite (84-86%),
dolomite (8-10%), quartz (6-8%) and trace amount of micrite and hence classified as calcitic-marble. Owing to
less contents of dolomite and unstrained quartz, the calcitic-marble reveals very low reactive quartz and
magnesium in the rock, hence no expansion if used in concrete with ordinary Portland cement (OPC). The
petrographic and chemical investigations, therefore, endorse their innocuous non-reactive character for both
alkali silica reactivity (ASR) and alkali carbonate reactivity (ACR). In contrast, the marble from Qaroon
Ghundai quarry is mineralogically dolomitic and texturally fine grained, where subhedral to anhedral dolomite
constitutes the major phase (97˗98 %), while quartz and micrite occur as the minor phases. The results of the
cube test of the dolomitic-marble demonstrate an expansion by 0.28 % which lies above threshold limit of
0.10% thus endorse the potential to initiate ACR. Hence, this marble is declared deleterious with respect to
ACR. With the exception of soundness value, the dolomitic-marble produces relatively higher values for UCS,
specific gravity, bulk density, LA and Schmidt hammer as compared to the calcitic-marble. The comparative
analysis shows that the calcitic-marble is suitable for high alkali cement-concrete and asphalt-works as a coarse
aggregate. Alternatively, the dolomitic-marble is only declared suitable for asphalt-based concrete due to its
ACR potential, which endorses the significance of mineralogy and textures in controlling the physical and
mechanical properties of rocks.