Mechanical and microstructural properties of Cameroonian CPJ NC CEM II/B-P 42.5R cement substitution by glass powder in the cement paste and mortar

Abstract

The present study deals with the mechanical and microstructural properties of CPJ NC CEM II/B-P 42.5R cement mortar with glass powder (ϕ < 80 µm) substitution. Three types of glass powders were used as cement additive from 0 to 25 wt% with 5 wt% interval. These were white glass powder (WGP), green glass powder (GGP), brown glass powder (BGP) and their mixture (MGP). The physical properties of the cement paste show an increase in setting time from 240 min for OPC to 290 min for 25 wt% addition of all glass powder types. The compressive strength of the cement mortar after 28 days increased from 21.5 MPa for the OPC to 23.5 MPa, 26.2 MPa, 24.4 MPa and 24.0 MPa for 10 wt% addition of WGP, GGP, BGP and MGP, respectively. By cons, the compressive strength decreased from these values to 21.3 MPa for 25 wt% addition of WGP, GGP on the one hand and 21.5 MPa for 25 wt% addition of BGP, MGP on the other hand. Up to 20 wt% addition, compressive strength of cement mortar containing glass powder was greater than ordinary Portland cement (OPC) mortar. Further analysis was performed on the cement paste from 0 to 15 wt% glass powder addition. The infrared spectroscopy (FTIR) was used to analyse the surface functional groups of different samples. The X-ray diffractometry analysis revealed the presence of gypsum, portlandite, calcium carbonate, ettringite, C–S–H, di-calcium aluminate, tetra-calcium alumina ferrite minerals and sodium carbonate resulting from the glass powder addition on all samples. The intensity of portlandite was reduced by the addition of glass powder, suggesting its consumption due to pozzolanic reaction. Scanning electron microscopy images exhibited the excess of micropores when glass powder contents increased, explaining a decrease in compressive strength of mortars from 10 to 25 wt% addition of glass powder. From these results, regardless of the colour of glass, the optimum percentage substitution of CPJ NC CEM II/B-P 42.5R cement by glass powder in a mortar, considering mechanical properties, is 10 wt%.