Particles size and distribution on the improvement of the mechanical performance of high strength solid solution based inorganic polymer composites: A microstructural approach

This research reports on the influence of particle size and distribution on the physical, mechanical and microstructural features of solid solutions (feldspathic materials) based inorganic polymer composites (IPCs). Both granite and pegmatite were ground to different degree of finess making four different granulometry with particles of 63, 80, 125 and 200 μm. The respective mixes receive 15 wt% of metakaolin and were activated with a well designed alkaline solution. Matrices obtained showed high compressive and flexural strengths in the range 101.2–131.3 MPa, and 29–35.5 MPa, respectively. It was observed that the optimum mechanical performance of these matrices can be achieved through a mix-design of different grades of granulometry. This was suggested by mechanism combining reactivity and particles packing. In fact, although it can be expected that the finess of the combination of the particles size under 63 μm might present the better reactivity, it is showing that the combination of fine, medium and coarse particles is efficient in achieving denser and tougher microstructure. Lower cumulative pore volume (17 mL g−1) of the composites based on pegmatite, value not far from that of natural stones, resulted in a higher impact resistance of 3.03 J. It was concluded that designing the feldspathic rock-based composites with high strengths appear as sustainable, low energy consumption and environmentally-friendly materials for the structural construction

Reaction kinetics and microstructural characteristics of iron-rich-laterite-based phosphate binder

Due to their intriguing properties, phosphate cement, also known as chemically bonded phosphate cement, have been developed for the past decade. The need for sustainable building material with low cost and easy availability has prompted research into the use of laterites, which are abundant in Cameroon. The purpose of this research was to synthesize laterite-based phosphate cement (LPCs) with phosphoric acid as the sole activator. The parameters taken into consideration were the molar concentration of phosphoric acid, liquid to solid ratio and the type of solid precursors. Early reactivity of the LPCs was assessed using a semi-adiabatic calorimeter and the results showed an increase in the heat of reaction proportionally to the concentration of phosphoric acid, except for 10 M solutions where early reactivity was inhibited. The results of the 14-day compressive strengths of the studied LPCs were in the range of 23–98 MPa for LPE and 31–105 MPa for LPN, respectively depending on the specific formulation. For both laterite phosphate cement, molar concentrations of 6 and 8 M resulted in the optimum strength. The phase composition was determined using X-ray powder diffraction, and the amorphous and crystalline phases of the raw materials and phosphate cement were quantified using Rietveld measurement. The X-ray pattern of the laterite-phosphate cement revealed that the intensity peak of hematite decreases in the presence of phosphoric acid and led to the formation of an amorphous product, which is supported by phase analysis quantification using Rietveld refinement. The micrographs of LPCs revealed a dense matrix