calcium carbonate (Cimascal / Cimascal D Forte)

Physico-mechanical and chemical performance of Portland cement modified with eggshell powder for sustainable construction.

Sanusi Abdulganiyu A, Ndububa Emmanuel Eberechukwu EE, Adeleke Adekunle Akanni AA, Obianyo Ifeyinwa Ijeoma II et al.

Cement is one of the most used materials in the construction industry. Its production contributes about 8% to the global emissions. This study explores the use of eggshell powder (ESP) that contains over 80% calcium carbonate (CaCO3) as a partial substitute for ordinary Portland cement (OPC), such as Types B and D, to substitute limestone within the cement matrix. The physical (consistency and setting time), compressive strength, and chemical (Scanning Electron Microscope with Energy Dispersive Spectroscopy, (SEM-EDS), and X-ray Diffraction (XRD), X-ray fluorescence (XRF)) properties were evaluated against British, Indian, and established standards in the literature. The results showed that cement consistency (31-35%) and setting times were within acceptable limits according to BS EN 197-1 (initial ≥ 60 min) and IS 8112 (initial ≥ 30 min, final ≤ 600 min). The mechanical strength of the samples exceeded the required strength (42.5 N/mm2) recommended by the British Standards, except for samples B10N and D10N, which showed strength reductions of 8.4% and 12.3%, respectively. The SEM-EDS and XRD analyses confirmed a high CaCO3 content in the samples. The study suggests that incorporating ESP into OPC should not exceed 5% by weight, as higher proportions could negatively impact the cement's physical and strength properties. This approach will promote environmental sustainability by using agro-waste while ensuring the cement remains suitable for construction.

The rheological behavior, particle properties and supramolecular structure of low acyl gellan gum fluid gels: impact of the calcium concentration before fluid gel formation.

D'Oria Gabriele G, Zhu Yanshen Y, Limbach Hans Joerg HJ, Hartmann Christoph C et al.

Fluid gels are jammed microgel suspensions obtained by shearing a gelling hydrocolloid during its sol-gel transition. This study focused on calcium-induced low acyl gellan gum (LAGG) fluid gels and investigated the impact of calcium concentration before fluid gel formation on the resulting rheological behavior, fluid gel particle properties, and supramolecular structure. The elasticity and yield stress of fluid gels and quiescently cooled gels reached a maximum when the calcium concentration was increased from 0.78 to (approx.) 30 mmol/kg. Small angle X-ray scattering (SAXS) of fluid gels revealed a progressive increase in gel network connectivity up to the calcium concentration where the peak in rheological properties was observed followed by a less interconnected network at calcium concentrations above the peak. Furthermore, rheological measurements supplemented with free calcium and zeta-potential measurements, support that the decrease after the peak in rheological response is due to the combination of fluid gel particle softening with a decrease in surface charge. The results of this study enable to establish clearer links between rheological behavior, particle properties and supramolecular structure of calcium-induced LAGG fluid gels. This work enables a more effective design of fluid gel properties for different applications from food to pharma and biomaterials.

Highly Porous Carbonate Apatite Scaffolds Fabricated via Freeze-Drying for Accelerated Bone Replacement.

Taleb Alashkar Ahmad Nazir AN, Hayashi Koichiro K, Ishikawa Kunio K

Bone scaffolds should ideally possess good osteoconductivity and biodegradability, form abundant bone at an early stage, maintain the regenerated bone tissue, and be completely replaced by newly formed bone. Therefore, highly porous scaffolds composed of resorbable bioactive ceramics are promising candidates for bone repair. However, the methods for fabricating such scaffolds remain underdeveloped, and the in vivo efficacies of the generated structures have not been sufficiently evaluated. Therefore, the aims of this study were to develop a novel method for fabricating a highly porous carbonate apatite (CA) scaffold via a freeze-drying technique and to evaluate its structural, chemical, mechanical, and in vivo performance using a rabbit model of femoral condyle defect. The CA scaffold structure consisted of three-dimensionally interconnected pores, exhibiting high porosity (91.7%). Despite its high porosity, the scaffold did not collapse during implantation into the bone defect and was easy to handle. When implanted into critically sized bone defects, the CA scaffolds formed three times more new bone than that formed by clinically used CA granules after 4 weeks, with the bone area percentages in the CA scaffold, CA granule, and sham groups being 51.7% ± 8.1%, 14.0% ± 4.9%, and 1.2% ± 0.4%, respectively. After 12 weeks, the CA scaffolds maintained approximately three times the bone area of that formed by the CA granules and were almost completely replaced by newly formed bone. These findings indicate that the highly interconnected porous CA scaffold can achieve rapid bone regeneration and dynamically adjust its structure to accommodate newly formed bone, making it a promising candidate for bone regeneration applications.

Reinventing the coronary calcium scan.

Arbab-Zadeh Armin A