Materials Science Forum Vol. 1180

Abstract: CO₂ emissions from cement production have significantly increased, leading to the search for alternative materials that optimize the process and reduce environmental impact. In this context, the present study investigates the use of microsilica (MS) and fan shell powder (PCA) as cement replacements. Material characterization tests were conducted, and six mix designs were made, including 5% PCA and 10% MS replacements individually, as well as combinations of 10% MS with 5%, 7.5%, and 10% PCA. Additionally, compression strength properties were analyzed at 3, 7, and 28 days, and flexural strength at 7 and 28 days. The findings regarding mechanical strength were favorable, except for the mix with 10% MS and 10% PCA, which indicates the maximum substitution percentage. Furthermore, a CO₂ emission analysis was conducted according to the Greenhouse Gas Protocol, achieving a reduction of up to 11.16% compared to the control concrete. In conclusion, the study demonstrates that the combination of 10% MS and 5% PCA is the optimal replacement, improving compressive strength by 6.99% and flexural strength by 1.33%, while reducing CO₂ emissions by 10.44%.

Abstract: The greening of cement industry has become a necessity and obligation in many countries and the Global Green Cement market is projected to grow at a Compound Annual Growth Rate of 9.9% in the 2024-2032 period. The race for more sustainable concretes includes a number of key strategies, such as the substitution of cement/clinker with other cementitious materials. In the current research a CEMI (complying with EN197-1:2011) based industrial mix of self-compacting concrete (SCC) is modified with an experimental mix based on CEMII/B-M(P-W-L)42.5N conforming to EN 197-1:2011. The experimental mix presents a dual reduction in CO2 footprint, since not only it is formulated with CEMII, instead of CEMI, but it also contains 320 kg of CEMII/m³ instead of 420 kg of CEMII/m³, by substituting the remaining mass of binder with emery powder. nanoparticles of silicon dioxide (nanosilica) and 12 mm polypropylene fibres were also added. The 7-day compressive strength reached 45 MPa and the 28-day strength reached 51 MPa, marginally lower than that of the industrial mix (60.3 MPa). The performance of nanosilica is discussed. Selected fresh properties in terms of density, slump-flow, air entrainment and strength testing, coupled with surface morphology observations with the use of stereo microscopy shed light into the potentials of such sustainable SCC mixes.

Abstract: This review utilizes bibliometric analysis to examine global research trends and the chronological development of studies on the incorporation of mine wastes and tailings in concrete. A total of 345 publications were extracted from the Web of Science (WOS) database, and their analysis revealed a clear upward trajectory in scientific output since 2000. Respectively, China, India, Canada, and the USA were identified as the countries contributing the most to this research area. Among the 1139 author keywords extracted from the collected papers, 103 keywords with a minimum of three occurrences were analyzed using the VOSviewer software. VOSviewer further supports identifying research gaps and emerging trends by visualizing relationships among authors, publications, and keywords, facilitating a deeper understanding of the dynamics within the field. The analysis of keyword occurrences shows convergence towards research that focuses on the development of sustainable and high-performance materials that equate environmental responsibility with industrial economy demands. The current review also uses Biblioshiny, a web-based tool that explores topic timelines. It reflects that, in recent years, research focuses have shifted toward more sustainability, advanced materials, and performance optimization in the use of mine tailings in concrete.

Abstract: The bulk density of the injection grout is an important factor, as its additional weight could cause damage to hardened decorative plasters. This can be particularly noticeable on larger surfaces. This study used five types of lightweight filler as a density-reducing component in hydrated lime-based grouts. The commonly used limestone filler was completely replaced by an expanded or granulated filler with a loose bulk density of up to 900 kg m⁻³; the rheological properties of the prepared grouts were then studied using a hybrid rheometer. The lime grouts were non-Newtonian, shear-thickening fluids exhibiting rheopectic behaviour (i.e. they stiffened over time). The type of filler dramatically affected the flowability of the grouts. The yield stress and plastic viscosity of the grouts decreased when lightweight fillers were used. As the filler density decreased, the grouts became expectantly less stiff. However, they showed a higher proportion of elastic behaviour than viscous behaviour, indicating that they have a strong microstructure that is resistant to external influences. There was no increase in loss factor values at higher frequencies, indicating that there was no separation of the liquid from the grout structure. From a rheological point of view, expanded glass appeared to be the most effective of the lightweight fillers used.