This paper studied the effect of fly ash (FA) and natural pozzolana (NP) as partial cement substitutes on sustainable concrete permeability and mechanical and microstructural properties. Batches with 10, 20, 30, 40, and 50% FA and NP replacements for cement were prepared and tested for compressive strength after 7, 28, and 56 curing days and for flexural strength after 28 curing days. Permeability testing was conducted on all samples. A qualitative microstructural analysis was performed using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). The mechanical properties results showed slight strength improvements when replacing the cement with low percentages of the pozzolanic materials. The compressive strengths of the batches with 10% FA and NP replacements of cement showed compressive strength increases of 11.63 and 8.75%, respectively, compared to that of plain concrete. On the other hand, the flexural strength for the batches with FA replacement of cement achieved at least a 15.6% increase compared to that of the control. Moreover, FA and NP replacement of cement had a positive impact on batch permeability, with decreased permeability values reaching 78.3 and 56.5%, respectively, compared to that of the control. Furthermore, the microstructural analysis indicated that adding FA and NP would enhance cement hydration by the formation of dense hydration products such as calcium–silicate–hydrate (C-S-H) crystals, which increased hardened concrete strength. Finally, the cost analysis showed that the batch with a 10% FA replacement of cement is the ideal one in this study.

This study underscores the potential of utilizing natural volcanic tuffs (NVTs) as supplementary cementitious materials (SCMs) in alignment with global sustainability efforts aimed at mitigating the cement industry’s negative impacts on both the economy and the environment. Experimental investigations were conducted on concrete mixtures containing 10%, 20%, 30%, 40%, and 50% NVT as partial cement replacements to assess their influence on concrete’s mechanical and microstructural properties. Based on the findings, concrete samples with 10% NVT replacements exhibited increased flexural and compressive strengths of 35.6% and 5.6%, respectively, compared with ordinary concrete after 28 days. The depth of water penetration in the concrete samples was significantly reduced by the inclusion of NVT, with a maximum reduction of 56.5%. Microstructural analysis using scanning electron microscopy (SEM) revealed enhanced densification of the concrete microstructures, attributed to the high pozzolanic activity of NVT use in cement-based composites. Analysis of variance (ANOVA) revealed statistically significant relationships between NVT content and both the compressive and flexural strengths of the concrete samples. In conclusion, substituting 10% cement with NVT not only enhances the mechanical properties of concrete but also decreases the energy demand for cement production and reduces carbon dioxide (CO₂) emissions, thus contributing to more sustainable construction practices.

This paper presents a study on the effects of graphene nanoplatelets (GNPs) on the mechanical behavior of 3D-printed burnt clay, the most sustainable and green construction material, under constant printing parameters. Mixes with different nanofilament contents—0.1%, 0.2%, and 0.3% by clay weight—were printed and tested under compression and bending loadings. The results obtained on the printed samples were compared with those fabricated using the molding method. The samples’ microstructures were then analyzed using a scanning electron microscope (SEM). Energy dispersive X-ray (EDX) analysis was employed to obtain the elemental distributions. The testing results were then statistically analyzed using a t-statistical method to investigate the impact of using GNPs on the properties of 3D-printed clay. Strength test results showed that mixes containing a low GNP content, i.e., 0.1 wt.%, attained higher compressive and flexural strengths than those containing higher contents, i.e., 0.2 and 0.3wt.%. The results additionally highlighted that the efficiency of GNPs was better observed in the printed samples rather than the molded ones, indicating that the printing process contributed to a better and more uniform dispersion of GNPs in the clay matrix. The t-statistical analysis confirmed that a significant improvement in compressive strength could be obtained using a GNP content of 0.1 wt.%, regardless of the fabrication method. On the other hand, significant flexural strength improvements were observed in the printed samples at all GNP dosages. Micrographs of GNP-modified clay supported the strength results obtained in this study. In summary, this research work signified the importance of using nanofilaments in 3D printing applications in order to achieve the desired elements’ mechanical properties.

This study investigates the influence of basalt fiber on the rheological, mechanical, and microstructural properties of sustainable self-compacting concrete (SCC) incorporating fly ash and microsilica as supplementary cementitious materials (SCMs). Various SCC mixes were prepared, incorporating five different volume fractions of basalt fiber (0.05%, 0.1%, 0.5%, 1%, and 1.5%), along with a control mix. The rheological properties of fresh SCC were evaluated using slump flow and V-funnel flow tests. Subsequently, the mechanical properties, including compressive strength, splitting tensile strength, and flexural strength, were measured after 28 days of curing. Additionally, microstructural analysis was conducted using scanning electron microscopy (SEM) on fractured specimen surfaces. The results indicated that the inclusion of basalt fiber adversely affected the flowability of fresh SCC mixes, with increased fiber volume. However, the hardened concrete exhibited significant improvements in mechanical properties with the addition of basalt fibers. The optimal performance was observed in the SCC70-85/0.10 mix specimens, which demonstrated a 69.90% improvement in flexural strength and a 23.47% increase in splitting tensile strength compared with the control specimen. SEM analysis further revealed enhanced microstructural density in the concrete matrix containing basalt fiber. A two-factor analysis of variance (ANOVA) with repetitions was conducted to evaluate the effects of varying basalt fiber concentrations on the compressive, flexural, and tensile strengths of SCC mixes. The ANOVA results indicated significant effects for both SCC grade and basalt fiber concentration, demonstrating that each factor independently affected the compressive, tensile, and flexural strengths of SCC. These findings suggest that the incorporation of basalt fibers holds promise for extending building lifespans and enhancing concrete quality, representing a valuable advancement in structural engineering applications.

This experimental study evaluated the performance of modified asphalt mixtures prepared by incorporating 2%, 4%, and 6% linear low-density polyethylene (LLDPE) by weight of asphalt binder through a series of tests. The microstructural analyses using scanning electron microscopy (SEM) were conducted on asphalt samples to assess the engineering properties of the asphalt mixes. Finally, ANOVA statistical analysis has been employed to determine the statistical significance of the differences in all tests’ means. Based on laboratory findings, the Marshall stability test result showed that the modified asphalt mixes up to 4% LLDPE had enhanced performance by 12.7% compared to the control mix. A significant decrease (up to 31.3%) in binder penetration was demonstrated due to the incorporation of LLDPE into the asphalt mix. The softening point of the LLDPE–asphalt mixes was increased by up to 17.6%. It was also demonstrated that the incorporation of such LLDPE dosages maintains the flow limits within the specified range; however, the flow of the asphalt mix with 4% LLDPE was 3.17 mm which is the nearest to the average value of the upper and lower acceptable limits. The air voids of mixes with LLDPE content more than 4% by was decreased to less than 4% which is not recommended in high-temperature climates to control mixture bleeding. Microscopic analysis revealed an improvement in the densification of asphalt microstructures, attributed to the LLDPE particles significantly changing the rheology and viscosity of the base mixture and making the hot asphalt mixture more homogeneous. Based on the physical and rheological properties investigated in this study, it could be concluded that 4% LLDPE produces the best performance in asphalt mixtures. Overall, the ANOVA analysis demonstrated that the incorporation of LLDPE into asphalt mixes has a significant impact on all of their properties.

This study investigates the effect of Natural Pozzolana (NP) and Fly Ash (FA) substitutes on concrete's mechanical and microstructural properties. Mixes containing 10 - 50 % cement substitute ratios were prepared and tested for flexure and compressive strength after 28 days of curing. Then, qualitative microstructural analysis was performed using Scanning Electron Microscope (SEM). In terms of compressive strength, the mixes containing only 10 % replacement ratios of both NP and FA showed an improvement of 10 % compared to the plain control mix. On the other hand, all mixes containing FA could attain at least a 25 % development in their flexural strength compared to the control mix. The microstructural analysis illustrated that adding FA and NP enhances cement hydration by improving the formation of dense hydration products such as calcium silicate hydrate (C-S-H) and calcium hydroxide (C-H), which are mainly responsible for the performance of the improved mechanical properties of concrete.