As the human population grows and technology advances, the demand for concrete and cement grows. However, it is critical to propose alternative ecologically suitable options to cement, the primary binder in concrete. Numerous researchers have recently concentrated their efforts on geopolymer mortars to accomplish this objective. The effects of basalt fiber (BF) on a geopolymer based on fly ash (FA) and basalt powder waste (BP) filled were studied in this research. The compressive and flexural strength, Charpy impact, and capillary water absorption tests were performed on produced samples after 28 days. Then, produced samples were exposed to the high-temperature test. Weight change, flexural strength, compressive strength, UPV, and microstructural tests of the specimens were performed after and before the effect of the high temperature. In addition, the results tests conducted on the specimens were compared after and before the high-temperature test. The findings indicated that BF had beneficial benefits, mainly when 1.2 percent BF was used. When the findings of samples containing 1.2 percent BF exposed to various temperatures were analyzed, it was revealed that it could increase compressive strength by up to 18 percent and flexural strength by up to 44 percent. In this study, the addition of BF to fly ash-based geopolymer samples improved the high-temperature resistance and mechanical properties.

This research aims to study the bacterial healing process of cement mortar samples exposed to durability effects using bacteria characterized by their ability to precipitate calcium carbonate. Sporosarcina pasteurii is widely used for bacterial healing. This research investigates the performance of S. pasteurii with five types of bacteria isolated from caves (Viridibacillus arenosi, Streptomyces spororaveus, Bacillus zhangzhouensis, Stenotrophomonas rhizophila, and Serratia quinivorans). Cement mortar samples were exposed to high temperatures and freeze–thaw effects to create microcracks. Microcracks were also induced by applying flexural strength loads. Then, the formed microcracks were healed using spraying and injection of the bacterial solution for the first group for 90 days. The control and healed samples were assessed using flexural and compressive strength, water absorption, capillary water absorption, and ultrasonic pulse velocity (UPV) tests. Microstructural analysis was also conducted to evaluate the bacterial healing products. Subsequently, statistical analysis was performed using the results of these tests to compare the various bacterial efficiencies. As a result of the statistical analysis, the total efficiency scores obtained in the statistical analysis were 119 for Stenotrophomonas rhizophila, 112 for Viridibacillus arenosi, and 105 for S. pasteurii. Thus, Stenotrophomonas rhizophila and Viridibacillus arenosi showed the best healing performance compared to the other types of bacteria.

Unlike conventional concrete materials, Engineered Cementitious Composites (ECC) use a micromechanics-based design theory in the material design process. Recently, the use of nanoparticles in various concretes and mortars has increased. This study used nanocalcite to investigate the mechanical, microstructural fractal analysis of environmentally friendly nanocalcite-doped ECC (NCa-ECC). This paper investigated the effects of nanocalcite (NCa) with different contents (0.5, 1, and 1.5% by mass of binder) on the mechanical properties of engineered cementitious composites (ECC). For this purpose, compressive strength, ultrasonic pulse velocity (UPV), and flexural strength tests were conducted to investigate the mechanical properties of the ECC series. In addition, SEM analyses were carried out to investigate the microstructural properties of the ECC series. The content of nanocalcite improved the mechanical and microstructural properties of the nanocalcite-modified ECC series. In addition, the 1 NCa series (1% nanocalcite modified to the mass of the binder) had the best performance among the series used in this study.

The present research investigates the influence of different sodium hydroxide (NaOH) molarities on the mechanical characteristics and hydrochloric acid (HCl) resistance of geopolymer grouts manufactured from ground granulated blast-furnace slag (GGBS). Geopolymer mortars have attracted interest as sustainable substitutes for traditional cementitious materials due to their advantageous environmental effects and enhanced durability features. This study involved the fabrication of geopolymer mortar specimens by altering the NaOH molarity (M) from 6 M to 14 M. The mechanical and physical qualities were assessed using compressive strength, capillary water absorption, flexural strength, slump flow, and ultrasonic pulse velocity (UPV) tests. Subsequently, the geopolymer mortar specimens with various molarities were exposed to 5% HCl to evaluate the HCl resistance of these specimens by subjecting the specimens to a 5% HCl solution for 28 days. Compressive strength, microstructural analysis, flexural strength, UPV, and mass changes tests were also conducted after 14 and 28 days of exposure to HCl. The results indicate that the molarity of NaOH substantially affects both mechanical strength and resistance to acid degradation. After 28 days of HCl exposure, an increase of 59.63% was observed in the compressive strength of the 10 M containing sample compared to the 6 M containing sample, while this increase decreased to 43.84% in the 14 M sample. This work highlights the essential significance of NaOH molarity in optimizing geopolymer formulations for use in harsh settings, providing insights into the equilibrium between strength enhancement and durability.

In order to popularize the use of geopolymers, it is necessary to investigate the usability of geopolymers in water structures in or on the shores of seas and rivers. For this purpose, underwater geopolymer mortar with different percentages of polypropylene (PP) fiber was produced in this study. In the first stage, the effect of PP fiber on fresh underwater geopolymer mortar was investigated by performing slump and pH tests. In the next stage, mechanical tests were performed on the hardened mortars that were poured and waited underwater for 3, 7, and 28 days. Finally, microstructural analyses were carried out to verify the mechanical experiments and to examine the microstructural state of the underwater geopolymer mortar. As a result of this study, after 28 days, the compressive and flexural strengths of underwater geopolymer specimens containing 0.5% PP fiber were boosted by 3.90% and 210.75%, respectively, compared to the fiber‐free underwater geopolymer specimens. In addition, the 28‐day compressive strength achieved 53.05 MPa, demonstrating the geopolymer mortar's potential to achieve sufficient strength in a submerged condition. These findings underscore the viability of underwater geopolymer mortar for marine structures and other submerged building applications.