Cement-based mortar is recognized as a popular and cost-effective material for the rehabilitation and repair of reinforced concrete structures. However, the development of high-performance cement-based mortar is in high demand in order to not only enhance compressive strength but also to prolong the mortar lifespan and minimize maintenance costs as much as possible. In the current study, high-strength mortars incorporating both silica fume and graphene nanoplatelets (GNPs) were investigated and evaluated based on compressive and flexural strength. The graphene powder was added in amounts ranging from 0.5% to 2%, by cement weight, while silica fume was added as a partial replacement for cement (10%). The optimal content of the graphene was determined using response surface methodology (RSM). In addition, field emission scanning electron microscopy (FESEM) was used to assess the proposed mortar at the micro-scale level. The outcome revealed that the graphene-based mortar imparted superior mechanical properties compared to the control mixture. The compressive and flexural strength of the mortars containing 10% silica fume and 1% graphene increased by 33% and 35%, respectively. This positive result was attributed to the refinement of the nanopores and tiny cracks by the inclusion of GNPs, which was supported by microstructure testing. The RSM model was also shown to be capable of optimizing and predicting compressive and flexural strength with less error. It is possible to conclude that graphene-based high-strength mortar will serve as a sustainable material in the near future.

Bagasse is produced as a waste in the sugar production process, which is used as fuel to stoke boilers in the sugar mills. The concluding product of this burning is residual sugarcane bagasse ash (BA), which is normally dumped or used as low-quality fertilizer. The ash for this study was collected from a reputed sugar mill located in the northern region of Bangladesh. Type I Portland cement (PC) was partially replaced with that finely ground bagasse ash without any pretreatment. The ground BA was used as a replacement for Portland cement at 5, 10, 15, 20, 25 and 30% of BA, respectively, in structural mortar. In addition, chemical characterization, specific gravity, X-ray diffraction (XRD), scanning electron microscopy (SEM), setting time, a strength activity index, compressive strength, water absorption, density and durability in a chloride environment of mortar were determined. The strength activity index result indicates that the used BA has the pozzolanic properties to be used as a partial cement replacement. The results showed that, at the age of 56 days, the mortar samples containing 5–15% ground bagasse ash had higher compressive strengths than the control mixture (mortar without ground bagasse ash). Mortar containing 15% ground bagasse ash had the highest mechanical and durability properties. Therefore, the substitution of 15% BA is acceptable for producing good quality structural mortar in the civil engineering construction field except in chloride environments.