This study investigates the properties of a binary binder system consisting of calcined dolomite powder (CDP) and rice husk ash (RHA). To conduct the study, a reference mixture containing 100% ordinary Portland cement (OPC) and six other concrete mixtures containing a binary binder system with different proportions of CDP and RHA were prepared and tested. Testing was conducted for workability, setting time, dry shrinkage, and mechanical strength at different curing times. The results indicate that the binary system CDP-RHA have mechanical properties better than that of OPC. In addition, the results indicate that the mixture containing 50% CDP and 50% RHA is optimal in terms of mechanical strength.

Concrete structures in marine environments face significant degradation due to reinforcement corrosion caused by chloride ingress and sulfate attack. Poor construction quality, inadequate standards, and suboptimal design can further accelerate deterioration. Non-destructive testing (NDT) has proven valuable for durability assessment, yet its application remains limited due to the complex microstructural characteristics of concrete. This study establishes a comprehensive procedure for evaluating precast concrete degradation in marine environments using multiple characterization techniques. Two precast concrete elements with different cement types, CEM II A-L 42.5R and CEM I 42.5 R/SR, were analyzed through compressive strength tests, open porosity measurements, mercury intrusion porosimetry (MIP), ultrasonic wave transmission, and scanning electron microscopy (SEM). The results indicate that CEM I 42.5 R/SR exhibits superior compressive strength and lower porosity, making it more durable and suitable for load-bearing applications. Higher ultrasonic pulse velocity (UPV) further confirms its resilience. In contrast, CEM II A-L 42.5R shows lower mechanical performance and greater susceptibility to marine-induced degradation. Over time, pore size distribution shifts, potentially compromising mechanical integrity. SEM analysis reveals gypsum and brucite formation in degraded regions, demonstrating microstructural changes due to seawater exposure. A strong negative correlation between porosity and UPV underscores the detrimental effect of increased porosity on material density and structural stability. This study highlights the effectiveness of UPV and porosity analysis as reliable NDT techniques for assessing concrete deterioration. The strong correlation between UPV and porosity trends suggests that UPV serves as an early indicator of durability loss, enabling timely maintenance interventions. These findings provide valuable insights into material selection for enhanced structural performance in marine environments and emphasize the role of NDT in long-term structural health monitoring.

The global demand for environmentally sustainable and cost-effective materials that reduce carbon emissions and energy consumption has significantly risen. In this context, geopolymer binders, primarily sourced from industrial by-products or agricultural waste, have emerged as viable alternatives to traditional Ordinary Portland Cement (OPC). This study examines the characteristics and microstructure of two types of geopolymer mortars: one utilizing an alumina-rich binder, namely calcined clay, and the other employing a silica-rich binder, namely rice husk ash. Both mortar types incorporate a consistent 30% Ground Granulated Blast Furnace Slag (GGBFS), with Calcined Dolomite Powder (CDP) added in varying proportions of 10%, 15%, 20%, and 25%. A total of eight geopolymer mortar mixes, along with a reference mix consisting of 100% OPC, were prepared and evaluated for setting time, flowability, compressive strength, flexural strength, and dry density. Additionally, microstructural analysis was conducted using electron microscopy techniques. The results indicated that the clay-based geopolymer mortars outperformed those based on rice husk ash. Notably, the mixes containing 30% GGBFS, 50% calcined clay, and 20% calcined dolomite powder, as well as those with 30% GGBFS, 45% calcined clay, and 25% calcined dolomite powder, exhibited performance levels comparable to, or slightly exceeding, those of the reference mix.