Use of Süphan and Nemrut volcanic ashes in cement based material production

In recent years, numerous studies have been conducted to reduce the use of Portland cement and to produce more environmentally friendly materials. Research has shown that materials exhibiting binding and pozzolanic properties can be used as partial replacements for cement. Volcanic ashes are among the materials commonly utilized as pozzolans. In this study, the use of Süphan (SVK) and Nemrut (NVK) volcanic ashes, located in the Eastern Anatolia region of Türkiye, in cement-based materials and their effects on the physical, mechanical, and microstructural properties of mortars were investigated. Workability properties were evaluated through flow diameter tests, while mechanical properties were analyzed using compressive strength tests. Microstructural characteristics were examined in detail using XRD and SEM analyses. For this purpose, SVK and NVK samples were first collected from the field. The collected ashes were subjected to size reduction and sieving processes in the laboratory, after which their characterization properties were determined. Following material characterization, mortar specimens were produced. SVK and NVK were used as cement replacements at ratios of 10%, 20%, and 30%. According to geochemical data, SVK is classified as rhyolite and NVK as trachyte. Chemical analysis results revealed that the total content of SiO₂, Al₂O₃, and Fe₂O₃ oxides in both volcanic ashes exceeded 70%, indicating pozzolanic properties in accordance with ASTM C618. According to the flow diameter test results, workability was positively affected at low replacement ratios (10% and 20%), particularly in SVK-containing mortars. In contrast, the use of NVK at all replacement levels (10%, 20%, and 30%) negatively affected workability. Water absorption tests showed that all volcanic ash-containing mortars exhibited higher water absorption rates compared to the control specimens. This increase was more pronounced at higher replacement ratios, and NVK-containing mortars demonstrated higher water absorption values than those containing SVK. Compressive strength results indicated that an increase in compressive strength was achieved only in mortars with 10% SVK replacement. Conversely, NVK replacement led to a reduction in compressive strength, with the strength loss being more pronounced in NVK-containing mortars compared to SVK-containing ones. XRD and SEM analyses further demonstrated that SVK replacement reduced the amount of portlandite and promoted the formation of secondary C–S–H gel to a greater extent. In conclusion, the use of Süphan volcanic ash (SVK) at a replacement ratio of 10% was identified as the most suitable substitution level in terms of workability, strength, and microstructural performance. Keywords: Building Material, Cement, Sustainability, Volcanic Ash