Assessment of Karacadağ Basalt as a Sustainable Material for Eco-Friendly Road Infrastructure

Road construction has historically played a pivotal role in infrastructure development, addressing society’s growing mobility needs. Selecting sub-base and base layer aggregates requires materials that are mechanically durable, compliant with engineering standards, cost-effective, and sustainable. Locally sourcing aggregates enhances economic efficiency while reducing the environmental impact. In Southeastern Anatolia, particularly in Diyarbakır, extensive investments in roads, highways, and high-speed rail have increased the demand for high-quality aggregates. Karacadağ basalt, a locally abundant volcanic rock, offers a promising alternative. Its use not only reduces raw material costs but also aids in rehabilitating surface agricultural lands, supporting sustainable urban development and resource conservation. This study assesses the suitability of Karacadağ basalt as a sub-base and base material for highway construction. Two mixtures, namely PMT (Primary Mixture Type) and PMAT (Primary Mixture Alternative Type), were prepared and tested by the Ninth Regional Directorate of Highways using standardized methods including sieve analysis, methylene blue index, Los Angeles abrasion, Weather Resistance, and California Bearing Ratio (CBR) tests. Results indicate that Karacadağ basalt meets all relevant Turkish Highways Technical Specifications. These findings highlight the material’s potential as a sustainable, locally sourced aggregate for infrastructure applications, while suggesting that further testing across diverse quarry sites could enhance reliability and promote wider adoption.