Assessment of Tin Slag 2 as a Fine Aggregate Substitute in Mortar: Characterization and Compressive Strength Evaluation

Tin slag 2 is a by-product of the tin smelting industry that has the potential to be reused as a construction material. However, its utilization remains limited due to the presence of naturally occurring radionuclides and the need to evaluate its engineering performance. This study aimed to assess the material characteristics and compressive strength of mortar incorporating tin slag 2 as a fine aggregate substitute under different cement-to-fine aggregate ratios (1:3 and 1:4). Tin slag 2 obtained from PT Sariwiguna Bina Sentosa was characterized through gamma spectrometry measurements and physical property testing. Mortar specimens were prepared with tin slag 2 substitution levels of 0%, 5%, 10%, 15%, and 20% of the fine aggregate weight and were tested for compressive strength at curing ages of 7, 14, and 28 days. The results showed that raw tin slag 2 contained 226Ra, 228Ra, and 228Th with activity concentrations of 5.7 Bq/g, 16.6 Bq/g, and 14.3 Bq/g, respectively, exceeding the standard safety exemption criterion of 1 Bq/g. Regarding mechanical properties, the compressive strength increased with curing age across all mixtures. At a 1:3 ratio, the optimum compressive strength reached 11.172 MPa at 28 days with 5% tin slag 2 substitution. Meanwhile, at a 1:4 ratio, the compressive strength continuously improved up to the 20% substitution level, reaching 9.471 MPa at 28 days. The results demonstrate the initial mechanical feasibility of utilizing tin slag 2 as a partial fine aggregate substitute; however, comprehensive radiological dose assessments of the final products are mandatory in subsequent studies before widespread structural application can be recommended. Keywords: tin slag 2, fine aggregate substitute, mortar, compressive strength, NORM