The Dimethyl Sulfoxide (DMSO) Accelerated Weathering Test for Aggregates
A standard accelerated weathering test using dimethyl sulfoxide (DMSO) was developed to simulate the chemical degradation of basaltic rock. The final development of the standard test involved a study of the interaction of DMSO with clay standards and an investigation of the test condition parameters affecting an existing DMSO test procedure. The weighted loss reported under the existing test procedure (similar to the sodium sulfate soundness test) was affected by the aggregate particle size, specimen mass, immersion time, and container geometry. In the recommended standard DMSO accelerated weathering test, aggregates in the particle size range of 2.4 to 4.8 mm are immersed in a container of DMSO for a period of five days. The mass loss determined by re-sieving the material on a 2.4-mm (No. 8) sieve after five days immersion provides a measure of durability. Immersion of basaltic aggregates in DMSO results in a greater breakdown owing to the type and concentration of ions contained in the rock matrix. Specifically, it was found that DMSO reacts with the cations held to the swelling clay minerals in the aggregate. The results from Atterberg limits tests indicate that DMSO substantially reduces the liquid limit for clays with high activities and increases the liquid limit for clays with low activities. The changes in the liquid limits were influenced by the interaction of DMSO with cations held on the surface of the clay mineral and the ability of DMSO to donate hydrogen ions.