Effects of Mild Acid Immersion and Freeze–Thaw Cycling on P-Wave Velocity-UCS Relationships in Dolostone

Accurate estimation of uniaxial compressive strength (UCS) is essential in geotechnical engineering, but conventional UCS testing is destructive and time-consuming. This study investigates the effects of mild acid exposure and freeze–thaw (F–T) cycling on the relationships between P-wave velocity (Vp) and UCS, density (ρ) and UCS, and Vp and selected physical properties in Apulian dolostone. Thirty-four cylindrical specimens were tested, comprising ten untreated specimens, five specimens in each acid-treatment group (3, 7, and 28 days), five specimens subjected to 10 F–T cycles, and four specimens monitored progressively during F–T cycling. Chemical weathering was simulated by static immersion in sulfuric acid (initial pH ≈ 5) without solution renewal and pH adjustment. Measurements included Vp, density, UCS, apparent porosity, and water absorption, together with thin-section petrography using optical microscopy and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS), SEM morphology, and X-ray diffraction (XRD) mineralogical analysis (four thin sections per treatment group; one representative specimen per treatment for SEM and XRD). Under the investigated conditions, both weathering processes produced moderate changes in the physical, ultrasonic, and mechanical properties, accompanied by minor microstructural modifications but without detectable mineralogical phase changes. The treatments also modified the empirical relationships between Vp, UCS, and the measured physical properties. These findings indicate that weathering influences the reliability of Vp-based UCS estimation for Apulian dolostone under the investigated conditions and provide new insights into the early-stage deterioration of this material.