Predicting the long-term durability of limestones subjected to freeze–thaw cycles (case study: Guilan province, north of Iran

Mesozoic limestones with Cretaceous and Jurassic age are widely seen in the Guilan province, north of Iran. Regarding the climate of this area, the development of limestone with a high percent of CaCO3 (rather than 80%) and karst morphology development was investigated to evaluate the effect of freezing-thawing (F-T) cycles concerning the karst development. In this way, the physical and mechanical properties of the four lithology units (Kl1, Kl2, Km2, and Jkl) were assessed before and after F-T cycles to study the weathering effects. The survey of the petrography of rocks shows that the samples were grainstone and packstone type, according to Donham classification. The highest deterioration occurred in sample Kl2 after 60 F-T cycles. The physical and mechanical properties of rock samples such as ɣ (unit weight), wa (water absorption), Pv (P-wave velocity), and UCS (uniaxial compressive strength) for both dry and saturated conditions, and after 60 cycles of freezing-thawing (F-T) were attained. The softening coefficient (K1) and freezing coefficient (K2) of samples were calculated using the UCS values. The F-T cycles caused significant losses in the UCS values. The measured Vp during the F-T cycles provided a suitable tool for calculating the damage value and decayed constant (λ). This study showed that the F-T test is capable of creating microcrack and fractures within the rock as the initial factors for increasing the contact surface in the dissolution process. The increase in Dn (damage variable), porosity, water absorption, and decrease of Vp after 60 F-T cycles confirm this result. Also, the increase in tangent Young’s modulus and decrease in strain show that the samples were brittle after 60 F-T periods. Therefore, it is concluded that the freezing and softening coefficient and Vp are effective tools for assessing the rock damage during F-T periods.