Predicting the Uniaxial Compressive Strength of a Limestone Exposed to High Temperatures by Point Load and Leeb Rebound Hardness Testing

Abstract

The effect of exposure to high temperature on rock strength is a topic of interest in many engineering fields. In general, rock strength is known to decrease as temperature increases. The most common test used to evaluate the rock strength is the uniaxial compressive strength test (UCS). It can only be carried out in laboratory and presents some limitations in terms of the number, type and preparation of the samples. Such constrains are more evident in case of rocks from historical monuments affected by a fire, where the availability of samples is limited. There are alternatives for an indirect determination of UCS, such as the point load test (PLT), or non-destructive tests such as the Schmidt’s hammer, that can also be performed in situ. The aims of this research are: (i) measuring the effect of high temperatures and cooling methods on the strength and hardness of a limestone named Pedra de Borriol widely used in several historic buildings on the E of Spain, and (ii) studying the possibility of indirectly obtaining UCS by means of PLT and Leeb hardness tests (LHT), using Equotip type D. Limestone samples were heated to 105 (standard conditions), 200, 300, 400, 500, 600, 700, 800 and 900 ºC and cooled slowly (in air) and quickly (immersed in water). After that, UCS, PLT and LHT tests were performed to evaluate the changes as temperature increases. Results show decreases over 90% in UCS, of between 50 and 70% in PLT index and smaller than 60% in LHT index. Insignificant differences between cooling methods were observed, although slowly cooled samples provide slightly higher values than quickly cooled ones. The results indicate that LHT can be used to indirectly estimate UCS, providing an acceptable prediction. Research on correlating strength parameters in rocks after thermally treated is still scarce. This research novelty provides correlations to predict UCS in historic buildings if affected by a fire, from PLT and non-destructive methods such as LHT whose determination is quicker and easier.

Investigation of Some Property Changes of Light-Colored Turkish Natural Stones after High-Temperature Treatments

“…Point load strength is a simple, fast and inexpensive index test method that can be applied both in the field and in the laboratory. To determine this strength, core samples (for diametric and axial tests), cut block samples or irregular-sized samples can be used [35,36]. In this study, cut block samples were preferred.…”

Experimental study on thermal fatigue damage and failure mechanisms of basalt exposed to high‐temperature treatments

“…The thermal fatigue effects of rock have been considered as an important factor that can evidently affect the physical–mechanical behaviors of rocks like its microstructure, strength, and deformation instability process 1–5 . The thermal fatigue damage induced by high temperature will induce the change of internal structure of rocks, 6,7 resulting in the destructive instability of rock mass in some geotechnical engineering applications such as enhanced geothermal system, nuclear waste storge, deep mining, rock drilling, and rock engineering exposed to fire or explosion 8–12 . Currently, the thermal fatigue damage of rock has become a design factor that cannot be ignored in rock engineering under high‐temperature environment 13,14 .…”

“…As a hot research topic, the thermal fatigue effects of rock have been widely studied, which primarily concentrated on the physical properties and mechanical behaviors for different types of rocks, such as P‐wave velocity, 15,16 permeability, 17–19 density, 20,21 mineral characteristics, 22,23 porosity, 18,24 elastic modulus, 25,26 tensile strength, 21,27 compressive strength, 12,28 fracture toughness, 5,8,29 and fracture behaviors 30–33 . For example, Rong et al 15 revealed the evolution behaviors of P‐wave velocity for bedrocks subjected to thermal cycling.…”

“…The experimental results suggest that the tensile strength of rocks decreases with an increase in the temperature. Garrido et al 12 forecasted the uniaxial compressive strength of limestone at high temperature based on the tests of point load and leeb rebound hardness. Yin et al 5 conducted a series of mixed‐mode I and II fracture tests to analyze the evolution characteristics of fracture toughness for thermally treated granite.…”

Comparative Study on Convolutional Neural Network and Regression Analysis to Evaluate Uniaxial Compressive Strength of Sandy Dolomite

“…Rock mass strength is one of the most important mechanical properties of rock (Garrido et al, 2022), which is affected by particle arrangement, discontinuity, saturation, temperature, humidity, and/or weathering (Ji and Arson, 2020). Determining the rock mass strength and deformation is a key field of rock mechanics (Walton, 2019).…”