Effects of freezing–thawing and thermal shock cycles on physical and mechanical properties of filled and unfilled travertines

Construction and Building Materials, Volume 47, October 2013, Pages 1395-1401

S. Demirdag

Abstract:The usage of travertine as a natural building and facing stone shows a gradually rising trend in construction sector around the world. Due to natural structure travertine consists of many pores during formation of rocks. White Portland cement, calcite and coloring agent are used to obtain filling material through the pores with optimum setting time as a cement filling technique.

In this study, application of cement filling method in travertine and the effects of freezing–thawing and thermal shock cycles on the rock structure were experimentally investigated. Unfilled and filled travertines were compared based on the technical data of rock parameters before and after freezing–thawing and thermal shock cycles. Filled and unfilled travertine tiles were prepared in the form of 40 cm × 40 cm × 2 cm. Test samples were prepared from these tiles according to related standards analyzed in terms of open porosity, unit volume weight and point load strength index measurements. According to test results, it was tried to compare the filled and unfilled material properties such as physical and mechanical parameters of rock at the end of the each periods of freezing–thawing and thermal shock for 10, 20, 30, 40 and 50 cycles.

The results showed that the very remarkable influence of rock weathering level on mechanical resistance of filled travertine than unfilled travertine after F–T and T-S cycles. F–T has a more destructive effect on the porosity than T-S.

Numerical modeling of thawing in frozen rocks of underground mines caused by backfilling

International Journal of Rock Mechanics and Mining Sciences, Volume 48, Issue 7, October 2011, Pages 1068-1076

S.A. Ghoreishi-Madiseh, F. Hassani, A. Mohammadian, F. Abbasy

Abstract:The thawing effect due to backfilling in permafrost mining rocks is investigated. The heat transfer equation in rock and backfill is obtained by considering the effect of phase change, heat generation due to cement hydration and temperature dependent material properties. The governing equations are solved using a finite volume numerical method and the phase change phenomenon is modeled based on the manipulation of specific heat, thermal conductivity and density of rock and backfill. The harmonic mean method was employed to handle the change of thermal properties. The effects of different influential parameters such as cement content of backfill, water content of rock and backfill, thermal conductivity of rock and filling material, and the number of adjacent stopes are investigated. Eventually, using the resulting temperature and phase field, a new parameter regarded as the radius of thawing, is introduced.

A prediction model for uniaxial compressive strength of deteriorated pyroclastic rocks due to freeze–thaw cycle

Journal of African Earth Sciences, Volume 120, August 2016, Pages 134-140

İsmail İnce, Mustafa Fener

Abstract:Either directly or indirectly, building stone is exposed to diverse atmospheric interactions depending on the seasonal conditions. Due to those interactions, objects of historic and cultural heritage, as well as modern buildings, partially or completely deteriorate. Among processes involved in rock deterioration, the freeze–thaw (F–T) cycle is one of the most important. Even though pyroclastic rocks have been used as building stone worldwide due to their easy workability, they are the building stone most affected by the F-T cycle. A historical region in Central Anatolia, Turkey, Cappadoia encompasses exceptional natural wonders characterized by fairy chimneys and unique historical and cultural heritage. Human-created caves, places of worship and houses have been dug into the pyroclastic rocks, which have in turn been used in architectural construction as building stone.

Using 10 pyroclastic rock samples collected from Cappadocia, we determined the rock’s index-mechanical properties to develop a statistical model for estimating percentage loss of uniaxial compressive strength a critical parameter of F-T cycle’s important value. We used dry density (ρd), ultrasonic velocity (Vp), point load strengths (IS(50)), and slake-durability test indexes (Id4) values of unweathered rocks in our model, which is highly reliable (R2 = 0.84) for predetermination of percentage loss of uniaxial compressive strengths of pyroclastic rocks without requiring any F-T tests.

The effect of antifreeze additives on fresh concrete subjected to freezing and thawing cycles

Cold Regions Science and Technology, Volume 127, July 2016, Pages 10-17

Rıza Polat

Abstract:This study focused on the effect of antifreeze additives on the microstructural changes and physical and mechanical properties of fresh concrete subjected to freezing–thawing cycles produced by cold weather. For this purpose, antifreeze additives, urea and calcium nitrate, were used at the level of 6% by weight of cement dosage and were compared with control samples. After casting, one group of control samples was cured in moist curing conditions for 1 day and then cured in lime-saturated water at 23 ± 1 °C for 28 days. Another group of controls, urea and calcium nitrate mixtures, were subjected to freezing–thawing cycles 1, 3, 5, 7, 10, 15 and 28 times. Scanning electron microscopic (SEM) images, ultrasonic pulse velocity (UPV), water absorption and compressive strength tests were conducted. The results showed that the lowest water absorption value after 28 freezing–thawing cycles was 5.8% for the calcium nitrate mixes. The 28-day compressive strength of the control, calcium nitrate and urea mixes subjected to freezing–thawing 28 times was reduced by 72.0%, 27.8% and 52.9% compared to those of the control samples cured in lime-saturated water at 23 ± 1 °C for 28 days. The SEM images showed that the samples containing calcium nitrate had a more compact and denser micro-structure compared to urea and the control.

Experimental and modeling investigation of the thermal conductivity of fiber-reinforced soil subjected to freeze-thaw cycles

Applied Thermal Engineering, Volume 108, 5 September 2016, Pages 824-832

Muge Elif Orakoglu, Jiankun Liu, Fujun Niu

Abstract:The thermal conductivity of fine-grained soil, both unreinforced and reinforced with randomly oriented basalt, glass, and steel fibers, was tested by means of the transient hot-wire method with a Quickline-30 Thermal Properties Analyzer. The thermal conductivities of specimens were determined as a function of fiber volume fractions, freeze-thaw cycles, and temperature through laboratory studies. Thermal conductivity of the fiber-reinforced soil decreased for all freeze-thaw cycles and temperature values. The most remarkable reduction of thermal conductivity was measured on all ratios of the steel fiber-reinforced soil and 1% basalt fiber-reinforced soil. Moreover, the statistical-physical model proposed by Usowicz was applied to evaluate the thermal conductivity of fiber-reinforced soil by considering soil-fiber composites and environmental factors. The results showed a close match between the values estimated by the statistical-physical model and the experimental values for various fiber-reinforced soils in a wide range of fiber ratios, temperatures, water contents, and freeze-thaw cycles.

Experimental study on debonding of shotcrete with acoustic emission during freezing and thawing cycle

Cold Regions Science and Technology, Volume 111, March 2015, Pages 1-12

Ganesh Mainali, Savka Dineva, Erling Nordlund

Abstract:Studying the deterioration of shotcrete due to freezing and thawing is important for improvement of the understanding of the failure mechanisms/debonding of shotcrete in cold regions. Water leakage in a tunnel leads to ice growth during freezing temperature and ultimately creates favorable environment for fallouts of shotcrete and rock. Repeated freezing and thawing of shotcrete lead to development of new micro cracks and propagation of pre-existing micro cracks. In this study, test panels of granite with dimension 800 × 800 × 80 mm covered with 50-mm thick shotcrete were subjected to freezing and thawing action in a controlled environment. The initiation and the development of freeze-induced micro cracks in shotcrete-rock interface were studied by continuously monitoring acoustic emissions (AE) and temperature. The clustering of the AE events during freezing and thawing indicates that micro cracks appeared in the shotcrete-rock interface and caused adhesion failure. The larger number of AE events in the panels, with access to water during freezing, confirmed that water contributes to material deterioration and also reduces the adhesive strength. The test results showed that most of the acoustic emission occurred during the freezing cycle and the number of acoustic emission events did not increase with the successive increase of the number of freezing and thawing cycles.