Determination Of Frost Resistance Research Articles

Aging of Limestones and Silane–Siloxane-Based Protective Hydrophobics: The Impact of Heating–Cooling and Freeze–Thaw Cycles

Stones are traditionally used in construction and architectural applications as building elements due to their aesthetic and technical/structural performance. Like other environmental factors (rain, humidity, moisture, salt presence, biological activity, etc.), heating–cooling and freeze–thaw cycles significantly threaten the longevity of stone materials. Hence, considering the socio-economic and cultural value of stones, preventive measurements such as hydrophobic coatings are applied to prevent or mitigate damage. The scope of this study is the performance assessment of limestones with different characteristics and the efficiency of various commercial silane/siloxane-based hydrophobic coatings when exposed to thermal variation and freeze–thaw. For that purpose, the standards EN 14066:2013 (determination of resistance to aging by thermal shock) and EN 12371:2010 (determination of frost resistance) were followed. Open porosity and static contact angles were estimated to assess the stone durability and water protection capabilities of the hydrophobics. Additionally, sound speed propagation velocity, quality of building material index, elastic modulus and flexural strength were measured to evaluate the variation of mechanical properties. Static contact angle revealed that the coatings maintained an efficient level of hydrophobicity even after thermal-shock and freeze–thaw weathering tests. The study also revealed a critical interaction between freeze–thaw cycles, hydrophobic coatings and structural integrity of the stones, mostly on more porous ones. When they are subjected to harsh environmental conditions, untreated porous limestones keep structural cohesion, allowing for the natural absorption and release of water during freezing and thawing. On the contrary, when limestones are treated, the hydrophobic coatings can moderately obstruct the water release due to the partial saturation of the porous framework by the products. It also probably resulted from the different mechanical behavior between the inner matrix and layer of stone coated, resulting in a premature breakout and mechanical damage of the stone.

Influence of environmentally friendly Phytonorman oils on the adhesive properties of frost-resistant rubbers based on nitrile butadiene rubber

The use of plasticizers based on esters of various acids most effectively improves the processing of rubber compounds and the frost resistance of NBR-based rubbers. In this work, as a plasticizer, products based on vegetable raw materials were tested - Phytonorman oils produced by the Biochemical Holding ORGKHIM, which are di- and triglycerides containing fatty acids of tall oil. Model rubber compounds based on BNKS-18AMN contained 10, 20, 30 wt. including eco-oils of the Phytonorman 212 and Phytonorman 213 brands, a mixture without oil and with 10 wt. including dibutyl phthalate (DBPh). To assess the effect of the type and dosage of eco-oils on the properties of rubbers and rubber compounds, methods for studying technological, physical-mechanical and adhesive properties were used. Determination of frost resistance, a comparison was made of methods for determining the glass transition temperature: differential scanning calorimetry (DSC) and thermomechanical analysis (TMA, Fourier). When using vegetable oils Phytonorman -212 and Phytonorman -213, the technological properties of rubber compounds are significantly improved compared to the mixture without oil and are on the same level with DBPH traditionally used in nitrile rubbers. It has been established that the introduction of Phytonorman 213 eco-oil into the formulations of rubber compounds based on BNKS 18AMN up to 10 wt. hours allows you to improve the technological parameters, as well as lower the glass transition temperature of rubber. At the same time, the physical and mechanical parameters and adhesive properties of vulcanizates are reduced by an average of 10%. It is also worth noting that rubbers with Phytonorman 213 oil are not inferior to nitrile rubbers with DBPh in terms of basic characteristics, and they are superior in adhesive properties by 27%.

Influence of the Method of Production of Test Specimens on the Result of the Frost Resistance Test of Concrete

The paper deals with a comparison and interpretation of results of frost resistance tests of concrete specimens taken from a structure and test specimens produced in a laboratory using plastic moulds. A concrete block had to be produced for the experiment to simulate a real structure. The concrete used for the production of this block was also used in a laboratory to produce the test specimens. Core samples were drilled out from the concrete block and were subsequently used to make sets of core specimens. The test specimens, which differed in size, shape and the production method in particular, were subjected to frost resistance tests. The output of the paper is both a comparison of the results obtained on individual types of test specimens and a recommendation on how to approach the determination of frost resistance of concrete in a structure.

Unground granulated slag as a substitute for natural aggregate during concrete production

In order to evaluate the usefulness of unground granulated slag for the concrete production, as the partial replacement of fine aggregate – namely sand, the detailed studies of the influence of this addition on the properties of the fresh and hardened concrete were conducted. These studies included the compression strength and the modulus of elasticity determination, as well as the evaluation of durability by the determination of frost resistance. The evaluation of the properties of concretes hardened under winter conditions, at +10oC and summer conditions at +20oC. These studies also covered the resistance to chloride attack and carbonization. The long-lasting examination covered also the ASR. At the end, under real construction conditions in the Austrian prefabrication plant, the unground granulated slag was examined. Under these conditions especially the long-lasting measurements of the strength development of the precast elements were verifi ed. In order to evaluate the usefulness of the unground granulated slag, as partial replacement of fine aggregate, the concretes with the additions of slag of 10% and 15% were produced and examined. For this evaluation, the slags of two Austrian plants from Upper Austria and Styria were used. The old and fresh slags from these two plants were used because the old slags can also be adopted for concrete production. Presented in the paper results are confi rming that the natural aggregate of the fraction < 4 mm can be successfully replaced by unground granulated slag, without any negative influence on the properties of concrete.

СВОБОДНЫЙ ПРОЛИН В ЛИСТЬЯХ КАК ПОКАЗАТЕЛЬ ОПРЕДЕЛЕНИЯ МОРОЗОСТОЙКОСТИ ОЗИМОЙ ПШЕНИЦЫ

Free proline in leaves as an indicator of the determination of winter wheat frost resistance The article considers the results of the determination of frost resistance of winter wheat, grown in the sowing boxes. The amount of plants survived in such conditions (the temperature of freezing was -20 °С) ranged from 20.5 to 83.5% through three years. The standard variety “Tarasovskaya 29” had 55.3% of live plants. The varieties “Polina” (72.3%), “Volnitsa” (76%), “Donskaya bezostaya” (78.1%), “Asket” (78.1%). “Volny Don” (78.3%) and “Don 107” (83.8%) showed high indexes of frost resistance (НСР 05 ± 14.1%). The varieties “Kaprizulya” (37.0%), “Tanya” (38.0%), “Lilit” (38.4%) and “260/09” (20.5%) had low indexes of frost resistance in such conditions. There have been also given the results of the use of an indirect method - a determination of free proline concentration. The content of amino acid in winter wheat leaves during the period from autumn to spring has been determined. More frost tolerant varieties had a larger content of free proline. The content of proline in winter wheat leaves can tell about a level of frost resistance of this or that variety, comparing it with a variety-classifier with a known frost resistance. A close connection of these traits proves this. Thus, the determination of free proline content can become an express method for the determination of the level of winter soft wheat frost resistance. It will allow getting rid of less frost tolerant material during the early stages of the breeding process.

Determination of frost resistance for sorts of winter wheat and barley based on the insight of membranes

The results of the research dedicated to the indication of the optimal factors of the relative issue of electrolytes from the germs of the winter wheat and barley for the evaluation of their frost-resistance.

Mechanical and Durability Properties of Selected Types of Sandstones

Present paper is focused on the experimental assessment of three sandstones from different quarries. Mechanical testing was carried out besides water absorption test and determination of frost resistance what is the crucial material parameter for all types of porous rocks. Gradual deterioration due to action of frost was monitored using non-destructive testing – ultrasonic pulse method. Obtained results well describe failure mechanism of studied sandstones of different basic physical properties. It was conducted that main part of deterioration was performed at the beginning of the freeze-thaw cycling.

The Determination of Frost Resistance on Ultra High Performance Concrete

The ultra high performance concrete (UHPC) has very special properties that are expressively different of normal concrete. Due to its high compression strength greater than 150 MPa, tensile strength greater than 20 MPa and improved durability, these represent significant advances in concrete technology. These materials include Portland cement, silica fume, quartz flour, fine silica sand, high-range water-reducer, water and either steel or organic fibres. Depending on the type of fibres used can influence the compressive strength. The article describes the tests of frost resistance on UHPC plates with different types of textiles armatures. The aim of the testing is describe influence of textiles armatures in UHPC matrix in extreme conditions.

FROST HARDINESS OF PEACH AND APRICOT FLOWER BUDS

The determination of the frost resistance and winter hardiness of peach and apricot varieties is an important task in Hungary, as production can only be competitive if the location and variety are wisely chosen. Various overwintering organs of trees have very different levels of frost resistance, and this resistance also varies greatly over time. During dormancy flower buds are the most frost sensitive organs of peach and apricot trees. From the practical point of view frost resistance and winter hardiness of the flower buds deserve detailed study. The development rate of the overwintering organs of peach and apricot varieties and changes in their frost resistance during the dormancy period have been regularly investigated in recent years in the gene bank collection of Corvinus University of Budapest. The present paper provides an analysis of frost hardiness of flower buds based on the results obtained in three consecutive winters with very diverse weather conditions. The hardening processes of overwintering organs are fundamentally determined by environmental factors, particularly by temperature. Thus, even at the same location, the development rate of the flower buds and the development of frost resistance may differ from year to year. The determination of the maximum frost resistance genetically attainable and the description of changes in frost resistance are only possible in a series of experiments over several years.

Ability of winter wheat plants to become hardened against frost related to peculiarities of carbon dioxide exchange, biomass synthesis, and various forms of water-soluble carbohydrates

The donor-acceptor relation (DAR) in a plant under cold exposure to frost was studied in the plants of winter wheat (Triticum aestivum L.) Mironovskaya 808 cultivar and its allocytoplasmatic hybrid containing alien cytoplasm of goat grass (Aegilops ovata L.) and grown in a water culture until phenophase, from two leaves until branching. The alteration of DAR was processed by treatment of plant with solutions of diuron and paraquat the photosynthesis inhibitors, keeping plants in the dark, changing from mixotrophic to autotrophic nutrient, and also through the exchange of nutrient solution to distillate water. Determination of frost-resistance on the basis of survival percentage among frozen plants is more significant (R = 0.701-0.999) and related to the frost-resistance of leaves, the correlation P/Rd between speeds of true photosynthesis at light saturation (P) and plant dark respiration (Rd), the approximate speed of dry plant biomass alteration, the total content of water-soluble sugars, and the ratio of di- and monosaccharides (sucrose, glucose + fructose) in leaves. The importance of all the indexes mentioned above for acquiring resistance to low temperatures in plants is discussed in the present article.

On the effect of laboratory conditioning and freeze/thaw exposure on moisture profiles in HPC

The effect of selected conditioning (drying and resaturation) and freeze/thaw exposure on the moisture profile in a two-powder concrete (equiv. w/c=0.39, 8% silica fume) has been investigated. For comparison, the effect of conditioning and freeze/thaw testing according to SS 13 72 44 (“Borås method”) on moisture profiles in a three-powder concrete and two plain concretes (w/c=0.45) was measured. The investigations were supplemented by determination of frost resistance and chloride profiles after freeze/thaw exposure, as well as petrographic analysis. The investigations indicate that the present methods of conditioning only have very limited effect on high-performance concretes (HPC).