Concrete Frost Research Articles

Study on Deformation Characteristics and Damage Model of NMK Concrete under Cold Environment

To improve the ability of concrete structures to resist freeze-thaw damage in cold environments, explore the effect and mechanism of nano-metakaolin (NMK) on frost resistance of concrete. And make up for the deficiencies in the mechanical properties and deformation process of na-no-metakaolin concrete in freeze-thaw environments. Rapid freeze-thaw cycle experiment was car-ried out to detect the deterioration law of concrete. Physical and mechanical properties under freeze-thaw environment was measured. The modification mechanism of nano-metakaolin on con-crete frost resistance from micro and meso scales was analyzed. The effect of freeze-thaw damage on nano-metakaolin concrete was characterized. The influence law of stress strain is established, and the meso-statistical damage constitutive model of nano-metakaolin concrete under freeze-thaw action is established. The results show that: Compared with other nano-clays, adding 5% nano-metakaolin can effectively slow down concrete’s freeze-thaw cracking and crack propagation. After 125 freeze-thaw cycles, the surface crack width of concrete mixed with 5% nano-metakaolin is only 0.1mm. Without freeze-thaw cycles, the compressive strength of concrete mixed with 3% nano-metakaolin is the highest, which is 28.75% higher than that of ordinary concrete; after 125 freeze-thaw cycles, the loss rate of compressive strength of concrete mixed with 5% nano-metakaolin was 12.07%. After 125 freeze-thaw cycles, the peak strain is 0.45 times that of concrete without NMK, and the peak stress is 3 times that of concrete without NMK.

Data-Based Statistical Analysis of Laboratory Experiments on Concrete Frost Damage and Its Implications on Service Life Prediction.

To meet the requirements of durability design for concrete suffering frost damage, several test standards have been launched. Among the various damage indexes such as deteriorated compressive strength, relative dynamic elastic modulus (RDEM), residual deformation, etc., the concept of a “Durability Factor” (DF) is proposed by many standards to define the frost resistivity of concrete against frost action based on the experimental results from standard tests. Through a review of the literature, a clear tendency of strength/RDEM decay and residual deformation increase is captured with increasing cycles of freezing and thawing. However, tests following different standards finally derive huge scattering quantitative responses of frost resistance. Based on the large database of available laboratory experiments, this study presents a statistical analysis to propose a predictable model to calculate the DF with respect to other material factors. The statistical model is believed to be more convenient for engineering applications since the time-consuming experiment is no longer needed, and it is more precise compared with that developed according to only single experimental results to cover the uncertainties and unavoidable errors in specific tests. Moreover, the formula to calculate the DF is revised into a more general form so as to be applicable for all the laboratory experiments even for those cases without fully following the standards to derive a DF value.

Revisiting concrete frost salt scaling: On the role of the frozen salt solution micro-structure

We simulate the glue-spall stress due to mechanical interactions between a frozen saline solution (brine-ice composite) and a non-air entrained concrete surface including the impact of the micro-structure of the frozen solution. The presence of brine channels at the ice/concrete interface was found to be a prerequisite to induce stress during freezing and hence for scaling to occur. Pure ice does not result in scaling as it does not have brine channels. Furthermore, the size of the brine channels and their distribution was found determinant for the magnitude of the glue-spall stress in the concrete and the experimentally observed pessimum effect of a medium salt concentration was explained based on the change of the microstructure of the brine-ice composite at different salt concentrations and temperatures. The predicted results are in good agreement with the experimental observations and the few numerical demonstrations related to frost salt scaling in the literature.

Structure, Impermeability and Durability of Cement Concrete

The paper presents the main hypotheses of frost destruction of cement concrete. The influence of cyclic temperature changes and the effect of static and dynamic (shock) loads on concrete on changes in the structure and strength of concreteis considered. The paper provides results of comparative tests of frost resistance of concrete containing a porous additive and a plasticizer, which contribute to an increase in the density and impermeability of its structure. It has been shown experimentally that the introduction of air-entraining additives with an additional effect of hydrophobization is productive from the standpoint of ensuring frost resistance of concrete of relatively low classes (up to C30/37), compressive strength up to 50 MPa and water absorption by mass more than 4.0 %. It is advisable to increase the frost resistance of concrete with greater impermeability and strength by increasing these indicators, in particular, due to the maximum decrease in the initial water content and high-quality compaction. This conclusion is experimentally confirmed by the data presented in the paper, since the “mechanism” of frost destruction of cement concrete is multifactorial, and the growth of its density (impermeability) and strength provide a higher ability to resist “force” effects associated with repeated alternating deformations of concrete, as well as the action of external loads, accumulation of fatigue phenomena, hydrodynamics of liquid filtration under the influence of changing temperature fields, etc. A comparative assessment of concrete frost resistance has been carried out using standardized and patented techniques containing a porous (air-entraining) additive, as well as plasticizing and mineral additives of amorphous micro-silica, introduced into concrete in order to increase its density, impermeability and strength and on this basis – increasing frost resistance. Experimental data are presented, reflecting the relationship and patterns of decrease in frost resistance of concrete subjected to the simultaneous action of static (for compression – different levels from the corresponding indicator of concrete strength) and shock, concentratedly applied dynamic loads. The regularity of the relationship between the accelerated frost destruction of concrete and the action of mechanical loads that cause cracking in its structure has been confirmed.

Effect of surface treatment materials on frost resistance of damaged concrete

In order to study the effect of silicate infiltration agent, tetraethyl orthosilicate and nano-SiO2 surface treatment materials on the freezing resistance of damaged concrete, the peeling condition of damaged concrete after soaking in salt water was tested by single-side freeze-thaw method. The results showed that tetraethyl orthosilicate and silicon infiltration agent can effectively improve the damaged concrete frost resistance and can reduce the 7 d water quantity of concrete, the most significant is the effect of tetraethyl orthosilicate, 7 d water quantity reduced rate of 65%, after 28 times freeze-thaw cycle exfoliation volume is 679 g/m2. Silicon infiltration agent surface treatment also has a good effect, can increase the number of freeze-thaw cycles 8 times. Nano-SiO2 has the worst treatment effect and can not improve the number of freeze-thaw cycles of damaged concrete.

Properties of Old Concrete Built in the Former Leipziger Palace

This research aims to determine the mechanical, chemical, and physical properties of old concrete used in the former Leipziger Palace in Wrocław, Poland. The cylindrical specimens were taken from the basement concrete walls using a concrete core borehole diamond drill machine. The determination of the durability and strength of old concrete was based on specified chosen properties of the old concrete obtained through the following set of tests: measurements of dry density, tests of water absorption, specification of concrete compressive strength and frost resistance, determination of the modulus of elasticity, measurement of the pH value, determination of water-soluble chloride salts and sulphate ions, and X-ray diffraction analyses. Large dispersions of the compressive strength (10.4 MPa to 34.2 MPa), density (2049 kg/m3 to 2205 kg/m3), water absorption (4.72% to 6.55%), and stabilized secant modulus of elasticity (15.25 Gpa to 19.96 GPa) were observed. The paper is intended to provide scientists, civil engineers, and designers with guidelines for examining and assessing the long-term durability of old concrete, and also extending knowledge in the field of archaeological restoration and the protection of old concrete structures.

Study on Durability and Pore Characteristics of Concrete under Salt Freezing Environment.

The macroscopic mechanical properties and frost resistance durability of concrete are closely related to the changes in the internal pore structure. In this study, the two-dimensional and three-dimensional ICT (Industrial Computerized Tomography) pore characteristics of C30 concrete specimens before and after freezing and thawing in clean water, 5 wt.% NaCl, 5 wt.% CaCl2, and 5 wt.% CH3COOK solution environments are obtained through concrete frost resistance durability test and ICT scanning technology. The effects of pore structure changes on concrete frost resistance, durability, and compressive strength mechanical properties after freezing and thawing cycles in different salt solution environments are analyzed. This paper provides new means and ideas for the study of concrete pores. The results show that with the increase in the freezing and thawing times, the concrete porosity, two-dimensional pore area, three-dimensional pore volume, and pore number generally increase in any solution environment, resulting in the loss of concrete compressive strength, mortar spalling, and the decrease in the relative dynamic elastic modulus. Among them, the CH3COOK solution has the least influence on the concrete pore changes; the NaCl solution has the greatest influence on the change in the concrete internal porosity. The damage of CaCl2 solution to concrete is second only to the NaCl solution, followed by clean water. The increase in the concrete internal porosity from high to low is NaCl, CaCl2, clean water, and CH3COOK. The change in the pore volume of 0.1 to 1 mm3 after the freeze–thaw cycle is the main factor for reducing concrete strength. The test results have certain guiding value for the selection of deicing salt in engineering.

Research Of Asphalt Concrete Frost Resistance According To Fatigue Resistance And Stiffness Criteria

The formation of snow cover has been unsustainable in recent decades, which means that freezing and thawing are becoming more frequent in Latvia and that is one of the reasons why asphalt concrete frost resistance matters. Asphalt concrete beams were exposed to multiple freeze-thaw cycles and afterwards tested on a 4-point bending test for stiffness and fatigue resistance. Frost resistance testing for aggregates and concrete is a popular and widely described and used test method worldwide, but there is no such testing standard for asphalt concrete. This study is aimed to develop a methodology for determining the frost resistance of asphalt concrete by adapting the requirements of cement concrete standart AASHTO C666, as well as to experimentally evaluate the effect of frost resistance on the fatigue strenght and stiffness of asphalt concrete. The results show significant correlation between asphalt concrete void content and fatigue life after multiple freeze-thaw cycles and correlation between the amount of freeze-thaw cycles and asphalt concrete fatigue life.

Air Content in Fresh Air-Entraining Cement Mortars

The durability of a cement composite is the most important criterion for assessing this material. However, due to the durability of the cement composite, its frost resistance is an important property. In order to ensure concrete frost resistance, the European standard PN-EN 206-1: 2013 requires its aeration at the level of 4 - 7%. The Committee 201 of the American Concrete Institute (ACI) also requires the use of an air-entraining admixture in concretes exposed to frost damage. The amount of air-entraining admixture is significantly influenced by the composition of the cement used. In order to minimize the problems with obtaining frostresistant concrete, an attempt was made to create air-entraining cements. This article presents the effect of the amount and type of dosing of air-entraining admixtures (natural and synthetic) on the air content in fresh air-entraining cement mortars. The test cements used also differed in the production method: joint mixing of components and joint grinding of components. Based on the research, a lot of valuable information was obtained related to the influence of the preparation of air-entraining cements on the air content in the mortar, e.g. mortars with mixed cement with natural air-entraining admixture have a higher air content. The air content is higher in the cement co-ground with natural air-entraining admixture. A synthetic air entraining admixture added separately to mixed cements with silica fly ash and ground granulated blast furnace slag increases air entrainment in mortars. The synthetic air-entraining admixture added separately to co-milled cements causes an increase in air entrainment in the mortars, except for those containing cement with ground granular blast furnace slag.

Mechanical properties, durability, and ITZ characteristics of full-grade dam concrete prepared by aggregates with surface rust stains

Aggregates with surface rust stains (ASRS) is very common in the construction of water conservancy and hydropower projects. The purpose of this paper is to provide the possibility to utilize rusted raw rocks as aggregate in dam concrete. The physical and chemical properties of rusted raw rocks are measured. In addition, comparisons of their mechanics and the durability of dam concrete prepared by ASRS and rust-free limestone aggregates (RFLA) are investigated. The characteristics of interfacial transition zone (ITZ) between aggregate and paste are investigated by the means of scanning electron microscope with energy dispersive spectrum (SEM-EDS) and nano-indentation technology. The results show the apparent density and uniaxial compressive strength of ASRS are lower than the RFLA by 10 kg/m3 and 5.3 MPa, respectively. The compressive strengths of ASRS concrete are approximate those of RFLA concrete. The tensile strength of ASRS concrete is lower than that of RFLA concrete by 13 %. The ASRS slightly reduces the dam concrete frost resistance and impermeability. The ITZ average thickness of the ASRS sample is thicker than that of the RFLA sample by 15.0–20.0 μm. The values of indentation modulus and hardness observed across the ITZ in the ASRS sample are lower than those of the RFLA sample by 6.31 GPa and 0.11 GPa, respectively. The ASRS can be utilized as aggregates in dam concrete, such as in the structure with lower tensile strength requirements.

Ice pressure and icing volume expansion rate of acetate-based deicers under freezing conditions

Acetate-based deicers are frequently used as airport pavement de-icing fluids in cold regions. In this study, the ice pressure (Ip), icing volume expansion rate (ΔVP), freezing point (T0), and undercooling degree of acetate-based deicers were investigated. The above mentioned indices were also compared with that of water and NaCl deicers. The results showed that the cooling process and ice crystal growing process of acetate-based deicers could be divided into five stages. Additionally, the stabilised values of Ip and ΔVP decreased with the deicer concentration increases. Furthermore, the impulse concept of ice pressure (IPI) was proposed to evaluate the frost damage of concrete caused by deicers. The Ip, ΔVP , and T0 values of calcium magnesium acetate (CMA) deicer with different Ca/Mg mole ratios (i.e. 1/1, 0.91, 7/3, and 3/7) were tested in the ice pressure test. The value of CMA deicer with 3/7 Ca/Mg mole ratio was the lowest. However, the Ip values of CMA deicers with 0.91 Ca/Mg and 1/1 Ca/Mg mole ratios were the highest. Among all the tested acetate-based deicers, CMA deicers had the lowest values of Ip, ΔVP, and IPI. Moreover, the CMA deicer with 3Ca/7Mg mole ratio was recommended for deicing airport pavements to reduce the concrete frost deterioration caused by acetate-based deicers. In this study, we investigated the physical properties of acetate-based deicers, quantitatively analysed the destructive power of deicers in a freeze–thaw test, and studied the cause of freeze–thaw deterioration of concrete. Overall, this study provides a theoretical method for exploring new deicers.

On the Issue of Standardizing Concrete Frost Resistance to Ensure the Reinforced Concrete Structures Durability

When erecting monolithic reinforced concrete structures, the structure of concrete can differ significantly from the laboratory standard due to the complexity of providing favorable conditions for hardening, and therefore the compressive strength and especially the frost resistance of concrete may not meet the design requirements, which can negatively affect the reinforced concrete structure durability and require amplification, especially in earthquake-prone areas [1, 2]. Increasing the durability of reinforced concrete structures is possible by creating a rational stress field, for example, by prestressing, incl. variable along the length of the structure [3,4], but this technique is difficult to implement for monolithic reinforced concrete structures. It is possible to use effective materials or methods of manufacturing structures [5, 6]. But this is also mainly problematic for use in the construction of monolithic reinforced concrete structures. Generally accepted methods of calculating the reinforced concrete structures durability subjected to cyclic freezing-thawing during operation, incl. in a water-saturated state, do not exist. At the design stage, ensuring the durability of such reinforced concrete structures is mainly reduced to the reasonable assignment of requirements for concrete quality indicators, depending on the operating conditions, which is the focus of BC 28.13330.2017 (EN 206) and GOST 31384-2017 from the premise of ensuring durability of at least 50 years. In the above-mentioned norms of the Russian Federation, in fact, two approaches are presented to ensure the durability of reinforced concrete structures during cyclic freezing-thawing, incl. in a water-saturated state, namely: designing a concrete structure capable of working under such conditions by standardizing the values of cement consumption, W/C ratio, class of concrete in terms of compressive strength, amount of entrained air, or rationing of concrete grades in terms of frost resistance F1 (first base method GOST 10060-2012 provides for freezing in air, saturation and thawing in water) or F2 (second base method GOST 10060-2012 provides for freezing in air, saturation and thawing in 5% sodium chloride solution). The purpose of this work is to compare various approaches to ensuring the durability of reinforced concrete structures operated during cyclic freezing-thawing and to analyze the provision of durability with standardized indicators when designing the structure of concrete.

Cross-scale Study on the Mechanical Properties and Frost Resistance Durability of Aeolian Sand Concrete

Many researchers have been searching for the alternative for natural river sand as fine aggregate for concrete preparation. Thus, whether it is feasible to replace natural river sand by aeolian sand in concrete partially or totally is studied. At the macroscale, a universal testing machine and concrete rapid freeze-thaw equipment are applied in testing mechanical properties as well as frost resistance durability, respectively. At the mesoscale, a scanning electron microscope has been taken for observing and analyzing the interfacial transition zone in aeolian sand concrete. At the microscale, nuclear magnetic resonance is used for testing pore structure evolution. Simultaneously, the macro- and microrelationships between compressive strength and total and interval porosities are established. The grey correlation model is adopted to analyze the main microscopic pore parameters that affect aeolian sand concrete's frost resistance durability. Results show that the workability and mechanical properties of aeolian sand concrete first increase and subsequently reduce as aeolian sand content increases, and the optimum content is 30%. The influence mechanism is that aeolian sand particles with different contents change the linear packing density of fine aggregate and affect the aggregate gradation and pore structure. The compressive strength has a negative linear relation to total porosity and porosity of more harmful pores (>200 nm) and an insignificant correlation with the porosity of non-more harmful pores (<200 nm). A medium and low content of aeolian sand (10%–60%) partly improves concrete frost resistance, whereas a large content (80%–100%) significantly improves concrete frost resistance. Grey correlation analysis shows the most important microstructural factor influencing the macroscopic frost resistance durability in aeolian sand concrete should be the relative proportion of more harmful and harmless pores. The findings of this research expand aeolian sand concrete's application in cold areas and provide a new way for the reuse of waste resources.

Concept of design assurance for operational reliability of reinforced concrete structures in severe conditions

This work considers the concept of a systematic approach to the design assurance of equal reliability of structures under normal and severe operating conditions during their service life corresponding to the time of exhaustion of concrete frost resistance resource. It is proposed to analyze the reliability of structures in terms of the probability of a parametric failure, diagnosed as the achievement of the design and normative level by technical suitability indicators. The necessary (under conditions of equi-reliability!) correction of the initial values of concrete and reinforcement strength indicators is explained by dynamic models that take into account statistical patterns of their change during freezing-thawing cycles as well as the effect of reinforcement level. The time factor of the fatigue wear process is modeled by relative (to the design frost resistance) cycles, while the aggressiveness of external environment is modeled by an equi-consequential number of standard frost test cycles.

Assessment of Light Concrete Frost Resistance

Heat-insulating and structural-heat-insulating light concretes used in external enclosing structures significantly reduce the heat loss of a building in the cold season. The paper solves the problem of establishing criteria for evaluating the external walls made of light concrete blocks resistance to alternate freezing and thawing in laboratory conditions. A method for studying the frost resistance of masonry made of polystyrene concrete and cellular concrete of autoclave hardening during cycles of unilateral humidification-freezing-warming of wall fragments is proposed, which is closest to the actual operating conditions.Physical, mechanical and thermophysical characteristics of heat-insulating and structural concrete are obtained. The dependences of heat-protective qualities on the degree of moisture content of the material, as well as the strength of the thawing conditions of samples in water and air conditions are established.As the normalized parameters for assessing the frost resistance of light concrete masonry by unilateral freezing it is proposed to use the adhesion strength of blocks with plaster mortar, the strength of chemical anchors (breaking methods), as well as the passage speed of an ultrasonic impulse through the masonry thickness (non-breaking method).Based on the research results, recommendations for their implementation in regulatory documents are formulated.

Research on prediction of concrete frost resistance based on random forest

Poor frost resistance of concrete will accelerate the deterioration of concrete structure and shorten the service life of concrete. This paper predicts the frost resistance of concrete and selects the initial index of factors that affect the frost resistance of concrete. The random forest algorithm is introduced to remove the unimportant indicators in the initial indicator system of the concrete mix ratio and determine the optimal indicator combination. The relative dynamic elastic modulus is used as the output index of random forest to predict the frost resistance of concrete. The proposed random forest model provides a reasonable and effective method for concrete frost resistance prediction.

Frost Resistance of Thermoinsulating Recycled-Aggregate Concretes Containing Glazed Hollow Beads

Glazed hollow bead (GHB) is an innovative material that gives concrete very good thermal-insulation properties and improves concrete frost resistance, when used as a partial replacement of ordinary fine aggregate. The improvement in frost resistance under freeze-thaw cycles and the deterioration mechanisms of recycled aggregate thermoinsulating concretes (RATICs) is the objective of this study, after adding GHBs to the mix. Fifteen cubes and ninety prisms made of five RATIC mixes (GHB content = 0, 40, 65, 90 and 130 kg/m3) were tested in compression, to identify the optimum content of GHB. The degradation mechanisms of RATIC were identified based on mass loss, dynamic elastic modulus and uniaxial compressive strength. In addition, RATIC mesostructure was investigated by means of Computed Tomography Scanning, and the deterioration mechanisms by analyzing pore amount, average and maximum pore area and porosity. The experimental results demonstrate that adding glazed hollow beads to recycled aggregate concrete (RAC) moderately changes the mesostructure of the concrete, to the advantage of frost resistance, and that the optimum content of GHB is around 90 kg/m3.

Properties of Fibrous Concrete Made with Plastic Optical Fibers from E-Waste.

This article presents research results relating to the potential for waste utilization in the form of polymer optical fiber (POF) scraps. This material is difficult to recycle due to its diverse construction. Three different volumes of POF were used in concrete in these tests: 1%, 2%, and 3%. The experimental studies investigated the basic properties of the concrete, the elastic and dynamic moduli, as well as deformation and deflection of reinforced beams. The microstructures, including the interfacial transition zones (ITZs), were recorded and analyzed using a scanning electron microscope. It was observed that 180 freezing–thawing cycles reduced the concrete frost resistance containing 3% POFs by half compared to the control concrete. The resistance to salt crystallization of this concrete decreased by about 55%. POFs have significant effects on the splitting tensile and flexural strengths compared to the compressive strength. The control beams were destroyed during the four-point static bending tests at half the force applied to the beams that were reinforced with POFs.

The problem of the equivalent time to start the internal frost resistance test on self-compacting concrete with supplementary cementitious materials

The article presents the results of tests on frost resistance of self-compacting concretes made with the use of cement containing mineral additives after 150 freezing and thawing cycles. Concrete with types of cement containing 30 and 50% blast furnace slag, cement with 30% silica fly ash and with types of cement containing both slag and ash with a combined proportion of 60% (30% both mineral components) and 80% (45% slag and 35% ash). The relative dynamic modulus of elasticity determined based on the ultrasonic pulse transit time RDMUPTT was used as the basis for the measure of frost resistance. The tests were carried out on cubic specimens with a side length of 150 mm, which are standard for testing the compressive strength of concrete.The relative dynamic modulus of elasticity RDMUPTT has proved to be a qualitatively correct measure of concrete's frost resistance. The RDMUPTT values corresponded to the values of the auxiliary measure, which in this case was the relative decrease in specimen mass. It was confirmed that tests on frost resistance of concretes with mineral additives should be started in the so-called “equivalent time” depending on the cement composition. Due to the varied increases in concrete strength over time, the consideration of “equivalent time” is intended to improve the reliability of testing methods, including the ultrasonic method. Tests have also shown that the use of an additive in the form of silica fly ash can weaken concrete frost resistance, especially when the fly ash to clinker ratio is high. A positive effect of the addition of granulated blast furnace slag on the frost resistance of concrete was also noticed.

Feasibility of using of accelerated test methods for determination of frost-resistance for concrete

The article presents the results of studies of innovative materials in the field of testing frost resistance. In fact, present accelerated methods for the determination of concrete frost resistance have high labour consuming and low effectiveness. Moreover there is no such accelerated methods which can be sufficiently applicable fro different innovative concretes, for example, concretes with SAP or self-compacting concrete and so on. Therefore, it is highly important to investigate new accelerated test method with high operability, efficiency and sufficient precision. Previously, two new methods were developed. The main purpose of the research is to compare these methods by evaluation of their technology and accuracy and, consequently, to identify the more sustain and efficient one. First method is based on estimation of energy release due to mechanical fracture and thermo cycling. Second method consists of the calculation value z (relation between relative decreasing of strength and relative strain in the direction perpendicular to compression) and replacement of thermo cycles by mechanical cycles. Both methods have high operability and do not take a lot of time, in was tested on the 10 specimens made of concrete and results were compared with values derived by standard method.