Journal articles on the topic 'Concrete – Cracking'
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1
You, Chun Zi, Xiao Chun Fan, Di Wu, and Li Ping Pu. "Experimental Research on Temperature-Stress of Inorganic Polymer Concrete." Applied Mechanics and Materials 405-408 (September 2013): 2795–800. http://dx.doi.org/10.4028/www.scientific.net/amm.405-408.2795.
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The inorganic polymer concrete is a new environmentally material. Using the temperature - stress test machine to research its early cracking sensitivity, and compare it with the normal concrete. The deformation development process of inorganic polymer concrete consists three stages:early contraction, expansion, contraction to cracking; cracking temperature can effectively evaluate the overall cracking performance of concrete; the cracking temperature of inorganic polymer concrete is 14.2 °C, the normal concrete is 14.4 °C; the inorganic polymer concretes cracking stress is 2.658MPa, the normal concrete is 0.582MPa. The results show the inorganic polymers cracking performance is better than the normal concrete.
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Shao, Xiao Rong, and Liang Feng Zhu. "Application of Polypropylene Fiber Concrete in Underground Engineering." Advanced Materials Research 163-167 (December 2010): 1776–79. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.1776.
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Aimed to solve the problem that the mass concrete structures are apt to crack in underground engineering, this paper makes some research from the view of crack resistance performance of polypropylene fiber concretes. Since polypropylene fiber achieves waterproof through realizing of crack resistant, blending polypropylene fibers into concretes can reduce early contraction deformation of concretes, hinder emergence of plastic shrinkage cracking and improve impermeability of concretes, and its construction technology is simple. In practical application of this in anti-cracking and anti- seepage concrete structures in the International Terminal project of Hangzhou Xiaoshan International Airport, we find that mix of polypropylene fibers with concretes clearly improves anti-cracking and anti-seepage performance of concrete structures and meets design requirements of basements through measuring temperature and observing cracking condition of the mass concrete structures of basements on site. The project can provide experience for reference to similar projects.
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Chen, Bo, Jian Tong Ding, and Yue Bo Cai. "Influence of Aggregates on Cracking Resistance of Concrete at Early Age." Applied Mechanics and Materials 151 (January 2012): 474–79. http://dx.doi.org/10.4028/www.scientific.net/amm.151.474.
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In order to investigate influence of aggregates on cracking resistance of concrete at early age, four kinds of aggregates, i.e. syenite, basalt, marble and sandstone, were used for the test on cracking resistance of hydraulic concretes by the temperature stress testing machine. Analogy analysis was carried out with test results of concretes with two gradings of aggregates. The results show that aggregates affect elastic modulus, thermal expansion coefficients and tensile creep behavior of concrete at early age. However, the temperature rise of concrete was slightly affected by various types and gradings of aggregate. Moreover, the cracking temperature is reliably to be used to quantitatively evaluate the influence of aggregates on cracking resistance of concrete at early age.
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Dong, Chun Min, Ke Dong Guo, and Jia Jia Sun. "A New Calculation Method for Cracking Width of Beam with High Strength Rebar." Advanced Materials Research 243-249 (May 2011): 415–18. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.415.
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With the application of high strength concrete and rebar, the influence of concrete strength on cracking width of reinforced concrete beam with high strength rebar is becoming more and more important. To investigate the effect of concrete strength on cracking width of reinforced concrete beam with high strength rebar, the experiment including 6 simply supported T-beams with high-strength rebar and 2 beams with ordinary-strength rebar have been made. Then the relevant specifications advised in Code for Design of Concreter Structure (GB50010-2002) are revised according to the experiment results so as to considering the influence of concrete on cracking width. A new cracking width method considering the influence of concrete strength on cracking width for reinforced concrete beam with high strength rebar is proposed. Finally, the comparisons between predictions and experiment results have been conducted, which shown that the proposed new cracking width method agreed with experiment results well.
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Schindler, Anton, Benjamin Byard, and Aravind Tankasala. "Mitigation of early-age cracking in concrete structures." MATEC Web of Conferences 284 (2019): 07005. http://dx.doi.org/10.1051/matecconf/201928407005.
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Early-age cracking can adversely affect the behavior and durability of concrete elements. This paper will cover means to mitigate early-age cracking in concrete bridge decks and mass concrete elements. The development of in-place stresses is affected by the shrinkage, coefficient of thermal expansion, setting characteristics, restraint conditions, stress relaxation, and temperature history of the hardening concrete. The tensile strength is impacted by the cementitious materials, the water-cementitious materials ratio, the aggregate type and gradation, the curing (internal/external) provided, and the temperature history of the hardening concrete. In this study, restraint to volume change testing with rigid cracking frames (RCF) was used to directly measure and quantify the combined effects of all variables that affect the development of in-place stresses and strength in a specific application. The laboratory testing performed involved curing the concrete in the RCF under sealed, match-cured temperature conditions to simulate concrete placement in concrete bridge decks and mass concrete. Experimental results reveal that the use of low heat of hydration concretes, concretes that use fly ash and slag cement, and lightweight aggregate concretes (because of reduced modulus of elasticity and coefficient of thermal expansion), are very effective to reduce the risk of early-age cracking in these elements.
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Choe, Gyeongcheol, Yasuji Shinohara, Gyuyong Kim, Sangkyu Lee, Euibae Lee, and Jeongsoo Nam. "Concrete Corrosion Cracking and Transverse Bar Strain Behavior in a Reinforced Concrete Column under Simulated Marine Conditions." Applied Sciences 10, no. 5 (March 5, 2020): 1794. http://dx.doi.org/10.3390/app10051794.
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This study performed accelerated corrosion tests on reinforced concrete (RC) specimens reinforced with transverse steel bars to evaluate the concrete cracking and rebar strain behaviors caused by rebar corrosion. Seven RC specimens were created with variable compressive strengths, rebar diameters, and concrete cover thicknesses. To mimic in-situ conditions, the accelerated corrosion tests applied a current to the longitudinal bar and transverse bar for different periods of time to create an unbalanced chloride ion distribution. These tests evaluated the amount of rebar corrosion, corrosion cracking properties, and transverse bar strain behavior. The corrosion rate of the transverse bar was faster than that of the longitudinal bar, and cracking first occurred in the concreate around the transverse bar in the specimens with low concrete compressive strength and thin concrete cover. Corrosion cracking and rebar strain were greatly affected by the behavior of the corrosion products that resulted from the pore volume and cracking properties of the cement paste.
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Zhao, Zhifang, Cong Xiao, Bo Fang, Yongjiu Lu, Tao Shi, Zhigang Zhao, and Xiaofeng Gao. "Effect of CNTs and MEA on the creep of face-slab concrete at an early age." Nanotechnology Reviews 11, no. 1 (January 1, 2022): 2535–46. http://dx.doi.org/10.1515/ntrev-2022-0145.
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Abstract The creep of face-slab concrete in a rockfill dam is critical for determining the restrained stress and cracking resistance of the concrete at an early age. In this article, the mix proportion of the face-slab concrete for a rockfill dam under construction without any cracking resistance additive was taken as the reference concrete (called JC) mix proportion. The carbon nanotubes (CNTs) and magnesium oxide expansion agent (MEA) were incorporated into JC to prepare face-slab concretes called NC and PC, respectively. The temperature–stress tests under temperature matching curing (TMC) and constant temperature curing (CTC) modes were conducted on these three kinds of concretes to investigate the effects of CNTs and MEA on the early-age creep properties of the face-slab concrete under variable stress conditions. The results showed that the creep performance of NC concrete under CTC mode was lower than that under TMC mode. Combined with mercury intrusion porosimetry test results, the mechanism of the effect of CNTs and MEA on creep was analyzed. The results showed that the temperature change may lead to the CNTs debonding from the cementitious matrix or matrix cracking for the NC concrete. The incorporation of CNTs can increase the early-age creep and improve the cracking resistance of concrete.
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Mahmoud Abo El-Wafa. "Fiber incorporation and crack control: A synergistic approach to improving serviceability of RC concrete." Global Journal of Engineering and Technology Advances 15, no. 2 (May 30, 2023): 001–10. http://dx.doi.org/10.30574/gjeta.2023.15.2.0085.
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This research elaborates on how cracking affects RC fiber concrete serviceability. It describes the different forms of fibrous concrete and how they function under cracking impact, enhancing concrete structure serviceability. Practical mechanical behavior language is often used to assess materials' performance. Historical assessment should help create experiences using RC fiber concrete, which reduces cracking and enhances concrete structures' serviceability. The issue is chronologically linked through early and modern author references. However, fibrous concrete's construction path is desirable worldwide. Fibrous concrete is employed in many building applications, from rehabilitation to new construction, due to its advantages over conventional construction materials. Lightness, high mechanical performance, the ability to manufacture in any form, ease of assembly, and a reduced need for supporting structures, controlled anisotropy, high specific strength, and specific stiffness all improve the serviceability of concrete structures. Fibrous concrete's many properties are opening new construction industry pathways. Thus, this research reviews the present use of fibrous concrete on cracks to improve concrete structure serviceability.
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Li, Yun Feng, Rong Qiang Du, and Fan Ying Kong. "Analysis of Concrete Early-Age Shrinkage Based on the Theory of Humidity Diffusion." Key Engineering Materials 462-463 (January 2011): 183–87. http://dx.doi.org/10.4028/www.scientific.net/kem.462-463.183.
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The early-age shrinkage cracking of concrete plays an important role to the accelerated deterioration and shortening the service life of concrete structures. Modern concretes are more sensitive to cracking immediately after setting, which is due to material characteristics (lower water/binder ratio and higher cement content) and external environmental fluctuations (humidity and temperature change). Determination of concrete free shrinkage is the basis of shrinkage cracking research. Analytical models of the autogenous shrinkage and drying shrinkage are established in this paper. The calculated results agree well with the experimental results.
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Tolmachov, Serhii, Olena Belichenko, Dmytro Tolmachov, and Yurii Turba. "CURRENT PROBLEMS OF HARDENING MONOLITHIC ROAD AND AERODROME CEMENT CONCRETE CURING." Theory and Building Practice 2022, no. 2 (December 20, 2022): 98–104. http://dx.doi.org/10.23939/jtbp2022.02.098.
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Studies of moisture loss from hardening monolithic cement concrete have been carried out. It was found that there is no consensus on the critical value of moisture loss from hardening concrete, at which shrinkage and cracking are possible, and there is no common understanding of the possible critical width of the shrinkage crack opening. It is shown that when the concrete hardens in air-dry conditions, its indicators, including durability, decrease by a factor of 2 or more. The critical value of moisture loss from hardening concrete was experimentally determined, which is 2 kg/m2. In this case, the deterioration of concrete properties as a result of rehydration of cement does not exceed 5 % and does not affect its durability. The possibility of restoring the properties of concretes, which were lost as a result of cracking during plastic shrinkage and contraction, has been experimentally proved if, after cracking, the concretes are placed for further hardening in a humid environment.
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Shah, Surendra P., Shashidhara Marikunte, Wei Yang, and Corina Aldea. "Control of Cracking with Shrinkage-Reducing Admixtures." Transportation Research Record: Journal of the Transportation Research Board 1574, no. 1 (January 1997): 25–36. http://dx.doi.org/10.3141/1574-04.
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Shrinkage cracking can be a critical problem in concrete construction, especially for flat structures such as highway pavements, slabs for parking garages, and bridge decks. One way to reduce the shrinkage cracking is to provide reinforcement in the form of wire mesh to resist tensile forces. In recent years, short, randomly distributed fibers have been used to control shrinkage cracking. The efficiency of shrinkage-reducing admixtures (SRAs) in controlling restrained shrinkage cracking of concrete is reviewed. A ring-type specimen was used for restrained shrinkage cracking tests. The SRA selected for this investigation was a propylene glycol derivative, which was used at 1 and 2 percent by weight of cement. Free (unrestrained) shrinkage, weight loss, compressive strength, and fracture toughness were also investigated. The results of SRA concretes were compared with that of plain concrete with the same water-to-cement ratio. A theoretical model based on nonlinear fracture mechanics was developed for predicting transverse cracking of the concrete ring specimen caused by drying shrinkage. The model prediction of time to cracking compared well with the experimental data. The model can be extended to different geometries and dimensions than those considered in this research.
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Sayahi, Emborg, Hedlund, and Cwirzen. "Plastic Shrinkage Cracking in Concrete." Proceedings 34, no. 1 (November 18, 2019): 2. http://dx.doi.org/10.3390/proceedings2019034002.
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Plastic shrinkage cracking in concrete is mainly a physical process, in which chemical reactions between cement and water do not play a decisive role. It is commonly believed that rapid and excessive moisture loss, due to evaporation is the primary cause of the phenomenon. Once the concrete is cast, its solid particles start to settle due to gravity, causing an upward water-flow from the concrete interior and through its pore system to the surface, i.e., bleeding regime. When the amount of the evaporated water exceeds the amount of the water accumulated at the concrete surface, i.e., bleed water, concrete enters the so called drying regime, during which water menisci form inside the pores causing a build-up of a negative pore pressure, also known as capillary pressure. The progressive evaporation gradually decreases the radii of the menisci, which causes a further increase of the pore pressure and solid particles consolidation. Eventually, the skeleton of the concrete becomes stiff enough to resist the gravitational forces, which means that the vertical deformation of the concrete either completely stops or continues at a much lower rate. At this point, the capillary pressure is no longer able to further consolidate the concrete and move the pore water towards the surface. Instead, the developed tensile forces reduce the inter particle distances and the horizontal deformation continues. If the concrete member is restrained (e.g., due to reinforcement, variation in sectional depth, the friction of the form, etc.), the shrinkage can lead to tensile stresses accumulation. Once the tensile stresses exceed the early age tensile strength of the concrete, cracks start to form, preparing passageways for ingress of harmful materials into the concrete interior, which eventually may impair the durability and serviceability of the structure. This abstract reports the findings of a PhD research, carried out at Luleå University of Technology (LTU) to investigate the impact of parameters such as, admixtures, water-cement ratio (w/c), cement type, dosage of superplasticizer (SP), and steel fibers, on concrete’s cracking tendency while in plastic state. The results show that presence of accelerators, retarders, coarser cement particles, high w/c, and more SP increases the cracking risk, while stabilizers, air entraining agents (AEA), shrinkage reducing admixtures (SRA), and steel fibers notably decrease the cracking potential. Based on the findings of the above mentioned investigation a new model is proposed to estimate the severity of plastic shrinkage cracking, based on the initial setting time and the amount of the evaporated water from within the concrete bulk. The experimental results of the PhD research, alongside those reported by other researchers, were utilized to check the validity of the proposed model. According to the outcomes, the model could predict the cracking severity of the tested concretes with a good precision.
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Zvolánek, Lukáš, and Ivailo Terzijski. "Concrete Resistance to Cracking due to Shrinkage." Solid State Phenomena 249 (April 2016): 96–101. http://dx.doi.org/10.4028/www.scientific.net/ssp.249.96.
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This paper suggests an interpretation of the concrete resistance to cracking caused by shrinkage. Cement hydration leads to many chemical processes which cause volume changes and changes of the other physico-mechanical properties of concrete. It is necessary to know the development of residual stresses and corresponding capacity of concrete to establishing of the resistance to shrinkage cracking. Intersection of stress and capacity is a time point which determines that resistance. All necessary concrete properties was established experimentally. The three types of micro-concretes were monitored. On the basis of acquired results it can be stated that the optimal composition of micro-concrete was found because no shrinkage cracks should occur during its life-time.
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Jalal, Asif, Luqmanul Hakim, and Nasir Shafiq. "Mechanical and Post-Cracking Characteristics of Fiber Reinforced Concrete Containing Copper-Coated Steel and PVA Fibers in 100% Cement and Fly Ash Concrete." Applied Sciences 11, no. 3 (January 25, 2021): 1048. http://dx.doi.org/10.3390/app11031048.
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This experimental study investigated the effects of polyvinyl alcohol (PVA) and copper-coated steel (CCS) on the mechanical properties and the post cracking behavior of fiber reinforced concrete (FRC). In designing high-performance concrete mixes, cement replacement materials are the essential ingredients. Therefore, the research objective was to investigate PVA and CCS fiber’s post-cracking performance in 100% cement concrete and concrete with 80% cement and 20% fly ash. The fiber content was fixed as a 0.3% volumetric fraction. CSS fibers required 15% more superplasticizer to achieve the desired slump of fresh concrete than the PVA fibers. Simultaneously, CCS fibers showed a 10% higher compressive strength than the concrete made of PVA fibers. Both fibers exhibited a similar effect in developing tensile and flexural strength. PVA fibers showed a value of 47 Gpa of secant modulus, and CCS fibers resulted in 37 Gpa in 100% cement concrete. In post-cracking behavior, CCS fibers showed better performance than the PVA fibers. The reason for this is that CCS showed 2.3 times the tensile strength of the PVA fibers. In comparing the two concretes, fly ash concrete showed about 10% higher compressive strength at 56 days and about 6% higher tensile and flexural strength. Similarly, fly ash concrete showed more than 15% first crack strength and flexural toughness than the 100% cement concrete in post-cracking behavior. Fiber-reinforced concrete containing PVA or CCS fibers showed enhanced post-cracking characteristics and its use could be preferred in structural applications.
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Holt, Erika E., and Donald J. Janssen. "Influence of Early Age Volume Changes on Long-Term Concrete Shrinkage." Transportation Research Record: Journal of the Transportation Research Board 1610, no. 1 (January 1998): 28–32. http://dx.doi.org/10.3141/1610-05.
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Volume changes can occur in concrete during the first 24 hr and are generally missed in laboratory shrinkage evaluations. Unfortunately these early age volume changes are present in real pavements and structures and can contribute to the cracking behavior of the concrete at later ages. Early age volume changes can occur in two forms: drying shrinkage before the start of curing and autogenous volume changes. Although these early age volume changes are often dismissed as being insignificant, recent work in Europe has identified magnitudes for early age volume changes of some concretes that are equal to or greater than 28-day drying shrinkage measurements. Expansions have also been identified in some cases. The results of some investigations of volume changes in concrete during the first 24 hr under both drying and nondrying conditions are presented. An example of potential long-term cracking under partially restrained conditions (concrete slab-on-grade modeled by a concrete ring cast around a hollow steel ring) is used to illustrate the magnitude of influence of early age volume changes on concrete cracking. Both test procedures employ nonstandard methods to quantify the cracking potential of concrete.
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Jin, Caiyun, Jianglin Liu, Zigeng Wang, and Yue Li. "Early Cracking Risk Prediction Model of Concrete under the Action of Multifield Coupling." Advances in Materials Science and Engineering 2021 (July 15, 2021): 1–14. http://dx.doi.org/10.1155/2021/9920945.
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Through the adiabatic temperature rise experiment, the adiabatic temperature rise of concrete with hydration time was recorded. Based on the maturity degree theory, the relationship between the hydration degree of the concrete and the equivalent age was determined. Then, the hydration degree prediction model of the concrete's early elastic modulus and tensile strength was established. The local temperature and humidity of the concrete were measured by the shrinkage experiment, and based on the capillary water tension theory, a temperature-humidity prediction model for the early shrinkage of the concrete was designed. According to the ratio of the creep deformation and elastic deformation of concrete which were obtained through the restraint ring experiment, a model for predicting the early creep coefficient of concrete was proposed. Based on the coupling effect of “hydration-temperature-humidity,” a prediction model of early cracking risk coefficient of concrete under multifield coupling was proposed. Finally, several groups of slab cracking frame experiments were carried out, and the cracking risk prediction results of concrete were consistent with the actual situation, which indicated the correctness of the early cracking risk prediction model of concrete.
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Luosun, Yi Ming, Jun Zhang, and Yuan Gao. "Evaluation of Shrinkage Resulted Cracking of High Strength Calcium Sulfoaluminate Cement Concrete with Impact of Internal Curing." Key Engineering Materials 629-630 (October 2014): 144–49. http://dx.doi.org/10.4028/www.scientific.net/kem.629-630.144.
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In this paper, restrained ring test and shrinkage test are carried on three kinds of concrete—high-strength portland cement concrete, high-strength calcium sulfoaluminate cement concrete and high-strength calcium sulfoaluminate cement concrete with internal curing in order to evaluate the shrinkage induced cracking performance of the concretes. The experimental results show that calcium sulfoaluminate cement concrete exhibits lower shrinkage caused by surface drying comparing to portland cement concrete. Internal curing can eliminate most of the autogenous shrinkage of concrete. In the ring test, the latter two concrete did not crack during the whole test history—42 days, while high-strength portland cement concrete cracked at the 13th day after casting. High strength calcium sulfoaluminate cement concrete exhibits better anti-cracking ability than the high strength portland cement concrete with the same strength grade.
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Li, Yun Feng, Quan Xiang Wang, and Hua Xun Guo. "Shrinkage Cracking Ring Tests of Concrete with Compound Mineral Admixtures." Applied Mechanics and Materials 325-326 (June 2013): 59–62. http://dx.doi.org/10.4028/www.scientific.net/amm.325-326.59.
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Shrinkage cracking is the direct cause which leads to the deterioration of durability and integrity of concrete. In this paper, ring-test methods are used to study the early age cracking characterization of compound mineral admixtures concrete which includes steel slag, blast furnace slag and fly ash. The effect of compound admixtures on cracking characterization of concrete is discussed, restraint stress caused by concrete shrinkage and cracking age are analyzed. Through the comprehensive consideration of the free shrinkage strain, creep, restriction factors on the effect of the cracking of concrete specimens. The results show that suitable proportion mineral admixtures can be used to reduce cracking in concrete. The risk of cracking can be estimated for compound admixtures concrete, so that it will improve the durability of concrete structures.
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Morris, Peter, and Peter Dux. "Cracking of plastic concrete." Australian Journal of Civil Engineering 1, no. 1 (January 2003): 17–21. http://dx.doi.org/10.1080/14488353.2003.11463905.
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ZURER, PAMELA. "CRACKING THE CONCRETE CEILING." Chemical & Engineering News 84, no. 1 (January 2, 2006): 25. http://dx.doi.org/10.1021/cen-v084n001.p025.
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Chen, Xu Jun, Xiao E. Zhu, and Zhong Yang. "Study on Cracking Load of Normal Section for Concrete Beams Strengthened with BFRP Sheet." Applied Mechanics and Materials 578-579 (July 2014): 1343–46. http://dx.doi.org/10.4028/www.scientific.net/amm.578-579.1343.
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Based on the calculation method of cracking load for reinforced concrete beam, the formula to calculate cracking load of normal section for concrete beams strengthened with BFRP sheet is established. The cracking load experiment of seven concrete beams strengthened with BFRP and three concrete beams strengthened with CFRP is conducted, and the results showed that fiber sheet layers and fiber sheet types have little effect on cracking load of concrete beams strengthened, the cracking load of beams strengthened mainly depends on the strength of concrete. The comparison between estimated values and test values of concrete beams strengthened indicates that the estimated values are slightly smaller, the formula can be used to calculate the cracking load of concrete beams strengthened.
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ALBUQUERQUE, A. C., S. B. dos SANTOS, J. L. CALMON, and L. C. P. da SILVA FILHO. "Thermo-mechanical analysis of mass concrete elements made of rubberized concrete." Revista IBRACON de Estruturas e Materiais 12, no. 3 (June 2019): 580–89. http://dx.doi.org/10.1590/s1983-41952019000300008.
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Abstract In this study, mass concrete samples with tire rubber chips (rubberized concrete) were evaluated in order to determine if the addition of rubber particles would enhance cracking strength due to volumetric variations of thermal origin, compared to a reference concrete, without rubber. Samples of the concretes studied were initially tested to characterize their thermal and mechanical properties. The test results were used as parameters for the analysis of the thermo-mechanic behavior of the rubberized concrete by means of a software that determined the thermal and stress response on a bi-dimensional dominion of a structural element of hypothetical geometry, typical of dam construction, applying FEM (finite element method) analysis. The results obtained indicated that, although the maximum temperatures expected are similar for both concretes (reference and rubberized), those containing tire rubber chips are subjected to lower tensile stresses, about half the stress generated in the control concrete. This behavior indicates that the addition of tire rubber chips in concrete is an efficient strategy to minimize the risk of cracking due to thermal stresses.
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Safiuddin, Md, A. Kaish, Chin-Ong Woon, and Sudharshan Raman. "Early-Age Cracking in Concrete: Causes, Consequences, Remedial Measures, and Recommendations." Applied Sciences 8, no. 10 (September 25, 2018): 1730. http://dx.doi.org/10.3390/app8101730.
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Cracking is a common problem in concrete structures in real-life service conditions. In fact, crack-free concrete structures are very rare to find in real world. Concrete can undergo early-age cracking depending on the mix composition, exposure environment, hydration rate, and curing conditions. Understanding the causes and consequences of cracking thoroughly is essential for selecting proper measures to resolve the early-age cracking problem in concrete. This paper will help to identify the major causes and consequences of the early-age cracking in concrete. Also, this paper will be useful to adopt effective remedial measures for reducing or eliminating the early-age cracking problem in concrete. Different types of early-age crack, the factors affecting the initiation and growth of early-age cracks, the causes of early-age cracking, and the modeling of early-age cracking are discussed in this paper. A number of examples for various early-age cracking problems of concrete found in different structural elements are also shown. Above all, some recommendations are given for minimizing the early-age cracking in concrete. It is hoped that the information conveyed in this paper will be beneficial to improve the service life of concrete structures. Concrete researchers and practitioners may benefit from the contents of this paper.
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Ozyildirim, H. Celik, and Harikrishnan Nair. "Durable Concrete Overlays in Two Virginia Bridges." Transportation Research Record: Journal of the Transportation Research Board 2672, no. 27 (June 11, 2018): 78–87. http://dx.doi.org/10.1177/0361198118777606.
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The purpose of this study was to implement innovative concretes with low permeability and reduced cracking potential in overlays to reduce chloride infiltration into the bridge decks. Two parallel bridges on Route 64 over Dunlap Creek in Alleghany County, Virginia, were selected for this study. For low cracking potential, relatively low water contents, shrinkage reducing admixtures, and lightweight aggregates were used. For low permeability, concretes had supplementary cementitious material and relatively low water–cementitious material ratios. In the overlays, five different materials were used: latex-modified concrete with rapid set cement; silica fume concrete alone; and silica fume concrete with shrinkage reducing admixture, lightweight coarse aggregate, and partial lightweight fine aggregate. A compressive strength of 3,000 psi at 3 days was sought. The performance of the overlay concretes was observed after two to three winters. The overlays used in this study achieved the specified strength and low permeability. There were minimal tight cracks except for one section with the latex-modified concrete with rapid set cement in the left lane of the westbound bridge. The extensive cracks in that section were attributed to plastic shrinkage from adverse weather conditions at placement and the fact that a truck had caught fire in that lane. Silica fume concrete overlays with shrinkage reducing admixture, lightweight coarse aggregate, or lightweight fine aggregate are ready for implementation in the field for low cracking overlays.
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Xie, Ling Fei, and Li Yang. "Research on Autogenous Volume Deformation’s Influence on Thermal Creep Stress of Concrete High Arch Dam." Advanced Materials Research 282-283 (July 2011): 367–70. http://dx.doi.org/10.4028/www.scientific.net/amr.282-283.367.
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Autogenous volume deformation is an important parameter of anti-cracking behaviors of concrete. The sensitivity analysis of influence of concrete autogenous volume deformation on thermal stress of Xiaowan high arch dam is carried out based on simulation of temperature field. When presuming autogenous volume deformation, expansion concrete and shrinkage concrete are considered. The results show that early expansion and early shrinkage concretes have obvious influence on arch dam’s early thermal st ress; however have less influence on dam center’s maximum thermal stress. The longer of expansion period, the smaller of dam center’s maximum thermal stress; and the final residual thermal stress, which can benefit the concrete’s anti-cracking quality.
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Zhang, Peng, Qingfu Li, Yuanzhao Chen, Yan Shi, and Yi-Feng Ling. "Durability of Steel Fiber-Reinforced Concrete Containing SiO2 Nano-Particles." Materials 12, no. 13 (July 7, 2019): 2184. http://dx.doi.org/10.3390/ma12132184.
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An experimental study was conducted to investigate the effect ofnano-SiO2 and steel fiber content on the durability of concrete. Five different dosages of nano-SiO2 particles and five volume dosages of steel fiber were used. The durability of concretes includes permeability resistance, cracking resistance, carbonation resistance, and freezing-thawing resistance, and these were evaluated by the water permeation depth, number of cracks, total cracking area per unit area of the specimens, carbonation depth of the specimens, and the relative dynamic elastic modulus of the specimens after freezing-thawing cycles, respectively. The results indicate that the addition of nano-SiO2 particles significantly improves the durability of concrete when the content of nano-SiO2 is limited within a certain range. With the increase of nano-SiO2 content, the durability of concrete first increases and then decreases. An excessive number of nano-SiO2 particles could have an adverse effect on the durability of the concrete. The addition of the correct amount of steel fibers improves the carbonation resistance of concrete containing nano-particles, but excessive steel fiber reduces the carbonation resistance. Moreover, the addition of steel fibers reduces the permeability resistance of concrete containing nano-particles. The incorporation of steel fiber enhanced the freezing-thawing resistance and cracking resistance of concrete containing nano-particles. With increasing steel fiber content, the freezing-thawing resistance of the concrete containing nano-particles increases, and the cracking resistance of the concrete decreases gradually.
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Sun, Jia Ying, Hua Qin Jiang, and Shao Feng Sui. "Cracking Appraisal and Anti-Crack Measures Research of Cross Sea Bridge Concrete." Key Engineering Materials 405-406 (January 2009): 367–72. http://dx.doi.org/10.4028/www.scientific.net/kem.405-406.367.
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Through the experiment, this paper carries on the appraisal to the cracking risk of cross-sea bridge concrete. Analyzed the influence of active admixture, sand ratio, cement content and water-cement ratio to the cracked degree of concrete. And proposed control measure of the plastic shrinkage cracking of concrete. Finally, through research to the concrete used in pile cap of the Shanghai Yangtze River Bridge, it obtains that all can be allowed to reduce the cracking risk of concrete by reducing active admixture, increasing to fly ash amount, reducing sand ratio, the slag powder has little effect the cracking risk of concrete, the silica fume can increase the cracking risk of concrete.
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Peng, Zhang. "The Cracking Mechanism and Anti-Cracking Measures for Hydraulic Mass Concrete." Advanced Materials Research 1025-1026 (September 2014): 68–73. http://dx.doi.org/10.4028/www.scientific.net/amr.1025-1026.68.
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The article describes and analyzes the process of mass concrete casting and crack problems during the period of construction. The article illustrates the necessity of crack control for mass concrete structures and introduces the present application situation of commercial software used to analyse the temperature field and stress field. Combining the engineering practice, the article sums up the measures to deal with hydraulic mass concrete structure cracks and the application situation of various methods. Then the article puts forward the future research direction to solve the problem of hydraulic mass concrete crack.
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Nguyen, Duy-Liem, Duc-Kien Thai, and Dong-Joo Kim. "Direct tension-dependent flexural behavior of ultra-high-performance fiber-reinforced concretes." Journal of Strain Analysis for Engineering Design 52, no. 2 (February 2017): 121–34. http://dx.doi.org/10.1177/0309324716689625.
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This research investigated the effects of direct tensile response on the flexural resistance of ultra-high-performance fiber-reinforced concretes by performing sectional analysis. The correlations between direct tensile and flexural response of ultra-high-performance fiber-reinforced concretes were investigated in detail for the development of a design code of ultra-high-performance fiber-reinforced concrete flexural members as follows: (1) the tensile resistance of ultra-high-performance fiber-reinforced concretes right after first-cracking in tension should be higher than one-third of the first-cracking strength to obtain the deflection-hardening if the ultra-high-performance fiber-reinforced concretes show tensile strain-softening response; (2) the equivalent bottom strain of flexural member at the modulus of rupture is always higher than the strain capacity of ultra-high-performance fiber-reinforced concretes in tension; (3) the softening part in the direct tensile response of ultra-high-performance fiber-reinforced concretes significantly affects their flexural resistance; and (4) the moment resistance of ultra-high-performance fiber-reinforced concrete girders is more significantly influenced by the post-cracking tensile strength rather than the tensile strain capacity. Moreover, the size and geometry effects should be carefully considered in predicting the moment capacity of ultra-high-performance fiber-reinforced concrete beams.
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Wang, Lei, Xiaoman Zeng, Yang Li, Huamei Yang, and Shengwen Tang. "Influences of MgO and PVA Fiber on the Abrasion and Cracking Resistance, Pore Structure and Fractal Features of Hydraulic Concrete." Fractal and Fractional 6, no. 11 (November 15, 2022): 674. http://dx.doi.org/10.3390/fractalfract6110674.
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Abrasion resistance and cracking resistance are two important properties determining the normal operation and reliability of hydropower projects that are subjected to erosion and abrasive action. In this study, polyvinyl alcohol (abbreviated as PVA) fiber and magnesium oxide expansive agents (abbreviated as MgO) were used together to solve the problems of cracking and abrasive damage. The effects of PVA fiber and MgO on the mechanical property, abrasion and cracking resistance, pore structures and fractal features of high-strength hydraulic concrete were investigated. The main results are: (1) The incorporation of 4–8% Type I MgO reduced the compressive strength, splitting tensile strength and the abrasion resistance by about 5–12% at 3, 28 and 180 days. Adding 1.2–2.4 kg/m3 PVA fibers raised the splitting tensile strength of concrete by about 8.5–15.7% and slightly enhanced the compressive strength and abrasion resistance of concrete. (2) The incorporation of 4–8% Type I MgO prolongs the initial cracking time of concrete rings under drying by about 6.5–11.4 h, increased the cracking tensile stress by about 6–11% and lowered the cracking temperature by 2.3–4.5 °C during the cooling down stage. Adding 1.2–2.4 kg/m3 PVA fibers was more efficient than adding 4–8% MgO in enhancing the cracking resistance to drying and temperature decline. (3) Although adding 4% MgO and 1.2–2.4 kg/m3 PVA fibers together could not enhance the compressive strength and abrasion resistance, it could clearly prolong the cracking time, noticeably increase the tensile stress and greatly lower the racking temperature; that is, it efficiently improved the cracking resistance to drying and thermal shrinkage compared with the addition of MgO or PVA fiber alone. The utilization of a high dosage of Type I MgO of less than 8% and PVA fiber of no more than 2.4 kg/m3 together is a practical technique to enhance the cracking resistance of hydraulic mass concretes, which are easy to crack. (4) The inclusion of MgO refined the pores, whereas the PVA fiber incorporation marginally coarsened the pores. The compressive strength and the abrasion resistance of hydraulic concretes incorporated with MgO and/or PVA fiber are not correlated with the pore structure parameters and the pore surface fractal dimensions.
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Ballim, Yunus. "Minimising the risk of thermally induced cracking in mass concrete structures through suitable materials selection and processing." MRS Advances 3, no. 34-35 (2018): 2051–61. http://dx.doi.org/10.1557/adv.2018.371.
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ABSTRACTThe hydration of cement is an exothermic reaction which generates around 300 kJ/kg of cement hydrated. In mass concrete structures such as dams and large foundations, this heat of hydration causes a significant rise in temperature in the internal sections of the concrete. If thermal gradients between the internal sections and the near-surface zone of the concrete element are sufficiently large, the thermal stress can cause cracking of the concrete. This cracking may cause functional or structural problems in the operation of the structure. In order to minimise the potential for such cracking, it is necessary to minimise the rate and amount of heat that is evolved, particularly during the early period of the hydration process. This can be achieved by design engineers and concrete technologists through judicious selection and processing of concrete-making materials. This paper presents the observations and results obtained over a number of years from adiabatic testing of concretes, computational modelling of temperature development in large concrete structures and direct temperature measurements in actual structures, with a view to understanding the effects of concrete-making materials on temperature development in concrete. The paper considers the effects of different types of rock aggregates, different types of Portland cement, fineness of grinding of the cement, the addition of supplementary cementitious materials and variations in the concrete starting temperature on temperature development in a large concrete element over time. The results indicate that using a coarser ground cement, adding significant amounts of supplementary cementitious materials and cooling the concrete mixture before placing has a more significant effect in reducing the risk of cracking than varying the aggregate type of the Portland cement type.
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Martínez-Ibernón, Ana, Marta Roig-Flores, Josep Lliso-Ferrando, Eduardo J. Mezquida-Alcaraz, Manuel Valcuende, and Pedro Serna. "Influence of Cracking on Oxygen Transport in UHPFRC Using Stainless Steel Sensors." Applied Sciences 10, no. 1 (December 28, 2019): 239. http://dx.doi.org/10.3390/app10010239.
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Reinforced concrete elements frequently suffer small cracks that are not relevant from the mechanical point of view, but they can be an entrance point for aggressive agents, such as oxygen, which could initiate the degradation processes. Fiber-Reinforced Concrete and especially Ultra High Performance Concrete increase the multi-cracking behavior, reducing the crack width and spacing. In this work, the oxygen availability of three types of concrete was compared at similar strain levels to evaluate the benefit of multi-cracking in the transport of oxygen. The types of concrete studied include traditional, High-Performance, and Ultra-High-Performance Fiber-Reinforced Concrete with and without nanofibers. To this purpose, reinforced concrete beams sized 150 × 100 × 750 mm3 were prepared with embedded stainless steel sensors that were located at three heights, which have also been validated through this work. These beams were pre-cracked in bending up to fixed strain levels. The results indicate that the sensors used were able to detect oxygen availability due to the presence of cracks and the detected differences between the studied concretes. Ultra High Performance Concrete in the cracked state displayed lower oxygen availability than the uncracked High Performance Concrete, demonstrating its potential higher durability, even when working in cracked state, thanks to the increased multi-cracking response.
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Zhang, Yao, Wei-Hua Ma, Hong-Zhen Kang, and Qiang Li. "Fracture behaviour of concrete with different replacement rates of iron tailings sand based on double-K criterion." Frattura ed Integrità Strutturale 17, no. 64 (March 21, 2023): 171–85. http://dx.doi.org/10.3221/igf-esis.64.11.
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The article conducts a study on the iron tailings sand concrete's fracture behaviour based on the double-K criterion. Five sets of standard three-point bending beam specimens of concrete with 0%, 25%, 50%, 75% and 100% iron tailings sand replacement river sand respectively were fracture tested, and the P-CMOD and P- ε curves of each set of specimens were measured to determine the pertinent fracture parameters. The specimens were also microscopically tested using scanning electron microscopy and mercury intrusion porosimetry. The results demonstrate that the fracture processes and damage patterns of iron tailings sand concrete and river sand concrete are comparable; the addition of iron tailings sand improves initial cracking load and initial cracking toughness more significantly than unstable cracking load and unstable cracking toughness; the ductility of iron tailings sand concrete is marginally inferior; and the results of microscopic tests demonstrate that the addition of iron tailings sand can improve the morphology and pore structure of the interface transition zone. Therefore, from the assessment of fracture mechanics, iron tailings sand can totally replace river sand in equivalent quantities for concrete preparation, which will provide great potential for the secondary use of iron tailings sand.
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Marzouk, H., and Z. W. Chen. "Nonlinear analysis of normal- and high-strength concrete slabs." Canadian Journal of Civil Engineering 20, no. 4 (August 1, 1993): 696–707. http://dx.doi.org/10.1139/l93-086.
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Concrete slabs supported on four edges and loaded axially and transversely are used in many civil engineering applications. High-strength concrete slabs are commonly used for marine structures and offshore platforms. The catastrophic nature of the failure exhibited by reinforced concrete slabs when subjected to concentrated loads has been a major concern for engineers over many years. Therefore, there is a great need to develop accurate numerical models suitable for normal-strength or high-strength concrete in order to reflect properly its structural behaviour.Proper simulation of the post-cracking behaviour of concrete has a significant effect on the nonlinear finite element response of such slabs. Cracking and post-cracking behaviour of concrete which includes aggregate interlock, dowel action, and tension-stiffening effects is especially crucial for any nonlinear concrete analysis. The post-cracking behaviour and the fracture energy properties of high-strength concrete are different from those of normal-strength concrete. This can be realized by comparing the experimental testing results of plain normal- and high-strength concrete. The experimental results of testing plain high-strength concrete in direct tension indicated that the total area under the stress - crack width curve in tension is different from that of normal-strength concrete.A suitable softening and tension-stiffening model is recommended for high-strength concrete; other existing models suitable for normal-strength concrete are discussed. The proposed post-cracking behaviour models are implemented in a nonlinear finite element program in order to check the validity of such models by comparing the actual experimental data with the finite element results. Finally, a parametric study was conducted to provide more insight into the behaviour of high-strength concrete slabs subjected to combined uniaxial in-plane loads and lateral loads. The effects of the magnitude of in-plane load and the sequence of loading on the structural behaviour of such slabs are examined. Key words: high-strength concrete, slabs, punching shear, fracture energy, tension-softening, tension-stiffening, parametric study.
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Shakib, Sheikh, and Abu Zakir Morshed. "Modeling of Cover Concrete Cracking Due to Uniform Corrosion of Reinforcement." Journal of Engineering Science 12, no. 1 (April 21, 2021): 43–49. http://dx.doi.org/10.3329/jes.v12i1.53100.
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Cracking of cover concrete due to the corrosion of reinforcing steel is one of the main causes of deterioration in Reinforced Concrete (RC) structures. An outbound stress is developed in concrete surrounding the reinforcing steels due to the expansive corrosion products of reinforcement leading to cracking of the concrete cover. In this paper, the cracking pressure was simulated through a finite element modeling. The effect of geometrical and material parameters, i.e. concrete cover thickness, bar diameter, and concrete tensile strength, on the cracking pressure was also investigated. Abaqus 6.14 was used as modeling platform. The cracking pressure was found to dependent on the cover thickness and tensile strength of concrete. A higher pressure was required to initiate crack for a higher cover thicknesses and tensile strength. The cracking pressure was decreased with the increase in bar diameter. Finally the crack initiation and propagation has been simulated successfully for different arrangements of reinforcements.
Journal of Engineering Science 12(1), 2021, 43-49
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Li, Yun Feng, Hua Xun Guo, and Ling Ling Wang. "Shrinkage Cracking of High Performance Concrete Mixed with Steel Slag Admixture." Key Engineering Materials 462-463 (January 2011): 867–71. http://dx.doi.org/10.4028/www.scientific.net/kem.462-463.867.
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Cracking due to the restrained shrinkage stress has been frequently observed at early age in concrete structures. Early-age deterioration of concrete due to cracking and higher maintenance cost for poor durability cause serious troubles to concrete structures. Steel slag includes a certain scale mineral such as C2S and C3S, and can be applied in cement and concrete as mineral admixtures. Two tests are outlined to quantify the behaviour of concrete under restrained shrinkage using plate and ring specimens. The results show that mineral admixtures can be used to reduce cracking in concrete. The risk of cracking can be estimated for steel slag concrete, so that it will improve the durability of concrete structures.
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Duan, Jintao, Peiyun Qiu, Jianyong Liu, and Xin Wu. "Experimental Study of the Concrete Cracking Behavior of an Immersed Tunnel under Fire." Buildings 13, no. 6 (May 30, 2023): 1412. http://dx.doi.org/10.3390/buildings13061412.
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This study investigates the impact of fire on the cracking behavior of immersed tunnels. A reduced-scale (1:5) model of an immersed tunnel was constructed to conduct fire tests in both traffic tubes using the HCinc curve as the applied fire. Temperature field changes were carefully monitored during the test by thermocouples and infrared thermography on the outer surface of the tunnel’s ceiling. The continuous temperature field and temperature changes in the concrete cracks were recorded by infrared thermography. By integrating the temperature field distribution in concrete and the behavior of concrete cracking, an analysis of the depth of concrete cracking in the immersed tunnel under fire was conducted. The concrete cracks exceeded 150 mm at 95 min of the fire test. The results indicate that the inner concrete exposed to fire undergoes thermal expansion, leading to tensile cracking of the outer concrete. Additionally, the fire-exposed surface of the tunnel is vulnerable to cracking due to a temperature decrease. Thus, the design of fire resistance of immersed tunnels should take into consideration the potential for concrete cracking caused by thermal strain.
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Li, Qiang, Hong Fa Yu, and Jing Tong. "Full-Field Displacement and Strain Measurement: Application of Digital Image Correlation to Reinforcement Corrosion Induced Concrete Fracture and Cover Cracking." Applied Mechanics and Materials 738-739 (March 2015): 889–92. http://dx.doi.org/10.4028/www.scientific.net/amm.738-739.889.
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Cracking of the cover concrete due to steel corrosion is considered as one of the major issues of durability of reinforced concrete (RC) structures. This paper tentatively studies the feasibility of DIC to reinforcement corrosion induced concrete fracture and cover cracking measurement. Advantages and limitations of DIC-based non-contact full-field measurement for corrosion induced concrete fracture and cover cracking are discussed. Drawbacks in this test need improvement are pointed out and test method for further study of whole process of simulating the real reinforced concrete cracking is put forward.
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Ji, Tao, Chang Bin Hu, and Yong Ning Liang. "Preliminary Study on a New Evaluation Method of Concrete Cracking Resistant Behavior." Key Engineering Materials 400-402 (October 2008): 459–63. http://dx.doi.org/10.4028/www.scientific.net/kem.400-402.459.
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A restrained ring setup with a clapboard was developed. Because the clapboard can cause a stress concentration of concrete annulus placed in the ring setup, a crack of the concrete annulus can rise at the tip of the clapboard at an early age of curing. Then the time-span of the evaluation of concrete cracking behavior is shortened. The new evaluation method can avoid the disadvantages of applying the conventinal restrained ring setup without a clapboard when evaluating the cracking resistant behavior of concrete, such as the longer time-span, randomicity and chanciness of concrete cracking. Based on experimental data, in which the effect of polypropylene fiber and expansive agent on the cracking resistant behavior of concrete was investigated, the cracking age of concrete loops and the ratio of tensile strength to compressive strength of concrete were obtained, and the validity of the proposed ring setup has been verified.
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Wright, Jared R., Farshad Rajabipour, Jeffrey A. Laman, and Aleksandra Radlińska. "Causes of Early Age Cracking on Concrete Bridge Deck Expansion Joint Repair Sections." Advances in Civil Engineering 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/103421.
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Cracking of newly placed binary Portland cement-slag concrete adjacent to bridge deck expansion dam replacements has been observed on several newly rehabilitated sections of bridge decks. This paper investigates the causes of cracking by assessing the concrete mixtures specified for bridge deck rehabilitation projects, as well as reviewing the structural design of decks and the construction and curing methods implemented by the contractors. The work consists of (1) a comprehensive literature review of the causes of cracking on bridge decks, (2) a review of previous bridge deck rehabilitation projects that experienced early-age cracking along with construction observations of active deck rehabilitation projects, and (3) an experimental evaluation of the two most commonly used bridge deck concrete mixtures. Based on the literature review, the causes of concrete bridge deck cracking can be classified into three categories: concrete material properties, construction practices, and structural design factors. The most likely causes of the observed early-age cracking were found to be inadequate curing and failure to properly eliminate the risk of plastic shrinkage cracking. These results underscore the significance of proper moist curing methods for concrete bridge decks, including repair sections. This document also provides a blueprint for future researchers to investigate early-age cracking of concrete structures.
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Layang, Samuel. "CRACKS IN REINFORCED CONCRETE BEAM." BALANGA: Jurnal Pendidikan Teknologi dan Kejuruan 10, no. 1 (June 30, 2022): 6–12. http://dx.doi.org/10.37304/balanga.v10i1.3277.
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Cracks in concrete cannot be prevented but the size of the cracks can be controlled. Cracks that occur in concrete are strongly influenced by the nature and characteristics of the concrete constituent materials, especially cement and water. Cracks can occur in the fresh and hard concrete phases. Cracks that occur in concrete can be grouped into two, non-structural cracks and structural cracks. There are several types of non-structural cracks such as crazing, map cracking, plastic cracking due to shrinkage, plastic cracking due to settlement, cracking due to drying shrinkage, cracking due to temperature changes, cracking due to chemical reactions. Structural cracks can be caused by the effects of vibration, earthquake and loads that work beyond capacity. Cracks in concrete beams can be in the form of flexural cracks, web shear cracks, flexure-shear cracks, torsion cracks, bond cracks. The failure that occurs in the beam has a close relationship with the pattern of cracks formed. Cracks that occur in the beam must be repaired so that the damage does not get worse and efforts to strengthen the structure to ensure it remains safe
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Chen, De Peng, Chun Lin Liu, and Chun Xiang Qian. "Study on Shrinkage and Cracking Performance of SAP-Modified Concrete." Materials Science Forum 675-677 (February 2011): 697–700. http://dx.doi.org/10.4028/www.scientific.net/msf.675-677.697.
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SAPs (Super Absorbent Polymers) are a group of polymeric materials that have the ability to absorb a significant amount of liquid many times their own weight from the surroundings and to retain the liquid within their structure without dissolving and to desorb it in the dry environment. The shrinkage and cracking performance of SAP-modified concrete was studied by experimental investigation, which express as total cracking area from early-age plastic cracking tests and shrinkage rate (restrained and unrestrained) from shrinkage tests respectively. The effect of SAP on shrinkage and cracking of concrete was compared with that of using pre-soaked ceramsite or perlite. The results show that SAP can effectively improve the cracking and shrinkage of concrete with achieving a 30-50% decrease. SAP particles improve the shrinkage and cracking performance of concrete in three ways as absorption-desorption, some absorbed water being bonded with hydrogen bond of macromolecule and filmforming on SAP particles. The coupling effect of SAP retards the water losing and change the moisture distribution in concrete, and thus reducing the cracking and shrinkage of concrete.
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Mohamed Sayed, Ahmed, Mohamed Mohamed Rashwan, and Mohamed Emad Helmy. "Experimental Behavior of Cracked Reinforced Concrete Columns Strengthened with Reinforced Concrete Jacketing." Materials 13, no. 12 (June 24, 2020): 2832. http://dx.doi.org/10.3390/ma13122832.
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Reinforced concrete (RC) columns often need to be strengthened or rehabilitated to allow them to carry the loads applied to them. In previous studies, RC columns have been strengthened by jacketing, without considering the occurrence of cracking. In this study, the behavior of RC columns strengthened externally by jacketing after cracking is analyzed. The accuracy of the existing models was verified by analyzing the performance of fifteen RC columns with different cross-sections to determine the effect of new variables, such as the column size, amount of steel reinforcement, and whether the column was cracked or not, on the effectiveness of strengthening. The analysis demonstrated that this strengthening technique could effectively improve both the ductility and strength of RC column cross-sections. The results indicate that the model suggested by the ACI-318 code can predict the ultimate load capacity of RC columns without strengthening, or strengthened by RC jacketing before or after cracking, with higher accuracy and material efficiency. The RC columns without strengthening met the safety limit of the ACI-318 model. However, for strengthened columns, a reduction coefficient must be used to enable the columns to meet the safety limit, with values of 94% and 76% for columns strengthened before and after cracking, respectively. Furthermore, strengthening after cracking affects the ultimate load capacity of the column, with 15.7%, 14.1%, and 13.5% lower loads for square, rectangular, and circular columns than those strengthened before cracking, respectively.
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Wang, Hai Bo. "Cracking Risk Analysis of Concrete Dam at Early Age under Concrete Fast Pouring Method." Applied Mechanics and Materials 638-640 (September 2014): 735–39. http://dx.doi.org/10.4028/www.scientific.net/amm.638-640.735.
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In order to speed up the progress of the concrete dam construction, the concrete thick layers and short time intervals fast pouring method is proposed. The temperature cracking and stress safety of the dam under concrete fast pouring method is a big trouble. From the concrete cracking safety point of view, a concrete gravity dam is introduced as a case study, the influence of different thickness of layers, different time intervals and different pouring temperature on the temperature and thermal stress characteristics of the concrete dam at the early age as well as the cracking risk of the concrete are deeply studied. According to the analysis, the corresponding cracking prevention technology is put forward. The research provides a technical support for establishing the concrete temperature control criteria and the relevant temperature control measures for the concrete fast pouring method.
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Li, Ke Liang, Zhong Zheng Yang, and Wei Ping Nie. "Fiber Reinforced Hydraulic Concrete Using Four Gradations of Aggregates." Advanced Materials Research 243-249 (May 2011): 4614–18. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.4614.
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Controlling crack of hyperbolic arch dam with a height of 305 m in Jinping hydropower station is an important problem. To improve the anti-cracking ability and reduce cracking risk of hydraulic concrete, polyvinyl alcohol (PVA) fiber and polypropylene thick fiber were used in hydraulic concrete using four gradations of aggregates. Indoor and productive tests were carried through to comparatively analyze workability, physical and mechanical properties and anti-cracking ability. Workability of fiber reinforced concrete was improved to be in favor of construction. When two kinds of fiber were used in concrete, the anti-cracking ability was greatly enhanced with lower elastic modulus-to-strength ratio and lager ultimate tensile strain. Concrete using PVA fiber had better anti-cracking ability than that of concrete using polypropylene thick fiber. PVA fiber reinforced concrete was applied in Jinping hydropower station. It is proved that PVA fiber reinforced concrete has good properties reaching design requirements of workability, compressive strength, ultimate tensile strain, frost resistance, permeability resistance.
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Zhang, Shi Ping, and Xiang Dong. "Effect of Steel Fiber on the Performance of Concrete Materials." Applied Mechanics and Materials 193-194 (August 2012): 337–40. http://dx.doi.org/10.4028/www.scientific.net/amm.193-194.337.
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This paper presents the results of testing performed to evaluate the influence of steel fiber on the performance of concrete materials. The performance of concrete materials was studied through frost resistance, carbonation testing and restraint cracking testing. Experimental results show that the steel fibers can improve the frost resistance and carbonation of concrete, compared with plain concrete. Steel fibers can also reduce cracking, and improve the cracking resistance of concrete materials.
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Qin, Hong Gen, Zhi Hua Fei, Wei Guo, and Qian Tian. "The Effects of Water-Reducer on Early-Age Plastic Shrinkage of Concrete." Applied Mechanics and Materials 174-177 (May 2012): 1113–18. http://dx.doi.org/10.4028/www.scientific.net/amm.174-177.1113.
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Water-reducer is one of the dispensable components in modern concrete, can improve the workability and mechanical performance of concrete, and also has an important influence on the plastic cracking resistance of concrete. In this paper, the flat cracking test was used to evaluate the effect of water reducer on the plastic cracking resistance of concrete, meanwhile, capillary pressure; plastic settlement and evaporation rate were also tested. The results showed that water-reducer could improve the plastic cracking resistance of concrete significantly, and the effectiveness of polycarboxylate water reducer were o better than that of wood calcium and naphthalene water reducer.
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Shi, Nannan, Jianshu Ouyang, Runxiao Zhang, and Dahai Huang. "Experimental Study on Early-Age Crack of Mass Concrete under the Controlled Temperature History." Advances in Materials Science and Engineering 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/671795.
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Thermal deformation under restrained conditions often leads to early-age cracking and durability problems in mass concrete structures. It is crucial to monitor accurately the evolution of temperature and thermal stresses. In this paper, experimental studies using temperature stress testing machine (TSTM) are carried out to monitor the generated thermal cracking in mass concrete. Firstly, components and working principle of TSTM were introduced. Cracking temperatures and stress reserves are selected as the main cracking evaluation indicators of TSTM. Furthermore, effects of temperature controlling measures on concrete cracking were quantitatively studied, which consider the concrete placing temperature (before cooling) and cooling rates (after cooling). Moreover, the influence of reinforcement on early-age cracking has been quantitatively analyzed using the TSTM. The experimental results indicate that the crack probability of reinforced concrete (RC) is overestimated. Theoretical calculations proved that the internal stress can transfer from concrete to reinforcement due to creep effect. Finally, the experimental results indicate that the reinforcement can improve the crack resistance of concrete by nearly 30% in the TSTM tests, and the ultimate tensile strain of RC is approximately 105% higher than that of plain concrete with the same mix proportions.
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Barzegar, Fariborz, and William C. Schnobrich. "Post-cracking analysis of reinforced concrete panels including tension stiffening." Canadian Journal of Civil Engineering 17, no. 3 (June 1, 1990): 311–20. http://dx.doi.org/10.1139/l90-038.
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In finite element analysis of reinforced concrete structures, the effect of bond forces between concrete and reinforcement, referred to as tension stiffening, is discussed. To account for this phenomenon, the post-cracking constitutive model for concrete is modified by assigning a linear strain softening branch to its stress–strain curve in the tensile stress direction. For analyzing orthogonally reinforced concrete panels, a simple procedure for determining the termination strain on the softening branch is then developed. Appropriate constitutive models for steel and uncracked concrete along with the post-cracking model to simulate the behavior of cracked reinforced concrete are implemented in a finite element program. Three orthogonally reinforced concrete test panels subjected to pure shear loadings causing inclined cracking are analyzed. It is shown that the adopted numerical procedures are capable of predicting the post-cracking responses, ultimate capacities, and modes of failure for the analyzed panels with good accuracy. The capabilities of the employed post-cracking model to simulate the crack shifting behavior observed during testing of a highly anisotropically reinforced panel is also demonstrated. Key words: reinforced concrete panels, finite element, post-cracking, tension stiffening, crack shifting, ultimate load.
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Watanabe, Takeshi, and Chikanori Hashimoto. "Evaluation of shrinkage and cracking in concrete of ring test by acoustic emission method." Modern Physics Letters B 29, no. 06n07 (March 20, 2015): 1540033. http://dx.doi.org/10.1142/s0217984915400333.
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Drying shrinkage of concrete is one of the typical problems related to reduce durability and defilation of concrete structures. Lime stone, expansive additive and low-heat Portland cement are used to reduce drying shrinkage in Japan. Drying shrinkage is commonly evaluated by methods of measurement for length change of mortar and concrete. In these methods, there is detected strain due to drying shrinkage of free body, although visible cracking does not occur. In this study, the ring test was employed to detect strain and age cracking of concrete. The acoustic emission (AE) method was adopted to detect micro cracking due to shrinkage. It was recognized that in concrete using lime stone, expansive additive and low-heat Portland cement are effective to decrease drying shrinkage and visible cracking. Micro cracking due to shrinkage of this concrete was detected and evaluated by the AE method.