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Journal articles on the topic "Concrete blocks Effect of temperature on Testing"
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Bai, Yin, Yue Bo Cai, Jian Tong Ding, and Xi Ning Guo. "Study on the Damage Risk of Dam Concrete Suffering Alkali-Silicareaction Based on 7 Years Outdoor Field Exposure Testing, Part I: The Influence of Maximum Size of Aggregate." Key Engineering Materials 768 (April 2018): 341–46. http://dx.doi.org/10.4028/www.scientific.net/kem.768.341.
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Alkali-aggregate reaction is one of the most serious concrete durability problems threating the safety of dam. Some accelerated test methods with high temperature and high alkalinity are usually used in laboratory to evaluate the reactivity of aggregates or the effectiveness of suppression measures. In this paper, an outdoor field exposure station was built to objectively assess the damage risk of real dam concrete suffering alkali-silica reaction. 25 concrete blocks measuring 450 by 450 by 450 mm in size were tested at first stage, all immersed into water to simulate the environment of dam concrete. The influences of the size of aggregate and the amount of cementing materials were tested at the same time. After 7 years field exposure testing, the results showed that: the crack risk of blocks was not proportional to the expansion rates, but influenced by the maximum diameter of aggregate. The block with bigger aggregate had smaller expansion rate, but cracked more easily. If the sizes of aggregate were the same, less cementing materials would cause bigger expansion. The constraint effect is bigger than the effect of alkali content increasing caused by increasing the amount of cementing materials.
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Peng, Haoyang, Peng Lin, Yunfei Xiang, Jinwu Hu, and Zongli Yang. "Effects of Carbon Thin Film on Low-Heat Cement Hydration, Temperature and Strength of the Wudongde Dam Concrete." Buildings 12, no. 6 (May 26, 2022): 717. http://dx.doi.org/10.3390/buildings12060717.
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Research on the mechanism of carbon thin film (CTF) is a hot issue in the field of concrete materials and is of great significance to the temperature control and crack prevention of concrete structures, but little research has been conducted regarding this issue. In this paper, the composition of CTF and its influence on cement hydration, concrete temperature and strength are studied in the context of the Wudongde (WDD) dam project. Through observations of hand specimens, rock slice identification and X-Ray Fluorescence (XRF) analysis, it was shown that the CTF has the same chemical composition as the limestone component, except for the presence of low-crystalline graphite. Based on hydration testing using TAM Air, it was found that CTF promotes the dissolution of cement and the hydration of C3A in the very early stage but exerts a lowering effect on the second exothermic peak of cement hydration. In addition, the greater the CTF content, the greater the hydration heat release. According to temperature measurements of the Wudongde (WDD) dam, CTF could promote an increase in the maximum temperature of concrete blocks. Finally, compressive strength analysis revealed that the content of CTF was proportional to the compressive strength of concrete specimens and provides a reference for the effect of CTF on the performance of low-heat cement concrete.
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Mathi1, A. Mathu, and G. Lavanya. "Study on the Light Weight Geopolymer Concrete Made of Recycled Aggregates from Lightweight Blocks." International Journal for Research in Applied Science and Engineering Technology 10, no. 8 (August 31, 2022): 1551–59. http://dx.doi.org/10.22214/ijraset.2022.46440.
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Abstract: This study studied the properties of lightweight geopolymer concrete that contained recycled lightweight block aggregate. The recovered blocks are classified as coarse aggregates after being crushed.To reduce greenhouse gas emissions, geopolymers have the potential to be used to create new, environmentally beneficial materials. A new class of building materials called geopolymer concrete (GPC) has a replacement for regular Portland cement concrete (OPCC) and are capable of revolution in the construction sector. The impact of On the strength characteristics, alkaline activators have been investigated. Used fly ash was obtained for this study from a nearby thermal power plant. Samples were produced from low-calcium fly ash through activation with a combination of sodium silicate solution and sodium hydroxide. Fly ash was added to the concrete with a ratio of 0.5. Using a mix proportion and 5,10,15 Molar of sodium hydroxide solution, geopolymer specimens were cast. The samples underwent compression testing. test with ambient temperatures for curing. From the analysis ofLiterature suggests that the combination of the aforementioned ingredients is healing. FromAccording to a review of the literature, the amalgamation of the aforementioned elementshas a favorable effect on the strength properties of geopolymer concrete. Since fly ash is viewed as a waste product, geopolymer concrete made from low-calcium fly ash costs less than Portland cement concrete as a result. Lowcalcium fly ash-based geopolymer concrete has good compressive strength, very little drying shrinkage and minimum creep, great resistance to sulphate attack, and superior acid resistance.
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Girskas, Giedrius, Džigita Nagrockienė, and Gintautas Skripkiūnas. "The effect of synthetic zeolite admixture on the durability of concrete paving blocks." Baltic Journal of Road and Bridge Engineering 11, no. 3 (September 30, 2016): 215–21. http://dx.doi.org/10.3846/bjrbe.2016.25.
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Concrete paving blocks that were started to be used in the last century have become very popular. They became an alternative to the natural stone. Concrete paving blocks are used for the paving of pedestrian and vehicle zones. Durability is one of the main characteristics in the production of high-quality concrete paving blocks in the Baltic region climate zone. The article describes tests with concrete paving blocks, the top layer of which contains 5% of synthetic zeolite admixture obtained by means of low temperature synthesis in laboratory conditions. This zeolite admixture is obtained from aluminium fluoride production waste. The durability of concrete paving blocks was tested according to abrasion resistance, tensile splitting strength, absorption and frost resistance. The test results revealed that 5% of zeolite admixture added to the top layer of concrete paving blocks reduce the absorption, increase the tensile splitting strength by more than 10%, and decrease abrasion by 6.5%. The zeolite admixture used in concrete paving blocks reduces the scaling about 4 times after 28 freeze-thaw cycles when 3% NaCl is used as the freezing solution. The tests revealed that synthetic zeolite admixture can be used in concrete elements production by means of vibropressing (pavement elements) to increase their durability.
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Yao, Ze Liang, Guo Liang Bai, and Fa Ning Dang. "Analysis on a Steel-Concrete Hybrid Structure Temperature Effect and Supporting Block Design." Applied Mechanics and Materials 29-32 (August 2010): 1862–65. http://dx.doi.org/10.4028/www.scientific.net/amm.29-32.1862.
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The steel-concrete hybrid structure is a new special industrial structure in large thermal power plants. It is composed of a spatial steel truss and steel-concrete tubular columns. Its stiffness and mass is highly non-uniform at vertical direction. Its temperature effect is obvious because its steel truss is a high order statically indeterminate structure. Types and characteristics of temperature load prescribed in codes are introduced. Temperature effect of the steel-concrete hybrid structure is calculated by FEM analysis software SAP2000 in four different supporting blocks. The structural internal force and distortion under temperature effect is analyzed. The influence of supporting blocks on the structual temperature effect is analyzed. The structural supporting block form to advantageously release its temperature effect is presented. Some advice is presented based on the analysis results.
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Lee, Mi Hwa, Bae Su Khil, and Hyun Do Yun. "Thermal Analysis of Hydration Heat in Mass Concrete with Different Cement Binder Proportions." Applied Mechanics and Materials 372 (August 2013): 199–202. http://dx.doi.org/10.4028/www.scientific.net/amm.372.199.
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This study is conducted to evaluate analytically the effect of cement binder proportions (ordinary Portland cement, blast-furnace slag and fly ash) on the hydration heat of mass concrete with specific compressive strength of 30 MPa. Two types of blended concretes were mixed; binder of PSLB_352 consists of ordinary Portland cement (OPC) : blast-furnace slag (BFS) : fly ash (FA) = 3 : 5 : 2 and binder of PSLB_442 comprise OPC : BSF : FA = 4 : 4 : 2. For comparison, a control concrete mixture was mixed with commercial low-heat cement. To measure temperature characteristics due to hydration heat of each mixture, large concrete blocks were cast and temperature within concrete blocks was measured until the equilibrium temperature was reached. Finite element model was developed for predicting hydration heat of mass concrete based on thermal characteristics of mass concrete derived from large concrete blocks. The effect of cement binder proportions on the hydration heat of mat foundation was evaluated by developed finite element model.
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B. Abdurrahman, R., Z. A. Mohammed, and Dr A. H. Ahmed. "Effect of High Temperature on Engineering Properties of Light Weight Blocks Concrete." AL-Rafdain Engineering Journal (AREJ) 18, no. 6 (December 28, 2010): 1–9. http://dx.doi.org/10.33899/rengj.2010.35165.
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Konrád, Petr, Peter Gallo, Radoslav Sovják, Šárka Pešková, and Jan Valentin. "Effect of Various Input Parameters on Compressed Earth Block’s Strength." Key Engineering Materials 838 (April 2020): 81–87. http://dx.doi.org/10.4028/www.scientific.net/kem.838.81.
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In the framework of this study, compressed earth blocks (CEB) were produced using waste materials and various parameters. Material parameters included waste soil, recycled concrete, fly ash, cement, admixtures and water contents. Manufacturing parameters were vibration during manufacturing, confinement pressure, curing environment and curing time. Specimens used in this study were cubes and compressive strength testing was used to evaluate different mixtures and manufacturing methods. In terms of compressive strength, compressed earth blocks made of these materials could be used for manufacturing bricks and other structural elements.
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Dong, Shu Hui, De Cheng Feng, Shou Heng Jiang, and Wei Zhong Zhu. "Effect of Freezing Temperature on the Microstructure of Negative Temperature Concrete." Advanced Materials Research 663 (February 2013): 343–48. http://dx.doi.org/10.4028/www.scientific.net/amr.663.343.
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The pore size distribution and the microstructure of negative temperature concrete was studied with different temperature, combining with some testing methods, such as MIP and SEM. Moreover, the change of the compressive strength was also studied with different ages. In addition, the relationship between the microstructure and the macro-mechanical properties on negative temperature concrete was explored further with different freezing temperature. It indicated that the lower the early curing temperature, the looser the original structure of cement paste; the total volume of gel pore whose pore size was less than 20nm was decreasing apparently, and the compressive strength declined. When changing to standard curing, the pore size trended to be thinner, the compressive strength was increasing sharply. The concrete was cured from -5°C to standard curing, the volume of pore that was less than 200nm was equal to that of the concrete with the standard curing in the age of 28d, so was the compressive strength. However, the volume of the macro pore of the concrete curing under -10°C and -15°C was greater than the concrete curing the standard condition, the compressive strength was less.
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Almusawi, Aqil Mousa, Rana Shabbar, and Qusay A. Jabal. "Effect of Elevated Temperature on the Physical and Mechanical Properties of Crushed Clay Bricks Aggregate Concrete." Key Engineering Materials 924 (June 30, 2022): 223–31. http://dx.doi.org/10.4028/p-372w5h.
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In this study concrete block was produced with waste crushed clay bricks (CCB). CCB is used as a conventional coarse aggregate replacement with the range of 0, 25, 50 and 75%. Physical and mechanical properties of concrete blocks were examined at room temperature (25°C) and elevated temperatures of 400, 600 and 800°C. The results indicated that concrete specimens with 50% CCB exhibited the greatest flexural strength characteristics compared to that containing natural aggregates, whereas a slight decline indicated at the density and compressive strength. However, the specimens with 75% CCB have the highest residual strength at an elevated temperature of 800°C. Accordingly, it is suitable for load-bearing wall application when exposed to elevated temperature in confirmation to ASTM-C55. Keywords: Concrete Masonry Units; Crushed Clay Bricks; Elevated Temperature; Coarse Aggregate Replacement.
Dissertations / Theses on the topic "Concrete blocks Effect of temperature on Testing"
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Ideker, Jason H. "Early-age behavior of calcium aluminate cement systems." 2008. http://hdl.handle.net/2152/18120.
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Compared to the knowledge base for ordinary portland cement concrete (OPCC), relatively little information exists for calcium aluminate cement concrete (CACC), despite its existence for over 100 years. There is particularly a lack of knowledge related to early-age behavior of CACC, specifically volume change and cracking potential. To assess these early-age properties, two unique pieces of equipment were developed and employed: a rigid cracking frame and free deformation frame which enabled quantification of restrained stress generation and unrestrained autogenous deformation, respectively. These two pieces of equipment employed active temperature control and allowed a wide range of isothermal and realistic temperature conditions to be imposed upon hydrating cementitious samples. Match-cured samples (i.e. identical temperature curing to that in the frames) enabled the quantification of mechanical property development. Samples cured at discrete isothermal temperatures up to 30 °C developed tensile forces in the rigid cracking frame and exhibited shrinkage phenomena in the free deformation frame. At temperatures above 30 °C, the converse was true and significant compressive forces developed in restrained testing and expansion was observed in unrestrained testing. It was found that this was a direct result of microstructural development related to the formation of metastable phases (associated with shrinkage) and stable phases (expansion as a result of conversion from metastable to stable phases). Proper use of this material must take into account behavior associated with both types of hydrate assemblages, metastable and stable. Realistic time-temperature histories were also investigated based on field-scale concrete cast as part of this research project. It was found that volume change at earlyage was dominantly controlled by thermal history. Furthermore, it was not simply the maximum temperature reached, but the rate of temperature rise during hydration and the resulting duration of time spent at high temperature that profoundly influenced volume change and property development. The research described in this dissertation represents a significant advancement of the state-of-knowledge of this unique material and has further elucidated the role of temperature during hydration of CACC.text
Books on the topic "Concrete blocks Effect of temperature on Testing"
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Korhonen, C. J. Assessing cryogenic testing of aggregates for concrete pavements. [Hanover, N.H.]: U.S. Army Corps of Engineers, Cold Regions Research & Engineering Laboratory, 1995.
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Bažant, Z. P. Concrete at high temperatures: Material properties and mathematical models. Harlow: Longman, 1996.
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1937-, Walker M. J., International Association of Testing and Research Laboratories for Materials and Structures., RILEM Technical Committee 94-CHC on Concrete in Hot Climates., Concrete Society, and International RILEM Conference on Concrete in Hot Climates (3rd : 1992 : Torquay, England), eds. Concrete in hot climates: Proceedings of the third international conference. London: E & FN Spon, 1992.
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M, Setzer, Auberg Rainer, and International Union of Testing and Research Laboratories for Materials and Structures., eds. Frost resistance of concrete: Proceedings of the International RILEM Workshop on Resistance of Concrete to Freezing and Thawing with or without De-icing Chemicals, University of Essen, September 22-23, 1997. London: E & FN Spon, 1997.
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Morales-Valentin, Gustavo E. Temperature differential effect on the falling weight deflectometer deflections used for structural evaluation of rigid pavements. [Austin]: Center for Transportation Research, Bureau of Engineering Research, University of Texas at Austin, 1987.
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Hsiung, Kuang-Hua. Evaluation of fire damage of concrete slabs. 1992.
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Cameron, MacInnis, ACI Committee 201., and International Symposium on "How to Produce Durable Concrete in Hot Climates" (1992 : San Juan, P.R.), eds. Durable concrete in hot climates. Detroit, Mich: American Concrete Institute, 1993.
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A, Willoughby Kim, Washington (State). Dept. of Transportation. Research Office., Washington State Transportation Center, and University of Washington. Dept. of Civil Engineering., eds. Construction-related asphalt concrete pavement temperature differentials and the corresponding density differentials. [Olympia, Wash.]: Washington State Dept. of Transportation, 2001.
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Evaluation and repair of fire damage to concrete. Detroit (P.O. Box 19150, Redford Station, Detroit 48219): American Concrete Institute, 1986.
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Concrete at High Temperatures (Concrete Design & Construction). Prentice Hall, 1996.
Find full textBook chapters on the topic "Concrete blocks Effect of temperature on Testing"
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Li, Songhui, Ruiqiang Liu, Shaokong Feng, Huihong Zhong, and Yan Zhang. "Research on Void Defect Distribution Law and Structural Optimization Design of Sandwich-Structured Immersed Tunnel in the Shenzhen-Zhongshan Channel." In Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde220893.
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A sandwich-structured immersed tunnel (SSIT) is composed of a fully enclosed steel shell and internal self-compacting concrete. The SSIT has the advantages of both steel and concrete structures and is the optimal solution for the high water pressure and long span that will characterize the future submarine tunnel projects. However, the immersed tube of the structure cannot be vibrated during casting of the self-compacting concrete, and thus the joint surface between the steel plate and concrete is prone to void defects. This reduces the bearing capacity of the immersed tube structure and affects its overall safety. Based on a large number of defect detection data from the SSIT in the Shenzhen-Zhongshan Channel project, this study analyzed and revealed the distribution law of void defects and the corresponding influencing factors. The results show that (1) the casting quality of self-compacting concrete is significantly affected by high temperature, and the necessary temperature control measures should be taken to reduce the defect rate of immersed tubes during construction in the high temperature season; (2) the size of a single casting compartment should not be excessively large. The statistical results show that the pouring effect is the best when the distance from the casting hole is 1.2–1.4 m; (3) The T-stiffener structure blocks the transverse flow of self-compacting concrete, and the aspect ratio (B/L) of the compartment structure should be controlled within the range of 0.8–0.85; and (4) the void defects tend to occur near the pouring hole, on both sides of the T-stiffener structure, and at the edge of the bulkhead far from the pouring hole. Therefore, on the premise of meeting the force requirements, the layout of the T-stiffener structures should be reduced and exhaust holes should be increased to reduce the probability of defects.
Conference papers on the topic "Concrete blocks Effect of temperature on Testing"
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Parida, F. C., S. K. Das, A. K. Sharma, P. M. Rao, S. S. Ramesh, P. A. Somayajulu, B. Malarvizhi, and N. Kasinathan. "Sodium Exposure Tests on Limestone Concrete Used as Sacrificial Protection Layer in FBR." In 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89593.
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Hot sodium coming in contact with structural concrete in case of sodium leak in FBR system cause damage as a result of thermo-chemical attack by burning sodium. In addition, release of free and bound water from concrete leads to generation of hydrogen gas, which is explosive in nature. Hence limestone concrete, as sacrificial layer on the structural concrete in FBR, needs to be qualified. Four concrete blocks of dimension 600mm × 600mm × 300mm with 300mm × 300mm × 150mm cavity were cast and subjected to controlled sodium exposure tests. They have composition of ordinary portland cement, water, fine and coarse aggregate of limestone in the ratio of 1 : 0.58 : 2.547 : 3.817. These blocks were subjected to preliminary inspection by ultrasonic pulse velocity technique and rebound hammer tests. Each block was exposed for 30 minutes to about 12 kg of liquid sodium (∼ 120 mm liquid column) at 550° C in open air, after which sodium was sucked back from the cavity of the concrete block into a sodium tank. On-line temperature monitoring was carried out at strategic locations of sodium pool and concrete block. After removing sodium from the cavity and cleaning the surfaces, rebound hammer testing was carried out on each concrete block at the same locations where data were taken earlier at pre-exposed stage. The statistical analysis of rebound hammer data revealed that one of the concrete block alone has undergone damage to the extent of 16%. The loss of mass occurred for all the four blocks varied from 0.6 to 2.4% due to release of water during the test duration. Chemical analysis of sodium in concrete samples collected from cavity floor of each block helped in generation of depth profiles of sodium monoxide concentration for each block. From this it is concluded that a bulk penetration of sodium up to 30 mm depth has taken place. However it was also observed that at few local spots, sodium penetrated into concrete up to 50 mm. Cylindrical core samples of 50 mm × 150 mm long were obtained from the exposed cavity and tested for compressive strength and longitudinal ultrasonic pulse velocity (UPV). These are compared with core samples obtained from concrete cubes used as standard reference. The average reduction in UPV and compressive strength were 7% and 29% respectively indicating marginal degradation in mechanical properties of sodium-exposed concrete.
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Ghadban, Ahmad, Mohammed Albahttiti, Kyle Riding, and David Lange. "The Effect of HRWR and AEA on the Air System of Vibrated Concrete." In 2015 Joint Rail Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/jrc2015-5788.
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Air entrainment in concrete railroad ties is typically included to prevent freeze-thaw damage. Uniformly-distributed microscopic air voids in concrete ties helps to resist against freeze-thaw. The air entrainment system stability with time after mixing is dependent on a number of factors which include chemical, environmental, and construction related parameters. These resulting differences in the air void system can in turn lead to different performances of concrete under freeze-thaw loading. Vibration is mainly used to consolidate concrete but can also alter the air structure of concrete. This study investigates the effect of different chemical admixtures and rheological properties on the stability of the air system inside vibrated concrete. Form vibration of 75 Hz frequency and 3 g or 10 g peak acceleration was applied to the tested concrete after the lapse of several time durations. This was done to investigate the stability of the air system of concrete as time passes on under different vibration conditions. The testing included slump, unit weight, temperature, rheology and fresh air content before vibration and after vibration for each elapsed time duration. Fresh air content tests showed that the air loss increases linearly with time for almost all mixtures. Concrete rheological properties immediately after mixing were not a good indicator of the concrete air system stability after delayed placement. Tall oil based air entraining agents (AEA) was found to produce slightly lower air instability; however, the differences between AEA were small. The results showed that for precast concrete railroad ties, any instability with time of entrained air should not be a significant problem for precast concrete railroad tie plants if the concrete is placed and consolidated within 30 minutes from mixing at room temperatures.
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White, Greg, and Matthew Johnson. "Investigating Alternates to Flexural Beams for Airport Concrete Strength Compliance." In 12th International Conference on Concrete Pavements. International Society for Concrete Pavements, 2021. http://dx.doi.org/10.33593/6aa8kpnf.
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Concrete for airport rigid pavement construction is generally specified to achieve a minimum characteristic flexural strength of 4.5 MPa and acceptance testing during construction aims to verify this key design assumption. The large flexural beam specimens are cumbersome and the testing is expensive. Consequently, industry desires a more convenient test and a laboratory-based conversion to an estimated flexural strength for acceptance testing during production. This research developed and trialed a protocol for the conversion of indirect tensile strength and compressive strength to estimate the flexural strength. The laboratory correlation was encouraging. However, when trialed on a real construction project, the conversions significantly underestimated the measured flexural strength and the risk of rejecting compliant batches of concrete was significantly higher. Further research is required to understand why the reliable conversions developed in the laboratory failed in the field. This may be related to the effect of ambient temperature on 28 day flexural strength, despite the constant curing condition.
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Dalzhonak, Andrei, and Aliaksandr Bakatovich. "Wall blocks based on the aggregates from plant wastes." In The 13th international scientific conference “Modern Building Materials, Structures and Techniques”. Vilnius Gediminas Technical University, 2019. http://dx.doi.org/10.3846/mbmst.2019.037.
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The article considers the possibility of using agricultural waste in the development of new building materials in the form of wall blocks. When selecting the compositions, the ideal fractions and ratios of straw to flax were determined, providing the forming of the densest frame of coarse and fine aggregates. Cement and lime were used as a binder. The effect of humidity on the durability and thermal conductivity of straw wall blocks and straw flax boon blocks were investigated. The conditions for the possible occurrence of mold on the block surface of aggregates were studied. According to the results of full-scale tests, the obtained dependencies of the temperature distribution during the coldest period of the winter season were analyzed and the high insulating ability of wall blocks was confirmed. The dependencies of the distribution of humidity over the thickness of the wall blocks after the end of the winter season testing operations were revealed. As a result of the research, a solution for the rational use of plant waste building wall blocks was proposed. The blocks can be applied to the construction of load-bearing and nonload-bearing walls in one-story buildings and multi-story frame construction when filling exterior wall openings.
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Guerrero, Hector N., Christine A. Langton, and Michael L. Restivo. "Testing and Analysis of Early Age Stress-Strain Development of Concrete Overlay for Reactor In-Situ Decommissioning." In ASME 2011 Pressure Vessels and Piping Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/pvp2011-57902.
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Non-uniform moisture distribution during early age drying and curing of protective concrete overlays for Savannah River Site reactors decommissioned in-situ were expected to result in differential shrinkage that lead to tensile stresses and possible cracking. The goal was to not exceed the concrete tensile strength of 2.8 MPa or compressive strength of 23.8 MPa. An experimental study was performed on the development of shrinkage and creep strains in concrete slab specimens embedded with strain gages and relative humidity sensors at controlled ambient temperature and relative humidity conditions. The experimental data was used to verify the validity of available physics-based methods and code calculations to predict early age shrinkage and creep strains, respectively. Data on the expansive effect of a shrinkage compensating admixture based on CaO was also obtained. Prediction of the surface stress in the test specimen suggests that without the shrinkage compensating admixture, the tensile strength would be slightly exceeded. However with the admixture, the combined effects of shrinkage, creep and expansion due to the admixture is predicted to result in all compressive stresses within the full scale slab, eliminating the possibility of cracking.
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Momeni, Amir Farid, Robert J. Peterman, B. Terry Beck, Chih-Hang John Wu, and Naga Narendra B. Bodapati. "Effect of Concrete Release Strength on the Development Length and Flexural Capacity of Members Made With Different Prestressing Wires Commonly Used in Pretensioned Concrete Railroad Ties." In 2015 Joint Rail Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/jrc2015-5736.
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A study was conducted to determine the effect of concrete release strength on the development length and flexural capacity of members utilizing five different 5.32-mm-diameter prestressing wires that are commonly used in the manufacture of prestressed concrete railroad ties worldwide. These included two chevron-indented wires with different indent depths, one spiral-indented wire, one dot-indented wire, and one smooth wire (with no surface indentation). A consistent concrete mixture was used for the manufacture of all test specimens, and the different release strengths were obtained by allowing the specimens to cure for different amounts of time prior to de-tensioning. Each prismatic specimen (prism) had a 3.5″ (88.9 mm) × 3.5″ (88.9 mm) square cross section with four wires arranged symmetrically. The prisms were identical except for the wire type and the compressive strength at the time of de-tensioning. All four wires were each initially tensioned to 7000 pounds (31.14 KN) and then de-tensioned gradually when the concrete compressive strength reached 3500 (24.13 MPa), 4500 (31.03 MPa) and 6000 (41.37 MPa) psi. Precise de-tensioning strengths were ensured by testing 4-in.-diameter (101.6 mm) × 8-in.-long (203.2 mm) compression strength cylinders that were temperature match-cured. The prisms were loaded in 3-point-bending to determine the ultimate bond characteristics of each reinforcement type for the different concrete release strengths. A loading rate of 300 lb/min (1334 N/min) was applied at mid-span and the maximum sustained moment was calculated for each test. Two 69-in.-long (175.26 cm) prisms, each having different concrete release strength, were tested with each of the 5 wire types. These prisms were tested at both ends, with a different embedment length assessed at each end. Thus, for each wire type and concrete release strength evaluated, a total of 4 tests were conducted for a total of 60 tests (5 wire types × 3 release strengths × 4 tested embedment lengths). Test results indicate that the concrete compressive strength at de-tensioning can have a direct impact on the ultimate flexural capacity of the members, and this has significant design implications for pretensioned concrete railroad ties. Results are discussed and recommendations made.
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Zieliński, Piotr. "Asphalt concrete mixtures with addition of reclaimed asphalt pavements." In 6th International Conference on Road and Rail Infrastructure. University of Zagreb Faculty of Civil Engineering, 2021. http://dx.doi.org/10.5592/co/cetra.2020.1123.
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The effect of using reclaimed asphalt pavements (RAP) to asphalt concrete mixtures besides their utilization is to reduce the amount of the new bituminous binder and aggregate added to hot mix asphalt. This publication presents studies on asphalt mixtures with an increased up to 40% amount of RAP additive with the simultaneous use of 2 types of added bitumen, i.e. 35/50 and PMB 25/55-60. The aim of the paper is the evaluation of the basic mixture properties in a wide range of operating temperatures, as a part of the AC testing at high temperatures, the resistance to rutting at 60° C and indirect tensile strength at 40° C. The assessment of properties at intermediate operating temperatures is based on indirect tensile tests, including: elastic stiffness modulus at 5° C, 15° C and 30° C and static strength at 25° C. The low temperature properties have been tested in water and frost resistance tests by indirect tensile strength ratio. The results of the study were subjected to the analysis of the statistical significance of differences, which showed an improvement in the resistance of AC with the addition of RAP to the formation of permanent deformations and an increase in the stiffness modulus as well as indirect tensile strength. There was no adverse effect of the RAP additive on asphalt mixtures resistance to water and frost action.
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Momeni, Amir Farid, Robert J. Peterman, B. Terry Beck, Chih-Hang John Wu, and Naga Narendra B. Bodapati. "Effect of Concrete Release Strength on the Development Length and Flexural Capacity of Members Made With Different Prestressing Strands." In 2016 Joint Rail Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/jrc2016-5762.
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Load tests were conducted on pretensioned members made with five different strands (three 7-wire strands and two 3-wire strands) to determine the effect of concrete release strength on the development length and flexural capacity of members. Strands named generically SA, SC, SD, SE and SF and they were all indented except SA (no surface indentation). All strands had diameter of 3/8″ (9.52 mm) except SC which had diameter of 5/16″ (7.94 mm). Among all types of strands used in manufacturing of test prisms, SC and SF were 3-wire strands, while SA, SD and SE were 7-wire strands. A consistent concrete mixture was used for the manufacture of all test specimens, and the different release strengths were obtained by allowing the specimens to cure for different amounts of time prior to de-tensioning. For SA, SD, SE and SF strands, each prismatic specimen (prism) had a 5.5″ (139.7 mm) × 5.5″ (139.7 mm) square cross section with four strands arranged symmetrically. However, prisms made with SC strand had 4.5″ (114.3 mm) × 4.5″ (114.3 mm) square cross section with four strands arranged symmetrically. The prisms were identical except for the strand type and the compressive strength at the time of de-tensioning. All four strands were pulled and de-tensioned gradually when the concrete compressive strength reached 3500 (24.13 MPa), 4500 (31.03 MPa) and 6000 (41.37 MPa) psi. Precise de-tensioning strengths were ensured by testing 4-in.-diameter (101.6 mm) × 8-in.-long (203.2 mm) compression strength cylinders that were temperature match-cured. The prisms were loaded in 3-point-bending to determine the ultimate bond characteristics of each reinforcement type for the different concrete release strengths. A loading rate of 900 lb/min (4003 N/min) for 5.5″ (139.7 mm) × 5.5″ (139.7 mm) prisms was applied at mid-span and the maximum sustained moment was calculated for each. Same procedure with loading rate of 500 lb/min (2224 N/min) was applied to 4.5″ (114.3 mm) × 4.5″ (114.3 mm) prisms. Three 69-in.-long (175.26 cm) prisms, each having different concrete release strength, were tested with each of the 5 strand types. Two out of three testing prisms were tested at only one end and one was tested at its both ends. Thus, for each strand type and concrete release strength evaluated, a total of 4 tests were conducted for a total of 60 tests (5 strand types × 3 release strengths × 4 tested embedment lengths). Test results indicate that the concrete compressive strength at de-tensioning can have a direct impact on the ultimate flexural capacity of the members, and this has significant design implications for pretensioned concrete railroad ties. Results are discussed and recommendations made.
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Nagar, Arvind. "Fatigue Damage at Open Holes in Laminated Composite Under Thermo Mechanical Loads." In ASME 2002 Engineering Technology Conference on Energy. ASMEDC, 2002. http://dx.doi.org/10.1115/etce2002/cmda-29080.
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The high temperature composites have been studied for applications to secondary structures due to their light weight and thermal resistance. Relatively few studies have been conducted to consider them for primary structural load bearing capabilities. These studies focused on titanium matrix composites to characterize their material behavior [1], unidirectional [2], simple loading conditions [3, 4] in a laboratory environment or unrealistic structural geometry [5]. The purpose of this work was to study fatigue damage and determine fatigue life in titanium matrix composite panels at unloaded fastener holes subjected to thermo-mechanical fatigue loads with variable amplitudes and temperature ranges. The test panels were machined from a prefabricated structural component with pre-drilled fastener holes. The test material was a 32 ply, quasi-isotropic, approximately .224 inch thick titanium matrix laminated composite with SCS-6 fibers and Ti-15-3 metal matrix. The material was HIP consolidated followed by slow cool to room temperature. The thermal zone area was 2 inches long along specimen length and 1.875 inch wide with a .3125 inch fastener hole at the center of the thermal zone. All specimens were machined using a 3-D water jet cutter. The test system consisted of a closed loop servo-hydraulic 30 Kip test system equipped with an MTS model 458 control system, a 486 PC containing a Keithley Metrabyte DAS 1601 computer card. The specimens were gripped using MTS model 647 side load hydraulic wedge grips equipped with surfalloy grip surface. The thermal loads were provided by an Ameritherm 5 kilowatt induction power supply and a total temperature instrumentation model MC-125 temperature controller. The temperature controller was equipped with analog set point and recorder output of temperatures with both set for 1–5 volt signal levels for 0 to 1832 F. The computer generated the temperature and load profiles and monitored error band for temperature. The computer system was set to null pace the temperature and loads if the temperature exceeded a 18 degree F variation. In effect all processes would hold until the temperature error returned inside the error band. This temperature error control was accomplished by comparing the command signal to the temperature controller to the process temperature signal from the temperature controller. The nominal uniform temperature zone was one inch long centered at the specimen geometric center and maintained required temperatures within 10 degrees. The variations in temperatures along the crack line were controlled to with in 5 degrees. Cooling blocks were attached to the test samples at the end of uniform sections near the fillet blend. These blocks were cooled with water passages and compressed air was passed through holes in the blocks and impinged on the samples to provide additional cooling at the end of the thermal ramp during cool -down. The air was turned on by the computer at about 400 degrees F during each block. On all notched test samples, an extensometer was mounted across the center flaw to obtain load-deflection data (COD). The optical crack lenth measurements were made using a 20 X Gaertner traveling microscope. The load versus crack mouth opening displacement readings were taken to compare with the optical measurements of the crack length. The thermomechanical load spectrum was developed from the distribution and frequency of loading that the airframe will experience based on the design service life and typical design usage. The loads and environmental spectra are used to develop design flight by flight stress environment spectra. The data and failure surfaces were analyzed to study the high stress and low stress failure, environmental degradations, surface cracks in matrix and the effect of notch on crack initiation failure mechanism. During this investigation it was observed that the most difficult task in thermomechanical fatigue testing is to control the cooling rate as required by the thermal profile. The results show that the fatigue life depend on the applied maximum stress, increased temperatures and hold levels of both the loads and the temperatures. The variation in experimental fatigue life is with in the order of magnitude typical of fatigue data considering the complexity of the test and loading conditions. The SEM photographs and micrographs showed that in titanium matrix composite, the mode of cracking is under partial bridging of fibers at the matrix crack. The COD data was of little use for totally automated measurements when comparing with the crack sizes measured.
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Trownson, Glenn, Peter Gill, William Brayshaw, James Watson, and Jonathan Mann. "Thermomechanical Fatigue Initiation in Nuclear Grades of Austenitic Stainless Steel Using Plant Realistic Loading." In ASME 2022 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/pvp2022-84760.
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Abstract The effect of a Pressurised Water Reactor (PWR) environment on fatigue life is currently assessed using methods such as NUREG/CR-6909 for initiation and ASME Code Case N809 for crack growth, which may be inherently conservative for certain components, especially when considering plant relevant loading. The thermal shock testing with thick-walled specimens as discussed in this paper allows for more plant relevant loading regimes to be utilised in assessments, incorporating through-wall stress gradients, thick walled test specimens and out-of-phase temperature/strain characteristics. This should lead to improvements in reducing the levels of excess conservatism in current assessment methodologies. The capability of the test facility was first presented in PVP2016-63161 [4]. Since then, significant modifications have been made in order to maximise the achievable strain amplitudes in the thick-walled specimen geometry, alongside minimising typical test durations. This was achieved by maximising the temperature differential between the hot and cold cycles and tuning the cycle length in order to ensure that the cycle is long enough to achieve a target strain amplitude, whilst ensuring that it is not so long as to unreasonably increase test durations. This paper details the results of the thermal shock testing performed to date, the development of accompanying Finite Element Analysis (FEA), preliminary initiation data and the development of the various Non Destructive Testing (NDT) techniques used to detect fatigue crack initiation on the thick-walled specimens. Owing to the long testing times needed to achieve the required cycling, various NDT techniques were developed and employed to confirm the presence of fatigue cracking in the thick-walled test specimens before considering more in-depth characterisation using destructive techniques. Eddy Current Array (ECA) testing has been specifically developed for this testing and uses a 360-degree custom bore probe to conduct non-contact ECA measurements on the inner surface of the test specimens. Calibration blocks containing various sized Electrical Discharge Machining (EDM) notches were used to provide a calibration (amplitude and phase) of eddy current responses for prospective flaw depth sizing from indications. The ECA testing performed has provided indications that fatigue cracking is present within the thick-walled specimens tested and subsequent Visual Testing (VT) was performed to assess the highlighted indications from the ECA testing. The VT methods employed included a video borescope for imaging the inner walls of the specimen. In order to increase the detection capabilities (by improving the contrast) the VT was used in conjunction with fluorescent Dye-Penetrant (fDP) testing, whereby a method was developed for using fDP within the inside bore of the specimen alongside a custom ultraviolet (UV) source to better highlight cracking. This paper discusses the success of the NDT developments and testing performed to date and details the latest complementary crack growth assessment work.
Reports on the topic "Concrete blocks Effect of temperature on Testing"
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Ramakrishnan, Aravind, Ashraf Alrajhi, Egemen Okte, Hasan Ozer, and Imad Al-Qadi. Truck-Platooning Impacts on Flexible Pavements: Experimental and Mechanistic Approaches. Illinois Center for Transportation, November 2021. http://dx.doi.org/10.36501/0197-9191/21-038.
Full textAbstract:
Truck platoons are expected to improve safety and reduce fuel consumption. However, their use is projected to accelerate pavement damage due to channelized-load application (lack of wander) and potentially reduced duration between truck-loading applications (reduced rest period). The effect of wander on pavement damage is well documented, while relatively few studies are available on the effect of rest period on pavement permanent deformation. Therefore, the main objective of this study was to quantify the impact of rest period theoretically, using a numerical method, and experimentally, using laboratory testing. A 3-D finite-element (FE) pavement model was developed and run to quantify the effect of rest period. Strain recovery and accumulation were predicted by fitting Gaussian mixture models to the strain values computed from the FE model. The effect of rest period was found to be insignificant for truck spacing greater than 10 ft. An experimental program was conducted, and several asphalt concrete (AC) mixes were considered at various stress levels, temperatures, and rest periods. Test results showed that AC deformation increased with rest period, irrespective of AC-mix type, stress level, and/or temperature. This observation was attributed to a well-documented hardening–relaxation mechanism, which occurs during AC plastic deformation. Hence, experimental and FE-model results are conflicting due to modeling AC as a viscoelastic and the difference in the loading mechanism. A shift model was developed by extending the time–temperature superposition concept to incorporate rest period, using the experimental data. The shift factors were used to compute the equivalent number of cycles for various platoon scenarios (truck spacings or rest period). The shift model was implemented in AASHTOware pavement mechanic–empirical design (PMED) guidelines for the calculation of rutting using equivalent number of cycles.