Strengthening techniques of reinforced concrete structures have significantly changed in recent years. Such improvements happened mainly because of the development of new materials and their associated strengthening techniques. For example, polymeric composites of synthetic fibers (carbon, aramid, glass, etc.), high-strength concrete, and other high-performance cement-based composites have been introduced to construction market. The application of these materials in the strengthening of reinforced concrete (RC) columns implies a review of the design methods and the execution procedures, because if the strengthening materials change, the performance of the strengthened column also changes. This paper intends to characterize, even though in a superficial form, the main strengthening mechanisms associated with some rehabilitation techniques. Also, based on an exploratory experimental analysis, this paper reports the potential of hybrid strengthening techniques by combining different strategies. Six plain concrete short columns were strengthened using several combinations of high-strength concrete (HSC) and fiber-reinforced polymer (FRP) jackets, which resulted in so-called hybrid techniques. The columns had 150 mm diameter and 600 mm height as initial dimensions that, depending on the applied strengthening technique, had the diameter increased to 200 mm. The test results demonstrate that hybrid strengthening techniques are feasible and they can be used in different ways to optimize the rehabilitation strategy.
{"title":"Hybrid Techniques for RC Column Strengthening","authors":"Alexandre Luis Sudano, J. B. Hanai","doi":"10.14359/20169","DOIUrl":"https://doi.org/10.14359/20169","url":null,"abstract":"Strengthening techniques of reinforced concrete structures have significantly changed in recent years. Such improvements happened mainly because of the development of new materials and their associated strengthening techniques. For example, polymeric composites of synthetic fibers (carbon, aramid, glass, etc.), high-strength concrete, and other high-performance cement-based composites have been introduced to construction market. The application of these materials in the strengthening of reinforced concrete (RC) columns implies a review of the design methods and the execution procedures, because if the strengthening materials change, the performance of the strengthened column also changes. This paper intends to characterize, even though in a superficial form, the main strengthening mechanisms associated with some rehabilitation techniques. Also, based on an exploratory experimental analysis, this paper reports the potential of hybrid strengthening techniques by combining different strategies. Six plain concrete short columns were strengthened using several combinations of high-strength concrete (HSC) and fiber-reinforced polymer (FRP) jackets, which resulted in so-called hybrid techniques. The columns had 150 mm diameter and 600 mm height as initial dimensions that, depending on the applied strengthening technique, had the diameter increased to 200 mm. The test results demonstrate that hybrid strengthening techniques are feasible and they can be used in different ways to optimize the rehabilitation strategy.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114422776","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper describes how permeability measurements in cement-based materials are one of the important ways to estimate their durability. Several methodologies have been applied for permeability measurements in this kind of materials but large discrepancies in results due to different assumptions of each methodology have prevented strong conclusions about a definite measurement method. Considering that a better understanding of flow mechanisms in permeability measurements can provide an improvement in present methods, the authors propose to apply the Thenoz methodology in permeability analysis of cement-based materials. Thenoz methodology was developed to measure the rock air permeability and has shown good results for cement-based materials. It consists in measurements of air permeability in porous media applying a pressure gradient on both transversals sides of samples. This pressure gradient forces air to flow through the concrete resulting in a reliable analysis of the permeability coefficients. A major question in this method is the right model definition in function of fluid compressibility and flow characteristic, laminar or turbulent. This paper applies Thenoz methodology to describe air permeability in concrete made with granulated blast-furnace slag cement. Concrete specimens were made with constant water/cement (w/c) = 0.42 and submitted to curing in air during 28 days (named conventional concrete). The results were compared with high-strength concrete specimens tested in accordance with the same methodology. At the age of the tests, specimens were oven-dried for 24 hours at 80°C before air permeability tests. Four different pressure gradients were used in permeability tests to describe the flow versus pressure gradient behavior. The degree of accordance with Darcy’s law is shown by the results. Both Mach number and Reynolds number were determined. The results did not show air compressibility during the test, in accordance with Mach number, and results show a laminar flow during tests, in accordance with Reynolds number results. The results show a laminar flow during tests and a good agreement with Darcy’s law, suggesting that Thenoz methodology is an interesting alternative to measure air permeability in cement-based materials.
{"title":"Evaluation of Thenoz Methodology to Measure Concrete Air Permeability","authors":"G. Camarini, P. S. Bardella, Valdir M. Pereira","doi":"10.14359/20176","DOIUrl":"https://doi.org/10.14359/20176","url":null,"abstract":"This paper describes how permeability measurements in cement-based materials are one of the important ways to estimate their durability. Several methodologies have been applied for permeability measurements in this kind of materials but large discrepancies in results due to different assumptions of each methodology have prevented strong conclusions about a definite measurement method. Considering that a better understanding of flow mechanisms in permeability measurements can provide an improvement in present methods, the authors propose to apply the Thenoz methodology in permeability analysis of cement-based materials. Thenoz methodology was developed to measure the rock air permeability and has shown good results for cement-based materials. It consists in measurements of air permeability in porous media applying a pressure gradient on both transversals sides of samples. This pressure gradient forces air to flow through the concrete resulting in a reliable analysis of the permeability coefficients. A major question in this method is the right model definition in function of fluid compressibility and flow characteristic, laminar or turbulent. This paper applies Thenoz methodology to describe air permeability in concrete made with granulated blast-furnace slag cement. Concrete specimens were made with constant water/cement (w/c) = 0.42 and submitted to curing in air during 28 days (named conventional concrete). The results were compared with high-strength concrete specimens tested in accordance with the same methodology. At the age of the tests, specimens were oven-dried for 24 hours at 80°C before air permeability tests. Four different pressure gradients were used in permeability tests to describe the flow versus pressure gradient behavior. The degree of accordance with Darcy’s law is shown by the results. Both Mach number and Reynolds number were determined. The results did not show air compressibility during the test, in accordance with Mach number, and results show a laminar flow during tests, in accordance with Reynolds number results. The results show a laminar flow during tests and a good agreement with Darcy’s law, suggesting that Thenoz methodology is an interesting alternative to measure air permeability in cement-based materials.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"133 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128069880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Parsekian, N. Shrive, T. Brown, J. Kroman, Perry, A. Boucher
This paper describes how static and fatigue flexural tests were performed on transverse sections of a 33.6 m (110.2 ft) Ductal® ultra-high performance fiber-reinforced concrete (UHPFRC) girder for a single-span, 53 m (173.9 ft) pedestrian overpass to be built in the City of Calgary, Canada. Load tests were performed on three 1 m long, full-width and full-depth slab sections. In the first and second tests, the concrete was reinforced with, 13 mm (0.51 in.) long steel fibers (2% by volume). The sections were also reinforced with glass fiber reinforced polymer (GFRP) bars and tested to failure under monotonic loading. The specimens cracked and failed at similar loads. The third specimen had no reinforcement other than the steel fibers. Initially, the specimen was loaded until it cracked. Subsequently the specimen was subjected to 1 million cycles between 20 and 80% of the design service load, followed by a second million load cycles over a load range of 20 to 80% of the observed first-crack load. As the specimen did not fail under this loading regimen, nor was there any observed degradation of stiffness, a third million load cycles were applied to 20 to 80% of the failure load of the sections with GFRP reinforcement. Static tests were performed to evaluate the specimen stiffness several times during the fatigue test. The service load range was not observed to cause damage to the specimen. Some stiffness degradation was noted during the beginning of the third million cycles of loading, but stabilized at about two thirds of the original stiffness. Subsequent to fatigue testing, the specimen was loaded to failure, with collapse occurring at a load higher than predicted. The compressive strength of the Ductal® concrete used in these tests was over 200 MPa (29,008 psi) and the tensile strength at first crack was over 8 MPa (1,160 psi).
{"title":"Static and Fatigue Tests on Ductal® UHPFRC Footbridge Sections","authors":"G. Parsekian, N. Shrive, T. Brown, J. Kroman, Perry, A. Boucher","doi":"10.14359/20180","DOIUrl":"https://doi.org/10.14359/20180","url":null,"abstract":"This paper describes how static and fatigue flexural tests were performed on transverse sections of a 33.6 m (110.2 ft) Ductal® ultra-high performance fiber-reinforced concrete (UHPFRC) girder for a single-span, 53 m (173.9 ft) pedestrian overpass to be built in the City of Calgary, Canada. Load tests were performed on three 1 m long, full-width and full-depth slab sections. In the first and second tests, the concrete was reinforced with, 13 mm (0.51 in.) long steel fibers (2% by volume). The sections were also reinforced with glass fiber reinforced polymer (GFRP) bars and tested to failure under monotonic loading. The specimens cracked and failed at similar loads. The third specimen had no reinforcement other than the steel fibers. Initially, the specimen was loaded until it cracked. Subsequently the specimen was subjected to 1 million cycles between 20 and 80% of the design service load, followed by a second million load cycles over a load range of 20 to 80% of the observed first-crack load. As the specimen did not fail under this loading regimen, nor was there any observed degradation of stiffness, a third million load cycles were applied to 20 to 80% of the failure load of the sections with GFRP reinforcement. Static tests were performed to evaluate the specimen stiffness several times during the fatigue test. The service load range was not observed to cause damage to the specimen. Some stiffness degradation was noted during the beginning of the third million cycles of loading, but stabilized at about two thirds of the original stiffness. Subsequent to fatigue testing, the specimen was loaded to failure, with collapse occurring at a load higher than predicted. The compressive strength of the Ductal® concrete used in these tests was over 200 MPa (29,008 psi) and the tensile strength at first crack was over 8 MPa (1,160 psi).","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122223243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. I. Moreno, Rómel G. Solís-Carcaño, C. Serrano-Zebadua
This paper describes how the weather of the Yucatan Peninsula is classified as hot sub-humid, with minor differences of relative humidity and temperature during the year. Local builders, in their search for process optimization and cost reduction, usually do not cure concrete beyond wetting the concrete surface immediately after removing the formwork. Teaching of concrete technology has been based on classic reports, where it is affirmed that the strength gain is enhanced when moist curing is applied. Preliminary studies in the Yucatan region have not shown that moist curing helped to improve strength gain. Based on the meteorological conditions of the Yucatan region, it is possible that natural curing occurred with no need for additional curing for most of the cases. The objective of this study was to obtain the strength-gain curves as a function of the moist curing time from 0 to 90 days. Preliminary results confirm the hypothesis about the sufficiency of the natural curing under the weather conditions of the Yucatan region. The use of porous aggregate may have contributed to curing during storage in air.
{"title":"Natural Concrete Curing under Hot Sub-Humid Climate","authors":"E. I. Moreno, Rómel G. Solís-Carcaño, C. Serrano-Zebadua","doi":"10.14359/20181","DOIUrl":"https://doi.org/10.14359/20181","url":null,"abstract":"This paper describes how the weather of the Yucatan Peninsula is classified as hot sub-humid, with minor differences of relative humidity and temperature during the year. Local builders, in their search for process optimization and cost reduction, usually do not cure concrete beyond wetting the concrete surface immediately after removing the formwork. Teaching of concrete technology has been based on classic reports, where it is affirmed that the strength gain is enhanced when moist curing is applied. Preliminary studies in the Yucatan region have not shown that moist curing helped to improve strength gain. Based on the meteorological conditions of the Yucatan region, it is possible that natural curing occurred with no need for additional curing for most of the cases. The objective of this study was to obtain the strength-gain curves as a function of the moist curing time from 0 to 90 days. Preliminary results confirm the hypothesis about the sufficiency of the natural curing under the weather conditions of the Yucatan region. The use of porous aggregate may have contributed to curing during storage in air.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123604823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a comparative analysis of the predicted shear capacities of beams obtained by using several design criteria with respect to test results of reinforced concrete beams built with high-performance concrete (fc > 50 MPa). The database contains a total of 234 test beams with and without web reinforcement. The employed design criteria are EUROCODE 2 and the simplified methods of ACI 318 and Canadian CSA A23.3. The Brazilian code (NBR 6118) procedures and Zsutty’s method are also included in the study. Statistics of the ratio of test-to-predicted shear capacity are used to evaluate the adequacy of these design models in terms of safety, precision, and economy. The effects of the depth of the beams, concrete compressive strength, and the amount of longitudinal and web reinforcement are also investigated. The results show that for the beams without web reinforcement, EUROCODE 2, and Zsutty’s method are the most suitable procedures; NBR 6118 provisions, on the other hand, need adjustments because they can have inadequate margins of safety. The performance of the shear predicting models of ACI 318, the CSA A23.3 and NBR 6118 (θ = 45°) for beams with web reinforcement are similar but significantly biased; EUROCODE 2, in this case, is extremely conservative and consequently not economical. Overall, Zsutty’s method was the best predicting model among those included in this study.
{"title":"Analysis of Design Criteria for Shear Strength of High-Performance Reinforced Concrete Beams","authors":"J. Calixto, A. Ribeiro","doi":"10.14359/20172","DOIUrl":"https://doi.org/10.14359/20172","url":null,"abstract":"This paper presents a comparative analysis of the predicted shear capacities of beams obtained by using several design criteria with respect to test results of reinforced concrete beams built with high-performance concrete (fc > 50 MPa). The database contains a total of 234 test beams with and without web reinforcement. The employed design criteria are EUROCODE 2 and the simplified methods of ACI 318 and Canadian CSA A23.3. The Brazilian code (NBR 6118) procedures and Zsutty’s method are also included in the study. Statistics of the ratio of test-to-predicted shear capacity are used to evaluate the adequacy of these design models in terms of safety, precision, and economy. The effects of the depth of the beams, concrete compressive strength, and the amount of longitudinal and web reinforcement are also investigated. The results show that for the beams without web reinforcement, EUROCODE 2, and Zsutty’s method are the most suitable procedures; NBR 6118 provisions, on the other hand, need adjustments because they can have inadequate margins of safety. The performance of the shear predicting models of ACI 318, the CSA A23.3 and NBR 6118 (θ = 45°) for beams with web reinforcement are similar but significantly biased; EUROCODE 2, in this case, is extremely conservative and consequently not economical. Overall, Zsutty’s method was the best predicting model among those included in this study.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129175354","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J.L.M.P. Lopes, E. Bacarji, E. P. Figueiredo, J. Rego
This paper describes how Brazil generates around 190,000 tons of mud from the residue of processing marble and granite (MGBR) annually. This has been the cause of a serious environmental problem because of a lack of destination for this residue. The objective of this paper is the evaluation of the technique viability of the use of the MGBR, generated for three marble shops, of Goiania city, state of Goias, in Brazil, as partial substitution for portland cement in the production of concretes. Characterizations have been made to determine the physical, chemical, mineralogical, and the pozzolanic reactivity of the residue. Reference concrete mixtures and concrete mixtures with 5%, 10% and 20% substitution of the MGBR of the cement were produced (w/cm) used were between 0.50 and 0.65. The properties of the concretes were determined, including workability, compressive strength, the modulus of elasticity, and absorption by immersion. The results show that the compressive strength of the concrete with the MGBR diminishes with contents of substitution at 10% and 20%. However, with 5% of substitution of the residue, the results of the analysis show that it did not have significant variations in any of the analyzed properties, indicating the viability technique of the substitution of this percentage of residue.
{"title":"Infl uence of the Marble and Granite Benefi cation of Residue (MGBR) as Filler on the Properties of Concrete","authors":"J.L.M.P. Lopes, E. Bacarji, E. P. Figueiredo, J. Rego","doi":"10.14359/20184","DOIUrl":"https://doi.org/10.14359/20184","url":null,"abstract":"This paper describes how Brazil generates around 190,000 tons of mud from the residue of processing marble and granite (MGBR) annually. This has been the cause of a serious environmental problem because of a lack of destination for this residue. The objective of this paper is the evaluation of the technique viability of the use of the MGBR, generated for three marble shops, of Goiania city, state of Goias, in Brazil, as partial substitution for portland cement in the production of concretes. Characterizations have been made to determine the physical, chemical, mineralogical, and the pozzolanic reactivity of the residue. Reference concrete mixtures and concrete mixtures with 5%, 10% and 20% substitution of the MGBR of the cement were produced (w/cm) used were between 0.50 and 0.65. The properties of the concretes were determined, including workability, compressive strength, the modulus of elasticity, and absorption by immersion. The results show that the compressive strength of the concrete with the MGBR diminishes with contents of substitution at 10% and 20%. However, with 5% of substitution of the residue, the results of the analysis show that it did not have significant variations in any of the analyzed properties, indicating the viability technique of the substitution of this percentage of residue.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125489982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper describes how the increase in knowledge about the potential of mixtures containing chemicals and mineral materials leads to the high-performance concretes, including high-strength concrete (HSC) in the last decade. When high strength, durability, and elevated service behavior are necessities high-strength concrete can be an economical solution. In general, it is known that increasing the compressive concrete strength leads to the deformability reduction resulting in a more brittle concrete. On the other hand, the low deformability of HSC doesn’t mean low deformability of the high-strength beams, because their behavior comes from a combined effect of concrete and reinforcement. One of the usual reinforcement elements is the stirrups (transversal reinforcement). By ensuring a sufficient concrete confinement in the compressive zone, and by its distribution along the beam length, this reinforcement can improve the plastic rotation capacity on the beam critical sections. This paper presents an experimental study about the influence of transversal reinforcement (stirrups) on the flexure plastic rotation capacity of high-strength beams. Flexural tests on five simply supported beams were carried out using a four-point bending load untill the failure load. The load position was favorable to create a central zone on the beam theoretically of pure flexure behavior without shear stress influence. The beams failures were governed by the pure flexure in the middle zone of the beams. In this study, only one solution of stirrups was used, corresponding to a transversal reinforcement ratio of 0.295%. The compressive concrete strength was between 75.0 and 90.6 MPa. The longitudinal reinforcement ratio was between 2.2 to 3.5%. The plastic rotation capacity in flexure is characterized by the use and definition of a plastic trend parameter. From the results of this study, a well-known positive effect on plastic rotation capacity caused by confinement with transversal reinforcement was shown. A bilinear law can induce the increment of plastic rotation capacity. This law states that the increment of plastic rotation capacity decreases in a large way as the longitudinal tensile reinforcement ratio increases, and becomes equal to zero from longitudinal reinforcement ratio 3.0 to 3.5%.
{"title":"Infl uence of Transversal Reinforcement on Plastic Rotation Capacity of High-Strength Beams","authors":"L. Bernardo, L. Oliveira, D. Pinto","doi":"10.14359/20182","DOIUrl":"https://doi.org/10.14359/20182","url":null,"abstract":"This paper describes how the increase in knowledge about the potential of mixtures containing chemicals and mineral materials leads to the high-performance concretes, including high-strength concrete (HSC) in the last decade. When high strength, durability, and elevated service behavior are necessities high-strength concrete can be an economical solution. In general, it is known that increasing the compressive concrete strength leads to the deformability reduction resulting in a more brittle concrete. On the other hand, the low deformability of HSC doesn’t mean low deformability of the high-strength beams, because their behavior comes from a combined effect of concrete and reinforcement. One of the usual reinforcement elements is the stirrups (transversal reinforcement). By ensuring a sufficient concrete confinement in the compressive zone, and by its distribution along the beam length, this reinforcement can improve the plastic rotation capacity on the beam critical sections. This paper presents an experimental study about the influence of transversal reinforcement (stirrups) on the flexure plastic rotation capacity of high-strength beams. Flexural tests on five simply supported beams were carried out using a four-point bending load untill the failure load. The load position was favorable to create a central zone on the beam theoretically of pure flexure behavior without shear stress influence. The beams failures were governed by the pure flexure in the middle zone of the beams. In this study, only one solution of stirrups was used, corresponding to a transversal reinforcement ratio of 0.295%. The compressive concrete strength was between 75.0 and 90.6 MPa. The longitudinal reinforcement ratio was between 2.2 to 3.5%. The plastic rotation capacity in flexure is characterized by the use and definition of a plastic trend parameter. From the results of this study, a well-known positive effect on plastic rotation capacity caused by confinement with transversal reinforcement was shown. A bilinear law can induce the increment of plastic rotation capacity. This law states that the increment of plastic rotation capacity decreases in a large way as the longitudinal tensile reinforcement ratio increases, and becomes equal to zero from longitudinal reinforcement ratio 3.0 to 3.5%.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120912964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Due to the different characteristics of higher strength concrete, this paper describes how some procedures traditionally used in the design of structures made of lower-strength concrete have to be changed. In order to evaluate the behavior of high-strength concrete (HSC) elements (fc > 50 MPa) with reasonable accuracy, an adequate compressive stress-strain relationship of concrete should be adopted. This is particularly important for predicting the behavior of columns—elements where the use of HSC is most advantageous. Different types of stress-strain relationships for HSC have been proposed for the nonlinear analysis of member behavior and for the ultimate state analysis of cross sections of elements under combined flexure and axial load. In this work, simplified rectangular stress blocks for the design of cross sections by different codes applicable to HSC structures are presented. It is shown that those concrete stress blocks can lead to quite different bending moment-axial load interaction diagrams and comparisons between experimental and calculated strengths of 403 tested columns give an idea of the level of safety related to the use of various concrete stress blocks.
{"title":"Evaluation of the Strength of High-Strength Concrete Columns","authors":"A. Paula, L. Shehata, I. Shehata","doi":"10.14359/20185","DOIUrl":"https://doi.org/10.14359/20185","url":null,"abstract":"Due to the different characteristics of higher strength concrete, this paper describes how some procedures traditionally used in the design of structures made of lower-strength concrete have to be changed. In order to evaluate the behavior of high-strength concrete (HSC) elements (fc > 50 MPa) with reasonable accuracy, an adequate compressive stress-strain relationship of concrete should be adopted. This is particularly important for predicting the behavior of columns—elements where the use of HSC is most advantageous. Different types of stress-strain relationships for HSC have been proposed for the nonlinear analysis of member behavior and for the ultimate state analysis of cross sections of elements under combined flexure and axial load. In this work, simplified rectangular stress blocks for the design of cross sections by different codes applicable to HSC structures are presented. It is shown that those concrete stress blocks can lead to quite different bending moment-axial load interaction diagrams and comparisons between experimental and calculated strengths of 403 tested columns give an idea of the level of safety related to the use of various concrete stress blocks.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"123 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134466928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper reports on an experimental study that was conducted on mortar phase for self-compacting concrete. A series of mortars were produced with similar flow properties, measured by spread and v-funnel tests, adequate to produce self-compacting concrete. The water content and the modified carboxylic superplasticizer dosage were determined experimentally for each mortar. Different percentages of cement replacement materials were used in binary blends, each one combining one of the two types of cement with one of the three mineral additions selected: limestone powder, granite filler, and fly ash. Each of the binary blends of powders was combined in five different proportions in volume with the fine aggregate (Vp/Vs). Mortars were tested for compressive strength at 28 days and this value was related to the water/cement ratio, the percentage of replacement materials, and Vp/Vs parameter. The analysis revealed the possibility of establishing adequate mortar parameters to obtain simultaneously the self-compactability and the required compressive strength of self-compacting concrete.
{"title":"Parameters for Self-Compacting Concrete Mortar Phase","authors":"Miguel Nepomuceno, L. A. Oliveira","doi":"10.14359/20183","DOIUrl":"https://doi.org/10.14359/20183","url":null,"abstract":"This paper reports on an experimental study that was conducted on mortar phase for self-compacting concrete. A series of mortars were produced with similar flow properties, measured by spread and v-funnel tests, adequate to produce self-compacting concrete. The water content and the modified carboxylic superplasticizer dosage were determined experimentally for each mortar. Different percentages of cement replacement materials were used in binary blends, each one combining one of the two types of cement with one of the three mineral additions selected: limestone powder, granite filler, and fly ash. Each of the binary blends of powders was combined in five different proportions in volume with the fine aggregate (Vp/Vs). Mortars were tested for compressive strength at 28 days and this value was related to the water/cement ratio, the percentage of replacement materials, and Vp/Vs parameter. The analysis revealed the possibility of establishing adequate mortar parameters to obtain simultaneously the self-compactability and the required compressive strength of self-compacting concrete.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"111 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115581410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Concrete curing is an essential stage in construction in order to obtain an adequate degree of hydration of cement. Frequently, this step is not carried out correctly, but an adequate structure performance depends to a great extent on curing. Today, blended cement concrete (BCC) is used widely in Argentina, despite the lack of long-standing BCC structures constructed to demonstrate adequate service-life performance. In this paper, the modification of BCC pore structure due to curing treatment is analyzed by evaluation of transport properties in concretes with different w/c and maximum coarse aggregate size. To simulate diverse weather conditions to which the same concrete type may be exposed according to geographical location, different curing conditions were applied during 28 consecutive days. Transport properties evaluated were water permeability under pressure, capillary suction, and chloride ingress rate. Total porosity and 24-h water absorption were also determined. According to the results obtained, a notable influence of curing conditions on the pore structure of BCC was observed, emphasizing the importance of a proper curing on the service life of BCC structures.
{"title":"Influence of Curing Conditions on Transport Properties of Blended Cement Concrete","authors":"V. Taus, Y. Villagrán, A. D. Maio","doi":"10.14359/20165","DOIUrl":"https://doi.org/10.14359/20165","url":null,"abstract":"Concrete curing is an essential stage in construction in order to obtain an adequate degree of hydration of cement. Frequently, this step is not carried out correctly, but an adequate structure performance depends to a great extent on curing. Today, blended cement concrete (BCC) is used widely in Argentina, despite the lack of long-standing BCC structures constructed to demonstrate adequate service-life performance. In this paper, the modification of BCC pore structure due to curing treatment is analyzed by evaluation of transport properties in concretes with different w/c and maximum coarse aggregate size. To simulate diverse weather conditions to which the same concrete type may be exposed according to geographical location, different curing conditions were applied during 28 consecutive days. Transport properties evaluated were water permeability under pressure, capillary suction, and chloride ingress rate. Total porosity and 24-h water absorption were also determined. According to the results obtained, a notable influence of curing conditions on the pore structure of BCC was observed, emphasizing the importance of a proper curing on the service life of BCC structures.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"21 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126032875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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