W. G. Moravia, C. Rodrigues, A. Gumieri, W. Vasconcelos
Durability is one of the key factors considered in the specification of concrete for most of its applications. When applied to industrial floors, road pavements, and sidewalks, abrasion wearing impairs the concrete performance. This work is focused on the abrasion resistance of lightweight concrete produced with expanded clay, comparing it to the performance of a conventional concrete produced with normal-weight aggregates, and with mixture proportion for an estimated compressive strength of 30 MPa. The lightweight aggregate structure was investigated through mercury intrusion porosimetry and water absorption tests. The parameters used to evaluate the abrasion phenomena were thickness and mass loss of the concretes, which resulted from the friction between the specimens and an abrasive material. Although the expanded clay presents lower abrasion resistance than the normal-weight aggregate, due to its higher porosity; for example, both concretes behaved similarly regarding their wearing resistance. The denser interfacial transition zone between the expanded clay and the cement paste in the lightweight concrete seems to compensate for the lower wear resistance of the aggregate.
{"title":"Influence of Expanded Clay Aggregates in Abrasion Resistance of Lightweight Concrete","authors":"W. G. Moravia, C. Rodrigues, A. Gumieri, W. Vasconcelos","doi":"10.14359/20167","DOIUrl":"https://doi.org/10.14359/20167","url":null,"abstract":"Durability is one of the key factors considered in the specification of concrete for most of its applications. When applied to industrial floors, road pavements, and sidewalks, abrasion wearing impairs the concrete performance. This work is focused on the abrasion resistance of lightweight concrete produced with expanded clay, comparing it to the performance of a conventional concrete produced with normal-weight aggregates, and with mixture proportion for an estimated compressive strength of 30 MPa. The lightweight aggregate structure was investigated through mercury intrusion porosimetry and water absorption tests. The parameters used to evaluate the abrasion phenomena were thickness and mass loss of the concretes, which resulted from the friction between the specimens and an abrasive material. Although the expanded clay presents lower abrasion resistance than the normal-weight aggregate, due to its higher porosity; for example, both concretes behaved similarly regarding their wearing resistance. The denser interfacial transition zone between the expanded clay and the cement paste in the lightweight concrete seems to compensate for the lower wear resistance of the aggregate.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"23 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":"122513996","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 will discuss how previous research presented a model to forecast chloride ion penetration over time in samples where chloride profiles form a peak, i.e. the concentration of chloride ions first increases as we move from the surface to the interior of the structure and then show a decrease after a specific depth. This study presents the variation of this profile over time through measurements at different ages and compares these results with the values forecast by the model of the authors using the first profile measured in the structure. The model showed good accuracy in this case study and should be confirmed in other structures in use.
{"title":"Confirmation of a Model to Predict Chloride Ion Penetration with Peak over Time","authors":"A. Guimarães, P. Helene","doi":"10.14359/20173","DOIUrl":"https://doi.org/10.14359/20173","url":null,"abstract":"This paper will discuss how previous research presented a model to forecast chloride ion penetration over time in samples where chloride profiles form a peak, i.e. the concentration of chloride ions first increases as we move from the surface to the interior of the structure and then show a decrease after a specific depth. This study presents the variation of this profile over time through measurements at different ages and compares these results with the values forecast by the model of the authors using the first profile measured in the structure. The model showed good accuracy in this case study and should be confirmed in other structures in use.","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":"128673587","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}
The heat of hydration in massive concrete structures can raise the temperature to a level where thermal cracks can pose a problem. Hardening retarders are admixtures that lower the rate of hydration, distribute the heat release over time, and lower maximum temperature in concrete. Such admixtures will inherently lead to lower early strength, but should lead to comparable 28-day strength to reference concrete. Relative large amounts of urea works, in particular when the additional retardation of setting (not hardening) is counteracted by the set accelerator calcium nitrate. However, these dosages are high, and urea will also slowly decompose to ammonia that may limit the urea application to outdoor use, if any. The latest potential admixtures are combinations of minor amounts of strong setting retarders like organic acids (0.1-0.3 %) with the setting accelerator calcium nitrate (1-3%), where a true synergy between the two leads to hardening retardation.
{"title":"Hardening Retarders for Massive Concrete","authors":"H. Justnes, F. Wuyts, D. Gemert","doi":"10.14359/20166","DOIUrl":"https://doi.org/10.14359/20166","url":null,"abstract":"The heat of hydration in massive concrete structures can raise the temperature to a level where thermal cracks can pose a problem. Hardening retarders are admixtures that lower the rate of hydration, distribute the heat release over time, and lower maximum temperature in concrete. Such admixtures will inherently lead to lower early strength, but should lead to comparable 28-day strength to reference concrete. Relative large amounts of urea works, in particular when the additional retardation of setting (not hardening) is counteracted by the set accelerator calcium nitrate. However, these dosages are high, and urea will also slowly decompose to ammonia that may limit the urea application to outdoor use, if any. The latest potential admixtures are combinations of minor amounts of strong setting retarders like organic acids (0.1-0.3 %) with the setting accelerator calcium nitrate (1-3%), where a true synergy between the two leads to hardening retardation.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"66 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":"126227972","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 self-compacting concrete (SCC), a high-fluidity concrete that maintains its stability, was developed in Japan in 1998. However, there is still a lack of knowledge about SCC, especially regarding the few practical mix design methods available. Without a standardized mixture proportioning method, researchers have to use the trial-and-error method, spending time and resources without being certain about the concrete quality. In this paper, a new mix design method for SCC is introduced that allows the production of concrete from local materials, in an attempt to reach the desired mechanical and durability properties at the lowest cost. This method is explained in detail elsewhere. To explain how to use such a method, a study of SCC was carried out and presented at the end of the paper. Moreover, this methodology has been applied successfully in Brazil, obtaining SCC with costs very close to those of normal vibrated concrete (NVC) for the same strengths or durability measures.
{"title":"A Practical Mix Design Method for Self-Compacting Concrete","authors":"B. Tutikian, D. D. Molin, R. Cremonini","doi":"10.14359/20178","DOIUrl":"https://doi.org/10.14359/20178","url":null,"abstract":"This paper describes how self-compacting concrete (SCC), a high-fluidity concrete that maintains its stability, was developed in Japan in 1998. However, there is still a lack of knowledge about SCC, especially regarding the few practical mix design methods available. Without a standardized mixture proportioning method, researchers have to use the trial-and-error method, spending time and resources without being certain about the concrete quality. In this paper, a new mix design method for SCC is introduced that allows the production of concrete from local materials, in an attempt to reach the desired mechanical and durability properties at the lowest cost. This method is explained in detail elsewhere. To explain how to use such a method, a study of SCC was carried out and presented at the end of the paper. Moreover, this methodology has been applied successfully in Brazil, obtaining SCC with costs very close to those of normal vibrated concrete (NVC) for the same strengths or durability measures.","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":"116592711","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 review of the application of concrete that has been used in offshore structures over the last 35 years. The state-of-the-art technology available for offshore oil platforms and other offshore applications is also described. Currently, there are around 350 offshore gravity and floating concrete platforms in operation in the North Sea, Northern Canada, Australia, Netherlands, Congo, Nigeria, Indonesia, Russia, the Philippines, Brazil, and the Gulf of Mexico. More recently, an important LNG offshore terminal has been designed and is now under construction in Algeciras, near the Gibraltar Strait in Spain. Over the past 30 years there has been a considerable improvement in the design and construction aspects of concrete production. Water-reducing admixtures and additions, such as metakaolin and silica, allowed the development of concretes with improved performance. These new concretes can easily achieve much higher strengths and durability which make them much more suitable for offshore applications. The liberal use of lightweight aggregates is considered crucial for a total weight reduction of the structure and for floating considerations. The evolving technology for the design and construction of this type of structures is discussed in the paper.
{"title":"A Review of the Application of Concrete to Offshore Structures","authors":"J. Fernandes, T. Bittencourt, P. Helene","doi":"10.14359/20187","DOIUrl":"https://doi.org/10.14359/20187","url":null,"abstract":"This paper presents a review of the application of concrete that has been used in offshore structures over the last 35 years. The state-of-the-art technology available for offshore oil platforms and other offshore applications is also described. Currently, there are around 350 offshore gravity and floating concrete platforms in operation in the North Sea, Northern Canada, Australia, Netherlands, Congo, Nigeria, Indonesia, Russia, the Philippines, Brazil, and the Gulf of Mexico. More recently, an important LNG offshore terminal has been designed and is now under construction in Algeciras, near the Gibraltar Strait in Spain. Over the past 30 years there has been a considerable improvement in the design and construction aspects of concrete production. Water-reducing admixtures and additions, such as metakaolin and silica, allowed the development of concretes with improved performance. These new concretes can easily achieve much higher strengths and durability which make them much more suitable for offshore applications. The liberal use of lightweight aggregates is considered crucial for a total weight reduction of the structure and for floating considerations. The evolving technology for the design and construction of this type of structures is discussed in the paper.","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":"130589584","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}
A. Castro, J. B. L. Liborio, F. Valenzuela, V. Pandolfelli
Traditionally, concrete workability is associated with its consistency, expressed in terms of the value measured by the slump test that, in spite of being a commonly used test, does not quantify it totally. It happens because, from a rheological point of view, the fresh concrete flows as a liquid and its behavior is similar to a Bingham fluid, being described by two rheological parameters: yield stress and plastic viscosity. Thus, this paper presents the evaluation of high-performance concrete workability by the traditional slump test and by the rheometer. The process of workability loss is associated with the increase of rheological parameter values and to a corresponding reduction of the slump value over time. The correlation among the parameters obtained by the rheometer and the value measured by the slump test showed that the slump value is much more sensitive to the yield torque than the torque viscosity.
{"title":"The Application of Rheological Concepts on the Evaluation of High-Performance Concrete Workability","authors":"A. Castro, J. B. L. Liborio, F. Valenzuela, V. Pandolfelli","doi":"10.14359/20171","DOIUrl":"https://doi.org/10.14359/20171","url":null,"abstract":"Traditionally, concrete workability is associated with its consistency, expressed in terms of the value measured by the slump test that, in spite of being a commonly used test, does not quantify it totally. It happens because, from a rheological point of view, the fresh concrete flows as a liquid and its behavior is similar to a Bingham fluid, being described by two rheological parameters: yield stress and plastic viscosity. Thus, this paper presents the evaluation of high-performance concrete workability by the traditional slump test and by the rheometer. The process of workability loss is associated with the increase of rheological parameter values and to a corresponding reduction of the slump value over time. The correlation among the parameters obtained by the rheometer and the value measured by the slump test showed that the slump value is much more sensitive to the yield torque than the torque viscosity.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"33 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":"125028412","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. Camarini, P. S. Bardella, D. Barbosa, Valdir M. Pereira
This paper describes how steam curing at atmospheric pressure is an important technique for obtaining high early strength values in precast concrete production. This paper explores the potential benefits of steam curing in concrete products made with different cements types and with supplementary cementitious materials. All concretes mixtures had the same workability and were produced with two cements both with and without silica fume replacement (10% by mass): high-early-strength portland cement and blast-furnace slag portland cement. For each mixture, specimens were subjected to three curing conditions. Immersion curing until the age of 7 days, curing in air and steam curing at temperatures of 60°C and 80°C maximum temperature over 4 h. Concretes were prepared and tested for initial surface absorption and air permeability. Compressive strength was also determined. The concretes were tested at different ages: 1, 3, 7, 28, 90, and 180 days. The results showed that the concretes with silica fume presented a lower air permeability and capillary absorption, mainly in later ages, when compared with concretes without silica fume for all curing procedures and both portland cements used. The inclusion of silica fume improved performance of concrete produced with blast-furnace slag portland cement at temperature of 80°C. High-early-strength portland cement had a good performance with silica fume replacement. The curing method adopted had significant effects on the near-surface properties of concrete incorporating silica fume.
{"title":"Silica Fume for Cement Replacement and its Influence on Strength and Permeability of Steam-Cured High-Strength Concrete","authors":"G. Camarini, P. S. Bardella, D. Barbosa, Valdir M. Pereira","doi":"10.14359/20174","DOIUrl":"https://doi.org/10.14359/20174","url":null,"abstract":"This paper describes how steam curing at atmospheric pressure is an important technique for obtaining high early strength values in precast concrete production. This paper explores the potential benefits of steam curing in concrete products made with different cements types and with supplementary cementitious materials. All concretes mixtures had the same workability and were produced with two cements both with and without silica fume replacement (10% by mass): high-early-strength portland cement and blast-furnace slag portland cement. For each mixture, specimens were subjected to three curing conditions. Immersion curing until the age of 7 days, curing in air and steam curing at temperatures of 60°C and 80°C maximum temperature over 4 h. Concretes were prepared and tested for initial surface absorption and air permeability. Compressive strength was also determined. The concretes were tested at different ages: 1, 3, 7, 28, 90, and 180 days. The results showed that the concretes with silica fume presented a lower air permeability and capillary absorption, mainly in later ages, when compared with concretes without silica fume for all curing procedures and both portland cements used. The inclusion of silica fume improved performance of concrete produced with blast-furnace slag portland cement at temperature of 80°C. High-early-strength portland cement had a good performance with silica fume replacement. The curing method adopted had significant effects on the near-surface properties of concrete incorporating silica fume.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"69 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":"124751121","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 structures submitted to the action of the environmental hazards can produce deterioration, mainly the corrosion of reinforcing steel. The structural repair can be an efficient solution for this problem. Then, the technological know-how of the materials and repair techniques used are very important. The adherence of the repair mortars on the old concrete is a decisive requirement of performance and durability of any repair. On the other hand, methods of analysis of images are being used more and more to evaluate and to understand, in a more precise way, the behavior of the materials. The objective of this work is the evaluation of commercial mortars of repairs by microscopy. In this study, four types of mortar were utilized: 1) high-resistance shrinkage-compensating mortar, 2) polymer-modified mortar, 3) high-resistance shrinkage-compensating with fiber- and polymer-modified mortar, and 4) epoxy coating with a similar mortar to the substratum concrete. The experiment was made in two concrete blocks of each type of material repair. In this research, 247 micrographs were analyzed from 24 samples. The typical morphologic characteristics of those materials were studied by optic microscope (OM), by dark field technique, with magnifying lenses of 50, 100, 200, and 400 times, and the scanning electron microscope (SEM) by secondary electron. The main result was to characterize the linking form and extension of the adherence among the repair materials mentioned and the concrete evaluated by comparison of images.
{"title":"Performance Evaluation of Interface of Reinforced Concrete and Repair Mortars by Microscopy","authors":"T. J. Silva, F. Gondim, L. Motta","doi":"10.14359/20168","DOIUrl":"https://doi.org/10.14359/20168","url":null,"abstract":"Concrete structures submitted to the action of the environmental hazards can produce deterioration, mainly the corrosion of reinforcing steel. The structural repair can be an efficient solution for this problem. Then, the technological know-how of the materials and repair techniques used are very important. The adherence of the repair mortars on the old concrete is a decisive requirement of performance and durability of any repair. On the other hand, methods of analysis of images are being used more and more to evaluate and to understand, in a more precise way, the behavior of the materials. The objective of this work is the evaluation of commercial mortars of repairs by microscopy. In this study, four types of mortar were utilized: 1) high-resistance shrinkage-compensating mortar, 2) polymer-modified mortar, 3) high-resistance shrinkage-compensating with fiber- and polymer-modified mortar, and 4) epoxy coating with a similar mortar to the substratum concrete. The experiment was made in two concrete blocks of each type of material repair. In this research, 247 micrographs were analyzed from 24 samples. The typical morphologic characteristics of those materials were studied by optic microscope (OM), by dark field technique, with magnifying lenses of 50, 100, 200, and 400 times, and the scanning electron microscope (SEM) by secondary electron. The main result was to characterize the linking form and extension of the adherence among the repair materials mentioned and the concrete evaluated by comparison of images.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"07 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":"129882754","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}
F. Bertolucci, M. Barbosa, G. Maciel, F. Santos, F. Salles
This paper describes how rheology has the objective to study the flux and deformation of materials that are submitted to some tension or outer mechanical solicitation. In practice, the effective scientific field broached by rheology is restricted only to the study of homogeneous fluids behavior, in which eminent liquids are included, particles suspensions, and emulsions. The viscosity (h) and the yield stress (t0) are the two basic values that define the fluids’ behavior. The first one is the proportionality constant that relates the shear rate (g) with the shear stress (t) applied, while the second indicates the minimal tension for the flowage beginning. The fluids that obey the Newton’s relation – Newtonians fluids – display the constant viscosity and the null yield stress. It’s the case of diluted suspensions and grate amount of the pure liquids (water, acetone, alcohol, etc.) in which the viscosity is an intrinsic characteristic that depends on temperature and, in a less significant way, pressure. The suspension, titled “Cement Paste,” is defined as being a mixture of water and cement with, or without, a superplasticizer additive. The cement paste has a non-Newtonian fluid behavior (pseudoplastic), showing a viscosity that varies in accord to the applied shear stress and significant deformations are obtained from a delimited yield stress. In some cases, systems can also manifest the influence of chemical additives used to modify the interactions fluid/particles, besides the introduced modifications by the presence of incorporated air. To the cement paste the rheometric rehearsals were made using the rheometer R/S Brookfield that control shear stress and shear rate in accord to the rheological model of Herschel-Bulkley that seems to better adapt to this kind of suspension’s behavior. This paper shows the results of rheometrical rehearsals on the cement paste that were produced with cements HOLCIM MC-20 RS and CP-V-ARI RS with the addition of superplasticizer additives based of napthaline and polycarboxilate, with and without a constant agitation of the mixture. The obtainment of dosages of superplasticizer additives, as well as the water/cement ratio, at the cement at the fluidity rate determination, was done in a total of 12 different mixtures. It’s observed that the rheological parameters seem to vary according to the cement type, the superplasticizer type, and the methodology applied at the fluidity rate determination.
{"title":"The Influence of the Mixing Time in the Rheological Behavior of Cement Pastes","authors":"F. Bertolucci, M. Barbosa, G. Maciel, F. Santos, F. Salles","doi":"10.14359/20179","DOIUrl":"https://doi.org/10.14359/20179","url":null,"abstract":"This paper describes how rheology has the objective to study the flux and deformation of materials that are submitted to some tension or outer mechanical solicitation. In practice, the effective scientific field broached by rheology is restricted only to the study of homogeneous fluids behavior, in which eminent liquids are included, particles suspensions, and emulsions. The viscosity (h) and the yield stress (t0) are the two basic values that define the fluids’ behavior. The first one is the proportionality constant that relates the shear rate (g) with the shear stress (t) applied, while the second indicates the minimal tension for the flowage beginning. The fluids that obey the Newton’s relation – Newtonians fluids – display the constant viscosity and the null yield stress. It’s the case of diluted suspensions and grate amount of the pure liquids (water, acetone, alcohol, etc.) in which the viscosity is an intrinsic characteristic that depends on temperature and, in a less significant way, pressure. The suspension, titled “Cement Paste,” is defined as being a mixture of water and cement with, or without, a superplasticizer additive. The cement paste has a non-Newtonian fluid behavior (pseudoplastic), showing a viscosity that varies in accord to the applied shear stress and significant deformations are obtained from a delimited yield stress. In some cases, systems can also manifest the influence of chemical additives used to modify the interactions fluid/particles, besides the introduced modifications by the presence of incorporated air. To the cement paste the rheometric rehearsals were made using the rheometer R/S Brookfield that control shear stress and shear rate in accord to the rheological model of Herschel-Bulkley that seems to better adapt to this kind of suspension’s behavior. This paper shows the results of rheometrical rehearsals on the cement paste that were produced with cements HOLCIM MC-20 RS and CP-V-ARI RS with the addition of superplasticizer additives based of napthaline and polycarboxilate, with and without a constant agitation of the mixture. The obtainment of dosages of superplasticizer additives, as well as the water/cement ratio, at the cement at the fluidity rate determination, was done in a total of 12 different mixtures. It’s observed that the rheological parameters seem to vary according to the cement type, the superplasticizer type, and the methodology applied at the fluidity rate determination.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"55 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":"129876216","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}
The shape and texture of coarse aggregate affect the properties of fresh and hardened concrete. However, there is limited information about the effects of aggregate characteristics on self-compactability, which can be relevant in countries like Argentina, where a large variety of aggregates is available even in the same region. This paper will analyze the effect of shape and texture of coarse aggregate on self-compacting concrete (SCC) properties. Three different types of coarse aggregate were selected: granitic crushed stone, quartzitic crushed stone, and a siliceous river gravel. The granitic crushed stone presents irregular shape, rough texture, and low absorption. The quartzitic crushed stone also has irregular shape and rough texture, but it has high water absorption. Finally, the natural siliceous river gravel is composed by strong particles with smooth surface and low porosity. SCC was prepared using each type of coarse aggregate with 19 mm maximum size and similar particle size distribution. Slump-flow, V-funnel, and J-Ring tests were carried out. Effects of the changing volume of batched and mixing energy were also studied. The homogeneity of the coarse aggregate distribution was evaluated along vertical cuts on 1 m in height tubes and along a U-tube with 1.80 m height, measuring the ultrasonic pulse velocity and the unit weight in different sections. In addition, the compressive strength and modulus of elasticity were determined. From the results, was concluded that, as expected, the shape and texture of coarse aggregate modify the flowability, but also the mixing energy can strongly affect the plastic viscosity of SCC.
{"title":"Effect of Coarse Aggregate Shape and Texture on Self-Compactability","authors":"J. M. Tobes, L. Anahí, G. Giaccio, R. Zerbino","doi":"10.14359/20164","DOIUrl":"https://doi.org/10.14359/20164","url":null,"abstract":"The shape and texture of coarse aggregate affect the properties of fresh and hardened concrete. However, there is limited information about the effects of aggregate characteristics on self-compactability, which can be relevant in countries like Argentina, where a large variety of aggregates is available even in the same region. This paper will analyze the effect of shape and texture of coarse aggregate on self-compacting concrete (SCC) properties. Three different types of coarse aggregate were selected: granitic crushed stone, quartzitic crushed stone, and a siliceous river gravel. The granitic crushed stone presents irregular shape, rough texture, and low absorption. The quartzitic crushed stone also has irregular shape and rough texture, but it has high water absorption. Finally, the natural siliceous river gravel is composed by strong particles with smooth surface and low porosity. SCC was prepared using each type of coarse aggregate with 19 mm maximum size and similar particle size distribution. Slump-flow, V-funnel, and J-Ring tests were carried out. Effects of the changing volume of batched and mixing energy were also studied. The homogeneity of the coarse aggregate distribution was evaluated along vertical cuts on 1 m in height tubes and along a U-tube with 1.80 m height, measuring the ultrasonic pulse velocity and the unit weight in different sections. In addition, the compressive strength and modulus of elasticity were determined. From the results, was concluded that, as expected, the shape and texture of coarse aggregate modify the flowability, but also the mixing energy can strongly affect the plastic viscosity of SCC.","PeriodicalId":410288,"journal":{"name":"SP-253: Fifth ACI/CANMET/IBRACON Int'l Conference on High-Performance Concrete Structures & Materials","volume":"57 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":"122149393","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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