The report generalizes the results of wide range investigations of silica fume based superplasticized high-performance concrete. The rules of the strength and rheological behavior of cement - silica fume - superplasticizer systems are discussed. Usage of optimal superplasticizer to silica fume ratio (as 1:10) allows to obtain ultra-dense packing for super fluid cement paste and provides high-performance properties of concrete. The mathematical models of fresh and hardened high-performance concrete based on processing and computerizing empirical results are created. The models provide a calculation of water/cement ratio required for the target compressive strength level up to 130 MPa as well as mixing water quantity for planning slump of 0-200 mm. For modelling purpose, concrete slump is considered as a function of aggregates proportioning, and volume and fluidity of cement paste. This approach became a basis of proposed high-performance concrete mixture proportioning method. Further, developing and integration of the mathematical models created a new computer program for high-performance concrete mixture proportioning. The program provides a solution for wide range design and optimization projects. The results of the computer program estimation can be easily transferred to any 3-dimensional plotting or data base program for consequent processing and performing.
{"title":"High-Performance Concrete Mixture Proportioning","authors":"K. Sobolev, S. Soboleva","doi":"10.14359/6053","DOIUrl":"https://doi.org/10.14359/6053","url":null,"abstract":"The report generalizes the results of wide range investigations of silica fume based superplasticized high-performance concrete. The rules of the strength and rheological behavior of cement - silica fume - superplasticizer systems are discussed. Usage of optimal superplasticizer to silica fume ratio (as 1:10) allows to obtain ultra-dense packing for super fluid cement paste and provides high-performance properties of concrete. The mathematical models of fresh and hardened high-performance concrete based on processing and computerizing empirical results are created. The models provide a calculation of water/cement ratio required for the target compressive strength level up to 130 MPa as well as mixing water quantity for planning slump of 0-200 mm. For modelling purpose, concrete slump is considered as a function of aggregates proportioning, and volume and fluidity of cement paste. This approach became a basis of proposed high-performance concrete mixture proportioning method. Further, developing and integration of the mathematical models created a new computer program for high-performance concrete mixture proportioning. The program provides a solution for wide range design and optimization projects. The results of the computer program estimation can be easily transferred to any 3-dimensional plotting or data base program for consequent processing and performing.","PeriodicalId":255305,"journal":{"name":"SP-179: Fourth CANMET/ACI/JCI Conference: Advances in Concrete Technology","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132764714","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}
K. Fujji, S. Adachi, M. Takeuchi, M. Kakizaki, H. Edahiro, T. Inoue, Y. Yamamoto
High-strength and high-fluidity lightweight concretes have been developed using silica fume blended cement and belite-rich cement with a designed compressive strength from 40 to 60 MPa. Test conditions and parameters were water-cement ratio of 0.22, 0.33 and 0.40, curing temperature of 5, 20 and 35 deg C, curing method of standard and sealed curing and 3 types of high-range AE water-reducing agent. Influences of above factors upon flow, flow time, compressive strength, permeability, pore size distribution and total pore volume were studied. The major findings of this study are as follows: (1) Compressive strength of silica fume blended cement concrete was higher than that of belite-rich cement concrete and the effect of water-cement ratio was small. Compressive strength at 7 days was 80 to 90% of the 28-day strength at any curing temperature. (2) Compressive strength of belite-rich cement concrete significantly increased at water-cement ratio of 0.3 to 0.4, and its evolution from 28 to 91 days became larger at lower curing temperatures. (3) Total pore volume of silica fume blended cement concrete at the age of 28 days was smaller than that of belite-rich cement concrete at all curing temperatures of 5, 20 and 35 deg C, and compressive strength became larger with a decrease of total pore volume.
{"title":"Properties of High-Strength and High-Fluidity Lightweight Concrete","authors":"K. Fujji, S. Adachi, M. Takeuchi, M. Kakizaki, H. Edahiro, T. Inoue, Y. Yamamoto","doi":"10.14359/6032","DOIUrl":"https://doi.org/10.14359/6032","url":null,"abstract":"High-strength and high-fluidity lightweight concretes have been developed using silica fume blended cement and belite-rich cement with a designed compressive strength from 40 to 60 MPa. Test conditions and parameters were water-cement ratio of 0.22, 0.33 and 0.40, curing temperature of 5, 20 and 35 deg C, curing method of standard and sealed curing and 3 types of high-range AE water-reducing agent. Influences of above factors upon flow, flow time, compressive strength, permeability, pore size distribution and total pore volume were studied. The major findings of this study are as follows: (1) Compressive strength of silica fume blended cement concrete was higher than that of belite-rich cement concrete and the effect of water-cement ratio was small. Compressive strength at 7 days was 80 to 90% of the 28-day strength at any curing temperature. (2) Compressive strength of belite-rich cement concrete significantly increased at water-cement ratio of 0.3 to 0.4, and its evolution from 28 to 91 days became larger at lower curing temperatures. (3) Total pore volume of silica fume blended cement concrete at the age of 28 days was smaller than that of belite-rich cement concrete at all curing temperatures of 5, 20 and 35 deg C, and compressive strength became larger with a decrease of total pore volume.","PeriodicalId":255305,"journal":{"name":"SP-179: Fourth CANMET/ACI/JCI Conference: Advances in Concrete Technology","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114176133","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}
Admixtures based on sulfonate melamine formaldehyde condensate polymer (SM) have been available commercially for more than three decades. These products are widely used by the precast concrete industry, but with some limitations on slump retention and early strength. To improve these properties, synthesis of a modified sulfonate melamine formaldehyde condensate polymer (MSM) was performed. In this paper its physical and chemical characteristics are reported. Dispersibility and adsorption tests, using cement pastes, were carried out to compare the superplasticizing effect of the new MSM polymer against the SM polymer. Concrete mixtures were also made to evaluate the performances of this MSM polymer in comparison with the other types of superplasticizers such as SM and beta-naphthalene sulfonate formaldehyde condensate (SN). Results of these tests show that MSM polymer has a better water reduction capacity, lower air content in the fresh concrete and higher early strength at 1 day as compared to the other superplasticizers under the test conditions. These characteristics are very much desired by the precast industry for easy placement of concrete and quick turn around of the formworks. Field tests also reported, confirm the laboratory findings.
{"title":"New Super-plasticizers Based on Modified Melamine Polymer","authors":"I. Torresan, R. Khurana","doi":"10.14359/6042","DOIUrl":"https://doi.org/10.14359/6042","url":null,"abstract":"Admixtures based on sulfonate melamine formaldehyde condensate polymer (SM) have been available commercially for more than three decades. These products are widely used by the precast concrete industry, but with some limitations on slump retention and early strength. To improve these properties, synthesis of a modified sulfonate melamine formaldehyde condensate polymer (MSM) was performed. In this paper its physical and chemical characteristics are reported. Dispersibility and adsorption tests, using cement pastes, were carried out to compare the superplasticizing effect of the new MSM polymer against the SM polymer. Concrete mixtures were also made to evaluate the performances of this MSM polymer in comparison with the other types of superplasticizers such as SM and beta-naphthalene sulfonate formaldehyde condensate (SN). Results of these tests show that MSM polymer has a better water reduction capacity, lower air content in the fresh concrete and higher early strength at 1 day as compared to the other superplasticizers under the test conditions. These characteristics are very much desired by the precast industry for easy placement of concrete and quick turn around of the formworks. Field tests also reported, confirm the laboratory findings.","PeriodicalId":255305,"journal":{"name":"SP-179: Fourth CANMET/ACI/JCI Conference: Advances in Concrete Technology","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116963119","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}
H. Fujiwara, R. Tomita, T. Okamoto, A. Dozono, A. Obatake
A new method of producing high-strength porous concrete has recently been developed in Japan. In this method, porous concrete is produced by coating the coarse aggregates with a high-strength mortar, then applying vibration to fuse them. Porous concrete produced by this method has the following properties. It has a continuous void system with a volume-to-total-void ratio exceeding 85% and a compressive strength of 20 MPa or greater when water permeability is 2 cm/sec. The porous concrete produced exhibited good durability in freezing and thawing tests (ASTM C666, Procedure B) and, while the amount of drying shrinkage is about 60%, or smaller than that of conventional concrete, such shrinkage occurred very rapidly.
{"title":"Properties of High-Strength Porous Concrete","authors":"H. Fujiwara, R. Tomita, T. Okamoto, A. Dozono, A. Obatake","doi":"10.14359/6038","DOIUrl":"https://doi.org/10.14359/6038","url":null,"abstract":"A new method of producing high-strength porous concrete has recently been developed in Japan. In this method, porous concrete is produced by coating the coarse aggregates with a high-strength mortar, then applying vibration to fuse them. Porous concrete produced by this method has the following properties. It has a continuous void system with a volume-to-total-void ratio exceeding 85% and a compressive strength of 20 MPa or greater when water permeability is 2 cm/sec. The porous concrete produced exhibited good durability in freezing and thawing tests (ASTM C666, Procedure B) and, while the amount of drying shrinkage is about 60%, or smaller than that of conventional concrete, such shrinkage occurred very rapidly.","PeriodicalId":255305,"journal":{"name":"SP-179: Fourth CANMET/ACI/JCI Conference: Advances in Concrete Technology","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114986760","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 "method of equivalent age" is one of the currently used nondestructive testing methods of concrete strength estimation. It is based on Arrhenius' law, which has shown itself to be the most accurate in describing the influence of temperature on concrete strength development at early ages. A proper estimation is directly related to a correct determination of the Apparent Activation Energy: Ea. This is the unique parameter which characterizes the concrete mixture and which can be found in Arrhenius' law. The major aim of this paper is to show how calorimetric tests under semi-adiabatic conditions can be an alternative to unwieldy compressive test procedures in determining Ea. The validity of the obtained Ea values has been verified by means of several mechanical tests. Moreover, the possibility of using either mortar or concrete is partially dealt with. The water to cement ratio appears to naturally be considered as a constant in proportioning an equivalent mortar. Finally, the evolution of the Apparent Activation Energy in relation to the degree of hydration is given. Hence, the widespread opinion that Ea depends on the degree of hydration is confirmed and a field of definition can be brought to the fore.
{"title":"Determination of the Apparent Activation Energy of Concrete: Ea. Semi-Adiabatic Tests of Heat Development","authors":"L. D'aloia, G. Chanvillard","doi":"10.14359/6061","DOIUrl":"https://doi.org/10.14359/6061","url":null,"abstract":"The \"method of equivalent age\" is one of the currently used nondestructive testing methods of concrete strength estimation. It is based on Arrhenius' law, which has shown itself to be the most accurate in describing the influence of temperature on concrete strength development at early ages. A proper estimation is directly related to a correct determination of the Apparent Activation Energy: Ea. This is the unique parameter which characterizes the concrete mixture and which can be found in Arrhenius' law. The major aim of this paper is to show how calorimetric tests under semi-adiabatic conditions can be an alternative to unwieldy compressive test procedures in determining Ea. The validity of the obtained Ea values has been verified by means of several mechanical tests. Moreover, the possibility of using either mortar or concrete is partially dealt with. The water to cement ratio appears to naturally be considered as a constant in proportioning an equivalent mortar. Finally, the evolution of the Apparent Activation Energy in relation to the degree of hydration is given. Hence, the widespread opinion that Ea depends on the degree of hydration is confirmed and a field of definition can be brought to the fore.","PeriodicalId":255305,"journal":{"name":"SP-179: Fourth CANMET/ACI/JCI Conference: Advances in Concrete Technology","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121625940","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}
M. Shoya, S. Sugita, Y. Tsukinaga, M. Aba, M. Ohba
In recent years, especially in Japan, various types of chemical admixtures have been developed, with emphasis on making highly durable concrete and on developing the highly flowable concrete for labor-saving. In this paper, one kind of water-repellent admixture incorporating highly reactive silica powder, denoted as WRP, was examined to confirm its effect on various concrete properties. The concept is not only to prevent water penetration due to water repellency provided by the siloxane compound but also to compensate for the hindered hydration due to its adsorption to cement particles by the use of the highly reactive pozzolanic material. The efficacy of the admixture was confirmed as to its ability reducing the water permeability with little lowering of mechanical properties dependent on the dosage of WRP. From the tests for carbonation, drying shrinkage, resistance to freezing and thawing and the air-void systems, the effect of WRP was confirmed as satisfactory for those properties.
{"title":"Use of a Water-Repellent Admixture to Improve Concrete Performance","authors":"M. Shoya, S. Sugita, Y. Tsukinaga, M. Aba, M. Ohba","doi":"10.14359/6041","DOIUrl":"https://doi.org/10.14359/6041","url":null,"abstract":"In recent years, especially in Japan, various types of chemical admixtures have been developed, with emphasis on making highly durable concrete and on developing the highly flowable concrete for labor-saving. In this paper, one kind of water-repellent admixture incorporating highly reactive silica powder, denoted as WRP, was examined to confirm its effect on various concrete properties. The concept is not only to prevent water penetration due to water repellency provided by the siloxane compound but also to compensate for the hindered hydration due to its adsorption to cement particles by the use of the highly reactive pozzolanic material. The efficacy of the admixture was confirmed as to its ability reducing the water permeability with little lowering of mechanical properties dependent on the dosage of WRP. From the tests for carbonation, drying shrinkage, resistance to freezing and thawing and the air-void systems, the effect of WRP was confirmed as satisfactory for those properties.","PeriodicalId":255305,"journal":{"name":"SP-179: Fourth CANMET/ACI/JCI Conference: Advances in Concrete Technology","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124364897","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 purpose of this paper is to develop pre-casting permanent forms which are effective in improving the durability and appearance of concrete structures, conserving wood and modernizing cast-in-place concrete work. The influences of various materials used and accelerated curing methods on the properties of polymer cement mortar (PCM) applied to the forms were investigated. In these experiments, polymer dispersions composed of styrene-acryl (SA), polyacrylic ester (PAE), ethylene-vinyl acetate (EVA) and styrene-butadiene rubber (SBR) were used. Mixtures contained aggregate - crushed silica and ferro-nickel slag sand; cement - normal portland, high-early strength portland and white portland cement; and color pigment - red, green, yellow and black. Steam curing and oven-dry curing were carried out. The fluidity, compressive strength, flexural strength, resistance to abrasion, chloride ion penetration, carbonation and sulfate resistance, and surface color of PCM were examined. From these investigations, the following conclusions were obtained: The use of SA type polymer, ferro-nickel slag sand, high-early strength portland cement and color pigments were effective in getting PCM with high fluidity, mechanical strength, durability and tinting strength. Additionally, steam curing and oven-dry curing are practical for the early-age strength development of PCM.
{"title":"Studies of Polymer Cement Mortar for use as Permanent Forms","authors":"K. Horii, T. Tsutsuzaki, K. Kohno","doi":"10.14359/6071","DOIUrl":"https://doi.org/10.14359/6071","url":null,"abstract":"The purpose of this paper is to develop pre-casting permanent forms which are effective in improving the durability and appearance of concrete structures, conserving wood and modernizing cast-in-place concrete work. The influences of various materials used and accelerated curing methods on the properties of polymer cement mortar (PCM) applied to the forms were investigated. In these experiments, polymer dispersions composed of styrene-acryl (SA), polyacrylic ester (PAE), ethylene-vinyl acetate (EVA) and styrene-butadiene rubber (SBR) were used. Mixtures contained aggregate - crushed silica and ferro-nickel slag sand; cement - normal portland, high-early strength portland and white portland cement; and color pigment - red, green, yellow and black. Steam curing and oven-dry curing were carried out. The fluidity, compressive strength, flexural strength, resistance to abrasion, chloride ion penetration, carbonation and sulfate resistance, and surface color of PCM were examined. From these investigations, the following conclusions were obtained: The use of SA type polymer, ferro-nickel slag sand, high-early strength portland cement and color pigments were effective in getting PCM with high fluidity, mechanical strength, durability and tinting strength. Additionally, steam curing and oven-dry curing are practical for the early-age strength development of PCM.","PeriodicalId":255305,"journal":{"name":"SP-179: Fourth CANMET/ACI/JCI Conference: Advances in Concrete Technology","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128027972","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}
Recently, accompanying the increase in higher strength and flowability of concrete, polycarboxylate-based superplasticizers have attracted much attention. In order to develop an advanced superplasticizer accommodating new functions, we attempted to develop polycarboxylate-based high-range water reducing superplasticizers with high durability as a new function. To increase the durability of concrete, we focused on shrinkage reduction, one of the factors affecting durability, and studied various compounds exhibiting shrinkage reduction. We investigated the relationship between their chemical structures and shrinkage reducing effects. In addition, we synthesized a new series of superplasticizers in which these compounds were attached to the structure of various polycarboxylate polymers, and determined the shrinkage reduction effect by testing concrete with these agents. As a result, we have developed a polycarboxylate-based advanced superplasticizer exhibiting excellent shrinkage reduction.
{"title":"Shrinkage Reduction Type of Advanced Superplasticizer","authors":"T. Sugiyama, A. Ohta, Y. Tanaka","doi":"10.14359/6039","DOIUrl":"https://doi.org/10.14359/6039","url":null,"abstract":"Recently, accompanying the increase in higher strength and flowability of concrete, polycarboxylate-based superplasticizers have attracted much attention. In order to develop an advanced superplasticizer accommodating new functions, we attempted to develop polycarboxylate-based high-range water reducing superplasticizers with high durability as a new function. To increase the durability of concrete, we focused on shrinkage reduction, one of the factors affecting durability, and studied various compounds exhibiting shrinkage reduction. We investigated the relationship between their chemical structures and shrinkage reducing effects. In addition, we synthesized a new series of superplasticizers in which these compounds were attached to the structure of various polycarboxylate polymers, and determined the shrinkage reduction effect by testing concrete with these agents. As a result, we have developed a polycarboxylate-based advanced superplasticizer exhibiting excellent shrinkage reduction.","PeriodicalId":255305,"journal":{"name":"SP-179: Fourth CANMET/ACI/JCI Conference: Advances in Concrete Technology","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129751776","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}
T. Fukushima, Y. Yoshizaki, F. Tomosawa, K. Takahashi
The relationship between the neutralization depth determined by a phenolphthalein 1% ethanol solution and the concentration distribution of CaCO3-Ca(OH)2 in carbonated concrete is discussed, based upon accelerated carbonation and outdoor exposure tests, and field survey research by making use of powder X-ray diffraction and thermal analytical methods. It was found that the neutralization depth exists in the partly carbonated zone of concrete where both CaCO3 and Ca(OH)2 are observed, and that carbonation front depth from which CaCO3 is not detected, exists much deeper in concrete. Further, it was confirmed that the neutralization depth is about half of the carbonation front depth. This fact is interpreted by theoretical research of unsteady state dynamic analysis for the diffusion of CO2 from the surface inwards into concrete accompanied by carbonation reaction with Ca(OH)2. Computer simulation was done for the converted CO2 concentration in carbonated concrete by using the effective diffusion coefficient estimated as a function of water cement ratio. If the converted CO2 concentration in the neutralization depth is assumed to be 10% of the surface concentration, the neutralization depth is almost the same as the depth calculated using Hamada's law which is considered to be adequately applicable for the progress of neutralization of concrete with a water cement ratio of 60% exposed outdoors in the rain. It is concluded that the relationship between the neutralization depth (X sub n) and the carbonation front depth (X sub f) is expressed by the following equation: X sub n = (1/2) X sub f.
{"title":"Relationship Between Neutralization Depth and Concentration Distribution of CaCO3 -Ca(OH)2 in Carbonated Concrete","authors":"T. Fukushima, Y. Yoshizaki, F. Tomosawa, K. Takahashi","doi":"10.14359/6049","DOIUrl":"https://doi.org/10.14359/6049","url":null,"abstract":"The relationship between the neutralization depth determined by a phenolphthalein 1% ethanol solution and the concentration distribution of CaCO3-Ca(OH)2 in carbonated concrete is discussed, based upon accelerated carbonation and outdoor exposure tests, and field survey research by making use of powder X-ray diffraction and thermal analytical methods. It was found that the neutralization depth exists in the partly carbonated zone of concrete where both CaCO3 and Ca(OH)2 are observed, and that carbonation front depth from which CaCO3 is not detected, exists much deeper in concrete. Further, it was confirmed that the neutralization depth is about half of the carbonation front depth. This fact is interpreted by theoretical research of unsteady state dynamic analysis for the diffusion of CO2 from the surface inwards into concrete accompanied by carbonation reaction with Ca(OH)2. Computer simulation was done for the converted CO2 concentration in carbonated concrete by using the effective diffusion coefficient estimated as a function of water cement ratio. If the converted CO2 concentration in the neutralization depth is assumed to be 10% of the surface concentration, the neutralization depth is almost the same as the depth calculated using Hamada's law which is considered to be adequately applicable for the progress of neutralization of concrete with a water cement ratio of 60% exposed outdoors in the rain. It is concluded that the relationship between the neutralization depth (X sub n) and the carbonation front depth (X sub f) is expressed by the following equation: X sub n = (1/2) X sub f.","PeriodicalId":255305,"journal":{"name":"SP-179: Fourth CANMET/ACI/JCI Conference: Advances in Concrete Technology","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130360773","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}
In this paper, a method to evaluation the crack size of concrete structures by infrared thermography was investigated. This method is based on the relation between the crack depth or width and thermal distribution in concrete. First, the influence of crack depth and width on thermal distribution was examined. Next, the influence of the distance between cracks and heater on thermal distribution was investigated. The effectiveness of this method was confirmed by the results of the experiment on flexural cracks in reinforced concrete beams. From these results, it was demonstrated that the thermal distribution measured at the surface of concrete by infrared thermography was effective in evaluating the crack size in concrete structures.
{"title":"Application of Infrared Thermography Technique for Evaluation of Cracks in the Concrete Structures","authors":"S. Nagataki, T. Kamada, A. Matsumoto","doi":"10.14359/6059","DOIUrl":"https://doi.org/10.14359/6059","url":null,"abstract":"In this paper, a method to evaluation the crack size of concrete structures by infrared thermography was investigated. This method is based on the relation between the crack depth or width and thermal distribution in concrete. First, the influence of crack depth and width on thermal distribution was examined. Next, the influence of the distance between cracks and heater on thermal distribution was investigated. The effectiveness of this method was confirmed by the results of the experiment on flexural cracks in reinforced concrete beams. From these results, it was demonstrated that the thermal distribution measured at the surface of concrete by infrared thermography was effective in evaluating the crack size in concrete structures.","PeriodicalId":255305,"journal":{"name":"SP-179: Fourth CANMET/ACI/JCI Conference: Advances in Concrete Technology","volume":"2 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130482113","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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