Eui-Bae Lee

Hydration Heat and Autogenous Shrinkage of High-Strength Mass Concrete

Abstract In this study, to evaluate autogenous shrinkage of high-strength mass concrete with specimen size and hydration delay effects, the thermal deformation was calculated using thermal expansion coefficient (TEC) corrected by the maturity method, and was subtracted from measured total deformation. And the properties and relations of hydration heat and autogenous shrinkage at early ages were numerically analyzed. In test and analysis results, hydration temperature is affected by specimen conditions such as size and admixture, and change of hydration temperature could affect autogenous shrinkage; the higher hydration temperature and the greater autogenous shrinkage. There is a close relationship between hydration temperature and autogenous shrinkage at early ages, especially between HHV (hydration heating velocity) and ASV (autogenous shrinking velocity); the higher HHV, the higher ASV and the greater ultimate autogenous shrinkage. The points where hydration temperature and autogenous shrinkage start to increase rapidly are due to the consumption of gypsum in the cement hydration process, and are strongly related to the setting time.

A Fundamental Study on the Correlationship between Hydration Heat and Autogenous Shrinkage of High Strength Concrete at an Early Age

In this study, to analyze the correlation between hydration heat and autogenous shrinkage of high strength concrete at an early age, hydration heating velocity and autogenous shrinking velocity as quantitative coefficients which represent the main properties of hydration heat and autogenous shrinkage were proposed. Two coefficients were calculated by statistical analysis and were equal with the regression coefficient. The complemented semi-adiabatic temperature rise test as test method to evaluate the hydration heat and autogenous shrinkage of concrete were proposed. In results of proposed test and analysis method, it was possible that early age properties of hydration heat and autogenous shrinkage of concrete were expressed numerically, and autogenous shrinkage was represented by equation with coefficients of hydration heat.

Hydration Heat and Autogenous Shrinkage of High-Strength Mass Concrete Containing Phase Change Material

Abstract In this study, to reduce the HHV of the high-strength mass concrete at early ages, PCM that could absorb the occurred hydration heat was applied, and the changes of autogenous shrinkage and the relationship between the hydration temperature and autogenous shrinkage were investigated. The addition of the PCM leads to a decrease of the fluidity and an increase of the air content in concrete. The acceleration of the cement hydration process by the PCM leads to an early setting and a higher development of the compressive strength and elastic modulus of concrete at very early ages. The function of PCM could be worked below the original melting point due to the eutectic effect. While the hydration temperature and HHV of high-strength mass concrete can be decreased with the use of the PCM. A close relationship could be found between the hydration temperature and autogenous shrinkage; the higher the HHV, the higher the ASV and the greater the ultimate autogenous shrinkage.

Evaluation of properties of concrete using fluosilicate salts and metal (Ni, W) compounds

Abstract To improve watertightness and antibiosis of sewage structure concrete, the antimicrobial watertight admixture was made with fluosilicate salts and antimicrobial compounds. And fresh properties, watertightness, harmlessness and antibiosis of concrete were investigated experimentally. As a result, the fresh properties of concrete were similar to those of an ordinary concrete, without setting time delay. Compressive strength and carbonation resistance of concrete were better than those of an ordinary concrete. Finally it was confirmed that the antimicrobial watertight admixture of concrete had an antibiosis inhibiting SOB growth.

The Analysis of Early Age Properties of Hydration Heat and Autogenous Shrinkage according to Specimen Size and Retardation of Hydration

Dept. of Architectural Engineering, College of Engineering, Chungnam National University, Daejeon 305-764, KoreaABSTRACT It has been reported that the magnitude and the development rate of autogenous shrinkage of cement paste, mortarand concrete were affected by history and magnitude of inner temperature at an early age. But it was not enough to explain therelation between hydration heat and autogenous shrinkage at an early age, because there was no certain analysis on histories ofhydration heat and autogenous shrinkage in previous studies. In our prior study, to understand the relationship between hydrationheat and autogenous shrinkage of concrete at an early age, the analysis method for histories of hydration heat and autogenousshrinkage was suggested. Based on this method, early age properties of hydration heat and autogenous shrinkage of high strengthconcrete with different sizes and hydration retardation were investigated in this study. As a result of the study, properties of hydra-tion temperature and autogenous shrinkage were different according to specimen size and hydration retardation. However, therewas a close relationship between hydration temperature and autogenous shrinkage at an early age, especially between HHV andASV as linear slopes of the sections where hydration temperature and autogenous shrinkage increase rapidly; the higher HHV, thehigher ASV and the greater ultimate autogenous shrinkage. And it was found that, among the setting time, bend point and tem-perature increasing point, they were close relationship each other on cement hydration process. Keywords : early age, hydration heat, autogenous shrinkage, specimen size, retardation of hydration

A Study on the Performance Development of Sewage Concrete by Application of Antibiotics

Recently sewage facilities mainly consisted of concrete structures are being deteriorated seriously by biodeterioration originated from sulfur-oxidizing bacteria. In this study, to prevent biochemical corrosion of the sewer concrete, antibiotics which prevent growth of sulfur-oxidizing bacteria were developed and antimicrobial performance of it was investigated. After that, to consider applicability of antibiotics to concrete, physical properties of concrete covered with antibiotics were investigated. As a results of the study, it was proved that the antimicrobial performance of antibiotics was available. Also compressive strength and bond strength of concrete didn`t closely connected with antibiotics, and resistance to abrasion, water absorption, air permeability, carbonation, salt damage and chemical attack of concrete was improved remarkably by covering with it.

A Study on the Performace Evaluation of Antimicrobial Concrete Using Liquid Reinforcing Antibiotics

In this study, researches for the development of antibiotics and antimicrobial concrete were conducted to reduce biochemical corrosion of sewage concrete. First of all, desired performance, such as watertightness, antibiosis, homogeneity, workability and harmlessness, was proposed and performance of antibiotics and antimicrobial concrete were evaluated by them. As results of this study, dispersibility and antibiosis of liquid antibiotics superior to powdery antibiotics. Antibiosis of antimicrobial concrete was verified, and amount of elution of harmful and effective ingredients was little. In workability, setting time of antimicrobial concrete was delayed. Compressive strength and resistance to carbonation of antimicrobial concrete were more increased than ordinary concrete. Also, as little pore volume and closed structure of antimicrobial concrete were observed, watertightness of it was verified. Finally artificial accelerating test for biochemical corrosion was proposed, and its suitability was experimentally proved.

An Experimental Study on Development of Physical Properties and Durability of Concrete Spread with Inorganic Antibiotics

Sewage facilities are positively necessary for environment improvement such as rainwater removal, sewage disposal, preservation of the quality of water and health of the citizens in present-day. Meanwhile, a deterioration of the concrete sewer pipe is increasing rapidly due to the chemical and physical attack and especially biochemical attack that is to say biodeterioration. So, in advanced countries, prediction techniques and corrosion inhibition system for sewer concrete are developed and are being applied. Also, antibiotics were developed already but application of that is low because it is not economical and has no practical use. But, in domestic, countermeasures for the corrosion of sewage concrete are not sufficient and biochemical attack is not reflected in those essentially. In this study, to prevent biochemical corrosion of the sewer concrete, surface of the concrete was spread with liquefied inorganic antibiotics and then its engineering properties were experimentally investigated. As a result, compressive strength of the specimen spread with antibiotics were similar to those of non spread, Both bond strength and abrasion amount of the specimen spread with antibiotics were inferior to non spread. Properties of absorption and air permeability of the specimen spread with antibiotics were superior to non spread. Finally, carbonation depth, chloride ion penetration depth and weight change ration of the specimen spread with antibiotics were smaller than non spread.