• Structural Engineering and Mechanics
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• v.52 no.1
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• pp.97-113
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• 2014

In the present work appropriate concrete material models have been proposed to predict drying shrinkage and specific creep of High-performance concrete (HPC) using Artificial Neural Network (ANN). The ANN models are trained, tested and validated using 106 different experimental measured set of data collected from different literatures. The developed models consist of 12 input parameters which include quantities of ingredients namely ordinary Portland cement, fly ash, silica fume, ground granulated blast-furnace slag, water, and other aggregate to cement ratio, volume to surface area ratio, compressive strength at age of loading, relative humidity, age of drying commencement and age of concrete. The Feed-forward backpropagation networks with Levenberg-Marquardt training function are chosen for proposed ANN models and same implemented on MATLAB platform. The results shows that the proposed ANN models are more rational as well as computationally more efficient to predict time-dependent properties of drying shrinkage and specific creep of HPC with high level accuracy.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.711-714
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• 2005

This paper focused on development of geopolymer for wood wool ceramic board. Geopolymer can substitude ordinary portland cement and its accelerator of wood wool cement board as inorganic polymer. In this study, what we would obtain geopolymer's properties such as initial setting time(KS L 5108), flow(KS L 5102) and compressive strength of 3days aged(KS L 5105), was less than 1 hour, more than $110\%$, more than 40Mpa. Geopolymer have three essential materials called filler, hardener and geopolymer liquor. So, We applied filler by quartz, hardener by blast furnace slag powder, metakaoline and fly ash, geopolymer liquor by NaOH, KOH and sodium silicate solution. As result of this experiment, what we could obtain best fitted geopolymer's properties such as initial setting time, flow and compressive strength of 3days aged, was 45min, $116\%$ and 43.6Mpa. This result can be applicable to commercial wood wool ceramic board.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.465-466
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• 2010

In this paper, an integrated system is proposed which can evaluate both the early-age properties and durability performance of concrete structures. This integrated system starts with a hydration model which considers both Portland cement hydration and chemical reactions of supplementary cementing materials (SCM). Based on the degree of hydration of cement and mineral admixtures, the amount of reaction products, the early age heat evolution, chemically bound water, porosity, the early age short-term mechanical behaviors, shrinkage and early-age creep are evaluated as a function of curing age and curing conditions. Furthermore, the durability aspect, such as carbonation of blended concrete and chloride attack, are evaluated considering both the material properties and surrounding environments. The prediction results are verified through experimental results.

• International Journal of Concrete Structures and Materials
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• v.8 no.3
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• pp.259-268
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• 2014

This paper presents results of an experimental study which investigates the effect of industrial pozzolan made from calcined silt of dam at $750^{\circ}C$ for 5 h, on mechanical properties and durability of ordinary mortar, compared to the silica fume. Mortar specimens prepared with 5, 10 and 15 % of calcined silt to substitute cement were evaluated for their compressive and flexural strength, sulfate, acid and penetration of chloride ions resistance. The results were compared with ordinary mortar (without addition) and mortar containing 10 % of silica fume. The results obtained showed that the calcined silt of dam has a high potential to be used as a pozzolanic material, it improves the strength and the durability of mortar and compete the silica fume.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.5
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• pp.99-103
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• 1999

This study examines the stress-strain and acid-resistance of pine needle ash (PNA) concrete. Materials used for this experiment are PNA , normal portland cement, natural fine and coarse aggregate. Test results show that the highest static modulus of elasticity are achieved by 5 % PNA filled PNA concrete. Acid-resistance of PNA concrete is increased with increase of the content of PNA. It is 1.29 times of the normal cement concrete for 5 % PNA filled PNA concrete and 2.57 times fo r15% PNA filled PNA concrete, based on the elased days for 25% mass loss of original mass immersed in the 5% H2SO4 solution. Accordingly, PNA concrete will greatly improve the properties of concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.225-231
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• 1996

Prediction of the early-stage strength of concrete is useful for modernized concrete construction. An experiment was attempted on the high-strength of concrete produced by ordinary portland cement under the curing temperatures of 30, 20, $10^{\cire}C$ and the various mixing proportions such as water-binder ratio of 0.30, 0.35 and silica fume content of 10% by weight of cement. It is the aim of this study to investigare and compare the development of concrete strength with maturity and analyze the application of Maturity as a parameter to correlation estimate test results of concrete. They are statistically analyzed to infer the correlation coefficient between the Maturity and the compressive strength of high-strength concrete.

• Journal of Environmental Science International
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• v.19 no.1
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• pp.105-114
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• 2010

The objective of the paper is to experimentally investigate the compressive strength of the concrete incorporating fly ash. Ordinary Portland cement(OPC). Water to binder ratio(W/B) ranging from 30% to 60% and curing temperature ranging from $-10^{\circ}{\sim}65^{\circ}C$ were also adopted for experimental parameters. Fly ash was replaced by 30% of cement contents. According to the results, strength development of concrete contained with fly ash is lower than that of plain concrete in low temperature at early age and maturity. In high curing temperature, the concrete with fly ash has higher strength development than that of low temperature regardless of the elapse of age and maturity. Fly ash can have much effect on the strength development of concrete at the condition of mass concrete, hot weather concreting and the concrete products for the steam curing.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.73-74
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• 2020

Predicting the compressive strength of concrete is important for shortening construction time and reducing construction costs. In this study, the coefficients required for maturity method and compressive strength prediction equation were calculated by measuring the cement hydration reaction rate, concrete setting time and ultimate strength. The experiment was conducted in an isothermal environment of 10℃, 20℃ and 30℃ using a normal Portland cement, and the experiment was conducted with a total of 9 levels of W/C (40%, 50%, 60%) of 3 levels for each temperature. As a result of comparing the predicted strength and the measured strength for each blend, only an error of less than 5% was found for all blending and curing periods.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.4
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• pp.635-650
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• 2017

Acoustic emission (AE) sensors have broadly used to monitor the damage of underground structures and tunnels. The reliability of measured signal is determined by the coupling condition of the AE sensors which are embedded in the target underground structure. To secure the reliability of health monitoring results, it is important to understand the characteristics of the coupling materials. In this study, laboratory tests were performed using portland cement, micro cement, and gypsum as coupling materials in order to verify the bleeding characteristics. The effective parameters for bleeding were determined to be water-cement ratio, material type, curing time, and injected volume of coupling materials. As a results of the experimental study, the bleeding rate increases with an increase in a water-cement ratio and an injected volume; for portland cement, water-cement ratio and injected volume effects are larger than the micro cement. However, curing time is not much effective for occurrence of the bleeding phenomenon. It is anticipated that this study may be useful for the selection of suitable coupling materials for installation of acoustic emission sensors.

• Journal of the Korea Institute of Building Construction
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• v.16 no.4
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• pp.321-329
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• 2016

The use of ternary blended cement consisting of Portland cement, granulated blast-furnace slag (GGBFS) and fly ash has been on the rise to improve marine concrete structure's resistance to chloride attack. Therefore, this study attempted to investigate changes in chloride attack resistibility of concrete through NT Build 492-based chloride migration experiments and test of concrete's ability to resist chloride ion penetration under ASTM C 1202(KS F 2271) when 1.5-2.0% of alkali-sulfate activator (modified alkali sulfate type) was added to the ternary blended cement mixtures (40% ordinary Portland cement + 40% GGBFS + 20% fly ash). Then, the results found the followings: Even though the slump for the plain concrete slightly declined depending on the use of the alkali-sulfate activator, compressive strength from day 2 to day 7 improved by 17-42%. In addition, the coefficient from non-steady-state migration experiments for the plain concrete measured at day 28 decreased by 36-56% depending on the use of alkali-sulfate. Furthermore, total charge passed according to the test for electrical indication of concrete's ability to resist chloride ion penetration decreased by 33-62% at day 7 and by 31-48% at day 28. As confirmed in previous studies, reactivity in the GGBFS and fly ash improved because of alkali activation. As a result, concrete strength increased due to reduced total porosity.