• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.177-188
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• 2006

Conventional nonlinear finite element analysis requires complicated modeling and analytical technique. Furthermore, it is difficult to interpret the analytical results presented as the stress-strain relationship. In the present study, a design-oriented analytical method using the truss model was developed. A reinforced concrete member to be analyzed was idealized by longitudinal, transverse, and diagonal line elements. Basically, each element was modeled as a composite element of concrete and re-bars. Simplified cyclic models for the concrete and re-bar elements were developed. RC beams and walls with various reinforcement details were analyzed by the proposed method. The inelastic strength, energy dissipation capacity, deformability, and failure mode predicted by the proposed method were compared with those of existing experiments. The results showed that the proposed model accurately predicted the strength and energy dissipation capacities, and to predict deformability of the members, the compression-softening model used for the concrete strut element must be improved.

• Journal of the Korean Professional Engineers Association
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• v.19 no.3
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• pp.23-30
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• 1986

This study summarizes the results of tests on 18 two-slab push out specimens. The main purpose of tile survey was to evaluate the capacity and behavior of stud shear connectors embedded in high strength normal concrete (F$\sub$c/=260～390kg/$\textrm{cm}^2$). The normal concrete was made with crushed stones and natural sand near the Han River. Two different diameters (ø19mm, ø16 mm) of stud shear connectors were used for push out specimens. The following conclusions were drawn from this study. 1) The shear strength of stud connectors embedded in high strength concrete (F$\sub$c/=260～390kg/$\textrm{cm}^2$) was influenced by tensile stress of the stud shear connectors. The following empirical function described the test results: q$\sub$u/=0.5A$\sub$s/√F$\sub$c/E$\sub$c/$\leq$0.7A$\sub$u/F$\sub$u/ 2) The maximum load in this study was reached at slips varying from 2.5～6mm.

• International Journal of Highway Engineering
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• v.6 no.4 s.22
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• pp.25-33
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• 2004

The waste concrete produced by the process of the highway construction and management, has been crushed in-situ, and the waste aggregate has been experimentally used for anti-freezing layer and lean concrete. After testing the bearing capacity on anti-freezing layer, it was found that when the waste aggregates mixed with natural sand would be within the required gradations, the layer meets the requirements of limitation and the percentage to passing 2$\sim$20mm sieve increased by 5$\sim$13% because the flimsy mortars on aggregate were re-crushed by vibrated-roller compactor. The compressive strength of lean concrete using recycled aggregate was 71$\sim$85% of the natural coarce aggregate made, but nevertheless the recycled aggregates are applicable to the lean concrete because they largely exceeded the required strength, $57.5kgf/cm^2$.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.159-160
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• 2018

In this study, the characteristics of the Mock-up test were reviewed to analyze the applicability of the coal gasification slag (CGS) from the integrated gasification combination Cycle (IGCC) to the concrete fine aggregate. The analysis shows that CGS and crushed sand mix is the best combination of CGS combined with about 50 % of CGS based on the effects of promoting liquidity and strength. This is expected to be a positive factor in securing the strength and flexibility of concrete given the optimal mix of CGS, and may also contribute to the improvement of quality.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.21-22
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• 2018

In this study, the characteristics of the Mock-up test were reviewed to analyze the applicability of the coal gasification slag (CGS) from the integrated gasification combination Cycle (IGCC) to the concrete fine aggregate. The analysis shows that CGS and crushed sand mix is the best combination of CGS combined with about 50 % of CGS based on the effects of promoting liquidity and strength. This is expected to be a positive factor in securing the strength and flexibility of concrete given the optimal mix of CGS, and may also contribute to the improvement of quality.

• Journal of the Korea Concrete Institute
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• v.26 no.5
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• pp.607-614
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• 2014

The purpose of this dissertation was to investigate the effect of mineral admixtures, such as fly ash, blast furnace slag powder, meta kaolin and silica fume, on the basic properties and durability of crushed sand shotcrete, selecting a series of shotcrete mixtures with a variable admixture. Compressive strength increased as the content of mineral admixtures increased, specially it was the most effective when using meta kaolin both at sample specimen and core after shotcreting. Rapid chloride ion permeability test and sulfuric acid resistance test showed that both durability increased as the substitute rate of mineral admixture increased. In air void analysis with image analysis, the targeted the spacing factor and specific surface were not satisfied because air-entrained agent was not used.

• Advances in nano research
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• v.16 no.4
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• pp.375-394
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• 2024

The extensive utilization of concrete has given rise to environmental concerns, specifically concerning the depletion of river sand. To address this issue, waste deposits can provide manufactured-sand (MS) as a substitute for river sand. The objective of this study is to explore the application of machine learning techniques to facilitate the production of manufactured-sand concrete (MSC) containing stone nano-powder through estimating the splitting tensile strength (STS) containing compressive strength of cement (CSC), tensile strength of cement (TSC), curing age (CA), maximum size of the crushed stone (Dmax), stone nano-powder content (SNC), fineness modulus of sand (FMS), water to cement ratio (W/C), sand ratio (SR), and slump (S). To achieve this goal, a total of 310 data points, encompassing nine influential factors affecting the mechanical properties of MSC, are collected through laboratory tests. Subsequently, the gathered dataset is divided into two subsets, one for training and the other for testing; comprising 90% (280 samples) and 10% (30 samples) of the total data, respectively. By employing the generated dataset, novel models were developed for evaluating the STS of MSC in relation to the nine input features. The analysis results revealed significant correlations between the CSC and the curing age CA with STS. Moreover, when delving into sensitivity analysis using an empirical model, it becomes apparent that parameters such as the FMS and the W/C exert minimal influence on the STS. We employed various loss functions to gauge the effectiveness and precision of our methodologies. Impressively, the outcomes of our devised models exhibited commendable accuracy and reliability, with all models displaying an R-squared value surpassing 0.75 and loss function values approaching insignificance. To further refine the estimation of STS for engineering endeavors, we also developed a user-friendly graphical interface for our machine learning models. These proposed models present a practical alternative to laborious, expensive, and complex laboratory techniques, thereby simplifying the production of mortar specimens.

• Structural Engineering and Mechanics
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• v.47 no.4
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• pp.545-557
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• 2013

Disposal of construction wastes poses major challenge to the municipal administration in the developing countries. At the same time new developments in these countries are unscrupulously exploiting the natural resources. The sustainable development requires judicious and careful utilization of natural resources. In this context, reuse of construction and demolition waste can save the global natural resources to greater extent. In this work the bricks and concrete waste from construction sites were crushed to the desired sizes and mixed in various proportions to study its properties in the concrete both in fresh and hardened states. Six mixes of natural and recycled aggregates were used to make the coarse aggregates for the concrete. From each mix nine cylinders were cast, which were tested at 7,14 and 28 days. The properties of concrete with recycled aggregates were compared with the control mix having natural aggregates. The nominal ratio of cement sand and coarse aggregates were kept at 1:2:4 by weight for all mixes. The tests have shown that concrete with recycled aggregates made from old concrete and brick bats provide greater opportunities for reuse of construction wastes in concrete.

• Journal of the Korea Institute of Building Construction
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• v.17 no.1
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• pp.55-61
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• 2017

This paper is to investigate experimentally the effect of substitution of recycled coarse aggregate(RCA) under 13mm on the engineering properties of the concrete using gap graded coarse aggregates. Concretes with 0.4 of water to cement ratio(W/C) were fabricated to achieve 30MPa of design strength with coarse aggregate over 13mm in size with the maximum size of 25mm. RCA was substituted for coarse aggregate over 13mm from 10% to 50% and crushed coarse aggregate under 13mm was also substituted for coarse aggregate over 13mm from 20% to 40%, respectively. Test results indicated that the replacement of RCA up to 20% resulted in an increase of fluidity and strength. It also caused a decrease in the drying shrinkage due to dense packing effect by achieving continuous grading of mixed aggregates. For practical application of RCA, when properly substituted, the use of RCA enabled the concrete to reduce water contents and sand to aggregate ratio in mixing design stage of the concrete. And, it can also enhance the compressive strength of the concrete.

• Journal of the Korea Institute of Building Construction
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• v.19 no.5
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• pp.391-399
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• 2019

This study reviewed the possibility of recycling into exhausted aggregate resources in Korea as a means of utilizing coal gasification slag(CGS) from integrated gasification combined cycle(IGCC) while being commissioned in order to introduce the new system to Korea. In other words, in order to solve the problem of insufficient aggregate resources, CGS generated by IGCC as a residual aggregate for concrete secondary products, which is an empty mortar, was considered to replace CGS in the range of 0 to 100 % for mixed residual aggregate mixed with crushed sand A(CSa) of good quality and sea sand(SS) of deep particles, which are the most commonly used in the domestic construction industry. According to the study, replacing CGS with CSa or crushed sand B(CSb)+SS by 25 % to 50 % resulted in good results in the aspect of the granularity of the aggregate and the workability and compressive strength of cement mortar, which were found to be usable.