• Journal of the Korean Society of Industry Convergence
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• v.4 no.4
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• pp.419-426
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• 2001

Concrete mix proportioning is a process of selecting the right combination of many materials such as cement, fine aggregates, coarse aggregates, water, and admixtures to make concrete satisfying for specification and cost. In determining proportioning of concrete mixes, code information, specification, and the experience of experts are needed. However, all factors regarding mix proportioning factor cannot be considered. Therefore, the final acceptance depends on concrete quality control test results. The proportioning of concrete mixes and the adjustments are somewhat complicated, time-consuming, and uncertain tasks. In this paper, as a tool to predict the factor of the proportioning of concrete mixes, an artificial neural network is used. To consider the varieties of material properties, the standard mixed table of two companies of ready mixed concrete are used. The results show that neural net works is successfully applied to the prediction of concrete mix proportioning factor.

• Bulletin of the Korean Chemical Society
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• v.23 no.4
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• pp.580-586
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• 2002

We investigated the effect of ionic component on crystalline morphology development during isothermal annealing in a sodium neutralized sulfonated poly(ethylene terephthalate) ionomer (Ion-PET) by time-resolved small-angle x-ray scattering (TR-SAX S) using synchrotron radiation. At early stage in Ion-PET, SAXS intensity at a low annealing temperature (Ta = 120 $^{\circ}C)$ decreased monotonously with scattering angle for a while. Then SAXS profile showed a peak and the peak position progressively moved to wider angles with isothermal annealing time. Finally, the peak intensity decreased, shifting the peak angle to wider angle. It is revealed that ionic aggregates (multiplets structure) of several nm, calculated by Debye-Bueche plot, are formed at early stage. They seem to accelerate the crystallization rate and make fine crystallites without spherulite formation (supported by optical microscopy observation). From decrease of peak intensity in SAXS,it is suggested that new lamellae are inserted between the preformed lamellae so that the concentration of ionic multiplets in amorphous region decreases to lower the electron density difference between lamellar crystal and amorphous region. In addition, analysis on the annealing at a high temperature (Ta = 210 $^{\circ}C)$ by optical microscopy, light scattering and transmission electron microscopy shows a formation of spherulite, no ionic aggregates, the retarded crystallization rate and a high level of lamellar orientation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.2
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• pp.149-160
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• 2013

In the mix proportion of shotcrete, it was analyzed as required in terms of eco-friendly technology to take advantage of the screenings. Screenings of recycling can be a solution in order to overcome the quality degradation due to the recent lack of good quality sand as well as the utilization of waste materials. Five regional screening and screening replaced fine aggregates for physical characteristics were analyzed to evaluate the usability screenings as shotcrete's combined aggregate. It was analyzed the effect of particle size distribution in the combined aggregate for shotcrete and maximum replacement was estimated according to the type of screenings.

• Computers and Concrete
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• v.30 no.4
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• pp.257-267
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• 2022

Two different types of rubber aggregates (40 mesh rubber powder and 1-4 mm rubber particles respectively) were devised to substitute fine aggregates at 10%, 15%, 20% and 30% by volume in self-compacting concrete to investigate their basic mechanical properties. The results show that with the increase of rubber content, the reduction of compressive strength, splitting tensile strength and static modulus of elasticity gradually increase, and energy dissipation performance gradually increase. The rubber addition significantly reduces brittleness and decelerates damaged process. Whilst, the effect of rubber particles is greater when they are finer. Considering the mechanical properties, the optimal rubber content is 10%. It is recommended that the rubber volume content in rubberized concrete (RC) should not be higher than 20%. In addition, a constitutive model under uniaxial compression was proposed basing on the strain equivalent principle of Lemaitre and the damage theory, which was in good agreement with the test curves.

• Geomechanics and Engineering
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• v.33 no.1
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• pp.19-27
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• 2023

A series of experiments were performed to evaluate the effects of activated carbon on the compressive strength and air content of Portland Cement Concrete (PCC). Activated carbon/PCC composites were prepared by mixing concrete components with commercial activated carbon granules with weight fractions of 0, 0.5%, 1%, and 2% to cement. All PCC specimens were then tested for compressive strength on 7, 14, 21, and 28 days. The experimental results showed that adding 0.5% of activated carbon increased the compressive strength significantly over the curing periods compared to the normal PCC without activated carbon. For the specimens has 0.5% activated carbon, the 7, 14, 21, and 28-day compressive strengths increased by 28.7%, 22.2%, 26.8%, and 22.9%, respectively. However, adding excessive amounts of more than 1% activated carbon had a minimal effect on the compressive strength or even decreased it, which agrees with other studies. Regarding the air contents of the mixtures, adding activated carbon decreased the air content from 3.6% to around 1.5%. The surface morphologies of fine aggregates and activated carbon particles were compared using a novel image processing technique. The results indicated that the surface of activated carbon significantly differs from that of aggregates.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.145-151
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• 2019

The Physical performance of use materials was evaluated to improve durability of fast-paced repair mortar used at rapid construction sites. The fastening performance and basic performance were evaluated by substituting ferronickel grinding slag residues, rapid settlement, and EVA-based polymer for mortar. As a result, the compressive strength, flexural strength and adhesion strength were increased due to the use of FS Fine Aggregate and RS Fine Aggregate. The chloride ion promotion test of fast-polymer mortar kept the chloride inhibitory performance from 7 days to 28 days when fNS was used less than 50%. Durability degradation due to the use of FS Fine Aggregate and RS Fine Aggregate has not been found, and it is believed that further consideration of economic and long-term durability will be required for use as alternative Aggregate for construction and civil engineering.

• Journal of the Korea Institute of Building Construction
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• v.23 no.4
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• pp.359-367
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• 2023

This experimental study investigates the replacement of conventional Portland cement and sand with non-sintered cement and ferro-nickel slag to formulate eco-friendly cement mortar. The examination aimed to understand the strength properties of non-sintered cement mortar using ferro-nickel slag as fine aggregate by classifying mortar production types, fine aggregates, and curing methodologies. From flexural and compressive strength tests, it was observed that non-sintered cement mortars, incorporating ferro-nickel slag as fine aggregate, exhibited superior strength when compared to both plain mortar and steam-cured non-sintered mortar. This increased strength is attributed to the influence of the particle size, density, and absorption capabilities of the ferro-nickel slag. Furthermore, X-ray Diffraction(XRD) analyses of the mortars verified the presence of MgO, a component of ferro-nickel slag, in the form of a composite oxide. This finding substantiates the consistent strength manifestation of non-sintered cement mortars utilizing ferro-nickel slag as a fine aggregate.

• Journal of the Korea Institute of Building Construction
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• v.24 no.2
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• pp.169-180
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• 2024

In this study, to suggest an efficient method of using coal gasification slag(CGS), a byproduct from integrated gasification combined cycle(IGCC), as a combined fine aggregate for concrete mixture, the diverse performances of concrete mixtures with combined fine aggregates of CGS, river sand, and crushed sand were evaluated. Additionally, using CGS, the reduction of the hydration heat and the strength developing performance were analyzed to provide a method for reducing the heat of hydration of mass concrete by using combined fine aggregate with CGS and replacing fly ash with cement. The results of the study can be summarized as follows: as a method of recycling CGS from IGCC as concrete fine aggregate, a combination of CGS with crushed sand offers advantages for the concrete mixture. Additionally, when the CGS combined aggregate is used with low-heat-mix designed concrete with fly ash, it has the synergistic effect of reducing the hydration heat of mass concrete compared to the low-heat-designed concrete mixture currently in wide use.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.2
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• pp.83-92
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• 2006

Recently, interest grew recently on the quality of aggregates following the diminution of primary resources from river and the growing construction demand which exhausted high-quality sand sources around large cities and incited the use of low grade aggregates like shore sand and sea sand that can be supplied in natural state. Especially, the environmental preservation concern and the augmentation of public grievance about the exploitation of sea sand as substitute to river sand are gradually impeding the supply. This situation aggravated by the recent interdiction to extract sea sand which resulted in sand crisis that even led once to the suspension of construction works. The lack of sea sand and river sand increased the exploitation of crushed sand which occupies now nearly 20% of the whole quantity of fine aggregates. And, the use of crushed sand may be expected to grow continuously in the future. This paper described that the properties of crushed sand and the concrete using the crushed sand, the technologies to improve quality of crushed sand and the concrete in order to provide information for the production of high-quality concrete using crushed sand.

• Journal of computational fluids engineering
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• v.20 no.4
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• pp.70-80
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• 2015

Construction waste is known to include a large part of coarse and fine aggregates, which can be recirculated in the industry. Separating those aggregates economically from the waste has been thus considered to be one of the most important issues in this field. In particular, paste mixed in the waste causes significant complain from the inhabitants living near the place where waste-processing equipments are built and operated. In this study, we investigate the operational principle of a newly developed paste separator by using theoretical (in this first part) and CFD (in the second part) analysis. The separator consists of a rotor which turned out to play a significant role in separating those pastes from the aggregates. Under suitable assumptions regarding the air flow velocity as well as the particle velocity, we show that particles can be stagnant at the outlet of the roto channel for a wide range of parameter values, which allow the particles to get enough time to settle down via the gravitation. We also demonstrate such phenomenon by using a simple numerical simulation.