• Applied Chemistry for Engineering
• /
• v.16 no.3
• /
• pp.317-322
• /
• 2005

Nowadays, recycling of aggregates from the waste concrete is in big demand due to the protection of environment and the shortage of aggregates that are needed for ever expanding construction projects. This study was undertaken to examine the feasibility of recycling waste concrete powder produced in the crushing process of demolished concrete as a filler material for polymer mortar. In this study, polymer mortar specimens were prepared by varying the mix proportion of polymer binder (ranging 9~15 wt%), waste concrete powder (ranging 0~20 wt%) substituted for silica powder, 0.1~0.3 mm fine aggregate (ranging 21~24 wt%) and 0.7~1.2 mm fine aggregate (ranging 44~47 wt%). For the prepared polymer mortar specimens, various physical properties such as strength, water absorption, heat water resistance, acid resistance, pore distribution and SEM observation were investigated in this work. As a result, physical properties of polymer mortar were observed to have remarkably improved with an increase of polymer binder, but greatly deteriorated with an increase of substitution quantity of waste concrete powder.

• Nuclear Engineering and Technology
• /
• v.2 no.3
• /
• pp.149-161
• /
• 1970

This paper describes a detailed investigational performance on the gamma radiation shield effect of heavy concretes that were manufactured by the use of mineral ores produced domestically and which may be possibly applied for the biological shield design. Ten different kinds of mineral ores were collected for use as the aggregates, physical test and chemical analysis for them were carried out to select the aggregate with a better property. Through the experimental investigation on the shielding effect of various concretes with different combination of concrete components such as water-cement and fine-coarse aggregate ratios, it was possible to derive some criteria for the best condition being capable of obtaining the concretes with high density and good uniformity. Data on the shielding-effectiveness of the different concretes were obtained by performing collimated beam experiment using 60Co gamma-ray. Analyzing the shielding-efficiency, shielding-concrete specific gravity and biological shield cost, the optimum condition of yielding the best economic shielding design, with low cost and good spatial distribution to some extent was determined.

• Economic and Environmental Geology
• /
• v.37 no.5
• /
• pp.555-568
• /
• 2004

The demand of aggregate resources in Korea has been increased with a rapid economic growth since the 1980s. About 25% of the total aggregate production is derived from riverine aggregates, 20% to 25% from marine sands, 40% to 45% from crushed aggregate and the rest 5% to 15% from old fluvial deposits. The abundance of crushed coarse aggregates varies in the uniform distribution of country, but in general it can be concentrated in the most densely populated areas, five main cities. Typical rock types of the Korean crushed stones are classified as plutonic rocks of 27%, metamorphic rocks of 32%, sedimentary rocks and volcanic rocks of 18%, respectively. The most abundant coarse aggregate used in the country is obtained from granite (25% of total) and subordinately gneiss (20%), sandstone (10%) and andesite (10%). Although rock types using as dimension stone are only fifteen, those as aggregate amount up to twenty nine rocks. These rocks consist of plutonic rocks such as granite, syenite, diorite, aplite, porphyry, felsite. dike and volcanic rocks such as rhyolite, andesite, trachyte, basalt, tuff, volcanic breccia and metamorphic rocks such as gneiss, schist, phyllite, slate, meld-sandstone, quartzite, hornfels, calc-silicate rock, amphibolite. And sandstone, shale, mudstone, conglomerate, limestone, breccia, chert are main aggregate sources in tile sedimentary rocks. The abundance of plutonic rocks is the highest in Chungcheongbuk-do, and decreases as the order of Jeollabuk-do, Gangwon-do and Gyeonggi-do. In Jeollanam-do, volcanic aggregates occupy above 50%, on the contrary sedimentary aggregates are above 50% in Gyeongsangnam-do.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.4 no.3
• /
• pp.69-74
• /
• 2009

This paper summarizes the analysis of granite microfines from California for use in portland cement concrete. For reference, the granite microfines were compared to microfines used in previous International Center for Aggregates Research(ICAR) projects. The particle shape characteristics, based on the packing density results, were assessed and apparent clay content, based on the methylene blue value test, was evaluated. Also, the physical properties of the microfines were confirmed in self-consolidating mortar mixtures.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1996.04a
• /
• pp.12-17
• /
• 1996

It is true that aggregate strength is usually not a factor in normal concrete strength because, the aggregate particle is several times stronger than the matrix and the transition zone in concrete. In other words, with most natural aggregates the strength of the aggregate is hardly utilized because the failure is determined by the other two phases. But aggregate characteristics that are significant to concrete technology include porosity, grading or size distribution, moisture absorption, shape and surface texture, crushing strength, elastic modulus, and the type of deleterious substances present. Therefore, in the area of high strength concrete, concrete is much more influenced by properties of aggregate. This experiment is performed to investigate how kinds of aggregare influence on the workability of high strength concrete. In this experiment, four types of aggregate is used, that is crushed river aggregate, crushed stone, recycled aggregate of low strength and recycled aggregate of high strength. In this study, we scrutinize a fundmental study on the workability of high strength concrete according to kinds of aggregate.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1995.10a
• /
• pp.1-7
• /
• 1995

In this paper, we decribed the basic elements required for the practical usage of super flowing concrete. The flowability and filingability of fresh concrete was measured by using six different testing methods. Also, two actual size members were used for investigating characteristics of the hardened concrete through variious experiments. As the result of the experimentation, the developed super flowing concrete shown high flowability and fillingability good enough for the requirement. Furthermore, inner uniformity of the no-vibrated concrete was verified by testing distribution of aggregates and core cylinders. Therefore, quality control and workability of concrete can be secured by using the super flowing concrete even without vibrating However, it ha been felt that development of easy evaluation methods for the super flowing concrete is in need.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1990.10a
• /
• pp.107-112
• /
• 1990

Chromatograms of asphalt cements were observed using high pressure - gel permeation chromatography (HP-GPC). The chromatogram characterzed profile of molecular size distribution of asphalt cements. Bituminous concretes using the asphalt cements were prepared in laboratory to measure mechanical properties, tensile strength (TS) and resilient modulus (MR), in dry and wet conditions. Three sources of AC-20 Asphalt cements and one aggregates were used for GPC test and strength test. Results of mechanical property tests and GPC tests were analyzed to evaluate correlation between those two results. Regression analysis showed strong correlation between a mechanical property and sliced percent areas of GPC profile. Mathematical models were developed for estimating mechanical properties of asphalt cement concrete based on HP-GPC data.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2004.04a
• /
• pp.162-166
• /
• 2004

This study investigated tile effect of ozonation on indigenous microorganisms distributed in different size fractions of soil aggregates. Soil was ozonated from 0 to 300 minutes. The treated soils were fractionated into 3 groups (small, <53 $\mu$m; medium, 53-500 $\mu$m; and large, 2000-500 $\mu$m) and total heterotrophic bacteria in the soils were enumerated. Cell number decreased rapidly within 120 minute ozonation and showed slow decrease upon longer ozonation. Abundance of total heterotrophic bacteria in each fraction was in the following order regardless of ozonation time: small>medium>large fractions. Difference in microbial abundance among the fractions was smaller as ozonation time increased.

• Resources Recycling
• /
• v.8 no.1
• /
• pp.44-51
• /
• 1999

Converter slag was reduced and modified by the simultaneous addition of carbon and waste foundry sand as a $SiO_2$ source. The basic properties such as phase distribution, composition, specific density, hardness. absorption of water and compressive strength of modified slags were measured. The Iron recovery was significantly affected by the basicity of slag. The properties of slow cooled-modified slags of basicity 1.34 arc very similar to the natural aggregates.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.7
• /
• pp.1020-1027
• /
• 2000

A simple model for describing the non-spherical particle growth phenomena has been developed. In this model, we solve simultaneously particle volume and surface area conservation sectional equations that consider particles' non-sphericity. From the correlation between two conserved properties of sections, we can predict the evolution of the aggregates' morphology. This model was compared with a simple monodisperse-assumed model and more rigorous two-dimensional sectional model. For comparison, formation and growth of silica particles have been simulated in a constant temperature reactor environment. This new model showed good agreement with the detailed two-dimensional sectional model in total number concentration and primary particle size. The present model successfully predicted particle size distribution and morphology without costing very heavy computation load and memory needed for the analysis of two dimensional aerosol dynamics.