• Geomechanics and Engineering
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• v.14 no.2
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• pp.151-159
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• 2018

Annually, the global production of construction aggregates reaches over 40 billion tons, making aggregates the largest mining sector by volume and value. Currently, the aggregate industry is shifting from sand to hard rock as a result of legislation limiting the extraction of natural sands and gravels. A major implication of this change in the aggregate industry is the need for understanding rock fragmentation and energy absorption to produce more cost-effective aggregates. In this paper, we focused on incorporating dynamic rock and soil mechanics to understand the effects of loading rate and water saturation on the rock fragmentation and energy absorption of three different sandstones (Red, Berea and Buff) with different pore sizes. Rock core samples were prepared in accordance to the ASTM standards for compressive strength testing. Saturated and dry samples were subsequently prepared and fragmented via fast and dynamic compressive strength tests. The particle size distributions of the resulting fragments were subsequently analyzed using mechanical gradation tests. Our results indicate that the rock fragment size generally decreased with increasing loading rate and water content. In addition, the fragment sizes in the larger pore size sample (Buff sandstone) were relatively smaller those in the smaller pore size sample (Red sandstone). Notably, energy absorption decreased with increased loading rate, water content and rock pore size. These results support the conclusion that rock fragment size is positively correlated with the energy absorption of rocks. In addition, the rock fragment size increases as the energy absorption increases. Thus, our data provide insightful information for improving cost-effective aggregate production methods.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.126-127
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• 2020

Recently, as interest in environmental issues increases, minimizing carbon dioxide generated during cement manufacturing is a problem to be solved. In order to solve such a problem, it is required to use an industrial by-product of recycled aggregate, blast furnace slag, and circulating fluidized bed boiler fly ash to replace it on the basis of geopolymer(=cementless). This study examines the characteristics of eco-friendly artificial stone according to the mixing ratio of geopolymer-based recycled aggregate. As a result of the experiment, when the addition rate of the alkali stimulant was 15% and the mixing ratio of the circulating aggregate was 70%, the flexural strength and compressive strength were the highest. Density and water absorption decreased as density of circulating aggregates increased and water absorption increased. However, when the mixing ratio of the circulating aggregate exceeded 70%, the flexural strength and compressive strength decreased. Therefore, in order to obtain strengths meeting the KS standards, the mixing ratio of recycled aggregate was set to 70%, and artificial stone was manufactured using industrial by-products.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.121-124
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• 2006

Lightweight aggregate is mainly consist of multi-crystalline structure. It may be abnormal water moving by the change of external circumstance because of its specific portion being between components and aperture. So it has some difficulty in forming without concise method about absorbing character and water-containing point even though it is used to water-containing condition over the 24 hours of absorbing amount in present. This study has main idea on the characteristics of absorption on the pressurization of lightweight aggregate.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.120-121
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• 2015

In this research, to evaluate the influence of using non-KS aggregate on concrete performance, the engineering properties of normal strength concrete were assessed depending on the KS aggregate and non-KS aggregate from various sources in mid-Korea. From the experiment, when the non-KS aggregate was used, low compressive strength was achieved with increased water-to-cement ratio caused by increased unit water due to high absorption rate of the non-KS aggregate.

• Journal of the Korea Institute of Building Construction
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• v.14 no.1
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• pp.11-20
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• 2014

This research examined the effect of the quality of aggregate on concrete workability and compressive strength through an investigation into regional aggregate used in domestic ready mixed concrete plants. Through the research, it was found that aggregate for ready mixed concrete shows poor quality overall. The main factor of deterioration in the quality of the concrete is the particle size of fine aggregate and fine particle content in coarse aggregate. The quality of aggregate significantly influences concrete's workability, which is defined based on 0.08mm passage related with powder and absorption. In addition, poor aggregate quality leads to increased water content in concrete to secure workability, which is related with a decline in the compressive strength and durability of concrete.

• Advances in concrete construction
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• v.3 no.3
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• pp.187-202
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• 2015

The present study addresses about the development of sustainable concrete utilizing recycled coarse aggregates manufactured form waste concrete and colloidal Nano-Silica. Experimental investigations are carried out to determine compressive and tensile strength of concrete mixes designed with recycled coarse aggregates and different percentages of Nano-Silica. Moreover, water absorption, density and volume voids of concrete mixes are also examined to ascertain the influence of Nano-Silica on behavior of recycled aggregate concrete. The outcomes of the research depict that properties of concrete mixes are significantly affected with the introduction of recycled coarse aggregates in place of the natural coarse aggregates. However, the study reveals that the depletion of behavior of recycled aggregate concrete could be restored with the incorporation of little amount (3%) of Nano-Silica.

• Journal of the Korea Institute of Building Construction
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• v.5 no.2 s.16
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• pp.131-138
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• 2005

Most concrete is recently made of an aggregate which is properly absorbed, and carried in it in order to do capability at every fields. We have been close to demand new rapability of high flowing and enduring for specific concretes. That is difficult to cope with claiming the efficiency on deterioration from lack of a high quality aggregate. Therefore, For solving the problems we apply to a packing method for using dried materials. That is to say that it is a kind of making into an instant. In this study. There is a purpose to present fundamental data, comparing and analyzing a phenomenon of aggregate's absorption following the rate of adding water, for using existing materials.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.141-144
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• 2005

This paper reports the results of experimental study on the effect of an amount of mortar attached to the surface of original aggregate on the physical properties of recycled aggregates such as specific gravity, and water absorption. An amount of attached mortar was evaluated by hydrochloric acid precipitation method. Test results indicated that a water absorption of recycled aggregates was proportional to the amount of mortar attached to the original aggregate.

• Journal of the Korea Institute of Building Construction
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• v.3 no.4
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• pp.119-122
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• 2003

Most concrete is recently made of an aggregate which is properly absorbed, and carried in it in order to do capability at every fields. We have been close to demand new capability of high flowing and enduring for specific concretes. That is difficult to cope with claiming the efficiency on deterioration from lack of a high quality aggregate Therefore, For solving the problems we apply to a packing method for using dried materials. That is to say it is a kind of making into an instant. In this study, There is a purpose to present fundamental data, comparing and analyzing a phenomenon about aggregate's absorption following the rate of adding water, for using existing materials.

• International Journal of Concrete Structures and Materials
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• v.8 no.2
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• pp.165-172
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• 2014

Recycled coarse aggregate (RCA) made from waste concrete is not a suitable structural material as it has high absorption of cement mortar, which adheres on the aggregate surface and on the tiny cracks thereon. Therefore, when using RCA made from waste concrete, much water must be added with the concrete, and slump loss occurs when transporting. Hence, its workability is significantly worse than that of other materials. In this study, surface of RCA was coated with water-soluble polycarboxylate (PC) dispersant so that its characteristics improved. Each possibility was evaluated: whether its slump loss can be controlled, by measuring its workability based on the elapsed time; and whether it can be used as a structural material, by measuring its strength. Moreover, the carbonation due to cement mortar adhesion was measured through a carbonation test. As a result, RCA coated with PC dispersant was found to be better than crushed coarse aggregate and RCA when the physical properties of the fresh concrete and the mechanical, durability of the hardened concrete were tested.