• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.132-133
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• 2015

In this research by examining the influence that low quality aggregate has on the strength of concrete through testing, the lowering of strength according to use of low quality coarse aggregate was reviewed. The results showed that when using low quality coarse aggregate, due to the quality of aggregate a high volume of units was required, and this caused the compression strength to be lowered. In conclusion it was confirmed that if the low quality aggregate was used as is without mix correction this would lead to faulty construction and if the aggregate was corrected to about 60 kg/m3 mix correction, this would lead to an economically infeasible concrete mix.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.299-306
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• 2016

In this research, influence of low quality aggregate on engineering properties of concrete was evaluated experimentally. From the experiment, the fresh properties of slump and air content were controlled with unit water and AE dosage and all mixture were designed to have similar fresh properties of slump and air content with various quality of aggregate. Under this conditions, comparing with the mixture with high quality aggregate, the mixture with low quality aggregate showed the unit water and AE dosage were increased about 18 and 98%, respectively, because of poor grading and quantity of fines. For compressive strength, the low quality aggregate, specifically, exploded debris, clay sand, and sea sand contributed on decreasing compressive strength about 20~35%. Additionally, the concrete mixture including low quality fine and coarse aggregate showed adverse quality in not only compressive strength but also durability of freeze-thawing resistance, drying shrinkage, carbonation, and chloride ingression. Therefore, it is considered that for low quality aggregate, extra treatment processes such as washing or controlling gradation, and regulation to limit the use of low quality aggregate are needed.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.187-194
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• 2016

In this research, the influence of low-quality aggregate on engineering properties of concrete was experimentally evaluated. From a series of experiment, the results can be summarized as follow: first, the low-quality aggregate in concrete mixture caused up to 83% of decreased slump. For air content, low-quality aggregate increased air content of concrete mixture. Especially, when sea sand was used, because of the narrow gradation with small size, the air content was significantly increased. The compressive strength of concrete mixtures with low-quality aggregates were decreased up to 29% while some cases showed slightly increased compressive strength at early age. Additionally, the concrete mixture mixed with the exploded debris as a coarse aggregate showed approximately 5 to 20% of decreased compressive strength comparing with high-quality of manufacturing rock. In summary, because of the decreased workability of concrete mixture mixed with low-quality aggregates such as exploded debris, clay, and sea sand, it is concerned that worse quality of the ready mixed concrete, produced with the extra water to compensate the decreased workability.

• Journal of the Korea Institute of Building Construction
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• v.18 no.3
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• pp.219-225
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• 2018

The aim of the research is improving the quality of concrete by using the alternative aggregate resources and recycling wastes. To make a combined aggregate fitted in standard particle size distribution curve, crushed sand from blasted rock debris was used as a base aggregate. Additionally, to increase the portion of fine particles, sea sand was mixed. Although these aggregate combination fit the standard particle size distribution curve, in this research, raw coal ash was replaced as a microfine. According to the experiment, by replacing 5% raw coal ash, the most favorable results were achieved in aggregate gradation and cement mortar quality.