• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.11a
• /
• pp.112-115
• /
• 2003

Aggregate may limit the strength of concrete, and aggregate with undesirable properties cannot produces strong concrete. Also, the properties of aggregate greatly affect the durability and structural performance of concrete. Recently, it has increased the using of crushed aggregate for concrete due to the exhaustion of good natural aggregate. In case of Korea, in 2002, the using ration of crushed stone occupies about 97% of whole coarse aggregate, and ratio of crushed sand occupies about 18.3% of whole fine aggregate. This is a study to compare and analyze the properties of crushed aggregate for concrete to do mix proportion and improve the concrete quality. According to results, it was found that nearly all the properties of crushed aggregate satisfied with the value recommended by KS.

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

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2016.10a
• /
• pp.154-155
• /
• 2016

Oyster shell is light weighted and its strength characteristic is similar to sand. So we produced mortar test piece using grounded oyster shell powder under 0.5mm, which is a standard of fine aggregate, and reviewed strength properties according to water cement ratio. In our test, we used two kinds of oyster shell particles: below 0.6mm and 1.2~2.5mm. Water cement ratio is varied 40% to 100% and we found that flexural strength and compressive strength are decreased in higher water cement ratio.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.11a
• /
• pp.129-134
• /
• 2001

The purpose of this study is to investigate properties of unsaturated polyester mortar using the shale as find aggregates. To evaluate properties of unsaturated polyester mortar using crushed sand from Black shale, Red shale, Gray shale, we peformed the experiment according the F/B ratio of 25, 30, 35% and the volume of fine aggregate of 50, 53, 56%. The Result of this study is as follows. the strength of unsaturated polyester mortar is higher than those of river sand. The F/B ratio is higher and the volume of find aggregate is lower, the strength of unsaturated polyester mortar is higher

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2017.05a
• /
• pp.71-72
• /
• 2017

The oyster shell is lightweight and exhibits strength characteristics similar to sand. In this study, mortar specimens were fabricated by crushing them and processed to 5mm or less of the fine aggregate standard, and examined the fire resistance of the mortar according to changes in particle size distribution. In this experiment, seven particle size distribution conditions were tested. In addition, the mixing ratio was fixed at 1: 3, and the experiment was conducted in terms of the volume ratio because the densities of sand and oyster shells were different.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.2 no.4
• /
• pp.321-327
• /
• 2014

Structural light weight aggregate concrete are made with both coarse and fine light weight aggregates, but it is common with the high strength concrete to replace all or part with normal weight sand be called class 1 structural light weight aggregate concrete. Fire resistance of structural light weight aggregate concrete are determined by properties of high water content ratio and explosive spalling. Especially, structural light weight aggregate concrete is occurred serious fire performance deterioration by explosive spalling stem from thermal stress and water vapor pressure. This study is concerned with experimentally investigating fire resistance of class 1 structural light weight concrete. From the test result, class 1 structural light weight concrete is happened explosive spalling. The decrease of cross section caused by explosive spalling made sharp increasing gradient of inner temperature.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2023.05a
• /
• pp.197-198
• /
• 2023

This study was conducted as part of research and development of high-strength grout. Accordingly, dolomite aggregate was used as a filler incorporated into the high-strength grout. Dolomite aggregate has a disadvantage of increasing the viscosity of the grout due to higher generation of fine powder than other aggregates. Accordingly, in this experiment, it was confirmed that the viscosity, flow time, and flow of high-strength grout change according to the volume composition ratio of dolomite aggregate and cement-based material. All experiments were conducted based on the Korean Industrial Standard KS F 4044, and the mixing factor was applied according to the composition ratio of the binder and the filler. In the experiment, the amount of fine powder contained in the dolomite aggregate rather than the silica sand used in the past is grasped, and after mixing with the grout accordingly, the mixture is proceeded to measure the viscosity in an unhardened state. In addition, the flow and flow time of the grout are evaluated according to the viscosity. As a result of the experiment, it was confirmed that the viscosity and flow time decreased and the flow increased as the volume composition ratio of the dolomite aggregate to the cement-based material increased.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.10a
• /
• pp.237-240
• /
• 1999

This study was performed to analyze strength characteristics of concrete using FWS(foundry waste sand), as a way of study for reusing the FWS disused in the foundry as the fine aggregate for concrete. As the experimental results, the slump of concrete showed a decline with the increase of replacement ratio of FWS. The compressive strength of concrete made with FWS 25% replacement river sand showed higher value than that of concrete not containing FWS, but the flexural strength of concrete containing FWS was decreased 21% compared with that of concrete not containing FWS at age of 28days.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2009.03a
• /
• pp.119-122
• /
• 2009

The gravel compaction pile method has been used as a soft foundation improvement method because bearing capacity and discharge capacity is excellent. But the discharge capacity decreased when the clogging was generated because the clay penetrate into a void of gravel compaction pile. Accordingly, the purpose of this study is to reduce the clogging generation in gravel compaction pile constructing in the soft ground and take a step to minimize a void of gravel compaction pile. And the proper mixing ratio was determined with the large scale direct shear test performed to get strength and permeability with mixing ratio of crushed stone and sand(100:0, 90:10, 85:15, 80:20, 75:25). As a result of the test, it was showed that internal friction angle was the highest at 85:15 mixing ratio of crushed stone and sand and we can make sure a tendency of internal friction angle's decrease when the mixing ratio of crushed stone and sand passed 15%.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.17 no.5
• /
• pp.77-86
• /
• 2013

This study investigates the fundamental properties of the water-binder (W/B) ratio and fine aggregate-binder (F/B) ratio in the alkali-activated slag cement (AASC) mortar. The W/B ratios are 0.35, 0.40, 0.45, and 0.50, respectively. And then the F/B ratios varied between 1.00 and 3.00 at a constant increment of 0.25. The alkali activator was an 2M and 4M NaOH. The measured mechanical properties were compared, flow, compressive strength, absorption, ultra sonic velocity, and dry shrinkage. The flow, compressive strength, absorption, ultra sonic velocity and dry shrinkage decreased with increases W/B ratio. The compressive strength decreases with increase F/B ratio at same W/B ratio. Also, at certain value of F/B ratio significant increase in strength is observed. And S2 (river sand 2) had lower physical properties than S1 (river sand 1) due to the fineness modulus. The results of experiments indicated that the mechanical properties of AASC depended on the W/B ratio and F/B ratio. The optimum range for W/B ratios and F/B ratios of AASC is suggested that the F/B ratios by 1.75~2.50 at each W/B ratios. Moreover, the W/(B+F) ratios between 0.13 and 0.14 had a beneficial effect on the design of AASC mortar.