• Proceedings of the Korea Concrete Institute Conference
• /
• 1998.10b
• /
• pp.940-945
• /
• 1998

Recently, serious cracking problems have been reported in this country while the process of actual massive concrete construction. he hydration heat arising from the chemical reaction of cement with water causes temperature differentials in between inside and outside of a structural member, and these temperature differentials induce thermal stresses. In this paper, we described on the practical application and quality control of the mass concrete mixed with fly-ash. This project is investigating adiabatic temperature rise test of concrete, mock-up test in the laboratory, ad B/P before placing the mass concrete in site. As a result, we can be prevent temperature cracking from the cement hydration heat of mass concrete and also can be showed up secure quality control flow chart of mass concrete.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05b
• /
• pp.629-632
• /
• 2006

This study investigated the engineering properties of crushed sand, based on improvement quality technology, and washed sand concrete by conducting mock-up test, in order to verify the availability of crushed sand for full sized structure. Test results showed that fluidity, air content, supersonic waves and corrosion state of concrete using crushed sand had favorable results. In addition, it is found that compressive strength, drying shrinkage length change, hydration heat and neutralization of crushed sand concrete exhibited similar tendency, with that of washed sand concrete. The crushed concrete using developed quality improvement technology shows comparable performance to washed sand concrete.

• Journal of the Korea Institute of Building Construction
• /
• v.7 no.4
• /
• pp.125-132
• /
• 2007

The use of Self-Leveling material is increasing recently. This paper assesses the quality of surface layer of concrete floor when Self-Leveling material is defective. The paper shows how to predict the defect of SL material before construction begins. The relationship between the quality of surface layer of concrete floor and the defect of SL material was determined and the quality of surface layer of concrete floor was then estimated. The relations between the quality of surface layer and the defect of SL material were determine considering surface strength, moisture, and consistency of surface layer. Absorbing amount was used as the indicator of consistency and the absorbing amount of test material was measured. Then the relations between the test material and surface strength were determined. Generally concrete floor with greater consistency has greater surface strength, however in this study, we hound that high impact concrete floor could have lower surface strength as the consistency gets bigger. The relations between the level of defect occurred in SL material and the quality of surface layer were examined and we clarified that the surface layer with lower consistency gets higher possibility to occur exfoliation in early stage, one or two weeks after constructing SL material. When the consistency is sufficient, the occurring situation of defect depends upon the moisture of surface layer. Little amount of moisture gets higher possibility not to occur the defect. As the amount increases, fissure generates and early exfoliation may occur. In addition, the level of fissure is highly related with the surface strength.

• Korean Journal of Construction Engineering and Management
• /
• v.1 no.2 s.2
• /
• pp.53-62
• /
• 2000

A concrete element is obtained through multi-steps, and its quality is affected by site conditions and control constituents of procedures. In these regards, in order to assure designed qualities of concrete and associated materials of the element good quality control method is necessary in various procedures. The existing quality control measures do not satisfy the requirements for the quality control activities at each production step. This study provides a more effective checklist for each phase of concrete work, which improves existing quality control checklist through extensive research on current practices and surveys from expertises. This paper also proposes the application of multi-facet codes to develop a customized checklist to improve the efficiency in field practices and the effectiveness in assuring the designed performance of concrete. This study finally provides a more effective checklist for each phase of concrete work by improving usability of the developed project sensitive matric quality control checklist through application experiments on construction project sites.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05b
• /
• pp.113-116
• /
• 2006

After laws for recycling promotion of construction wastes was established on December, 2003, successive technical and institutional measures related to construction wastes are driven. Typically quality standards for recycled aggregate were enacted and officially announced, and recently the quality assurance system for recycled aggregate is promoted to be established. In relation, this study reviewed major factors affecting certification examination necessary to carry out quality assurance system for recycled aggregate and related standards to guarantee the quality of recycled aggregate. More specifically it is suggested that working place examination related to manufacturing facility and planning, quality control manpower and system, environmental and safety control, etc, and quality inspection with classified by for road construction, for concrete, and for asphalt concrete are used as quality assurance standards.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.609-612
• /
• 2008

This study investigated effect of recycled fine aggregate quality on strength properties of concrete. Some investigations have been carried out to study the strength properties of recycled aggregate concrete. But these have some limitation due to small-scale test in the laboratory. Therefore concrete using this study were fabricated by ready-mix concrete. Variables were quality of recycled fine aggregate(high and low quality) and replacement ratio of 0%, 30%, 60%, 100%(high quality), 35, 70%(low quality). The change of air content of recycled aggregate concrete were similar to natural aggregate concrete. Replacement ratio of recycled aggregate was not necessarily correlated with compressive strength and modulus of rupture of recycled aggregate concrete.

• Proceedings of the Korean Society of Agricultural Engineers Conference
• /
• 2003.10a
• /
• pp.407-410
• /
• 2003

The actual quality of the concrete in the structure for Irrigation may differ from that represented by the cylinders because the age, consolidation, or curing of the in-place material may not be well represented by the standard test specimens. The objective of this paper is to offer a base data of specification is the best fit the ready-mixed concrete strength to the specified, and to address this deficiency, so that the strength information of the concrete in the structure for Irrigation can be rationally accounted for in the assessment of the quality condition of this. The strength of concrete in the hydraulic structures is checked using strength of core obtained from that, and 28-day-old cylinder strength is analyzed using cylinder data of the ready-mixed concrete.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.3 no.4
• /
• pp.33-45
• /
• 1983

In the course of transportation of ready mixed concrete, it sometimes happens that time of haul from mixing at a batching plant to placing of the concrete at a job site is prolonged too much. When it does happen, improvement in the concrete workability needs to be made by proper measures. It is proposed, therefore, to discuss the quality of concrete modified by time of haul and to search for methods for improvement of the quality by means of adding cement and water or superplasticizer. It was found in this experiment that retempering concrete with superplasticizer is useful in coping with the quality deterioration.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1995.10a
• /
• pp.164-168
• /
• 1995

As nation's infrastructure is getting old, nondestructive evaluation of existing structures and construction quality control are getting important. In this paper non-destructive evaluations of concrete members using impact echo and SASW methods are introduced. Both techniques are based on the stress wave propagations. Experimental tests were performed using beam type concrete member where voids and cracks are included. Within reasonable accuracy, void locations were detected using impact echo method and the dynamic modulus of concrete were measured using SASW method. Both NDT methods showed a feasibility for the implementation into quality evaluaton of concrete members in practice

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05b
• /
• pp.105-108
• /
• 2006

Recently, trouble of sand supplying is occurred according to exhaustion of natural sand resources. Therefore various measures are proposed for solution of trouble of sand supply and crushed sand among measures is used as one of most universal measures. But because crushed sand have poor particle shape and plenty of mikes micro particle, the quality of concrete using crushed sand deteriorated. Therefore, this study evaluated engineering property of concrete with replacement ratio of crushed sand and EEZ sand applied evaluation result to fundamental data for quality control of concrete using crushed sand and EEZ sand and The result of this study have shown that quality of concrete using crushed sand and EEZ sand and The compressive strengh of concrete up to 50, 70% EEZ sand replacement by crush sand, nearly equal to that of general sand.