• Journal of the Korea Concrete Institute
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• v.17 no.1 s.85
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• pp.105-112
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• 2005

Stabilizing and rousing sludge water generated from washing truck mixer and batcher plant can resolve inconsistency in quality and improve strength, therefore it is essential to review how to utilize it. This research conducted experiments and studied on solids of sludge water to find out the types of stabilizing agents available in conditions of producing ready mixed concretes in Korea. The result showed that oxy carboxylic acid retarder dedicated for stabilizing sludge water was most effective in decreasing solid. However, the setting time of cement paste was retarded due to surplus reactants, but it did not impede application of ready mixed concretes. When we left the sludge water mixed with stabilizing agent, it has been noted that initial retard effect recovered to the level using just service water in 7${\~}$8 days and that it is effective to use stabilized sludge water in 2${\~}$3 days. On the other hand, saccharic type super retarding agent was also outstanding in applicability by showing similar effect. The sludge water stabilizing agents currently marketed depend on imports, therefore it is necessary to locally manufacture usable stabilizing agents and to review its usability with multi-dimensional view.

• International conference on construction engineering and project management
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• 2011.02a
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• pp.187-194
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• 2011

Optimizing truck dispatching-intervals is imperative in ready mixed concrete (RMC) delivery process. Intervals shorter than optimal may induce queuing of idle trucks at a construction site, resulting in a long delivery cycle time. On the other hand, intervals longer than optimal can trigger work discontinuity due to a lack of available trucks where required. Therefore, the RMC delivery process should be systematically scheduled in order to minimize the occurrence of waiting trucks as well as guarantee work continuity. However, it is challenging to find optimal intervals, particularly in urban areas, due to variations in both traffic conditions and concrete placement rates at the site. Truck dispatching intervals are usually determined based on the concrete plant managers' intuitive judgments, without sufficient and reliable information regarding traffic and site conditions. Accordingly, the RMC delivery process often experiences inefficiency and/or work discontinuity. Automatic data collection (ADC) techniques (e.g., RFID or GPS) can be effective tools to assist plant managers in finding optimal dispatching intervals, thereby enhancing delivery performance. However, quantitative evidence of the extent of performance improvement has rarely been reported to data, and this is a central reason for a general reluctance within the industry to embrace these techniques, despite their potential benefits. To address this issue, this research reports on the development of a discrete event simulation model and its application to a large-scale building project in Abu Dhabi. The simulation results indicate that ADC techniques can reduce the truck idle time at site by 57% and also enhance the pouring continuity in the RMC delivery process.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.37-44
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• 1998

The objective of this study is development of high strength lightweight concrete and application or structural use. For this, mix proportions for each strength level were selected from lab tests, and adapted to producing ready-mixed concrete in batcher plant. It was very important to prewet the lightweight aggregates sufficiently for producibility and also workability. Splitting tensile strength of high-strength lightweight concrete produced has lower values than that of normal weight concrete, but modulus of rupture and modulus of elasticity are not less than normal weight concrete. The strength reduction factor ($\lambda$) for sand-lightweight concrete make higher than 0.85 present in structures using high-strength lightweight concrete. And it was showed that not parabola distribution but triangular distribution of stress in compression zone.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.357-362
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• 1996

The objective of this study is to investigate material properties and quality control of cast-in-place high strength concrete. High strength concrete with a design strength of 420 kgf/$\textrm{cm}^2$ is successfully produced at a ready-mixed concrete plant, and placed at a tall building. Many laboratory and field tests are carried out for the successful construction of the reinforced high strength concrete building. As the results of this study, the average actual 28-day compressive strength is 513 kgf/$\textrm{cm}^2$ and the coefficient of variation is 6.8%. The placing speed is comparable to normal strength concrete, however, the pump pressure is higher than that of normal strength concrete. To prevent cracks of massive and long concrete members, the control of hydration heat and shrinkage is very important.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.53-56
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• 2000

The performance of high-strength concrete is controlled by the fact, affecting the quality management, especially by revision error in water content of the ratio of surface moisture in fine aggregate. The difference in water content results from the revision error of the ratio of surface moisture and errors in sampled aggregate in the processing ready-mixed concrete plant. This study is to investigate the properties of flowing and hardening by investionally varying the revision error of the ratio of surface moisture in fine aggregate to compare and analyze the variance in quality.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.93-96
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• 2009

This study is to examine a change of quality and a material performance of fiber reinforced cement composite for mass production. It is necessary to make Strain-hardening cementitious composite(SHCC) by batcher plant for ready-mixed concrete and use the performance of SHCC which made based on laboratory level. This study makes a comparative performance of press and mechanics that is the property of Strain-hardening by direct tension. In case of making by batcher plant. This experiment has demonstrated that even if it takes long after being mixed small and compared with the one which made based on laboratory, it has a tendency to be dissatisfied with fiver's dispersion and lower its performance of Strain-hardening. The reason why the material performance of SHCC for mass production went down is through SHCC that mixed sometimes matrix's viscosity and fiber's dispersion.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.115-116
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• 2017

According to the experimental results of researchers recently seen, there is a case where a significant difference between data of several reports and measured powder is detected, and concrete examination on this is necessary. In this study, we compare the actual powdered degree of powdered aid on the report against 20 OPCs that are actually being brought into the raw concrete plant, and the OPC powder also influences the difference of OPC powder's strength characteristics on hardened mortar Was analyzed. As a result of the analysis, doubts were raised on the reliability of the OPC powder degree described on the certificate, and the bending and compressive strength tended to increase as the degree of fineness of the measured OPC increased.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.193-194
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• 2017

In this research, the density value of the turbid solution is measured by using the principle of inexpensive but easy Hydrometer method for cement delivered to the actual raw concrete plant, By analyzing the correlation of powder aid, we will try to present a scheme that can be utilized as a method of acquisition acquisition inspection. As a result of the analysis, it was found that there was a large difference between the measured powders assisted with cement powder on the report, and the correlation with the actually measured powder aid Hydrometer density value was good. Therefore, using the method of Fig. 3, it was possible to know that the degree of powder quality of cement delivered to the raw concrete factory can be evaluated quickly and utilized at the time of argument inspection.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.109-112
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• 2005

As civilization progresses amount of sewage sludge continues to increase from a sewage disposal plant with a huge expenditure of water resources. So It is necessary to reduce the high costs of sewage disposal and the pollution of the environment and also a unit cost of artificial lightweight aggregate by continual recycling. The purpose of this study is to put artificial lightweight aggregate concrete to practical use by using sewage sludge and clay

• Proceedings of the Korea Concrete Institute Conference
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• 1992.10a
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• pp.50-53
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• 1992

The damages due to alkali-aggregate reaction between the reactive silicia constituents of the aggregate and the alkalies in cement have been frequently reported since 1923 in America . Recently alkali-aggregate reaction, especially alkali-silica reaction, can be found all over the area using crushed stones. The first research, in 1990, was performed to identify the alkali-silica reactivity of 18 sets of crushed stones used in domestic ready-mixed concrete plant as coarse aggregates by 4 petrollgical, chemical and mortar bar method, And the study was continued with 10 sets of crushed stones in this research. It was found that all the aggregates used in this study are innocuous at alkali-silica reaction.