• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.4
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• pp.48-56
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• 2022

Controlling the setting time of cementitious materials is one of the most important factors in securing early-age performance of concrete structures. Recently, the use of retarding admixtures, which enable the inhibition of some hydration products to control the securing time due to average temperature rise is suggested. Although various non-destructive evaluation methods have been proposed to evaluate cement hydration and hardening of cement-based materials to overcome the limitations of Vicat needle test, experimental research is still required to use the non-destructive evaluation method with added retarding admixtures. In this study, measurements of electrical resistivity and ultrasonic wave velocity in early-aged cement pastes were performed according to the addition of retarding admixture(tartaric acid). The setting time of the cement pastes was evaluated by obtained rising time of the both non-destructive measurements. As a result, the possibility of evaluating the setting delay in cement pastes was confirmed through comparative analysis with the initial and final setting times by Vicat test. In addition, X-ray diffraction results at the rising time of electrical resistivity showed a key hydration product affecting the setting delay.

• Journal of the Korea Institute of Building Construction
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• v.23 no.6
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• pp.703-714
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• 2023

This research conducts a series of tests to investigate the setting retarding properties and strength development in cement pastes incorporating various types and dosages of sugar-based super retarding agents. Six such agents, including Sucrose, Sugar powder, Saccharin, Aspartame, Stevioside, and Mogroside, commercially available, were selected for evaluation. The study also examines the micro-structural properties of these cement pastes. The test mixtures were prepared using a 27.5% water-to-cement ratio and ordinary Portland cement. Micro-structural analyses were conducted using Scanning Electron Microscopy(SEM), X-Ray Diffraction(XRD), and Energy Dispersive Spectroscopy(EDS). The findings reveal that the incorporation of sucrose, sugar powder, and stevioside significantly retards the setting time. Particularly, adding 0.1% sucrose extended the setting time by approximately two-fold compared to the control(Plain) mixture. Most mixtures, barring those with sugar powder and stevioside, exhibited compressive strength comparable to the Plain mixture. Notably, with 0.2% sucrose, strength measurements were not feasible at 1 day, but at 3 days, the strength gains aligned with the Plain mixture. XRD, SEM, and EDS analyses confirmed the hydration delay(set retarding) of C3S due to sucrose, with further quantitative corroboration provided by EDS. SEM was used to verify the presence or absence of hydration products. The study concludes that sucrose, as a sugar-based retarder, offers effective set retarding capabilities and compressive strength development in concrete.

• Journal of the Korea Concrete Institute
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• v.14 no.4
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• pp.589-596
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• 2002

In this paper, setting and strength performances of concrete containing saccharic type super retarding agents are investigated under various kinds and contents of super retarding agents. According to test results, as super retarding agents contents increase, slump shows to be increased, while air contents decrease about 1∼2％. Setting time shows to be retarded considerably with increase of super retarding agents. It takes 20 days after mixing to reach final setting in case of concrete containing gluconic acid more than 0.3％. And 10 days after mixing in case of enhancing sucrose, white and brown sugar. Compressive strength of concrete containing super retarding agents is lower than that of plain concrete at early age. However, it keeps up with and exceeds the compressive strength of plain concrete at later age. White sugar md brown sugar shows positive performances in delaying setting time and strength compared to existing super retarding agents. n further investigations on durability are conducted, it is thought that application of white sugar as super retarding agent is available.

• Journal of the Korea Concrete Institute
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• v.25 no.2
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• pp.201-207
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• 2013

When hot weather concrete is utilized, the cooling methods of cooling pipe, liquid nitrogen, ice, etc., are used to prevent the poor consistency and cold joint due to high temperature. These methods, however, spike the production cost and energy consumption, and make quality control difficult. Among these methods is one that involves the use of a retarder. Although economical, retarder is caused difficulty of retarded hardening and setting time control due to inaccurate weighing and poor working condition. Therefore, how to make a tablet for hot weather concrete, as with the existing pharmacy and foods, is discussed in this study, including the following items: mortar setting time, flow test by elapsed time, physical and mechanical properties of concrete. As a result, gluconic acid is superior to lignosulfonic acid and the possibility of using them for such purpose without quality degradation was confirmed in this study, when retarder is tabletting.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.9-15
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• 2018

According to the development and use of self-consolidating concrete in field, interest in material properties of early-age concrete is rising. Setting time with hydration process of cement is one of significant indicator to evaluate the early-age material properties of concrete, various nondestructive methods including penetration resistance measurement have been proposed to estimate setting time. This study performed an experimental approach to evaluate setting time delay in mortar adding superplasticizer using electrical resistivity measurement. For this purpose, total nine types of mortar samples were prepared, and its electrical resistivity was monitoring during 24h after mixing. From the experimental result, rising time of electrical resistivity was used to evaluate setting delay of mortar, and penetration resistance was also measured for comparison. In addition, dynamic elastic modulus and compressive strength of 1day mortar were measured to investigate a possibility the use of electrical resistivity measurement for evaluation of early-age material properties.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.1
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• pp.80-91
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• 2022

This study is to provide an prediction model of setting time of super retarding mortar based on equivalent age method under various super retarding agent contents, curing temperature, and water-binder ratio (W/B). An equation for predicting setting time using maturity was proposed. Test results indicated that the setting time can be predicted by determining the curing temperature, W/B, and super retarding agent contents and substituting it into the equation proposed in this study. The coefficient of determination of the equation is 0.9 or more, and the reliability was confirmed through the F-test. Finally, using the equation proposed in this paper, reasonable quality control is possible regarding the setting of super retarding concrete in practice.

• Journal of the Korea Institute of Building Construction
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• v.23 no.6
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• pp.673-682
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• 2023

This study investigates the delay in setting characteristics of mortar influenced by variations in super retarding agent(SRA) content, curing temperature, and strength levels. Utilizing a settimeter, the research introduces an objective approach to accurately determine the setting time of concrete with SRA under diverse environmental and material mixing conditions at construction sites. The findings indicate that the settimeter, in conjunction with a nonlinear regression model, can effectively estimate the setting time of super retarding mortar. Optimal management of the initial setting is recommended at approximately 45ST and the final setting around 80ST. This methodology enables more effective quality control in the setting times of super retarding concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.127-128
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• 2020

This research is part of the research for unifying the mass concrete and utilizing the rate of super retarding agent. We analyzed the performance of super retarding agent 20℃ conditions. It was found that there was no deterioration in fluidity and air quality due to the change in the super retarding agent mixing rate. It was found that when super retarding agent was mixed up to 0.5 %, it was delayed for 22.3 hours at 20℃. Therefore in order to ensure the performance required at the site, the super retarding agent mixing rate must be determined by fully considering the situation at the site. In addition it will be analyzed that super retarding agent performance analysis at high temperature will be required in subsequent studies.

• Journal of the Korean Ceramic Society
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• v.41 no.4
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• pp.302-312
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• 2004

This paper presents the experimental results on the properties of the cement mortar with polycarboxylate-type superplasticizers PCA) which were synthesized by different mole ratio of methoxypoly(ethyleneglycol)monomethacrylate (MPEGMAA) and methacrylic acid (MAA) and by different length of polyethyleneoxide (PEO). As the PEO chain was longer and mole ratio of [MPEGMAA]/[MAA] was lower, the fluidity of cement mortar was better. The setting time of mortar with PCA was retarded, and as PEO chain was shorter and [MPEGMAA]/[MAA] was lower, it was more retared. Espeacially, when the molecular weight of MPEGMAA was 475(repeat unit of ethylene oxide=l0), the degree of retardation was the highest of them. The surface tensions of PCA solutions were lower than that of water due to the effect of PEO chain, and also the pore size distribution of cement mortar was influenced by it. The pores in cement mortar with PCA at 28 days were macropores in the range of 7 to 370$\mu\textrm{m}$, and accordingly, the densities and compressive strengths of mortar were lower than those of OPC mortar.

• 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.