• Journal of the Korea Institute of Building Construction
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• v.8 no.3
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• pp.111-117
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• 2008

This study provides the setting time prediction method of super retarding concrete incorporating mineral admixtures at the same time including fly ash(FA), blast furnace slag(BS) based on maturity method. The setting time was retarded, as super retarding agent contents increase and curing temperature decreases. In addition, apparent activation energy by Arrhenius function was ranged from $24{\sim}35KJ/mol$ with slightly difference along with mixture proportion. This value is smaller than existing value $30{\sim}50KJ/mol$. It is Indicated that equivalent age using setting time can be a proper method to predict setting time and it also exhibited comparable relativity between prediction value and measurement value. Therefore, this study provided setting time prediction value with super retarding agent contents and mineral admixture combination. Setting time prediction equation provided herein is possibly valid for estimating precise setting time of the super retarding concrete at the job site.

• Computers and Concrete
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• v.32 no.2
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• pp.185-206
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• 2023

This article aimed to explore the optimization of mineral admixtures and retarding admixture for high-performance concrete. In essence, fresh concrete can be regarded as a mixture in which both coarse and fine aggregates are suspended in a cement-based matrix paste. Based on this view, the test procedure was divided into three progressive stages of binder paste, mortar, and concrete to explore their rheological behavior and mechanical properties respectively. At each stage, there were four experimental control factors, and each factor had three levels. In order to reduce the workload of the experiment, the Taguchi method with an L9(3⁴) orthogonal array and four controllable three-level factors was adopted. The test results show that the use of the Taguchi method effectively optimized the composition of high-performance concrete. The slump of the prepared concrete was above 18 cm, and the slump flow was above 50 cm, indicating that it had good workability. On the other hand, the 28-day compressive strength of the hardened concretes was between 31.3-59.8 MPa. Furthermore, the analysis of variance (ANOVA) results showed that the most significant factor affecting the initial setting time of the fresh concretes was the retarder dosage, and its contribution percentage was 62.66%. On the other hand, the ANOVA results show that the most significant factor affecting the 28-day compressive strength of the hardened concretes was the water to binder ratio, and its contribution percentage was 79.05%.

• Journal of the Korea Institute of Building Construction
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• v.8 no.5
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• pp.119-125
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• 2008

In this paper, the estimation of super retarding concrete incorporating mineral admixtures at the same time including fly ash(FA), blast furnace slag(BS) are studied based on maturity method. The setting time was retarded, as super retarding agent contents increase and curing temperature decreases. In addition, apparent activation energy by Arrhenius function was ranged from $24\sim35$ KJ/mol with slightly difference along with mixture proportion. This value is smaller than existing value $30\sim50$ KJ/mol. Based on strength development estimation. it exhibited comparable relativity between prediction value and measurement value. Therefore, this study provided effective strength development prediction value with super retarding agent contents and mineral admixture combination. Strength development prediction equation provided herein is possibly valid for estimating accurate strength development of the super retarding concrete at the job site.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.747-750
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• 1998

The application of spent liquor(BSL) obtained from alkaline sulfite-anthraquinone cooking of pine bark to cement mortar significantly improved the water-reducing ability and decreased the rate of cement hardening. However, the compressive and flexural strength of BSL addition to cement mortar were lower than that of PLAIN. The application of 0.2% antifoamer to BSL slightly decreased water-reducing ability, but remarkably improved the compressive and flexural strength of cement mortar. On the other hand, BSL decreased the rate of hardening of cement, which exhibited the protperties of the lignosulfonated based retarding water-reducing type. but the setting time of cement could be controlled by addition of Na2CO3 could be used to convert BSL to normal or accelerating concrete admixtures.

• Journal of the Korean Society of Safety
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• v.30 no.3
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• pp.59-66
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• 2015

The undesirable effects of elevated external temperatures at placement on the properties of the fresh and hardened concrete are discussed briefly, and the possible use of the mineral admixtures to mitigate them and the association with water-reducing and retarding admixtures in terms of the mix design which are critical for minimizing slump loss and entrained air loss are examined in this study. To investigate the effects of such the mineral and chemical admixtures on the fresh and hardened properties of concrete exposed to high temperature, a series of concrete mixtures subjected to the high temperature were carried out and then fresh and hardened properties of the mixtures were analyzed and evaluated. Based on the results, new guide lines concerning the appropriate admixtures for hot weather are suggested.

• Proceedings of the Korean Institute of Building Construction Conference
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• v.y2004m10
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• pp.7-10
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• 2004

This paper investigated the possibility of quality restoration of deteriorated concrete caused by long distance delivery using chemical admixtures such as superplasticizer. AE agent and retarding agent. According to test results, long distance delivery lead to reducing fluidity and air content markedly, while setting time accelerated. Quality restoration agent(QRA) was made by combining super- plasticizer. AE agent and retarding agent with the proportion of 1:0.0025:0.1. It was confirmed that deteriorated concrete achieved quality restoration with the level of target slump, air content and setting time without strength loss when using QRA with proper amount.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.95-105
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• 1999

When superplasticizer is added to manufacture flowing concrete, the base concrete usually needs the adjustment to assure the sufficient fines contained to obtain flowable consistency without excessive bleeding or segregation. However, this may not only increase the cost, but also cause inconvenience in producing the base concrete. In this paper, the experiments are performed on normal base concrete to achieve a segregation-reducing flowing concrete by adding superplasticizer mixed with viscosity agents and AE admixtures. Three kinds of superplasticizer and two kinds of viscosity agent are selected. According to the results, with regard to the performance and cost of the admixtures, melamine type superplasticizer combined with the PEO viscosity agent and AE admixtures at the ratio 1:0.28:0.001 can acquire good quality and reduce the cost in producing the flowing concrete. With proper addition of combined superplasticizer, even though water to cement ratios of the base concrete are different, the segregation-reducing flowing concrete could be also achieved without reproportioning of the base concrete. However, it would be more desirable if the superplasticizer could be adjusted, before it is put into the practical use in order not to cause some other problems, such as rapid rate of slump loss and retarding of setting time.

• 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 Korean Ceramic Society
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• v.31 no.10
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• pp.1107-1114
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• 1994

Although various theories have been presented on the mechanism of setting retardation of plaster in addition to organic admixtures. The purpose of this paper is that Hydration studies of plaster of paris in the presence of carboxylic acids under alkalinity are examined in the coordination chemistry. Setting of plaster of paris is retarded by the addition of carboxylic acids except oxalic acid. And setting of plaster of paris contained 5 wt% of Ca(OH)2 is also retarded by the addition of above-mentioned carboxylic acids. The degree of retarding effect under alkalinity is found to be a function of the number of the functional group and the length of carbon chain of carboxyl acids. These reasons are attributed to the soluble complex formation, that is calcium complex formation between calcium ion and carboxylic acids. The author's proposal was confirmed by the results of electrical conductivity measurement. The formation of calcium complex was surpported by IR spectra.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.365-371
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• 2020

In this study, in order to recycle the stems of opuntia cactus discarded after harvesting the fruit, the cactus stems were powdered and applied as a cement-based admixture. The powder of cactus stem was mixed into the mortar, and its effect on the fresh properties and strength of the mortar was studied. The results were compared with the properties of mortars produced by mixing with a retarder sugar and a viscosity agent methyl-cellulose, which are conventional saccharide-based admixtures. Based on the test results, the cactus stem powder did not clearly show the effect as a retarding agent, whereas the flow and the air content were similar to those of the mortar mixed with methyl-cellulose. This indicated that the cactus stem powder can be used as a viscosity agent. It was found that the strength of the mortar tended to increase when the mixing ratio of the cactus stem powder was lower than 0.3%.