• Journal of the Korea Institute of Building Construction
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• v.12 no.1
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• pp.87-97
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• 2012

This paper presents a method of estimating the setting time of cement mortar incorporating recycled aggregate powder (RP) and cement kiln dust (CKD) at various curing temperatures by applying an equivalent age method. To estimate setting time, the equivalent age using apparent activation energy (Ea) was applied. Increasing RP and CKD leads to a shortened initial and final set. Ea at the initial set and final set obtained by Arrhenius function showed differences in response to mixture type. These were estimated to be from 10~19 KJ/mol in all mixtures, which is smaller than those of conventional mixture ranging from 30~50 KJ/mol. Based on the application of Ea to Freisleben Hansen and Pederson's equivalent age function, equivalent age is nearly constant, regardless of curing temperature and RP contents. This implies that the concept of maturity is applicable in estimating the setting time of concrete containing RP and CKD. A high correlation was observed between estimated setting time and measured setting time. A multiregression model was provided to determine setting time reflecting RP and CKD. Thus, the setting time estimation method studied herein can be applicable to concrete incorporating RP and CKD in the construction field.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.335-339
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• 2007

A jointed plain concrete pavement(JPCP) slab was tested in Incheon International Airport construction work to study the early-age property of JPCP slab. The temperature and moisture data of the concrete slab had been collected and analyzed. The setting time of the concrete was decided by using the maturity method. The initial setting time is 2 hours 40 minutes after the placement of the slab. The investigation and analysis of the slab began from the initial setting time. The strains of different locations and different depths of the slab show different variation character.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.935-938
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• 2001

This paper reports the relation of concrete setting characteristic and lateral pressure in mass concrete wall such as side wall of LNG underground storage tank. In order to estimate the lateral pressure, initial setting time of low heat cement concrete with type of mineral admixture was measured for three concrete mixtures(W/P=41.6%) containing limestone powder, fly ash, and slag powder. As a result, the lateral pressure of the concrete containing limestone powder was the smallest than those of other concretes as well as the initial setting time.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.358-366
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• 2019

The purpose of this study is to explore the possibility of estimating optimum surface finishing work time of the fresh concrete placed at the job site by applying a surface hardness test meter(Durometer). Tests are carried out by measuring and comparing the Proctor penetration resistance test and hardness test by Durometer. Correlations between Procter penetration test and hardness test by Durometer were obtained. Two different types Durometer were applied to estimate setting time. Test results indicate that the measurement of the Durometer and the test of the Proctor penetration resistance are highly correlated. When measuring the initial setting time with Durometer, initial setting time is reached when the hardness value by the type C Durometer is reached around 42HD, and when final setting is measured with the type D Durometer, the surface finishing work time limit and curing time can be estimated with 10HD of Durometer.

• Journal of the Korea Concrete Institute
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• v.29 no.4
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• pp.361-369
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• 2017

Setting time of cement-based materials can represent a developing strength in early-age mixture, and it can be used a significant parameter of high-performance concrete having various mix-proportions. Generally, initial and final setting time of concrete is measured by penetration resistance method that used a wet-sieving mortar mixture, therefore, it hardly represents the setting time of sound concrete including coarse aggregate. Recently, several nondestructive methods, such as ultrasonic velocity and impendence measurement, are proposed to evaluate the setting time of fresh concrete. This study attempts to measure an electrical resistivity using four-electrode method for evaluation of setting time in early-age cement-based materials. For this purpose, total 10 mixtures are prepared as different mix-proportions including chemical admixture. Based on the experimental results, two electrical parameters, such as initial electrical resistivity and rising time, are proposed to reflect a microstructure development by hydration of cement-based materials. As a result, proposed parameter is also discussed with the measured setting time by penetration resistance method.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.6
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• pp.144-152
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• 2003

Laboratory experiments were carried out to investigate the influence of pore water contamination on the treatment effect of sandy soil which was solidified by Portland cement. In the experiments, setting time of hydraulic cement that was mixed with contaminated mixing water was measured using Vicat equipment and observed the tendency of setting process with the kind of contaminants, organic or inorganic components. It was shown that organic contaminants of the mixing water affect largely on the initial setting process of hydraulic cement and inorganics, expecially heavy metals, did not affect on the initial setting process, otherwise it was appeared that setting time of the sandy soil that was contaminated with inorganic components was apparently faster than the sandy soil that did not include inorganic components even though organic concentrations was relatively low level (COD=200∼300) in the mixing water. The results of unconfined compression strength test (UCST) were well consistent with the results of Vicat equipment test.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.17-18
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• 2023

This study aims to compare the hardness value development characteristics according to the water-cement ratio during a series of experiments to develop a setting estimator for an AI-based concrete finishing automation system. For the test variables, water-cement ratios are varied with 30, 40 and 50%. Proctor penetration test and surface hardness test by setting time estimator are conducted to estimate the setting time. For the effect of water-cement ratios, they did not affect the surface hardness either, while initial set time and final set time are not constant with water-cement ratios.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.103-104
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• 2021

This study attempted to confirm the possibility of estimating condensation time and initial compressive strength with five types of estimation needles in the existing Durometer D type. In order to determine the surface finishing operation time and develop a method for estimating the initial age compression strength, an estimation needle capable of complexly measuring the estimation time and the initial age compression strength based on the Durometer D type was derived as 1.5, 2.0mm.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.707-711
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• 1998

Ultrasonic test usually was used for defect detection, crack depth measurements and strength estimation of hardened concrete. The essence of the pulse velocity method is that the transition time of an ultrasonic longitudinal pulse is measured in concrete. Ultrasonic velocity was propagated to the age of concrete, made a radical change at that time when concrete was setted. This study which monitored the change in a concrete by ultrasonic test was performed to estimate initial setting and final setting.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.269-275
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• 2022

In this study, the setting time and compressive strength of cement paste composites applied with nano-micro pozzolanic binders were experimental analyzed. The pozzolanic binder was reduced initial and final setting time and the compressive strength was increased. Micro silica was effective in decrease the initial setting and final setting time and impressing the compressive strength. When two or more cement binders were used, the using of silica fume and a small amount of nano silica at reduced the setting time to 62-64 % to OPC cement and the compressive strength was increased to 117 %. A small amount of mixing the nano silica was effect to pore filling and pozzolanic activation. However, the addition of a chemical admixture should be considered when mixing table design because pozzolanic binders high specific surface area causes a decrease in cement composites flow.