• Journal of the Korea Institute of Building Construction
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• v.17 no.2
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• pp.127-134
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• 2017

In this study, moist curing equipment was used in the exist gang-form system. By achieving sufficient spray curing, the quality of the concrete was improved and the cracking occurred in building's side wall was decreased. The following results could be made as the conclusion. For the compressive strength, all zones showed the similar results. Comparing with the zone without using moist curing equipment, the zone used moist curing equipment showed higher rebound hardness results. For the cracking, the zone utilized moist curing equipment showed the cracking averaged as 6.6 m and the zone without using moist curing equipment showed the cracking averaged as 10.3m. The effectof reducing cracking by utilizing moist curing equipment is about 36 %. Using moist curing equipment is considered as a good solution to reduce the cracking in the structure. Considering all the factors analysed, using moist curing equipment improved the quality of the concrete and decreased the cracking. When this equipment was used in the construction site, it is expected that the construction periodcan be shrunk and the ratio of defect caused by drying shrinkage can be decreased. In this research conditions, The 0.3mm sized moist curing equipment provided the most desirable results on concrete quality and preventing cracking.

• Advances in concrete construction
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• v.9 no.1
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• pp.33-41
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• 2020

In this study, polyethylene glycol (PEG) and polyacrylamide (PAM) have been used as self-curing agents to produce self-curing concrete (SC). Compressive strength, ultrasonic pulse velocity (UPV), bulk electrical resistivity, chloride ion penetrability, water permeability, and main microstructural characteristics were examined under different curing regimes, and compared to those of the control concrete mixture with no self-curing agents. One batch of a control mixture and one batch of a SC mixture were air-cured in the lab to act as non-water-cured samples. The water curing regimes for the control mixture included continuous water curing for 3, 7, and 28 days and periodical moist curing using wetted burlap for 3 and 7 days. Curing regimes for the SC mixtures included 3 days of water curing and periodical moist curing for 3 and 7 days. SC mixtures showed better microstructure development and durability performance than those of the air-cured control mixture. A short water curing period of 3 days significantly improved the performance of the SC mixtures similar to that of the control mixture that was water cured for 28 days. SC concrete represents a step towards sustainable construction due to its lower water demand needed for curing and hence can preserve the limited water resources in many parts of the world.

• Computers and Concrete
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• v.21 no.5
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• pp.485-493
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• 2018

Statistical analysis has found useful application in the design of experiments (DOE) especially optimization of concrete ingredients however, to be able to apply the concept properly using computer aided applications there has to be an upper and lower limits of responses fed to the system. In this study, the production of high-performance steel fiber concrete (HPSFC) at five different fiber addition levels by volume with two aspect ratios of 60 and 83 were studied under two curing methods completely dry cured (DC) and moist cured (MC) conditions. In other words, this study was carried out for those limits based on material properties available in North Cyprus. Specimens utilized were cubes 100 mm size casted and cured for 28 days and tested for compressive strength. Minitab 18 statistical software was utilized for the analysis of results at a 5 per cent level of significance. Experimentally, it was observed that, there was fluctuation in compressive strength results for the two aspect ratios and curing regimes. On the other hand P-value hypothesis evaluation of the response showed that at the stated level of significance, there was a statistically significant difference between dry and moist curing conditions. Upper and lower limit values were proposed for the response to be utilized in DOE for future studies based on these material properties. It was also suggested that for a narrow confidence interval and accuracy of the system, future study should increase the sample size.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.255-257
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• 2012

Epoxy resin without any hardener can harden in the presence of hydroxide ions in cement mortars and concretes at ambient temperature. The purpose of present study is to examine the hardening properties of hardener-free epoxy-modified mortars by curing conditions. The hardener-free epoxy-modified mortars using diglycidyl ether of A epoxy resin are prepared with various polymer-cement ratios, and subjected to initial moist/dry curing, initial steam(90℃) curing, initial steam/heat(80℃, 100℃) curing.As a result, degree of hardening of epoxy resin in initial moist/dry cured, initial steam cured and initial steam/heat(80℃) cured hardener-free epoxy-modified mortars is decreased with increasing polymer-cement ratio. However, it is markedly improved with additional dry-curing periods. On the other hand, regardless of the polymer-cement ratio and dry curing periods, degree of hardening of hardener-free epoxy-modified mortars with initial steam/heat(100℃) cure is over 95%.

• Structural Engineering and Mechanics
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• v.58 no.6
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• pp.989-999
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• 2016

Moist curing of concrete is a time consuming procedure. It takes minimum 28 days of curing to obtain the characteristic strength of concrete. However, under certain situations such as shortage of time, weather conditions, on the spot changes in project and speedy construction, waiting for entire curing period becomes unaffordable. This situation demands early strength of concrete which can be met using accelerated curing methods. It becomes necessary to obtain early strength of concrete rather than waiting for entire period of curing which proves to be uneconomical. In India, accelerated curing methods are used to arrive upon the actual strength by resorting to the equations suggested by Bureau of Indian Standards' (BIS). However, it has been observed that the results obtained using above equations are exaggerated. In the present experimental investigations, the results of the accelerated compressive strength of the concrete are used to develop the regression models for predicting the short term and long term compressive strength of concrete. The proposed regression models show better agreement with the actual compressive strength than the existing model suggested by BIS specification.

• International Journal of Concrete Structures and Materials
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• v.4 no.1
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• pp.9-15
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• 2010

Silica fume is a common addition to high performance concrete mix designs. The use of silica fume in concrete leads to increased water demand. For this reason, Florida Department of Transportation (FDOT) allows only a 72-hour continuous moist cure process for concrete containing silica fume. Accelerated curing has been shown to be effective in producing high-performance characteristics at early ages in silica-fume concrete. However, the heat greatly increases the moisture loss from exposed surfaces, which may cause shrinkage problems. An experimental study was undertaken to determine the feasibility of steam curing of FDOT concrete with silica fume in order to reduce precast turnaround time. Various steam curing durations were utilized with full-scale precast prestressed pile specimens. The concrete compressive strength and shrinkage were determined for various durations of steam curing. Results indicate that steam cured silica fume concrete met all FDOT requirements for the 12, 18 and 24 hours of curing periods. No shrinkage cracking was observed in any samples up to one year age. It was recommended that FDOT allow the 12 hour steam curing for concrete with silica fume.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.693-696
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• 2008

In order to assess time-dependent behaviors of the high-strength concrete that applied in actual FCM bridges with various curing environments, the shrinkages of air-dried, sealed, and moist 100${\times}$100${\times}$400 mm prism specimens were measured. And the compressive creep test of 3 and 28 days aged concrete in the tap water and 10% CaCl$_2$ solutions were carried out, then results were compared with traditional test results of air-dried and sealed specimens. Time-dependent behaviors of the concrete that according to curing circumstances between sealed and moist specimens show remarkable differences not only on the shrinkage but also on the creep. Hence there need some reconsiderations to the traditional creep test manners that predicting the creep and shrink age of actual concrete structures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.2
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• pp.67-73
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• 2016

When assessing crack initiation of fiber reinforced concrete, usually tensile strength or flexural strength is becomes indicator, but also depend on the curing effect take place during the production of specimen. In general, after conducting concrete specimen is cured by water at temperature $20{\pm}3^{\circ}C$ in laboratory, and accomplished the assessment of strength, but most of concrete structure is kept in drying condition after moist curing through the prescribed period. However, unlike these trends that technological advances have been made, influence of the difference of curing method on crack strength is not yet clear. Therefore, in this study, it is examined on the effect of curing methods affecting the mechanical property of fiber reinforced concrete, especially crack strength.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.2
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• pp.87-93
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• 2018

The use of high-strength concrete in construction have been increasing steadily. However, high-strength concrete has a low water-binder ratio, and the problems such as cracks due to hydration heat and shrinkage during the hydration process at the early age. Recently, as a method to reduce the shrinkage of concrete, study of internal curing has carried out according to increasing about interest about it. In this study, the effect of compressive strength on the curing condition(drying, moist, water) was investigated by using artificial lightweight aggregate(LWA) in high strength and high volume mortar. As a result of autogenous shrinkage, the effect of shrinkage reduction was enhanced depending on the increasing of LWA replacement. According to the curing condition, the results of compressive strength showed the different trend. The compressive strength has increased on the drying and moisture condition and decreased on the water condition.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.6
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• pp.501-508
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• 2007

This paper presents the feasibility of using electromechanical impedance based active sensing technique for nondestructive strength gain monitoring of early-age concrete by employing piezoelectric lead-zirconate-titanate (PZT) patches on concrete surface. The strength development of early age concrete is actively monitored by performing a series of experiments on concrete specimens under moist curing condition. The electrical admittance signatures are acquired for five different curing ages and compared with each other. The resonant frequency shifts of PZT patches with increasing days is observed which is on account of additional stiffening due to strength gain of concrete during curing and level of stiffening being related to strength obtained from compression tests on companion cylinder specimens. The proposed approach is found to be suitable for monitoring the development of compressive strength in early-age concrete. It is also observed in this study that root mean square deviation (RMSD) in admittance signatures of the PZT patches can also be used as an indicator of concrete strength development.