• Journal of the Korea Institute of Building Construction
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• v.1 no.1
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• pp.143-150
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• 2001

Permanent-Form is one of system forms for reducing human labor, work costs, oscillation, noise, construction wastes and so on. Permanent-Form is made from precast method in facilities, and carried in construction site to assemble with no demolding. The biggest expense to produce permanent-Form is about manufacturing mold. This papers about structural efficiency evaluation, construction efficiency test. The result of this study is below. (1) In the compressive strength test of column. Fly ash specimen and polymer specimen's strength developed as each 8%, 14% to comparison with standard specimen. The reason of this result from form section area increase and form's reinforcing bar (2) The Degree of column crack in permanent form is lower than another one's The glass fiber's fiber reinforcement effect brings like this. (3) In the flexural load test of beam, the early crack load and maximum load of permanent form use specimen showed 20% higher than standard specimen's. (4) In field application experiment, an constructional error is satisfied with the allowable margin of error, $\pm$5mm (5) When the concrete is placed into the form inside, The transformation degree of permanent form is lower than plywood form's. (6) The concrete packing ability of permanent form is satisfactory. (7) The bonding strength of permanent form shows enough strength - 6kgf/$\textrm{cm}^2$.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.159-160
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• 2023

Recently, interest in reducing cement has been growing. Hwangto, an eco-friendly material, has advantages such as air purification effect and humidity control, but when used, accidents such as form collapse may occur due to low strength and reduced durability. In order to quantitatively evaluate the timing of mold demolding, we would like to evaluate the timing of mold demolding through correlation with compressive strength using ultrasonic pulse velocity. As a result, the time at which 5 MPa is developed is after 20 hours for the test specimen of W/B 41 , in the case of W/B 33, NC33 and HTC33-15 were equally expressed at 12 hours, and HTC33-30 was expressed at 16 hours.

• Journal of the Korea Institute of Building Construction
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• v.23 no.6
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• pp.683-692
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• 2023

This research assesses the mechanical properties of concrete, utilizing both normal and lightweight aggregates, through measurements of compressive strength and ultrasonic pulse velocity. The study observed that concrete with normal aggregates exhibited higher compressive strength in its initial stages, whereas concrete with lightweight aggregates showed increased strength over time, likely attributed to the higher water absorption rate of lightweight aggregates. Ultrasonic pulse velocity generally registered higher in normal aggregate concrete, barring a specific duration, presumably due to variations in the internal pore structure of the aggregates. The correlation coefficient(R²) for the strength prediction equation, derived from the relationship between compressive strength and ultrasonic pulse velocity, exceeds 0.95. This high correlation suggests that the predictive equation based on these experimental findings is a reliable method for estimating concrete strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.152-153
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• 2017

In the construction site, it is necessary to estimate the compressive strength of concrete in order to adjust the demolding time of the form, and establish and adjust the construction schedule. The compressive strength of concrete is determined by various influencing factors. However, the conventional method for estimating the compressive strength of concrete has been suggested by considering only 1 to 3 specific influential factors as variables. In this study, six influential factors (Water, Cement, Fly ash, Blast furnace slag, Curing temperature, and humidity) of papers opened for 10 years were collected at three conferences in order to know the various correlations among data and the tendency of data. After using algorithm of various methods of machine learning techniques, we selected the most suitable regression analysis model for estimating the compressive strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.83-84
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• 2017

In the construction site, it is necessary to estimate the compressive strength of concrete in order to adjust the demolding time of the form, and establish and adjust the construction schedule. The compressive strength of concrete is determined by various influencing factors. However, the conventional method for estimating the compressive strength of concrete has been suggested by considering only 1 to 3 specific influential factors as variables. In this study, seven influential factors (W/B ratio, Water, Cement, Fly ash, Blast furnace slag, Curing temperature, and humidity) of papers opened for 10 years were collected at three conferences in order to know the various correlations among data and the tendency of data. The purpose of this paper is to estimate compressive strength more accurately by applying it to algorithm of the Deep learning.

• Journal of the Korea Institute of Building Construction
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• v.2 no.4
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• pp.169-176
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• 2002

To study of binder and fine aggregate a lot of replacement fly-ash concrete, initial characteristics, standard environment of curing temperature $20^{\circ}C$, hot-weather environment, cold weather environment of curing temperature $5^{\circ}C$. Flash concrete tested slump, air contest, setting and Hardening concrete valuated setting period of form, day of age 3, 7, 28 compression strength in sealing curing. Underwater curing specimen compression strength of age 3. 7, 28day used strength change accordingly fly-ash concrete curing temperature. Purpose of study is consultation materials in field that variety of fly-ash replacement concrete mix proportion comparison and valuation. (1) Setting test result, fly-ash ratio of replacement higher delay totting time. Same volume of fly-ash ratio of replacement is lower fly-ash ratio of replacement fine aggregate delay setting time. Setting test in curing temperature $35^{\circ}C$ over twice fast setting in curing temperature $20^{\circ}C$ and all specimen setting delay in curing temperature $5^{\circ}C$. F40 specimen end of setting about 30 time. (2) Experiment result age 28day compression strength more fisher plan concrete then standard environment in curing temperature $20^{\circ}C$, cold weather environment in curing temperature $5^{\circ}C$, most strength F43 is hot-weather environment in curing temperature $35^{\circ}C$ replacement binder 25%, fine aggregate 15%. (3) Hot-weather environment replacement a mount of fly-ash is a same of plan concrete setting period of form. Age 28day compression strength replacement a mount of fly-ash more hot-weather concrete then plan concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.965-968
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• 2008

The KS F 2403 method used on domestic sites for checking the compressive strength of a structure, sets the compressive strength of the concrete used in structural specimens as the compressive strength of testing specimens. Under this regulation, the curing method used for testing the specimens must be the standard ponding curing method (20$\pm$2$^{\circ}$C). However, because in-placed concrete is exposed to open air and cured under the seasonal temperature changes, the compressive strength of a real structure is different from the tested compressive strength. (Therefore,) This thesis first identifies the distinct characteristics of the strength development by applying the curing method listed under the KS and used for testing specimens on compressive strength tests; the atmospheric curing method, the sealed curing method, and the structural specimen core strength testing methods used for the in-sites quality checks including reckoning of the compressive strength of the structural specimens and form-demolding period; and the curing method suggested in this research, which sets the internal conditions of the structural specimens as the conditions of the applied curing method. Then, the thesis suggests the specimen curing method that most closely reenacts the compressive strength of the concrete used on the structural specimens

• Journal of the Korea Institute of Building Construction
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• v.10 no.4
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• pp.113-122
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• 2010

In this study, 150MPa ultra-high-strength concrete was manufactured, and its performance was reviewed. As technically meaningful autogenous shrinkage reportedly occurs at a W/B ratio of 40% or less, although it occurs in all concrete regardless of the W/B ratio, the effects of the use of expansive admixture and shrinkage reducer, or of the friction and restraint of forms that may result in the effective reduction of autogenous shrinkage, were reviewed. As a result, considering the flow and strength characteristics, it was found that the slump flow time was shorter with expansive admixture, and shortest with shrinkage reducer. All specimens with $30kg/m^3$ expansive admixture showed high strength at early material age. Their strength decreased due to the expansion cracks when there was excessive use of expansive admixture, and the use of shrinkage reducer did not influence the change in the strength according to the material age. The expansive admixture had a shrinkage reduction effect of 80%, while the shrinkage reducer had a shrinkage reduction effect of 30%, indicating that the expansive admixture had a stronger effect. It seems that mixing the two will have a synergistic effect. The shrinkage reduction rate was highest when the W/B ratio was 20%. The form suppressed the expansion and shrinkage at the early period, and the demolding time did not significantly influence the shrinkage. The results of the study showed that the excessive addition of expansive admixture leads to expansion cracks, and the expansive admixture and shrinkage reducer have the highest shrinkage reduction effect when they are mixed.