• Journal of the Korean Society of Safety
• /
• v.30 no.1
• /
• pp.52-59
• /
• 2015

The aim of the paper is to introduce the statistical definition of the specified compressive strength of the concrete to be used for safety evaluation of the existing structure in domestic practice and to present the practical method to obtain the specified strength by utilizing the non-destructive test data as well as the limited number of core test data. The statistical definition of the specified compressive strength of concrete in the design codes is reviewed and the consistent formulations to statistically estimate the specified strength for assessment are described. In order to prevent estimating an unrealistically small value of the specified strength due to limited number of data, it is proposed that the information from the non-destructive test data is combined to that of the minimum core test data. The the sample mean, standard deviation and total number of concrete test are obtained from combined test data. The proposed procedures are applied to an example test data composed of the artificial numerical values and the actual evaluation data collected from the bridge assessment reports. The calculation results show that the proposed statistical estimation procedures yield reasonable values of the specified strength for assessment by applying the non-destructive test data in addition to the limited number of core test data.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1995.10a
• /
• pp.235-240
• /
• 1995

A 36 stories high multi-use building was designed with the specified concrete strength range of 300~400kg/$\textrm{cm}^2$ On the ground of the concept of compressive strength, adequate mix designing for the concrete, which has the target strength range of 390-520kg/$\textrm{cm}^2$, was carried out to provide enough strength margin. And with due regard to the workability and transportation time, the slump and slump flow ranged 16~21cm and 30~45cm respectively, maintaining these properties up to 2-hours from the beginning of the mix. The high-range water reducer is incorporated into the mix as a admixture. The building construction is controlled satisfactorily, so far. The actual average 28-day compressive strength is 370kg/$\textrm{cm}^2$, the standard deviation is 28kg/$\textrm{cm}^2$ and the coefficient of variation is 7.6% for concrete of 300kg/$\textrm{cm}^2$ specified strength.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2017.11a
• /
• pp.11-12
• /
• 2017

The properties of concrete produced by ready mixed concrete company in Busan were tested. Because the concrete was mixed with blast furnace slag and fly ash, the compressive strength and chloride ion diffusion coefficient were lower than OPC concrete even though the specified concrete strength was same. If the durability about salt attack were satisfied, the concrete of lower specified concrete strength would be adopted to concrete mixing design.

• Journal of the Korea Institute of Building Construction
• /
• v.6 no.3 s.21
• /
• pp.123-129
• /
• 2006

In these days, as building structures are getting taller, larger, and more diversified, structural systems with more economy and more efficiency are being required and so are more efficient building materials, this study conducted a basic experiment to conclude an adequate selection of materials and to calculate an optimal mixing proportion of those materials to produce High-strength concrete in a 100MPa of specified concrete strength. And also we conducted an experiment to find out basic properties of this concrete such as slump-flow, strength.

• Magazine of the Korea Concrete Institute
• /
• v.17 no.1 s.84
• /
• pp.54-59
• /
• 2005

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2018.05a
• /
• pp.136-137
• /
• 2018

The properties of concrete produced by ready mixed concrete company in Busan were measured. Because the concrete was mixed with blast furnace slag and fly ash etc., the compressive, tensile strength and chloride ion diffusion coefficient were lower than OPC concrete even though the specified concrete strength was same. If the durability about salt attack were satisfied, the concrete of lower specified concrete strength would be adopted to concrete mixing design. FEM analysis was carried out to predict the life time expectancy.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1992.10a
• /
• pp.185-190
• /
• 1992

ACI318-89 Recommended that when the specified compressive strength of concrete in a column is greater than1.4 times that specified for a floor system, top surface of the column concrete shall extend 2ft(600mm)into the slab from the face of column to avoid unexpected brittle failure. The major variables are extension distance, flexural strength ratio(Mr), and shear reinforcement ratio(Vs). Test results are as follows ; (1) The failure modes of specimens under cyclic loading were concentrated at critical region from beam-column joint face. (2) Ductility index($\mu$f) were increased with increasing of shear confinement ratio and flexural strength ratio. (3)The specimens with 2ft extension distance showed more ductility than the specimens with 1ft extension distance.

• Journal of the Korea Institute of Building Construction
• /
• v.18 no.6
• /
• pp.543-550
• /
• 2018

The RC buildings which are constructed on the seaside are followed by KBC(2016) to achieve the minimization of durability damage. To control the corrosion of the reinforcing steel bar by salt attack, W/C should be under 0.4 and specified concrete strength is higher than 35MPa in the concrete/building construction standard specification. Even though it has been proved that the concrete mixed with mineral admixture such as blast furnace slag and fly ash etc. have high strength and durability in previous researches, the beneficial informations are not applied to the codes. Ready-mixed concretes which usually include the admixtures in Busan were tested to certify the salt attack durability. In the same specified concrete strength, remarkable salt attack durability was evaluated in comparison to OPC. For economical and reliable durability design, chloride ion diffusivity should be measured before applying to new building construction.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.83-88
• /
• 2003

In this paper, the medium strength self-compacting concrete with simple mix design method was manufactured and investigated about the properties of flowability and strength. Two types of binders like as fly-ash and RP(rock powder) were contained to the SCC in order to obtain the target medium strength of 270-350kgf/$cm^2$. The experimental tests about slump-flow, reaching time to the slump-flow of 50cm, V-funnel and U-box were carried out in accordance with the specified by the Japanese Society of Civil Engineering(JSCE). The mechanical properties such as compressive strength, splitting tensile strength and static modulus of elasticity were checked with the requirements specified by KS.

• Journal of the Korea Institute of Building Construction
• /
• v.8 no.2
• /
• pp.107-112
• /
• 2008

According to Korean Architectural Standard Specification (KASS) , at the design stage of the specified concrete strength, strength correction with each temperature level should be considered to secure required strength at 28 days even in low temperature condition, In this paper, the period for the strength correction at the stage of mixture design of the concrete using ordinary Portland cement(OPC) specified in KASS was determined with each region of south Korea based on the meteorological data of KMA(Korea meteorological administration) by applying KASS-5 regulation. In case of 28 days of strength control age, the period for strength correction with 6MPa was calculated to $50{\sim}60$ days and, with 3 MPa. to around 80 days. The period for the strength correction was shown to be decreased with the rise of altitude. The period to consider the delay of the strength development due to low temperature including the period of cold weather concrete was nearly 7 months around 1 year. References for determining the strength correction factors with each region of south Korea was provided in this paper. Further investigation of strength correction of the concrete containing blended cement is to studied.