Suggestion of the Prediction Model for Material Properties and Creep of 60~80MPa Grade High Strength Concrete

설계기준강도 60~80MPa급 고강도콘크리트의 재료 특성 및 크리프 예측모델식 제안

Abstract

The construction of super tall building which structure is RC and must be certainly considered on column shortening estimation and construction reflected concrete creep has been increased. Regarding the Fck 60~80MPa grade high strength concrete applied in the domestic super tall building project, the mechanical properties and creep deflection according to curing conditions(Drying creep/Basic creep) were reviewed in this research. Results of compressive strength and elastic modulus under sealed curing condition were 5% higher than unsealed condition and difference of results according to the curing condition was increased over time. Autogenous and drying shrinkage tendency showed adversely in the case of high strength concrete. Additionally, creep modulus under unseal curing condition was evaluated 2~3 times higher than sealed condition. Modified model of ACI-209 based on test result was applied to estimate long period shortening of vertical members(such as Core Wall/Mega Column) exactly, it is designed to modify and suggest the optimal creep model based on various data accumulated during construction, in the future.

초고층 RC구조물 건설은 콘크리트 크리프에 대한 반영이 반드시 검토되어야 한다. Fck60~80MPa를 적용하는 국내 초고층 건축물에 대하여 각종 역학적 특성과 양생조건(Dried/Sealed)별 크리프에 대해 검토하였다. Sealed 조건에서의 압축강도 및 탄성계수는 Unsealed 조건에 비해 약 5% 높게 나타났으며, 시간이 지날수록 차이가 크게 나타났다. 크리프 계수의 경우 Unsealed 조건에서 Sealed 조건 대비 2~3배 높게 평가되었고, ACI 209 모델을 보완한 수정 예측 모델의 경우 수직부재(코어월 및 메가칼럼)에서의 장기재령 예측식으로 적용하였다. 향후 실제 부재에서 측정되는 다양한 데이터를 바탕으로 최적 크리프 모델에 대해 보완 및 제안할 예정이다.

Figure 1. Creep strain with curing conditions

Figure 3. Compressive strength according to fck

Figure 4. Elastic modulus according to fck

Figure 5. Test Results of autogenous and drying shrinkage

Figure 6. Creep coefficient (unsealed condition–drying creep)

Figure 7. Creep coefficient (Sealed Condition– Basic creep)

Figure 8. Modified factor of Creep coefficient (@28Days)

Figure 2. Test method of concrete deformation

Table 1. Design of experiment

Table 2. Mix proportion of concrete

Table 3 Mechanical properties of material

Table 4. Mechanical properties of spalling resistance fiber

Table 5. Compressive strength and elastic modulus according to the ages