콘크리트 전기비저항 내구성 시험

영신컨설턴트 (02) 529 8803 ystcha@naver.com 2020 9

 

콘크리트에 물이나 염화물이 침투하면 알카리 콘크리트는 염화물로 전기저항이 작아지고 콘크리트 내구성이 떨어지고 철근이 부식될 수 있다. 콘크리트에 물이나 염화물이 침투하면 전기전도도 (electrical conductivity) 높아 전기비저항으로 콘크리트 내구성을 평가할 수 있다.

 

 

콘크리트 전기비저항 시험

 

 

콘크리트 전기비저항과 철근콘크리트 부식속도

 

 

시험실 콘크리트 몰드 수직 전기비저항 측정

 

콘크리트 몰드 수평 전기비저항 측정

 

시험방법

AASHTO T358 Surface Resistivity Indication of Concrete’s Ability to Resist Chloride Ion

 

 

콘크리트 염화물 침투에 대한 전기저항 측정

 

 

 

AASHTO T277 (ASTM C1202) test setup

 

흡수 시험 Absorption

콘크리트의 흡수는 공극과 관련된다.

AS 1012.21. BS 1881: Part 122 and ASTM C642 are the respective Australian, British and American Standard test methods for water absorption determination.

Absorption has been used as a measure for durability in concrete products such as pipes and blocks. It has not been commonly used to measure the chloride resistance of concrete, possibly because it is not a good indicator of chloride diffusion coefficient as shown

 

콘크리트 모세관압력 Sorptivity

a measure of one-dimensional capillary absorption rate as a function of time and provides a good indication of the pore structure and its connectivity of the near-surface concrete.

There are two methods of measuring sorptivity.

The first (RTA T362) measures the depth of penetrating water front into the concrete and the second (ASTM C1585-04) measures the depth of water penetration indirectly through the weight gain in the concrete.

 

The sorptivity is calculated from the slope of the curve of the depth of water penetration with time in mm/hour½ or the weight gain against time and converted into mm/min½ or mm/s½ for there spective methods.

 

The Roads and Traffic Authority of New South Wales (RTA) has used sorptivity16 as an alternative performance-based specification (Provision A) in RTA B 80 specifications 31. The RTA sorptivity for exposure classes B2 and C Table 5.3 is measured over a soaking period of 24 hours, hence RTA sorptivity of 1 mm is equivalent to 0.026 mm/min½, and RTA sorptivity of 3.8 mm is equivalent to 0.1 mm/min½

 

 

Influence of RTA sorptivity on medium-term effective chloride diffusion Sorptivity has been found to be a good performance indicator of chloride resistance of concrete. the relationship between sorptivity and medium-term effective chloride diffusion coefficients of a range of concretes (one Type GP and three Type GB) is shown to have reasonably good correlation (R = 76%). Lower sorptivity indicates better chloride resistance.

 

염화물 이동에 대한 시험방법

 

확산 Diffusion

Chloride diffusion coefficient, De. 28 (10–12 m2/s)

 

모세관압력 Capillary absorption

Absorption (%)

Sorptivity (mm/min1/2),

Initial Surface Absorption Test, ISAT (10–2 ml/m2/s)

Volume of Permeable Voids, VPV (%)

Compressive strength, f28 (MPa), an indirect measure of porosity

 

Permeability

Water Permeability Coefficients, K (m/s)

Migration Rapid Chloride Permeability Test, RCPT (Coulomb)

 

All transport

Water-cement ratio, w/c.

 

콘크리트 수화열 측정

 

 

현장 콘크리트 모세관 압력 측정 센서

 

 

콘크리트 타설 후 체적변화와 모세관 압력(capillary pressure)

콘크리트 타설 후 시간경과에 따른 bleeding,증발 water evaporation, 모세관 menisci형성 균열발생