Faculty of Engineering Division of Built Environment Laboratory of Engineering for Maintenance System Hokkaido University Clarification of Frost Damage Mechanism Based on Meso scale Deformation and Temperature and Moisture Change EVDON LUZANO SICAT, M1

LOGO Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for Maintenance System Contents RESEARCH OUTLINE B EXPERIMENTAL OUTLINE C BACKGROUND: FORST DAMAGE MECHANISM A

LOGO Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for Maintenance System Background Freeze-thaw Deterioration Concrete, like other highly divided porous media, has the ability to absorb and retain moisture. This characteristic has an important consequence since unprotected concrete structures in contact with water are usually susceptible to frost damage.

LOGO Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for Maintenance System Background Frost Damage Mechanism Concrete Condition: Unsaturated The pore structure is filled by small amount of water. Once temperature drops to 0 º C – Thermal contraction occurs. From 0 º C to minimum temperature – Water in larger pores freezes. From freezing temperature to thawing – ice melts and water flows to pore spaces. ice water

LOGO Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for Maintenance System Background Frost Damage Mechanism Concrete Condition: Saturation Process -Possible only if water is available outside during thawing at temperature above 0 º C. -When freezing for temperature below 0 º C – water freezes and volume expands (can create tension to concrete). -At temperature below -10 º C to minimum temperature – ice contracts in larger pores. - -From minimum temperature to -5 º C during thawing – ice expands more than surrounding concrete. Contracted Ice water Increment pore space

LOGO Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for Maintenance System Background Frost Damage Mechanism Concrete Condition: Saturated Condition -In this condition, the pore structure is totally filled by water. -As temperature continues to drop, the expansion of water creates a very high positive hydraulic pressure. -For lowest temperature – water in smaller pores also freezes. Ice Larger cracks Smaller pores begin to freeze

LOGO Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for Maintenance System Research Outline  Objective: To clarify the effect of temperature history and moisture conditions on concrete that are under the effect freezing and thawing actions.  Previous Model Consideration (Oiwa-san’s Model): Strains caused by temperature difference and ice formation. Where: ε T is linear expansion strain, α is linear expansion coefficient;10 [/ ℃ ], T d is temperature difference, ε i is expansion strain caused by ice formation, α i is freezing expansion coefficient; 6250 [μ], Ψ i is ice content.

LOGO Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for Maintenance System Research Outline Some considerations:  Residual strain was not taken into account during freezing and thawing cycles.  Specimens are analytical model, for its viability: results must have a comparison with experimental data.  Super cooling and expansion of water when freezing are not considered.

LOGO Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for Maintenance System Research Outline Model Proposal (Arai-san’s Paper): The total strain ε for the transformation model of mortar due to frost damage is assumed to be composed of three strains which are presented as follows: ε i : Expansion strain when freezing ε s : Shrinkage strain when freezing ε t : Temperature strain

LOGO Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for Maintenance System Research Outline  The model of expansion strain when freezing ε i is a function of ice content ratio Ψ i. When moisture content ratio is small, the expansion is not caused. Then, the following expressions are assumed. α i : Constant of proportion that changes by rigidity of mortar Ψ ic : Ice content ratio when transformation began to depend on ice content ratio  The shrinkage when freezing is thought to be shrinkage by the movement of the unfrozen water. It is expressed as follows by assumption that the transformation depends on the unfrozen rate. α s : Constant of proportion that shows unfrozen rate contributes to shrinkage. It changes by the rigidity of mortar.) ψ : moisture content ratio  The temperature strain is expressed as follows by linear coefficient of expansion αt. Δ T : Temperature difference

LOGO Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for Maintenance System Experimental Plans Purpose of the Experiment:  To obtain the following coefficients experimentally; thermal expansion, freezing expansion, and shrinkage contraction and then apply them in the proposed frost damage mechanism model. - Freezing strain - Shrinkage strain - Thermal Strain

LOGO Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for Maintenance System Experimental Plans  Specimens to be Used Mortar will be use as test specimen in this experimental program. A. Materials Characteristics: Cement – Ordinary Portland cement (Density: 3.14 g/cm3) Fine Aggregate (from Mukawa) (Size: 1.2mm and Density: 2.67 g/cm3) Air-Entraining Agent – None (To Promote Frost Damage) Water cement ratio （％） Water （ kg/m 3 ） Cement （ kg/m 3 ） Fine Aggregate （ kg/m 3 ） Table-1 Mix Proportions (Mortar)

LOGO Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for Maintenance System Experimental Plans  Preparation of Specimens Casting and mold - 40 x 40 x 160 mm form Curing Period – 60 days (Moist Condition - 23ºC) Specimen dimension - 40 x 40 x 2 mm Table -2 (Specimen set and Moisture Conditions) 5 Specimens/SetMoisture ConditionPurpose AAbsolutely DryThermal Expansion B(Nearly or Fully) SaturatedFreezing Expansion C % SaturatedShrinkage Contraction D80 –90% SaturatedComparison to Model’s Output

LOGO Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for Maintenance System Experimental Plans  To attain different kind of moisture conditions on specimens, they will be subjected in different desiccators with different kind of salt solution. Table-3 Salts solutionsDesiccators Salts (Potassium Nitrate) KNO 3 (Potassium Chloride) KCl Chloride) NaCl Graph from AGM Container Controls, Inc. (AGM)

LOGO Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for Maintenance System Experimental Plans  Experimental Set-up Specimens Data logger PC Environmental Chamber Temperature sensor Specimen support Temperature History Cycle for Set A, B, and C Specimens Temperature History Cycle for Set D Specimens Temperature increment: 0.5ºC/minute Coefficients,, and can be approximated by formula of coefficient of linear expansion.

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