EVDON LUZANO SICAT, M1

1. EVDON LUZANO SICAT, M1 Clarification of Frost Damage Mechanism Based on Meso scale Deformation and Temperature and Moisture Change

2. C B A RESEARCH OUTLINE EXPERIMENTAL OUTLINE BACKGROUND: FORST DAMAGE MECHANISM Contents Laboratory of Engineering for Maintenance System

3. 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. Laboratory of Engineering for Maintenance System

4. Background Frost Damage Mechanism Concrete Condition: Unsaturated • The pore structure is filled by small amount of water. • Once temperature drops to 0ºC – Thermal contraction occurs. • From 0ºC to minimum temperature – Water in larger pores freezes. • From freezing temperature to thawing – ice melts and water flows to pore spaces. ice water Laboratory of Engineering for Maintenance System

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

6. 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. Larger cracks Smaller pores begin to freeze Ice Laboratory of Engineering for Maintenance System

7. 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: εTis linear expansion strain, αis linear expansion coefficient;10 [/℃], Td is temperature difference, εi is expansion strain caused by ice formation, αi is freezing expansion coefficient; 6250 [μ], Ψi is ice content. Laboratory of Engineering for Maintenance System

8. 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. Laboratory of Engineering for Maintenance System

9. 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: εi: Expansion strain when freezing εs: Shrinkage strain when freezing εt: Temperature strain Laboratory of Engineering for Maintenance System

10. Research Outline • The model of expansion strain when freezing εi is a function of ice content ratio Ψi. When moisture content ratio is small, the expansion is not caused. Then, the following expressions are assumed. αi: Constant of proportion that changes by rigidity of mortar Ψic: 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. αs: 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. ΔT: Temperature difference Laboratory of Engineering for Maintenance System

11. 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 Laboratory of Engineering for Maintenance System

12. 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) Table-1 Mix Proportions (Mortar) Laboratory of Engineering for Maintenance System

13. 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) Laboratory of Engineering for Maintenance System

14. 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-3Salts solutions Desiccators Graph from AGM Container Controls, Inc. (AGM) Laboratory of Engineering for Maintenance System

15. Specimens PC Specimen support Data logger Environmental Chamber Temperature sensor Experimental Plans • Experimental Set-up Temperature increment: 0.5ºC/minute Temperature History Cycle for Set A, B, and C Specimens Coefficients , , and can be approximated by formula of coefficient of linear expansion. Temperature History Cycle for Set D Specimens Laboratory of Engineering for Maintenance System

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