1 Introduction
2 Materials and Methods
2.1 Specimen Preparation
Chemical formulation | CaO | SiO2
| Al2O3
| Fe2O3
| MgO | Na2O | K2O | SO3
| Cl |
---|---|---|---|---|---|---|---|---|---|
Percentage | 64 | 22.2 | 3.6 | 4.4 | 0.94 | 0.07 | 0.72 | 2.2 | 0.01 |
Specimens | Cement type | W/C | Aggregate fraction | Cement content (kg/m3) | Size of cast specimens (mm) | Size of specimens after cutting (mm) |
---|---|---|---|---|---|---|
Paste | CEM I 42.5 N MH/SR3/LA | 0.5 | – | 1225 | Ø50 × 250 | Ø50 × 75 |
Mortar | 0.5 | 0.5 | 635 | |||
Concrete | 0.48 | 0.7 | 350 | Ø50 × 250 and Ø100 × 200 | Ø50 × 75 and Ø100 × 50 | |
0.62 | 0.7 | 300 |
2.2 Electrochemical Acceleration Method
2.3 Natural Leaching Test
2.4 Assessments of the Changes in Hydrated Phases Due to Decalcification
2.5 Transport Properties
2.6 Mechanical Properties
3 Results and Discussions
3.1 Characterization of Degraded Specimens
REF (g) | Aged (g) | Mass depletion | V depletiona
| Porosity changeb
| Leached portlandite (g)c
| Porosity changed
| |
---|---|---|---|---|---|---|---|
W/C = 0.48 | 927 | 881 | 46.00 | 20.81 | 5.3 | 44.4 | 5.12 |
W/C = 0.62 | 907 | 878 | 29.00 | 31.12 | 3.3 | 29.6 | 3.41 |
3.2 Transport Properties
3.3 Mechanical Properties
Mass (g) | Length (m) | F (kHz) | E (GPa) | ||||||
---|---|---|---|---|---|---|---|---|---|
Ref | Aged | Ref | Aged | Ref | Aged | Ref | Aged | ||
Concrete | W/C = 0.48 | 390 | 325 | 0.078 | 0.078 | 27.4 | 21.6 | 46.5 | 24.1 |
W/C = 0.62 | 350 | 330 | 0.076 | 0.075 | 29.3 | 22.1 | 46.5 | 24.6 | |
Mortar | W/C = 0.5 | 323 | 326 | 0.072 | 0.076 | 25.7 | 17.6 | 30.4 | 15.18 |
Paste | W/C = 0.5 | 230 | 220 | 0.076 | 0.08 | 17.6 | 13.2 | 11.4 | 6.24 |
4 Conclusions
-
The electrochemically-induced leaching is not affected by the aggregate content in mortar or paste specimens.
-
Leaching of Portlandite causes considerable changes in physical and mechanical properties of concrete specimen, primary due to the increase in pore volume. It was concluded that larger pore volume due to complete leaching of portlandite can be expected which would cause up to 70 % decrease in mechanical strength and 40 % decrease in elastic modulus.
-
Larger pore volume after degradation causes more than 10 times increase in gas permeability and at least 3 times higher chloride diffusion rate.
-
The residual strength properties of the concrete specimens after complete leaching of portlandite are shown to be relatively similar no matter which initial water cement ratios the specimens have. This is to great extent due to similar pore structures in concrete specimens after leaching.