# Durability of High Volume Glass Powder Self-Compacting Concrete
## 3 Results
### Resistivity  
The determination of concrete electrical resistivity has become an important technique in the evaluation of risk of corrosion associated with concrete structures [37; 38]. The resistivity of concrete is affected by numerous factors such as pore solution composition, degree of hydration, pore structure,  
Figure 8: Porosity of SCC mixes containing glass powder with 20 \(\upmu\)m particle size at different replacement levels.  
Figure 9: Relationship between coefficient of permeability and porosity.  
moisture content and temperature [39]. Figure 10 compares the resistivity of control mixes and glass powder mixes at 30% replacement. In agreement with the permeability and porosity results, the electrical resistivity of all the SCC mixes increased with curing age. The increase in resistivity is due to the continuous evolution of pore structure parameters due to hydration. The permeable void space reduced due to the precipitation of the hydration products in the capillary space, which hinder the mobility of ions, thereby resulting in an increase in resistivity of concrete. [PERSON] et al. (2014) [27] reported six times lower resistivity for glass powder mortar as compared to GP.  
The replacement of cement with fly ash and glass powder resulted in an increase in electrical resistivity. The electrical resistivity of SCC containing glass powder increased as the glass particle size became finer. A comparison of FAF30% and 20G30%, with both having a similar particle size, showed higher electrical resistivity in glass powder containing mixes. Figure 11 shows a reduction in electrical resistivity of with increase in glass replacement level. However, even at 40% replacement 20G40% showed better electrical resistance as compared to PC.  
The higher resistance towards flow of ions in SCM incorporated concrete is generally attributed to a finer pore structure due to their pozzolanic reaction. A smaller threshold pore diameter has been reporter for glass powder mixes containing up to 45% cement replacement compared to GP cement using MIP measurement techniques [36]. The smaller the threshold pore diameter, the more tortuous is the microstructure, which directly hinders the movement of ions. It should be noted, however, that the resistivity of the concrete is also affected by the composition of the pore solution and the pore solution composition of the concrete varies with w/c ratio, the degree of hydration, and use of SCMs [38; 39; 40]. Nevertheless, changes in the pore structure of the concrete are generally considered to have a greater effect on the measured electrical resistivity than changes in the pore solution composition and concentration [40]. The permeability measurements, which are not dependent on the pore solution, showed a similar behavior, implying the higher resistance offered in glass powder SCC is primarily due to pore structure modification. Evaluation of the pore solution at the various replacement levels would need to be conducted to accurately separate the contribution of the refinement in the pore structure from any modification to the pore solution composition.  
Figure 10: Electrical resistivity of SCC mixes at 30% cement replacement at different ages.  
The electrical resistivity and porosity values of SCC mixes at different ages are compared in Figure 12. An inverse relationship was observed between the two indicators. As expected the higher the porosity the lower was the electrical resistivity offer by the concrete. It is interesting to note that for the electrical resistivity vs. porosity all the mixes seemed to show reasonably good agreement unlike the permeability vs. strength comparison or the permeability vs. porosity comparison where the GP samples clearly showed a difference in behavior.  
Figure 11: Electrical resistivity of SCC mixes containing glass powder with 20 \(\upmu\)m particle size at different replacement levels.  
Figure 12: Relation between electrical resistivity and porosity.