الفهرس 
Literature ReviewOnly 14 pages are availabe for public view
 |  | from | 114 |  |  |
| | | from | 114 | | |
Abstract
Seven RC slabs were considered in the experimental program in order to investigate the effect of important parameters on the efficiency of ECE. These parameters are:
1) Spacing between reinforcing steel bars (steel bars act as a cathode).
2) Type of cathode (internal and external cathode were considered).
3) Thickness of RC slab (which control the distance between external anode and external cathode).
4) Number of reinforcing steel meshes inside the slab.
5) Location measured from the external anode.
Of course there are other important parameters affect the efficiency of ECE (such as current intensity, duration of ECE, type of anode, concrete strength,…etc.), these parameters were kept constant during the experimental investigation.
5.2. Conclusions
Based on the obtained test results and the analysis and discussion of these results, the following points can be easily concluded:
1) The reduction of chloride concentration for the cases of 5, 10 and 20 cm spacing is about 43%, 53% and 58% respectively due to a more uniform field around the steel bars spaced by 20cm rather than those spaced by 5cm (steel bars work as a cathode). A more uniform field is achieved for the higher spacing up-to 20 cm. It is worthy to mention here that maximum allowed spacing between steel bars is 20cm according to ECOP.
2) The reduction of chloride concentration for the cases of 12, 18 and 24 cm slab thickness is about 52%, 44% and 36% respectively. This can be easily attributed to a more stronger attraction force done by the anode (with +ve charge) to the chloride ions (with –ve charge) for the smaller thickness rather than the bigger one. The smaller the distance between anode and cathode, the
higher the anode attractive forces.
3) The reduction of chloride concentration for internal and external cathodes is about 58% and 52% respectively. Internal cathode showed a slight better performance of ECE than the external cathode. This result can be attributed to that the distance between internal cathode and anode was about 9.5cm (there is 2.5 cm cover behind the steel mesh) while this distance is 12 cm for the case of the external cathode. The smaller the distance between anode and cathode, the higher the anode attractive forces.
4) The reduction of chloride concentration is about 44% and 35% for the cases of one mesh and two meshes respectively. One mesh showed a better performance of ECE than the case of two meshes. This result can be attributed to that the presence of upper reinforcement mesh in addition to the lower reinforcement mesh restricted the process of chloride extraction (restrict and reduces the anode attractive force).
5) The effectiveness of ECE is depend on the location of each point measured from the external anode (located at the top surface of the slabs). All points located close to the anode have a lower chloride content compared to the points far from the anode. This can be attributed to that the points located closer to the anode, the stronger the attraction forces applied by the anode and consequently more reduction in the chlorides content.
5.3. Recommendations
It is recommended to investigate the effect of the following parameters on the efficiency of ECE:
- New anode materials having higher electrical conductivity.
- Efficiency of ECE for the case of geo-polymer concrete due to its wide spread applications.
- Smart systems for ECE which operate automatically if the percentage of chlorides exceed a certain limit and shut down automatically if this percentage decreased under a certain value.