# Durability of High Volume Glass Powder Self-Compacting Concrete
## 3 Results
### Chloride Diffusion Coefficient
The beneficial effect of having a more finely ground glass powder was observed at the 30% replacement level, but no data was available in this study beyond this level for the most finely ground powder. It is likely that there is improved performance below a 30% replacement, with a more finely ground glass powder, however further work is needed to identify the optimal binder replacement level and powder size. Comparison of Service-Life in Chloride Exposure Condition  
In order to understand the effect of the higher diffusion decay index of glass powder concrete mixes, the service-life in terms of corrosion initiation time was predicted using Life 365(r) software [41]. A concrete cover depth of 50 mm, a threshold concentration of 0.05% (by mass of concrete) and a marine splash zone environment were used to estimate the time until de-passivation of the steel. The diffusion coefficient (D\({}_{\text{28}}\)) and diffusion decay coefficient (m) obtained from the reported experiments were also used in the model. Figure 16 shows the predicted time for the initiation of corrosion for the different concrete mixes. A distinct advantage in terms of increased time until corrosion initiation was observed for glass powder containing mixes. The predicted service-life for glass powder concrete mixes is greater than GP concrete irrespective of the particle size of the glass powder or the replacement levels. At a similar replacement level of 30%, an increase of approximately 2 to 3.5 times the service-life is observed for glass powder concrete mixes (10G30% and 20G30  
The service life of real structures is affected by numerous variables. As previously noted the workability of the concrete in the fresh state can influence the degree of compaction and thereby the permeability of the concrete. The binder type, w/c ratio and level of curing are additional parameters that can all dramatically affect the quality of the cover concrete and the overall service life. In addition to the material and construction components, the site specific exposure condition is another crucial component. While a chloride threshold concentration of 0.05% and 0.1% by mass of concrete were used in this example, the actual chloride threshold concentration (Ct) can vary significantly even in the same structure as the use of a single chloride threshold value may not be appropriate for estimate actual performance. The example was intended for illustrative purposed to show the potential impact of glass powder on the durability of reinforced concrete structures assuming all other variables remained constant. The wide range of tests carried out to corroborate the usage of glass powder as cement replacement shows promising results. The durability indicators (porosity, resistivity and oxygen permeability) of glass SCC mixes all indicate excellent durability according to the classification developed by [PERSON] et al. [22, 23]. The results show that by optimizing the glass powder properties and replacement level durable concrete with mechanical and durable performance better than GP and fly ash mixes can be obtained. The usage of waste glass powder could bring positive economic and environmental benefits for concrete construction applications.