# Durability of High Volume Glass Powder Self-Compacting Concrete
## 3 Results
### Oxygen Permeability  
Figure 4 shows the oxygen permeability coefficient for the SCC mixes at different curing ages. The GP concrete showed the highest permeability coefficient at all the ages. The permeability coefficient  
Figure 3: Drying shrinkage of SCC mixes containing glass powder with 20 \(\upmu\)m particle size at different replacement levels.  
Figure 2: Drying shrinkage of self-compacting concrete (SCC) mixes at 30% cement replacement (these figures show drying time not age and the initial point needs to start at zero days).  
of fly ash concrete mixes were similar to GP concrete at 3 and 7 days, however, thereafter the permeability coefficient continued to reduce for the fly ash mixes as hydration progressed whereas the change in GP concrete was minimal. The lower permeability for fly ash mixes is associated with refinement in pore structure due to the pozzolanic reaction, which in turn increases the tortuosity of the network and thus hinders the free movement of the fluid [31; 32]. The coefficient of permeability for glass powder mixes at the same replacement level was seen to be affected by their particle size. A lower resistance to gaseous permeation was observed for the coarser glass powder mixes. Similar to fly ash mixes, the permeability coefficient continued to reduce with time. Moreover, due to the long-term nature of the pozzolanic reaction, the advantages associated with glass replacement were more obvious after a long period of curing. The 10G30% and 20G30% both showed lower permeability coefficients compared to FAF30%. The finer particle size of glass powder helps in substantial pore refinement and hence creating an impermeable and denser microstructure [33]. In addition, the impervious nature of glass particle could also help in reducing the permeability. The 40G30% had a higher permeability as compared to GP at early ages (3, 7 and 28 days), however, the permeability coefficient reduced with progress in hydration. This shows that for coarser particle size, glass powder takes longer for the pozzolanic reaction to progress, which is also evident from the compressive strength data. [PERSON] et al. (2017) [21] also reported similar observations of a reduction in oxygen permeability for mortar samples comprising of glass powder. [PERSON] et al. (2014) [33] attributed the reason for lower permeability in glass powder concrete to the formation of a denser microstructure. In line with the above results, Figure 5 shows the effect of glass replacement level on the permeability coefficient. The lower the replacement level the greater was the permeation resistance. The 20G40% mix exhibited a higher permeability than FAF30% until 365 days, however it showed similar value at 545 days, implying glass powder mixes even at higher replacement level could achieve similar or better transport characteristics in the long run.  
The results of the oxygen permeability against compressive strength for the different mixes is provided in Figure 6. For same compressive strength concrete, lower permeability values were observed for glass mixes irrespective of their fineness and replacement level as compared to either  
Figure 4: Coefficient of permeability SCC mixes at 30% cement replacement.  
the GP or FAC30% mixes. It is well known that the compressive strength is not a good predictor of durability performance particularly when comparing different binder types [34; 35]. The compressive strength however can provide an indication of likely relatively performance when comparing concrete with the same general mix design. A correlation of 0.82 was obtained for power based relationship between compressive strength and permeability for glass mixes (K = \(2.18\times 10^{-9}f_{c}^{-1.33}\)).  
Figure 5: Coefficient of permeability of SCC mixes containing glass powder with 20 \(\upmu\)m particle size at different replacement levels.  
Figure 6: Relationship between compressive strength and coefficient of permeability of all the SCC mixes.