# Alkali-silica Reaction Elimination Potential of High-Performance Concrete Containing Glass Powder
## 4 Discussion
### Alkali-silica Expansion  
There are many different methods worldwide for testing and then evaluating the alkali-silica reaction. In the Czech Republic, the standard is valid since 1967 [19]. The tested specimens are 40 mm \(\times\) 40 mm \(\times\) 160 mm, and the experiment is long-term--the intermediate readings are usually done every month (for 3 months) and then every 3 months. If necessary, the experiment is continuously observed up to 18 months. The conditions are mild (humid air at 40 \({}^{\circ}\)C). The British standard BS 812-123 [18], which has a similar character, can be compared with the Czech standard. The British experimental design is used in research [30] and requires milder conditions (38 \({}^{\circ}\)C) and a longer testing period--the minimum is 52 weeks. However, measurements are taken until the values stabilize. Due to the high number of mixtures that were tested and the high time and space requirements, the short-term experiments were selected into this work. Nevertheless, measurement of expansion that is caused by the alkali-silica reaction is a lengthy process that does not require one result and does not end with one result. It is necessary to monitor the course of the measurements, monitor the points at which sudden changes occur, and ideally, wait until the end of the process of stabilization of the measured values. Given the unusual deflections, it is convenient to fit a curve through the resulting points to visualize the testing process; in this case, a second-degree polynomial curve was used. In Figure 3, there is a summary of the results that were established after the ASTM C1260 test. According to the standard definition of the potential risk of ASR, most of the mixtures passed the test successfully and were found to be harmless from the point of view of ASR. A similar result was obtained from the TP137 standard (Figure 4). Except for one mixture with a glass substitute (SGP HPC 100), all the mixtures were below the critical value of 0.1% after 14 days. Relative humidity (RH) expresses the water content in structures that are affected by ASR; nevertheless, it is known that the measurement of RH in the field is often inaccurate and uncertain, and therefore, the degree of capillary saturation (DCS) is often a more appropriately used method. The relationship between these quantities is influenced by several factors, the most important of which is the water-cement ratio [22; 31]. With a lower w/c concrete, the desorption isotherm is not as steep as with a higher w/c concrete, which means that the RH decreases less with higher porosity than with lower porosity [32]. During the investigation, the cross sections of the two samples were compared after the test according to ASTM C1260 (Figure 5). GPP HPC 100 is highly porous in comparison with REF HPC. It has been found that at w/c \(\geq\) 0.45, internal moisture develops, and thus the potential development of ASR occurs. Another study is on the lower number--w/c \(<\) 0.4 [32]. The mixtures that were proposed in this work were, therefore, designed with a w/c of \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Type** & **Material** & **SiO2** & **Al2O3** & **Na2O** & **CaO** & **Fe2O3** & **K2O** & **Sum** \\ \hline Reference & SF & 99.68 & 0.17 & \textless{}0.005 & 0.03 & 0.03 & \textless{}0.005 & 99.9 \\  & CWG & 68.94 & 2.06 & 14.50 & 10.50 & 0.37 & 0.75 & 97.1 \\ Glass & SGJ & 65.68 & 1.38 & 12.27 & 5.83 & 0.15 & 8.60 & 93.9 \\  & SGP & 63.58 & 0.51 & 16.61 & 2.64 & 0.08 & 7.02 & 90.4 \\  & GPP & 60.35 & 19.89 & 10.36 & 5.47 & 0.77 & \textless{}0.005 & 96.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Chemical analysis of glass powder on the basis of X-ray fluorescence. All values are expressed as %. 0.25-0.27 according to the specification of the given mixture and the glass dust that was used. The low rate of diffusion and the lack of moisture can reduce the possible expansion of ASR with a lower w/c [22]. This premise has been confirmed in this research.