## 4 Discussion
### Physico-Chemical Mechanisms  
The effect of T on CS is shown to be significant even though almost no variance of the SLR model is explained, because the temperature, theoretically, should affect the hydration reaction and, thus, the strength of concrete. This has been discussed above. However, despite the effect is significant, using the strategy of increasing T to improve the CS is sometimes unwise or questionable when the context involves the use of the BJPA as the substitution material, i.e., heating the admixture sample more (from 50 \({}^{\circ}\)C to 75 \({}^{\circ}\)C) to achieve an increase of only 1% in CS is not a good deal. That is, in our experiment, SR-BJPA is a manipulated factor that is rarely seen in other related studies, but as can be observed after the data analysis, it should be the main factor that diminishes the expected effect on CS while we are going to raise T further.  
Also, the W/B ratio (i.e., (the weight of water) \(\div\) (the weight of cementitious materials in concrete)) has been proven to have direct effects on other strength measures of concrete, too, than CS [34; 35; 36], and a lower W/B ratio will improve them [16; 22; 37]. This is exactly the theoretical basis of several previous observations.  
The effects of age on CS have also been shown to be significant. Theoretically, the CS of cementitious materials increases with age because of the hydration process. In addition, CS increases most rapidly in the first few days of age, but it increases more slowly when the hydration reaction slows down over time [12; 38]. Eventually, the rate of increase will slow to a steady or near-steady state. These are also reflected in the results.  
Moreover, the effects of replacing cement by the substitution material (BJPA in this study) should be similar to OPC (ordinary Portland cement). In this respect, the results of this study are also theory-reflexive, except for the extent to which the CS is decayed by the substitution ratios of different materials and the degree of CS development by age.  
One final note is that compared to [13], where calcined BJPA (CBJPA) is applied (rather than the normal, unprocessed BJPA), there are several interesting insights. [PERSON] et al. [13] concluded that with the increase in the SR of CBJPA, CS and the setting time both decreased without any exception, compared to the control group (wherein the SR of CBJPA is 0%). Although this study also continues to the'more BJPA cases' until 30% by following that CBJPA study (which also continued to 30%), the latter experimental cases, such as mixing 20% or 30% of BJPA or CBJPA, are nevertheless nonsense because these ratios have already reached the boundary conditions (i.e., it had been proven in [39] that the shortened setting time brought by a higher CBJPA SR, which affected workability, was unacceptable). As for CS, the downgrade in CS is evident from both studies (and this BJPA study simply confirms the results of the CBJPA study).  
To the authors' knowledge, as making BJPA as CBJPA might cost more energy (and produce more carbon), we have found the best practise to substitute the cement by 5% (rather than 0%) of BJPA with a higher T (during temperature) (75 \({}^{\circ}\)C or 50 \({}^{\circ}\)C; rather than the normal 25 \({}^{\circ}\)C), in order to ensure a relatively high level of CS without more carbon emission. Previous studies revealed a monotonous result that 'adding any % of CBJPA (rather than 0%) would erode the CS performance'. Now, this should be corrected as: 'adding 5% of non-processed BJPA (than none) would increase the desired CS performance, subject to the help by a raised T'.