# pH Measurement of Cement-Based Materials: The Effect of Particle Size
## 4 Conclusions  
As a part of durability and serviceability assessment of a concrete structure, the pH of structural concrete is one of the fundamental indicators to ensure that the concrete structure is in healthy condition or assess whether it needs rehabilitation and maintenance. Considering the lack of a standard for pH measurement, especially for high pH ranges, this work investigated the possibility of using large particle sizes, instead of fine particle sizes, for CBMs (cement mortar) to simplify the method of pH measurement.  
Cement mortar specimens with smaller particle sizes resulted in a higher pH value, consistent with the studies on cement paste and concrete. Using a particle size of less than 600 \(\upmu\)m (fine particle size) showed consistent pH measurement with a mean of 12.37-12.42 for cement mortar. In addition, large particle sizes (particle sizes between 2.36 mm and 600 \(\upmu\)m) can be used for accurate pH measurement if the solid-to-solvent ratio is increased from 1:2 (used for fine particle sizes) to 1:1 or the leaching time is doubled (from 5 min for fine particle sizes to 10 min). However, increasing the leaching time is recommended, rather than increasing the solid-to-solvent ratio to obtain similar pH readings as fine particle size.  
These findings are important for the development of a standardised pH measurement using the ESL method for CBMs. The effect of other variables should be investigated on  
Figure 7: Effect of changing leaching time to 10 min for large particle size.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Particle Size**} & \multicolumn{2}{c}{**Large Particle Size**} & \multicolumn{2}{c}{**Fine Particle Size**} \\ \cline{2-5}  & **2.36–4.75 mm** & **1.18–2.36 mm** & **600 \(\upmu\)m–1.18 mm** & **300–600 \(\upmu\)m** \\  & **(Particle Size Range I)** & **(Particle Size Range II)** & **(Particle Size Range III)** & **(Reference)** \\ \hline Leaching time (min) & 10 & 10 & 10 & 5 \\ pH value (mean \(\pm\) SD) & 12.32 \(\pm\) 0.03 & 12.38 \(\pm\) 0.02 & 12.43 \(\pm\) 0.03 & 12.35 \(\pm\) 0.02 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Effect of leaching time for different large particle sizes on pH.  
different types of CBMs to verify the applicability of all variables before a standardised pH measurement can be proposed.  
Conceptualization, P.Y.L. and P.S.; methodology, P.Y.L. and P.S.; software, P.Y.L.; validation, P.Y.L., P.S., H.Y.B.K., Z.I. and S.Y.; formal analysis, P.Y.L. and P.S.; investigation, P.Y.L.; resources, P.Y.L.; data curation, P.Y.L. and P.S.; writing--original draft preparation, P.Y.L.; writing--review and editing, P.Y.L., P.S., H.Y.B.K., Z.I. and S.Y.; visualization, P.Y.L.; supervision, P.S. and Z.I.; funding acquisition, P.S. and H.Y.B.K. All authors have read and agreed to the published version of the manuscript.  
This research is supported by Universiti Tenaga National Internal Research Grant OPEX (J5100D4103-BOLDREFRESH2025-CENTRE OF EXCELLENCE) and Universiti Malaya research grant (Grant No. GPF007F-2019).  
Not applicable.  
The data presented in this study are available within the article.  
The authors would like to express their gratitude for the provided support by Universiti Malaya and Universiti Tenaga National.  
The authors declare no conflict of interest.