Toward Standardized pH Measurement for Hardened Cement-Based Materials: Influencing Factors and Measurement...

Area of Science:

• Materials Science
• Analytical Chemistry
• Civil Engineering

Background:

• pH meters are standard in research and industry but underutilized in concrete.
• Cement-based materials (CBMs) present unique challenges for pH measurement, including high alkalinity, non-aqueous nature, limited sample size, and carbonation susceptibility.
• Standard pH electrodes struggle with CBMs due to low H+ ion concentration and high alkalinity, necessitating specialized electrodes and maintenance for accurate readings.

Purpose of the Study:

• To propose universal, reliable, and economical guidelines and procedures for pH measurement of hardened CBMs.
• To address the challenges associated with pH testing of alkaline, non-aqueous cementitious materials.
• To develop standardized methods for accurate pH assessment in concrete and related materials.

Main Methods:

• Discussion of variables influencing sample preparation and pH measurement, including sample processing, pH meter specifics, and environmental factors.
• Proposal of two distinct pH measurement approaches: a basic method and a comprehensive method.
• Development of a solution temperature-compensated pH (pHSTC) measurement for enhanced accuracy at 25 °C.

Main Results:

• The basic method provides a pH reading at the measured temperature, suitable for samples with pH differences > 1.
• The comprehensive method yields pHSTC, compensating for temperature variations, ideal for samples with pH differences < 1 and seasonal monitoring.
• Validation through test demonstrations confirms the reliability and applicability of the developed pH measurement methods for hardened CBMs.

Conclusions:

• Established guidelines and procedures enhance the reliability and economy of pH measurement for hardened CBMs.
• The proposed basic and comprehensive methods offer tailored solutions for different concrete pH analysis needs.
• Accurate pH measurement protocols are crucial for understanding CBMs' durability and performance, especially in applications requiring precise monitoring.