Abstract
If we are to monitor the chemical processes in cementitious materials, then pH assays in the pore solutions of cement pastes, mortars, and concretes are of key importance. However, there is no standard method that regulates the sample-preparation method for pH determination. The state-of-the-art of different methods for pH determination in cementitious materials is presented in this paper and the influence of sample preparation in each case. Moreover, an experimental campaign compares three different techniques for pH determination. Its results contribute to establishing a basic criterion to help researchers select the most suitable method, depending on the purpose of the research. A simple tool is described for selecting the easiest and the most economic pH determination method, depending on the objective; especially for researchers and those with limited experience in this field.
Highlights
The measurement of pH provides relevant information on the status of both living and inert systems
Highly alkaline systems are not suitable for organic contaminants, as the most effective method for fixing them requires the presence of microorganisms, which can grow and survive within a pH range of 5.5 to 8.5 that is required for biodegradation processes [6]
The measurement of this parameter in a cementitious material is a challenge; there is no standard method for pH determination in the pore solutions of concrete samples, nor is there a sample-preparation method for that purpose
Summary
The measurement of pH provides relevant information on the status of both living and inert systems. Highly alkaline systems are not suitable for organic contaminants, as the most effective method for fixing them requires the presence of microorganisms, which can grow and survive within a pH range of 5.5 to 8.5 that is required for biodegradation processes [6]. According to Grubb et al [13], “pH is an approximate measure of the acidity or the alkalinity of a solution and is defined as the negative logarithm of the hydrogen-ion (H+) concentration” The measurement of this parameter in a cementitious material is a challenge; there is no standard method for pH determination in the pore solutions of concrete samples, nor is there a sample-preparation method for that purpose. An experimental program was conducted to compare three of those methods, so as to determine whether the sample preparation procedure influenced the pH assay: full immersion in distilled water, dispersion in distilled water of crushed and ground samples, and superficial measurement by means of flat-surface pH electrodes
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