Extech meter offers new method for testing the ph of concrete

The value of pH is a crucial factor when assessing the deterioration and future performance of a concrete structure. However, measurement of pH in concrete is not well specified in national Standards. The current American Society for Testing Materials (ASTM) Standard(1) for determining the pH of concrete is a very brief method in which:

* water is used to rinse the concrete

* the pH of the water is measured using a pH meter or other method.

It is thought that the ASTM will at some time in the future move to a method that takes a pH reading of the concrete surface rather than using rinse water.

Critical measurement

The indirect nature of the process for testing the pH of concrete belies its importance. The pH of concrete is a critical measurement both because of its use in durability assessments and because it affects the success or failure of protective and decorative coatings, tiles and even carpeting. Many different types of decorative coatings are applied to concrete substrates for patios, entranceways, lobbies and foyers, and hence the importance of accurate pH determination cannot be overstated.

Alkalinity of concrete

The very nature of concrete can make it detrimental to materials that are placed over it. Freshly poured concrete is highly alkaline. This alkalinity is derived from the cement and hence the safety warnings on cement bags concerning skin and eye contact. Highly alkaline materials can burn skin and corrode metals. As concrete ages, the alkalinity on the surface usually decreases because of contact with acidic carbon dioxide in the atmosphere. However, in some cases, the concrete retains its alkalinity. If, for instance, vinyl flooring is installed over concrete, the moisture that becomes trapped at the adhesive/concrete bond becomes increasingly alkaline, as alkaline ions migrate to the moisture. This can result in deterioration and eventual failure of the adhesive as well as staining in the floor and can occur even when the vinyl flooring has been installed at a time when the concrete moisture content was at an acceptable value.

pH meters

In the absence of a robust and meaningful ASTM standard for determining concrete pH, it is essential to identify an effective pH testing method. The market now offers a wide spectrum of sophisticated pH meters that are affordable, accurate, and easy to use. These overcome the disadvantages which were associated with the bulb-type pH meter or pH paper that were employed prior to their introduction. About three years ago. Extech Instruments invested in developing its own pocket-sized. stick-style series of pH meters incorporating a patent-pending, flat surface electrode module. The result is the Waterproof ExStik pH Meter (PH 100).

Benefits of the flat surface electrode module

The PH 100, which offers one-, two- or three-point calibration, features a built-in smart chip that brings advanced functions and features to a stick style pH meter not found in any other pH meter. For a straight liquid application, similar stick-style meters are available of comparable accuracy. However, the major advantage is the Hat surface electrode, a design not incorporated into any other stick-style pH meter. Having the ability to make direct contact between the electrode surface and the material being measured presents a huge benefit. There are several companies that produce stick-style meters with the traditional glass bulb electrode, but Extech is the only one with the flat surface electrode. The flat surface of the electrode also makes the PH100 more durable than bulb-type meters as there is less breakage. A further benrit is that the replacement modules are less expensive. The PH100 is many times more accurate than pH paper and automatically tells the user through an on-screen message when it is time to calibrate and when it is time to replace the pH electrode. These capabilities are unique to this model, as is its memory, which allows the ExStik to retain readings.

Concluding remarks

Determining the pH of concrete is necessary in some situations; in fact, not performing this function properly can have serious ramifications. Fortunately, the PH100 pH meter now provides an effective and accurate way to carry out these tests.