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Measuring Concrete Carbonation Depth: Tips and for Accurate Results
March 18,2023

Why Carbonation Depth Measurement?

To answer this question, we must start with the characteristics of concrete: once the cement is hydrated, calcium hydroxide Ca(OH)2 will be precipitated, which plays a major role in the hardening of concrete. It reacts with carbon dioxide in the air to produce calcium carbonate CaCO₃ with higher hardness, that is, the carbonization of concrete occurs.

Due to carbonation, the hardness of the concrete surface increases, and the rebound value increases, but the internal compressive strength of the concrete does not change. During the test, the increased rebound value due to the carbonation of the concrete should be deducted. In order to further improve the accuracy of the rebound strength measurement, it is necessary to measure the carbonation depth.

How to measure carbonation depth?

According to the requirements of the regulations, it is recommended to measure the carbonation depth in compliance with the following steps:

1. In the rebound measurement area of the concrete surface, use appropriate tools to form a hole with a diameter of 15mm, and its depth should be greater than the carbonation depth of the concrete.

2. The powder and debris in the hole should be cleared and not washed with water.

3. Use a phenolphthalein alcohol solution with a concentration of 1%~2% to drop on the edge of the inner wall of the cavity. When the boundary between carbonized and non-carbonized is clear, use a carbonization depth measuring instrument to measure the interface between carbonized and non-carbonized (red and non-carbonized). The vertical distance from the interface which does not turn red) to the concrete surface shall be measured no less than 3 times, and each reading shall be accurate to 0.25mm.


4. The average value of three measurements should be taken as the test result, and it should be accurate to 0.5mm.

What are the points to pay attention to when measuring the depth of carbonation?

Point 1: Be sure to measure the carbonation depth in the component spring-back measurement area.

If the inspectors do not measure the carbonation depth on the ground, but only calculate the carbonation depth according to experience based on the time of concrete pouring. Because the carbonation of concrete is not only related to age but also related to various conditions such as the type of cement used in concrete, the strength level and compactness of concrete, and the CO2 concentration and air humidity in the atmospheric environment where the concrete is located. Therefore, it is wrong to use the concrete age to estimate the carbonation depth or not to measure the carbonation depth in the component rebound measurement area.

Point 2: It is not necessary to measure the carbonation depth in every measurement area of a component.

It has been proved by practice that the environmental conditions are basically the same in each measurement area of the same component with basically the same concrete properties, and the carbonation depth value has little difference. Therefore, in the same construction, no less than 30% of the measurement area of the component can be selected to measure the carbonization depth, otherwise unnecessary workload will be increased.


Why choose LANGRY digital carbonation depth gauge?

When measuring the carbonation depth, the error of measuring the carbonation depth with a steel ruler or a steel tape is relatively large, which will directly affect the evaluation result of the concrete strength. In order to ensure the accuracy of the measurement data to the greatest extent, it is recommended to use a special carbonation depth measuring instrument for corresponding data measurement.

LANGRY LR-TH10 digital carbonation depth measuring instrument is small in size and easy to operate; the digital display screen allows you to view the data intuitively; the measurement is accurate and the average value is automatically calculated; it also supports the batch data management function of the LANGRY online system software, which can maximize the Improve your inspection productivity.



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