# Recommendation of RILEM TC 281-CCC: RILEM CPC-18R1—guideline for measuring the carbonation depth of hardened concrete using a pH indicator solution

## TL;DR

This paper provides a new guideline for measuring carbonation depth in concrete using pH indicators, replacing an older method.

## Contribution

The paper introduces an updated and standardized procedure for measuring carbonation depth in hardened concrete.

## Key findings

- The new method includes definitions and descriptions of pH indicator solutions for carbonation depth measurement.
- Guidelines for sample preparation, CO2 exposure, and result reporting are provided.
- The new recommendation aims to replace the previous RILEM CPC-18 method.

## Abstract

This recommendation provides a procedure for determining the carbonation depth on the surface of concrete by applying a pH indicator. This includes definitions of carbonation, carbonation depth and carbonation front, as well as descriptions of the different pH indicator solutions that can be used. Recommendations for testing laboratory-prepared specimens and those obtained from concrete structures are also given. This involves guidelines for sample preparation and/or extraction, CO2 exposure duration, carbonation depth determination and reporting of results. A section on data interpretation is also provided, as carbonation results are used for determining durability of concrete, as well as a criterion for materials selection or for carbon uptake calculations. The new Recommendation CPC-18R1 is intended to supersede the former RILEM recommendation CPC-18, particularly when prescribed as the preferred method for evaluating and reporting carbonation depths.