How Do You Assess Cracked Concrete?

A crack in a concrete structure is not a pathology in itself, but the visible sign of an underlying defect. Treating a crack without knowing its cause means masking a problem that will inevitably reappear.

Before any repair work, it is therefore essential to identify the mechanism involved: shrinkage, overload, reinforcement corrosion, carbonation, chloride ingress, alkali-silica reaction (ASR), inadequate cover, freeze-thaw action or structural movement. This analysis phase is essential for bridges, car parks, façades, slabs, industrial structures and condominium buildings facing active cracks, crazing, spalling or concrete breakouts.

The appearance of the cracking provides initial hypotheses, but is never enough on its own. Superficial crazing may point to shrinkage or surface deterioration, while longitudinal cracks along reinforcement may indicate corrosion linked to carbonation or chlorides. Bulging, map cracking or efflorescence may suggest an alkali reaction. The analysis must also take into account mechanical loading, workmanship defects, curing, moisture, thermal cycles and environmental exposure.

Investigations are defined according to the nature of the defect and the accessibility of the structure. Concrete core sampling in the laboratory makes it possible to obtain representative samples to measure strength, observe compaction, check the condition of the paste/aggregate interface and assess the depth of deterioration. A concrete compression test can be carried out to evaluate the mechanical performance of the sampled material.

Measurements of carbonation depth are carried out with fine, millimetre-level reading to estimate the risk of reinforcement depassivation.

A specialist laboratory provides an independent, evidence-based interpretation of the defects. For an infrastructure manager, a property manager or a civil engineering contractor, the issue is not simply to note a crack, but to know whether it compromises the structure’s durability, safety or operation. An incomplete diagnosis often leads to unsuitable repairs, repeated interventions and higher overall costs.

The laboratory implements a concrete pathology diagnosis approach based on field observations, targeted sampling and laboratory analysis. The goal is to connect visual clues with the real physico-chemical mechanisms in order to establish a reliable and actionable diagnosis. Depending on the structure, the assessment may include concrete core sampling in the laboratory, millimetre-accurate measurement of carbonation depth, chemical chloride testing, concrete compression test, microscopic examination and petrographic examination to look for signs of ASR, segregation, abnormal porosity or internal deterioration.

The laboratory compares macroscopic observations with analytical results to avoid hasty conclusions. A crack may result from a single mechanism or a combination of mechanisms: steel corrosion due to loss of alkalinity, salt ingress, excessive porosity, an unfavourable water/cement ratio, reactive aggregates or lack of compaction.

This combined approach makes it possible to distinguish an aesthetic defect from an issue affecting the structure’s durability or load-bearing capacity.

The diagnosis is strengthened by targeted analysis: chloride testing to assess the corrosion risk, microstructure examination, observation of internal cracks, search for corrosion products and petrographic examination to identify reactive aggregates, gels linked to ASR, mix design defects or heterogeneities. Where needed, observation and microanalysis techniques can be used to characterise degraded areas in detail and highlight the failure mechanisms.

The expertise relies on sampling, testing and observation methods that make it possible to document the causes of deterioration objectively. The analysis are carried out by engineers and PhDs experienced in material failure issues, with a rigorous approach to characterisation. This organisation makes it possible to produce technical conclusions that can be used by the project owner, the design team, the insurance expert or the contractor responsible for the repairs.

The service can be initiated from a simple need: visible cracks, localized spalling, suspected corrosion, doubts about durability, or the need for qualification before work begins.

The laboratory then defines a suitable intervention program: inspect the structure, take representative samples, analyze the cores, measure carbonation, test for chlorides, look for RAG, and interpret the results in a cause-and-effect framework. The goal is to deliver a complete diagnosis that supports decision-making and is focused on solving the problem.