Concrete Evaluation in a Navigational Lock

Services Performed

C3S, Inc. evaluated concrete cores taken from the navigational lock and performed laboratory testing to assess concrete strength, composition, microstructure, and potential deterioration mechanisms.

Testing Methods

The investigation included:

• ASTM C42 — Compressive Strength of Concrete Cores
• Scanning Electron Microscopy (SEM) — examination of concrete microstructure and hydration products.
• X-Ray Diffraction (XRD) — identification of crystalline phases and potential reaction products.
• Petrographic Examination — evaluation of aggregate, cement paste, voids, cracking, and deterioration products.

4. Petrographic analysis of samples revealed varying levels of formation of ettringite in voids of Samples

Findings

Compressive strength testing of four selected cores produced results ranging from approximately 1,840 to 2,700 psi.

XRD analysis of mortar extracted from selected cores identified predominantly quartz and calcite, with minor amounts of ettringite and calcium hydroxide.

SEM examination revealed ettringite formation within concrete voids, including areas containing concentrated and densified hydration products. Petrographic examination similarly identified varying levels of ettringite formation, including clusters of needle-like crystals within voids and voids substantially filled with reaction products.

Outcome

C3S, Inc. determined that sulfate-related deterioration was a probable contributor to the observed concrete damage. The formation of ettringite within the concrete was associated with weakening of the cement paste and was consistent with the exposed aggregate and relatively low compressive strength observed in the tested cores.

Given the age of the structure and its navigational environment, exposure to sulfates potentially introduced through fertilizer-containing runoff into the river and lock system was identified as a possible source contributing to the deterioration.

The investigation provided stakeholders with technical information needed to understand the deterioration mechanism and evaluate appropriate repair requirements.

Featured Services:

• Concrete Durability Investigation
• Petrographic Analysis
• SEM Analysis
• XRD Analysis
• Compressive Strength Testing
• Sulfate Attack Evaluation