Concrete Evaluation in a Navigational Lock

A 40-year old Navigational Lock on the Kissimmee River showed several defects on the concrete walls including removal of patches of cement paste which has exposed several aggregates. Stakeholders needed a concrete evaluation to know the cause of damage prior to repairing the structure.

  • Date: 22 September, 2010
  • Project Type: Maintenance Phase

Concrete Evaluation in a Navigational Lock Project

About this Project

A 40-year old Navigational Lock on the Kissimmee River showed several defects on the concrete walls including removal of patches of cement paste which has exposed several aggregates. Stakeholders needed a concrete evaluation to know the cause of damage prior to repairing the structure.

Several cores were taken and sent to our laboratory and tests performed on them including compressive strength, scanning electron microscopy, X-ray diffraction and petrographic analysis.

Note – This featured project report is an abbreviatedย version of the actual report prepared for the client.

Concrete Evaluation in a Navigational Lock
Concrete Evaluation in a Navigational Lock
Figure 1 shows samples as received
Concrete Evaluation in a Navigational Lock
Figure 2 shows side view of two of the samples
Concrete Evaluation in a Navigational Lock
Figure 3 shows the top surfaces of two of the samples.

1. Compressive strength, as per ASTM C42, of four selected cores ranged from 1,840 psi to 2,700 psi

2. X-ray diffraction of mortar extracted from several sections of selected cores showed predominantly quartz, calcite, and minor components of ettringite and calcium hydroxide.

3. Scanning electron microscopy revealed ettringite in varying degrees of formation in voids of the samples.

Concrete Evaluation in a Navigational Lock
Figure 1 shows section of sample with hydration product in a void (arrowed) (Mag. 200X)
Concrete Evaluation in a Navigational Lock
Figure 2 shows section of sample with densified hydration product in voids. (Mag. 300X)
Concrete Evaluation in a Navigational Lock
Figure 3 shows โ€œan incubation chamberโ€ (arrowed) of ettringite crystals. (Mag. 200X)
Concrete Evaluation in a Navigational Lock
Figure 4 shows section of sample with densified hydration product in a void. (Mag. 500X)

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

Concrete Evaluation in a Navigational Lock
Figure 5 shows formation of cluster of needle-like crystals of ettringite in a void. (Mag. 400X)
Concrete Evaluation in a Navigational Lock
Figure 6 shows fully-filled voids in a porous paste mortar paste section. (Mag 400X)

DISCUSSION OF RESULTS

For a 40 year concrete in a navigation Lock environment with probable sulfates in fertilizers draining into the river and hence into the Locks may have contributed to the sulfate attack in the samples examined. Formation of ettringite causing a weakening of the surface of the walls as shown by exposed aggregates and the low compressive strength values.

ABOUT THE NAVIGATIONAL LOCKS

The Kissimmee Chain of Lakes, Kissimmee River and Lake Okeechobee offer some of the best boating and fishing opportunities in Central and South Florida. Navigation locks throughout this interconnected system ensure that it is accessible by the public for recreation.

Along the route, there are 11ย locks maintained by the South Florida Water Management District and five maintained by the U.S. Army Corps of Engineers.

It takes about 15 minutes to lock through most structures. This service is free to boaters locking through during normal operating hours.

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CONTACT INFORMATION

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7100 Regency Square Blvd.
Suite 183
Houston, TX 77036

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  • ๏˜Slab Thickness
  • ๏˜Concrete Cover and Rebar Location
  • ๏˜Voids โ€“ Location and Extents
  • ๏˜Pre Stressing Strands (PT Cables)
  • ๏˜Conduits