EH-90-1 Inadequate Strength of Concrete Columns
                          ENVIRONMENT SAFETY & HEALTH

                                    BULLETIN

Assistant Secretary for                              U.S. Department of Energy
Environment, Safety, & Health                        Washington, D.C. 20585

DOE/EH-0132                      Issue No. 90-1                   January 1990

Inadequate Strength of Concrete Columns

Holes were drilled by a carpenter into a building support column (located in
the basement) for installation of wall anchors associated with modification of
a 30-year old facility at a DOE contractor site.  The column provides support
for a 20-ton high-bay crane.  Inspection of the hole and cut material by the
carpenter and his supervisor revealed a soft area of granular material.  An
engineering analysis revealed concrete of inadequate strength.

From photographs showing placement of forms at various intervals during
construction, it was deduced that the deficient concrete had been placed some
time between April 13 and May 9, 1960.  Other support columns in the same
northwest area of the basement, which had been placed during the same time
period, were also checked.  Again, concrete of inadequate strength was
revealed.  These 4 columns provided support for a portion of the operating
floor.

An extensive set of characterization measurements were done throughout
representative locations in the building, including using 3 different
techniques and involving the services of an expert, independent testing
laboratory.  The problem was determined to exist in only 6 columns.

Cause

Engineers determined that the concrete of inadequate strength was caused by an
improper concrete mixture.  The sandy mixture found in the column indicated
that not enough cement was in the mixture.  The original specification of
concrete strength for columns was 3,000 lbs. per square inch.

Corrective Actions

1. Until the first 2 columns were repaired, the 20-ton high-bay crane was
   administratively prevented from loading the columns.  Furthermore, the
   loads on the existing columns were reduced by emergency shoring.

2. A proposed remedial design solution for the first 2 columns was accepted.
   The design solution involved chipping away suspect concrete from the bad
   vertical sections of each column.  The removed concrete was then replaced
   with a concrete mix which met current 4,000 lbs. per square inch
   specifications.

3. Shortly after the 4 remaining columns with concrete of inadequate strength
   were observed, the same design solution was proposed for 3 of the columns.

Lessons Learned

1. This incident demonstrates the importance of quality control of materials
   at the time of original construction, and the need for verification.

2. This incident also demonstrates the good working relationship between the
   carpenter and the supervisor.  The carpenter doing the drilling was correct
   in ceasing installation of the anchor bolts and informing his supervisor of
   the defective material.  This type of working relationship should be
   encouraged.



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This publication is one of several series of bulletins published so that DOE
program managers and contractors can share information about potential
occupational safety problems relevant to DOE operations.  For more information
or additional copies, contact Eleanor Crampton, Performance Evaluation
Division, Office of Safety Compliance, Assistant Secretary for Environment,
Safety & Health, U.S. Department of Energy, Washington, DC 20545; Telephone
FTS 233-3732, Commercial (301) 353-3732.
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