c. Independent Testing
Laboratory Reports ... The reports on samples taken either at the fabricator's shop
or from material shipped to the job site, offer verification of the producer's mill test
report.
d. Approved Placing Drawings ... The
latest approved placing drawings should be scheduled to be available for review and study
by field placing personnel and the inspector at least one day prior to the actual placing
of the rebar.
e. Material Shipment ... A schedule of
anticipated delivery dates should be provided and updated as necessary so that the
inspector can schedule his in-place inspection.
f. Potential Problems ... A discussion between
all parties to identify difficult-to-place details, lack of specific details or
information on the contract documents, possible structural drawing discrepancy, detailing
or placing errors, and verification and acceptability of implemented field changes.
g. Tolerances ... A discussion with all
parties regarding which tolerances are critical, the method of measurement, and the basis
for either rejection or acceptance.
h. Periodic Meetings ... It is recommended
that regular scheduled meetings be held in order to discuss the previous inspection
reports, any problems that were encountered, solutions to the problems, and the schedule
of work for the next period.
MATERIAL INSPECTION
In-place inspection of rebar starts with the mill test report which in
some cases is supplemented by a report from an independent testing laboratory. Both
reports should provide data as to grade of steel, tensile properties (yield and ultimate
tensile strengths), chemical composition and carbon equivalent (C.E.) in the event the
rebar is to be welded, spacing and height of deformations, and ductility (percentage of
elongation). The reported data should meet the applicable ASTM standard specified. A
visual examination of the mill markings on the bar will identify the material from the
producing mill, the type of steel, the grade of steel, and the bar size.
REINFORCING BAR INSPECTION
Inspection of the rebar installed in the forms is done
be visual examination of the layout pattern, by measurement and count. The bar diameter,
and if bent, the bar shape can be visually checked. Bar lengths, bar spacing, embedment,
bearing on a wall or beam are normally checked by measurement. In a slab, the total number
of pieces can be counted with the spacing of the slab bars verified by measurement, all
checked against the approved placing drawing in conjunction with the structural drawings.
Similarly, beam longitudinals, column verticals, and stirrup and tie spacings are checked.
BAR SUPPORTS
At the same time beam and slab rebar is inspected, the
chair heights should be measured to verify that the concrete cover and clearances will be
as specified. It is extremely important that the chairs or standees supporting slab or mat
top bars be checked not only for height but also for stability since they can easily be
displaces during the placement of concrete. In fact, the entire mat and cages of rebar
should be checked for stability for the same reason. Normally side supports are not
provided unless called for in the contract documents. If the project specifications
require corrosion-protection measures, the class of protection of the bar supports
furnished should be verified.
REBAR TYING REQUIREMENTS
Reinforcing bars are tied together to form a rigid mat
for footing, wall, and slab rebar. A rigid cage is formed when beam or column
longitudinals are tied to the stirrups and ties. Ironworkers are usually instructed to tie
a minimum number of rebar intersections. Unless the project specifications are very
specific about the number of intersections to be tied, the inspector should accept the
work as done unless it is apparent that the mats or cages of reinforcing steel will be
displaced from their inspected position during the casting, screeding, and finishing of
the concrete. The placer is responsible for tying bars in such a manner that the rebar
will not be displaced. The inspector should only verify and agree that this condition has
been achieved. Only coated tie wire should be used to tie coated bars.
SPLICES
The inspector should pay particular attention to the
location and length of lap splices. Lap splices should be specified as to length and
location on the contract documents, and in turn shown by length and location on the
approved placing drawings. In the event that mechanical splices are required in lieu of
lap splices, the placing foreman and/or the mechanical splice supplier should provide the
inspector with evidence that the architect or engineer has approved use of the mechanical
splice, and provide literature describing the recommended installation procedures.
COATINGS
A light coating of rust on rebar is not a cause for
rejection by the inspector. The ASTM standards describe how to inspect and test rusted
rebar. However, dirt, grease, or other deleterious adhesions to the rebar must be removed
prior to concrete placement. Tests have indicated that water soluble cutting oils (used
when threading ends of bars for attaching to mechanical splices) do not significantly
affect bond. If epoxy-coated or galvanized rebar is specified for corrosion protection,
the appropriate ASTM standard and the project specifications should be studied to
determine the criteria for acceptance or rejection in the event there is damage to the
coating. Any corrective actions should follow recommended touch-up procedures and should
be completed prior to acceptance by the inspector.
TOLERANCES
No structure is built exactly level, plumb, straight,
and true to line. Tolerances are the means used to establish permissible variations in
dimensions and locations. Thus the designer, constructor, and inspector have parameters
within which the work can be performed and inspected. Tolerances should neither be overly
restrictive nor lenient. The engineer or architect usually specifies the standard
tolerances to be followed, normally by reference to the ACI 117 Specification. Judgement
on the part of the inspector will establish a range of acceptability. Incompatible
tolerances should be referred to the design professional for resolution.
FABRICATING TOLERANCES
Fabricating tolerances for rebar are tabulated by ACI
117, the ACI Detailing Manual and CRSI's Manual of Standard Practice.
Fabricating shops do not have problems meeting the recommended tolerances. Shearing length
tolerance for straight bars is plus or minus 1 inch.* Out-to-out dimension of bars with
hooks or bends at one end or at both ends is plus or minus 1 inch. Stirrups, hoops, and
ties that fit into a beam or column form, bar sizes #3, #4, and #5 [metric bar sizes #10,
#13, and #16], with a gross length of 12'-0" or less, have a tolerance of plus or
minus 1/2 inch. When a gross length exceeds 12'-0", the tolerance is increased to
plus or minus 1 inch.
* 1 inch = 25.4 millimeters.
