Q14: From the previous answer, it appears that the emphasis or need for weldable
bars has apparently diminished. Is that a fair statement?
A: Yes, it appears that the anticipated demand for weldable bars in
cast-in-place construction never fully materialized.
Q15: Is there any basis for the diminishing interest or need for weldable reinforcing
bars?
A: Perhaps it is due to the increased usage of proprietary mechanical
connections for butt splicing rebars in cast-in-place construction. In most areas of the
country, including seismic regions, mechanical connections seem to be preferred for butt
splicing, particularly for the larger size bars.
Q16: The Answer to Question 13 focused on "cast
in-place" construction. Why?
A: It was necessary to differentiate or single out cast-in-place
construction because there is some usage, generally of the smaller bar sizes, in the
precast concrete industry.
Q17: Any other comments on usage?
A: A706 bars in the smaller sizes, like A615 bars, can be furnished in
coils. Coiled stock is preferred by some reinforcing bar fabricators for use with their
automatic stirrup and tie bending machines. While usage of coiled stock provides for
efficient and cost-effective fabricating practices, and the usage is growing, total
tonnage is rather small, Coiled stock, mainly A615 bars rather than A706 material, is also
used by manufacturers of reinforced concrete pipe.
AVAILABILITY
Q18: What about the availability of A706 bars?
A: A recent survey conducted by CRSI of the 35 known manufacturers of
rebars in the USA showed that 13 of the 35 manufacturers either currently produce, or plan
on producing A706 bars.
Q19: It is implied in the Answer to Question 13 that there
doesn't seem to be much demand for A706 bars. But the answer to Question 18 says that
about one-third of the currently- producing mills either make or plan to make A 706 bars.
This is a bit confusing. Please elaborate?
A: The key words are "currently produce" or "plan on
producing." Perhaps the latter should also include "capable of producing."
Several producers have made and currently produce A706 bars. Several others are interested
and capable of producing the bars. Two facets should be considered: demand in the
marketplace and economics.
First, the demand for A706 bars has never materialized, per se. As
mentioned in the Answer to Question 13, Structural Engineers specify and the Building
Codes permit the use of A615 bars with the special tensile properties of A706. The use of
weldable bars has diminished.
Regarding economics or costs; rebar producers make steel in units
called "heats." A heat of steel, depending on the mill, may range in size from
30 tons to 200 tons. Bars produced to meet the A706 specification have to be marked with a
"W" for the type of steel. See Figure 2. For orders of smaller
quantities, it might be prohibitive, costwise, for producers to dress their rolls to
accommodate the "W" mark. To make it economically feasible for a
producer to make the bars with the "W" mark, an order should comprise
at least 200 to 400 tons for one pass of the rolls. Smaller quantities may be available if
the "W' marking requirement is waived.
Fig. 2 - Required Marking for A706 Rebars.
Q20: Can more specific cost information be stated?
A: For the purpose of the discussion here and for cost estimating, and
using Reference 7 as a basis; if the cost of a relatively large order of A615 reinforcing
bars at a mill is $300 a ton, the cost of a comparable quantity of A706 bars might be 6 to
10 percent higher, say $320 to $330 a ton.
Q21: Production costs were addressed in the answer to the previous questions. Are
there other possible increased costs for A 706 bars?
A: Yes, fabricators of reinforcing bars might be reluctant to carry
and maintain another inventory of bars, because it would probably add to their costs of
doing business. In addition, rebar producers generally do not maintain a large inventory
of A706 bars, and those inventories that are maintained are often limited to 40-ft.
lengths. This limit on inventory would impact on the availability of A706 bars for a
particular project. For smaller jobs, it could be like a "Catch-22" situation; a
fabricator may experience difficulty in getting small quantities of A706 bars from a
producer; and a Contractor may not be able to find a supplier who can furnish the
fabricated bars for the job. For large projects with adequate lead time, the problems in
procuring A706 bars should be minimal.
Q22: Any further comments on relative costs?
A: For all intents and purposes, no track record has been established
regarding the demand, usage, and availability of A706 reinforcing bars. Thus realistic
costs are elusive. An Architect/Engineer should be cautious in assigning costs to A706
bars - in preliminary designs and cost estimates, and especially in cost estimates used in
comparisons with competitive structural materials and systems.
Q23: Another question about current usage; how many tons or
what percentage of the total tonnage is A 706?
A: The American Iron and Steel Institute (AISI) collects and
disseminates data on the production/usage, i.e., shipments of all steel products in the
USA. Regarding reinforcing bars, 5,479,000 tons were shipped in 1988 - the latest year's
figures available from AISI when this EDR was prepared. The reports by AISI do not break
down the rebar shipments by type of steel.
Recently CRSI conducted another survey of all known rebar producers in
the USA. Information requested in the survey included the type and grade of steel which
they produced in 1988. Not all producers responded to the survey. Responses regarding the
type of steel represented about 3,000,000 tons. Less than one percent of the surveyed
total was A706.
