Pre-Tied Cage and Mat Services
During the summer of 2004, Contractors Materials Company (CMC) and MMI of Kentucky (MMI) each installed a rebar resistance (fusion) welding machine at each of their locations. the machine resistance welds individual T-2, T-3, and other individual rebar stirrups into a skeletal cage into which longitudinal and/or vertical bars are then traditionally tied. The machine requires that the individual stirrups be ASTM A706 low alloy weldable rebar. The individual stirrups are resistance welded to three individually placed W5 (1/4″) holding or sacrificial wires meeting the specification of ASTM A82 low carbon rod. The machine’s welding and pitch (stirrup spacing) is computer controlled.
The advantages of the skeletal cages are that they provide a very rigid framework into which the vertical or longitudinal bars are to be tied. The spacing of the individual stirrups is accurately positioned and consistent in every cage every time. Because the individual stirrups have to be placed within the three established fixed welding positions, the outside dimension of the tied cage is consistently accurate insuring proper concrete cover. Besides the three “holding” wires providing dimensional accuracy, they also provide the framework for a very rigid tied cage assembly. In all but the largest cage assemblies, the tied cage assemblies require no additional “racking” bars to maintain their design dimension during field handling. This rigidity also enables the tied cage assembly to be placed easier and more safely than traditionally tied cages.
A706 steel was developed in 1974 for the California Department of Transportation and the Atomic Energy Commission. In other than the closed engineering circles that deal with nuclear and seismic construction, little is known of A706 rebar which is necessary for consistent success in the welding of rebar. In March of 2004, the Concrete Reinforcing Steel Institute (CRSI) published their Engineering Data Report (EDR) #53 titled “Assembling Reinforcing Bars by Fusion Welding in the Fabrication Shop.” This publication now endorses and recognizes the successes of shop resistance welding “by machines under a continuous controlled process” of “reinforcing bars conforming to ASTM Specification A706/A706M” to “holding wires conforming to ASTM Specification A82 or A496.” The free downloading of this publication is available at www.crsi.org/PDF/edr_53.pdf.
Cages can be made with #3, #4, or #5 A706 individual stirrups up to 4′-06″ wide and 8′-00″ tall. The skeletal cage assemblies can be made continuous of up to 40′-00″ in length. Longer cage assemblies of up to 60′-00″ in length can be made with multiple skeletal cages and continuous vertical or longitudinal ASTM A615 reinforcing steel. Cages are not limited to circular, square column, or drilled caisson cages. Median barrier and grade beam cages are excellent cage applications as well. Call your CMC or MMI representative for more information.
The SpinMaster literally ties together individual lengths of rebar with 12 gauge annealed wire into a single plane monolithic mat. Similar in construction to a “snow fence,” the rebar mat comes delivered to the jobsite in a convenient to handle “roll”. The roll of rebar is placed on continuous supports and rolled out into a single plane mat for the placing of either the longitudinal or transverse bar. Another roll is placed perpendicular to the first mat and rolled out into a mat that now provides both a longitudinal and transverse bar grid of the specified design. The SpinMaster can handle #3 through #11 black and epoxy coated rebar from 10’-00” up to 60’-00” in length. (When fabricating epoxy coated rebar, the spools of black annealed 12 gauge tie wire is replaced with PVC coated 12 gauge annealed wire.) The length (or width) of the roll is determined by the material handling capability on the jobsite, the bay or deck width, but not to exceed five tons in weight. Precise spacing, or pitch, of the individual rebar is computer controlled allowing either a constant or variable pitch within the mat from a 2″ spacing through an 18″ spacing. Variable length bars can be used for stagger or offset.
Although generally thought to only have horizontal applications, SpinMaster mats have also been successfully used in Europe in vertical applications as well!
Obviously, the advantage of the roll mat is from the time saved in the efficient material handling and layout of the steel. Additionally, to keep the mats from moving from the hydraulic pressure of the placed concrete, only base bars to their high chairs and a couple of intersections in the four corners and center of the mat grid need to be tied. More efficient handling of the steel layout and far fewer rebar intersections to tie all save valuable construction time and money.
As with our preassembled rebar cages, keep your project ahead of schedule with preassembled rebar mats from Contractors Materials and MMI of Kentucky!
Features & Benefits
- Preassembled mat of rebar in a “carpet” roll
- Less material handling and placing labor (up to 80% savings)
- Enhances accelerated project scheduling
- Reduces construction time
- Bars continuously tied @ 6’06” centers into single monolithic plane mat
- Virtually no chance of individual bars being displaced by concrete hydraulic flow
- Transverse and longitudinal grids formed by two intersecting perpendicular mats
- Once placed, only a minimal number of intersections require tying.
- Bar spacing or pitch from 2″ up to 18 inches is computer controlled
- Little chance of grid deviation from exact design specification
- SpinMaster ties and produces #3 through #11 rebar mats
- The ability to accommodate the majority of engineer designed reinforcement
- There is virtually no manual labor involved in placing SpinMaster rebar mats
- Less chance of lifting job related injuries.
- Minimal tying of rebar intersections required
- Reduced potential of back injuries caused from continuous stooping to tie bar intersections.
- Timely delivery of rebar roll mats.
- Reduced non-productive time
- Can be used in certain vertical construction applications as well
- Same as those in horizontal applications.
- SpinMaster can successfully produce epoxy coated rebar mats as well.
- The same precision and time saving benefits are available to projects sensitive to corrosion protection