I have a slab on grade that has been designed as 6" per the ACI/PCA method for point and distributed loading. The client wants an alterante which will include a heat/snowmelt system which will consist of PEX tubing at 8" c/c. Are there any ACI references to account for this within the structural slab? What if I pour 6" of structural slab and embed the tubing in a few additional inches of concrete under the 6"? Does this then become my "subgrade"? Any thoughts, references, or experience would be appreciated.
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PEX Tube in Slab on Grade
- Thread starter jjeng2
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TXStructural
Structural
ACI 302.1R-04
3.4.3 Radiant heating: piped liquids—Slabs can be heated
by circulating heated liquids through embedded piping.
Ferrous, copper, or plastic pipe is generally used with
approximately 2 in. (50 mm) of concrete cover (not less than
1 in. [25 mm]) under the pipe and with 2 to 3 in. (50 to 75 mm)
of concrete cover over the pipe. The slab is usually monolithic
and the concrete is placed around the piping, which is fixed in
place. Two-course slab construction has also been used,
wherein the pipe is laid, connected, and pressure tested for
tightness on a hardened concrete base course. Too often,
however, the resulting cold joint is a source of distress during
the service life.
Insulating concrete made with vermiculite or perlite
aggregate or cellular foam concrete can be used as a
subfloor. The piping should not rest directly on this or any
other base material. Supports for piping during concreting
should be inorganic and nonabsorbent; precast concrete bar
supports (Section 3.2.4) are preferred to random lengths of pipe
for use as supports and spacers. Wood, brick, or fragments of
concrete or concrete masonry should not be used.
Sloping of the slab, where possible, can simplify
sloping of the pipe. Reinforcement, such as welded wire
reinforcement, should be used in the concrete over the
piping. Where pipe passes through a contraction or
construction joint, a provision should be made for
possible movement across the joint. The piping should
also be protected from possible corrosion induced by
chemicals entering the joint. The piping should be pressure-
tested before placing concrete, and air pressure (not
water pressure) should be maintained in the pipe during
concreting operations. After concreting, the slab should
not be heated until curing is complete. The building owner
should be warned to warm the slabs gradually using lukewarm
liquid in the system to prevent cracking of the cold
concrete.
3.4.3 Radiant heating: piped liquids—Slabs can be heated
by circulating heated liquids through embedded piping.
Ferrous, copper, or plastic pipe is generally used with
approximately 2 in. (50 mm) of concrete cover (not less than
1 in. [25 mm]) under the pipe and with 2 to 3 in. (50 to 75 mm)
of concrete cover over the pipe. The slab is usually monolithic
and the concrete is placed around the piping, which is fixed in
place. Two-course slab construction has also been used,
wherein the pipe is laid, connected, and pressure tested for
tightness on a hardened concrete base course. Too often,
however, the resulting cold joint is a source of distress during
the service life.
Insulating concrete made with vermiculite or perlite
aggregate or cellular foam concrete can be used as a
subfloor. The piping should not rest directly on this or any
other base material. Supports for piping during concreting
should be inorganic and nonabsorbent; precast concrete bar
supports (Section 3.2.4) are preferred to random lengths of pipe
for use as supports and spacers. Wood, brick, or fragments of
concrete or concrete masonry should not be used.
Sloping of the slab, where possible, can simplify
sloping of the pipe. Reinforcement, such as welded wire
reinforcement, should be used in the concrete over the
piping. Where pipe passes through a contraction or
construction joint, a provision should be made for
possible movement across the joint. The piping should
also be protected from possible corrosion induced by
chemicals entering the joint. The piping should be pressure-
tested before placing concrete, and air pressure (not
water pressure) should be maintained in the pipe during
concreting operations. After concreting, the slab should
not be heated until curing is complete. The building owner
should be warned to warm the slabs gradually using lukewarm
liquid in the system to prevent cracking of the cold
concrete.
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