CEMP-E
TI 809-28
15 September 1999
(8) The concrete is exposed on Air Force projects; thence it is required that RRMS
be used only in areas covered by carpet or other appropriate covering that will not reflect
cracks.
d. The recommended method of analysis and design of RRMS is presented in CESWD-
ED-G Criteria Letter; additionally, the following items must be incorporated into the design of
RRMS:
(1) A water/cement ratio of less than or equal to 0.42.
(2) Maximum 230 mm (9 inches) spacing for slab steel reinforcement.
(3) Reinforcement at "t/4" (t = slab thickness in inches) below the slab surface with a
minimum of 38 mm (1.5 inches) and a maximum of 64 mm (2.5 inches) clear.
(4) Minimum reinforcement of 0.5% and maximum bar size of 15M (#5).
(5) Maximum coarse aggregate size of 25 to 38 mm (1.0 to 1.5 inches) with
aggregate gradations corresponding with ACI 301; coarse aggregate size must be compatible
with clear cover requirements.
(6) Specified 28-day compressive strength between 21 and 28 MPa (3.0 and 4.0
ksi).
(7) Rigid control on the use of high-range, water-reducing admixtures in accordance
with ACI 212.4R.
(8) Fly ash required as an admixture for a portion of the cement per ACI 226.3R.
(9) RRMS to be placed in 6 to 7.6 m (20 to 25 foot) wide lanes using lane placement
techniques. For Air Force projects use 6 m (20 foot) lane widths. For vehicular slabs, lanes will
have transverse joints spaced 20 to 30 times the slab thickness.
(10) Large and irregularly shaped slabs should be subdivided into smaller units.
Ensure compatibility with the architectural and/or structural framing systems and area functions.
(11) The use of shrinkage-compensating cement for extreme cases should be
investigated and applied in accordance with ACI 223.
(12) Special concrete requirements for RRMS should be included in the specifications.
(13) For Air Force projects, beam spacing should be limited to 6 m (20 feet).
(14) Beam trench bottoms should be moist (not soaked) prior to concrete placement.
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