CEMP-E
TI 809-02
1 September 1999
Table 4-3. Tolerable Crack Widths for Reinforced Concrete
(From ACI Committee 224 Report)
Exposure Condition
Tolerable Crack Width
Dry air or protective membrane
0.40 mm (0.016 inch)
Humidity, moist air, soil
0.30 mm (0.012 inch)
Deicing chemicals
0.20 mm (0.007 inch)
Sea water and saltwater spray
0.15 mm (0.006 inch)
Water retaining structures
0.10 mm (.004 inch)
(1) Shrinkage and Temperature Reinforcement. To keep cracks widths within
acceptable limits for buildings under normal exposure conditions the minimum shrinkage and
temperature reinforcement as required by ACI 318 will be provided. Shrinkage and
temperature steel requirements for buildings under severe exposure conditions are provided in
Chapter 12.
(2) Reducing Steel Stresses under Service Load Conditions. Cracking due to service
loads can be controlled by limiting the maximum stress in the reinforcing steel, and by
providing small diameter bars at close spacing, rather than large size bars at wide spacing.
Rules for distributing flexural reinforcement in beams and slabs to control flexural cracking are
provided in ACI 318. Suitable distribution of flexural reinforcement in beams and slabs is
measured by a z-factor. Z-factors for normal interior and exterior exposure conditions will
comply with ACI 318 requirements.
(3) Joints and Joint Sealants. The effects of deflection, creep, shrinkage, temperature
contraction and expansion, and the need for vibration isolation will all be addressed when
determining the location of expansion and contraction joints in concrete buildings. Appropriate
allowances for the aforementioned effects will be included in the design; location, details or
provisions for required contraction joints, control (weakened-plane) joints, expansions joints,
isolation joints, and seismic joints. The location of expansion, contraction, and seismic joints
will be shown on the drawings since joints are critical with respect to other design
considerations, e.g., configuration of the structural concrete, effects of joints on structural
strength and shrinkage cracking, and the appearance of joint lines on exposed concrete
surfaces. Where reinforced concrete foundation walls support masonry, crack control
measures will be designed to be compatible with crack control measures in the masonry. All
crack control joints in the foundation wall will be carried upward into masonry crack control
joints. The following are basic
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