Description
The quality of a concrete floor or slab is highly dependent on achieving a hard and durable surface that is flat, relatively free of cracks, and at the proper grade and elevation. Properties of the surface are determined by the mixture proportions and the quality of the concreting and jointing operations. The timing of concreting operations--especially finishing, jointing, and curing--is critical. Failure to address this issue can contribute to undesirable characteristics in the wearing surface such as cracking, low resistance to wear, dusting, scaling, high or low spots, poor drainage, and increasing the potential for curling.
Concrete floor slabs employing portland cement, regardless of slump, will start to experience a reduction in volume as soon as they are placed. This phenomenon will continue as long as any water, heat, or both, is being released to the surroundings. Moreover, because the drying and cooling rates at the top and bottom of the slab will never be the same, the shrinkage will vary throughout the depth, causing the as-cast shape to be distorted and reduced in volume.
This guide contains recommendations for controlling random cracking and edge curling caused by the concrete’s normal volume change. Application of present technology permits only a reduction in cracking and curling, not elimination. Even with the best floor designs and proper construction, it is unrealistic to expect crack-free and curl-free floors. Consequently, every owner should be advised by both the designer and contractor that it is normal to expect some amount of cracking and curling on every project, and that such occurrence does not necessarily reflect adversely on either the adequacy of the floor’s design or the quality of its construction (Ytterberg 1987; Campbell et al. 1976).
Refer to the latest edition of ACI 360R for a detailed discussion of shrinkage and curling in slabs-on-ground. Refer to the latest edition of ACI 224R for a detailed discussion of cracking in reinforced and nonreinforced concrete slabs.
This guide describes how to produce high-quality concrete slabs-onground and suspended floors for various classes of service. It emphasizes aspects of construction such as site preparation, concreting materials, concrete mixture proportions, concreting workmanship, joint construction, load transfer across joints, form stripping procedures, finishing methods, and curing. Flatness/levelness requirements and measurements are outlined. A thorough preconstruction meeting is critical to facilitate communication among key participants and to clearly establish expectations and procedures that will be employed during construction to achieve the floor qualities required by the project specifications. Adequate supervision and inspection are required for job operations, particularly those of finishing.
Keywords: admixture; aggregate; concrete; consolidation; contract docu-ments;
curing; curling; deflection; durability; form; fracture; joint; mixture
proportioning; mortar, paste, placing; quality control; slab-on-ground;
slabs; slump test; specification.
8/4/04
Table of Contents
Chapter 1—Introduction
1.1—Purpose and scope
1.2—Terminology
1.3—Related work of other committees
Chapter 2—Classes of floors
2.1—Classification of floors
2.2—Single-course monolithic floors: Classes 1, 2, 4, 5,and 6
2.3—Two-course floors: Classes 3, 7, and 8
2.4—Class 9 floors
2.5—Special finish floors
Chapter 3—Design considerations
3.1—Scope
3.2—Slabs-on-ground
3.3—Suspended slabs
3.4—Miscellaneous details
Chapter 4—Site preparation and placing environment
4.1—Soil-support system preparation
4.2—Suspended slabs
4.3—Bulkheads
4.4—Setting screed guides
4.5—Installation of auxiliary materials
4.6—Concrete placement conditions
Chapter 5—Materials
5.1—Introduction
5.2—Concrete
5.3—Portland cement
5.4—Aggregates
5.5—Water
5.6—Curing materials
5.7—Admixtures
5.8—Liquid surface treatments
5.9—Reinforcement
5.10—Evaporation reducers
5.11—Gloss-imparting waxes
5.12—Joint materials
5.13—Volatile organic compounds (VOC)
Chapter 6—Concrete properties and consistency
6.1—Concrete properties
6.2—Recommended concrete mixture
6.3—Concrete mixture analysis
Chapter 7—Batching, mixing, and transporting
7.1—Batching
7.2—Mixing
7.3—Transporting
Chapter 8—Placing, consolidating, and finishing
8.1—Placing operations
8.2—Tools for spreading, consolidating, and finishing
8.3—Spreading, consolidating, and finishing operations
8.4—Finishing Class 1, 2, and 3 floors
8.5—Finishing Class 4 and 5 floors
8.6—Finishing Class 6 floors and monolithic-surface
treatments for wear resistance
8.7—Finishing Class 7 floors
8.8—Finishing Class 8 floors (two-course unbonded)
8.9—Finishing Class 9 floors
8.10—Toppings for precast floors
8.11—Finishing lightweight concrete
8.12—Nonslip floors
8.13—Decorative and nonslip treatments
8.14—Grinding as a repair procedure
8.15—Floor flatness and levelness
8.16—Treatment when bleeding is a problem
8.17—Delays in cold-weather finishing
Chapter 9—Curing, protection, and joint filling
9.1—Purpose of curing
9.2—Methods of curing
9.3—Curing at joints
9.4—Curing special concrete
9.5—Length of curing
9.6—Preventing plastic-shrinkage cracking
9.7—Curing after grinding
9.8—Protection of slab during construction
9.9—Temperature drawdown in cold storage and freezer rooms
9.10—Joint filling and sealing
Chapter 10—Quality control checklist
10.1—Introduction
10.2—Partial list of important items to be observed
Chapter 11—Causes of floor and slab surface imperfections
11.1—Introduction
11.2—Cracking
11.3—Low wear resistance
11.4—Dusting
11.5—Scaling
11.6—Popouts
11.7—Blisters and delamination
11.8—Spalling
11.9—Discoloration
11.10—Low spots and poor drainage
11.11—Curling
11.12—Analysis of surface imperfections
Chapter 12—References
12.1—Referenced standards and reports
12.2—Cited references
12.3—Other references