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 are not 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 completely crack- and curl-free floors. Consequently, every owner should be advised by both the designer and contractor that it is completely normal to expect some amount of cracking and curling on every project, and that such an occurrence does not necessarily reflect adversely on either the adequacy of the floor’s design or the quality of its construction (Ytterberg 1987).
This guide describes how to produce high-quality concrete slabs-on-ground and suspended floors for various classes of service. It emphasizes such aspects of construction as site preparation, concrete materials, concrete mixture proportions, concrete 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; consolidation; contract documents; curing; curling; deflection; durability; form; fracture; joint; mixture proportioning; placing; quality control; slab-on-ground; slabs; slump test.
Table of Contents
CHAPTER 1—INTRODUCTION
1.1—Purpose
1.2—Scope
CHAPTER 2—DEFINITIONS
CHAPTER 3—PREBID AND PRECONSTRUCTION MEETINGS
3.1—Prebid meeting
3.2—Preconstruction meeting
CHAPTER 4—CLASSES OF FLOORS
4.1—Classification of floors
4.2—Single-course monolithic floors: Classes 1, 2, 4, 5, and 6
4.3—Two-course floors: Classes 3, 7, and 8
4.4—Class 9 floors
4.5—Special finish floors
CHAPTER 5—DESIGN CONSIDERATIONS
5.1—Scope
5.2—Slabs-on-ground
5.3—Suspended slabs
5.4—Miscellaneous details
CHAPTER 6—SITE PREPARATION AND PLACING ENVIRONMENT
6.1—Soil-support system preparation
6.2—Suspended slabs
6.3—Bulkheads
6.4—Setting screed guides
6.5—Installation of auxiliary materials
6.6—Concrete placement conditions
CHAPTER 7—ASSOCIATED MATERIALS
7.1—Introduction
7.2—Reinforcement
7.3—Special-purpose aggregates
7.4—Monomolecular films
7.5—Curing materials
7.6—Gloss-imparting waxes
7.7—Liquid surface treatments
7.8—Joint materials
7.9—Volatile organic compounds (VOCs)
CHAPTER 8—CONCRETE MATERIALS AND MIXTURE PROPORTIONING
8.1—Introduction
8.2—Concrete
8.3—Concrete properties
8.4—Recommended concrete mixture
8.5—Aggregates
8.6—Portland cement
8.7—Water
8.8—Admixtures
8.9—Concrete mixture analysis
CHAPTER 9—BATCHING, MIXING, AND TRANSPORTING
9.1—Batching
9.2—Mixing
9.3—Transporting
CHAPTER 10—PLACING, CONSOLIDATING, AND FINISHING
10.1—Placing operations
10.2—Tools for spreading, consolidating, and finishing
10.3—Spreading, consolidating, and finishing operations
10.4—Finishing Class 1, 2, and 3 floors
10.5—Finishing Class 4 and 5 floors
10.6—Finishing Class 6 floors and monolithic-surface treatments for wear resistance
10.7—Finishing Class 7 floors
10.8—Finishing Class 8 floors (two-course unbonded)
10.9—Finishing Class 9 floors
10.10—Toppings for precast floors
10.11—Finishing lightweight concrete
10.12—Nonslip floors
10.13—Decorative and nonslip treatments
10.14—Grinding as repair procedure
10.15—Floor flatness and levelness
10.16—Treatment when bleeding is a problem
10.17—Delays in cold-weather finishing
CHAPTER 11—CURING, PROTECTION, AND JOINT FILLING
11.1—Purpose of curing
11.2—Methods of curing
11.3—Curing at joints
11.4—Curing special concrete
11.5—Length of curing
11.6—Preventing plastic shrinkage cracking
11.7—Curing after grinding
11.8—Protection of slab during construction
11.9—Temperature drawdown in cold storage and freezer rooms
11.10—Joint filling and sealing
CHAPTER 12—QUALITY CONTROL CHECKLIST
12.1—Introduction
12.2—Partial list of important items to be observed
CHAPTER 13—CAUSES OF FLOOR AND SLAB SURFACE IMPERFECTIONS
13.1—Introduction
13.2—Random cracking
13.3—Low wear resistance
13.4—Dusting
13.5—Scaling
13.6—Popouts
13.7—Blisters and delamination
13.8—Spalling
13.9—Discoloration
13.10—Low spots and poor drainage
13.11—Slab edge curling
13.12—Evaluation of slab surface imperfections
CHAPTER 14—REFERENCES