Description
The concrete craftsman can greatly influence the quality, durability, and appearance of the finished product. This manual from the ACI Concrete Craftsman Series presents information on concrete that should be useful to concrete craftsmen and deals mainly with construction practices relating to slabs-on-ground. This information can be used to train concrete craftsmen and is especially useful for those interested in earning credentials as ACI certified finishers.
Information in this manual is a guide to good practice but does not supersede the provisions in the plans and specifications for any project. If provisions in the plans and specifications vary from the guidance given in this manual, discuss the variances with the design professional. For more detailed information, also read ACI 302.1R, “Guide for Concrete Floor and Slab Construction,” and other documents listed in the reference section of this manual. Prior editions of this manual included a considerable amount of information on concrete materials and testing. For expanded coverage of materials and testing information, the reader is referred to The Contractor’s Guide to Quality Concrete Construction (ASCC-1), published jointly by the American Society of Concrete Contractors (ASCC) and ACI.
This manual was first issued under the guidance of the ACI Educational Activities Committee in 1982 as the first book in the ACI Concrete Craftsman Series. A second edition was approved and issued in 1994. Since1987, when ACI launched the Concrete Flatwork Finisher/Technician certification program, ACI has been using this document as the primary reference for that program. The certification program was designed to provide a basis for certifying concrete finishers and to improve the quality of concrete construction. As a result of program growth, more than 7500 people have become certified Concrete Flatwork Finishers/Technicians.Some major retailers now specify that contractors constructing concretefloors for their stores have certified ACI Flatwork Finishers on site performing the work.
ACI Committee 301, Specifications for Concrete, took a major step toward formally recognizing the value of using ACI-certified finishers and technicians when, in 2002, they approved language in ACI 301, “Specifications for Concrete,” that states in part, “…Unless otherwise permitted, a minimum of one finisher or finishing supervisor shall be a certified ACI Flatwork Finisher/Technician or a certified Flatwork Technician as defined in ACI CP-10 or equivalent.” This was the first time ACI Committee 301 had included language requiring the use of qualified flatwork finishers for concrete placement.
ARCOM, a partner of the American Institute of Architects, also includes optional language in their MASTERSPEC® Specification System requiring cast-in-place concrete installers to be certified ACI Flatwork Finishers and Technicians, and installer supervisors to also be certified ACI Flat-work Technicians.
Table of Contents
Chapter 1—Planning for slab-on-ground placement
Introduction
Specification requirements
Determining the size of concrete placements
Ordering concrete
Concrete delivery
Equipment
Size of placing and finishing crews
Preconstruction meeting
Chapter 2—Concrete materials, mixture proportioning, and control tests
Portland cements
Supplementary cementitious materials
Blended cements
Aggregates
Maximum size of aggregate
Aggregate grading
Harmful substances in aggregate
Mixing water
Admixtures
Mixture proportioning
Control tests
Chapter 3—Preparation before placing concrete
Subgrade preparation
Compaction around buried pipes and excavations
Establishing grades
Placement sequence
Setting side forms and screed guides
Vapor retarders or barriers
Reinforcement for shrinkage control
Bulkheads and jointing
Checklist of tools and materials
Chapter 4—Floor flatness and levelness
Measuring floor flatness and levelness
The 10 ft (3 m) straightedge method
F-number system
Factors affecting floor flatness and levelness
Chapter 5—Placing equipment
Placing concrete directly from truck mixers
Manual or motorized buggies
Crane and bucket
Concrete conveyors
Concrete pumps
Chapter 6—Placing and finishing tools and equipment
Spreading tools
Consolidating or vibrating tools
Laser-guided screeds
Hand screeding tools
Tools for smoothing after screeding
Jointing and edging tools
Hand floats and trowels
Power floats and trowels
Power saws
Chapter 7—Procedures for finishing slabs-onground
Striking off (screeding) the concrete
Bull floating or darbying
Highway-type straightedging
Waiting period
Edging and jointing
Brooming
Floating
Troweling
Machine float and trowel direction and patterns
Floating-to-troweling sequence
Finishing when setting time varies from load to load
Floating edges
Walk-behind basics
Hand floating and troweling
Blade tilt
Chapter 8—Jointing
Isolation joints
Contraction joints
Construction joints
Joint filling
Chapter 9—Curing and protection of concrete
Importance of curing
When to start curing
Curing methods
Effects of high temperatures on concrete
Causes and prevention of plastic shrinkage cracking
Effects of low temperatures on concrete
Chapter 10—Finishing problems and possible solutions
Excessive or insufficient bleeding
Slow setting
Surface crusting
Blistering
Delamination
Fast setting
Erratic setting
Sticky concrete
Rained-on surfaces
Random cracking
Craze cracking
Discoloration
Dusting
Curling
Scaling