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A Focus on Slabs
Updates to CCS-1(10) Slabs-on-Ground from ACI’s Concrete Craftsman series.
The American Concrete Institute (ACI) produces hundreds of documents dedicated to improving the design, construction, maintenance, and repair of concrete and masonry structures. ACI documents are developed in numerous types and formats, including standards, handbooks and manuals, certification documents, and education documents.
One group of ACI education documents that has been gaining in popularity over the years is the Concrete Craftsman series, a useful guide and training resource for craftsmen and contractors, especially those interested in earning credentials by becoming ACI certified. It is also of interest to persons who are peripherally involved with the concrete industry, such as material supplier representatives or inexperienced engineers who are looking to increase their knowledge of construction materials. Titles in the Concrete Craftsman series include Concrete Fundamentals, Slabs-on-Ground, Shotcrete for the Craftsman, Supported Beams and Slabs and Placing and Finishing Decorative Concrete Flatwork.
CCS-1(10) Slabs-on-Ground was the first book issued in the ACI Concrete Craftsman Series. The most recent edition was updated with information to include placing with laser-guided screeds and finishing with walk-behind and riding power equipment.
The document covers: • Slab-on-Ground Planning—CCS1(10) Slabs-on-Ground discusses factors to consider when determining appropriate placement size, including variables in production rates, weather and operator experience. It explains the way concrete quantities are calculated, details regarding ordering concrete, and lays out requirements for handling concrete delivery. Discussion of crew size, required equipment, and procedures to follow during preconstruction meetings further help the reader understand the first phase of concrete slab placement. • Basic Concrete
Materials, Mixture Proportioning, and
Testing—Chapter 2 briefly explains concrete materials, how they are combined in mixture American Concrete Institute proportioning to obtain fresh and hardened concrete properties, and how to measure those with control tests. • Preparation before Concrete Placement—This section details how to prepare and compact the subgrade; accomplish elevation control; determine the placement sequence; set side forms, temporary bulkheads, and screed guides; install vapor retarders and/or reinforcement (if required); lay out and mark joint locations on forms, and a checklist of necessary tools and materials. • Floor Flatness and Levelness—Floor flatness is important when wheeled vehicles will operate on a slab and for floors where thin vinyl sheet goods or polishing will be installed. This section explains how to measure floor flatness and levelness and addresses
areas of concern when constructing floors to tight requirements. • Placing and Finishing Equipment—
Chapter 5 points out the importance of placing concrete without delays and without changing the concrete properties, in order to best facilitate proper concrete finishing. Methods discussed include direct placement from truck mixers as well as placement from manual or motorized buggies.
For multistory buildings, crane and bucket placement, concrete conveyors and pumps are common placement methods defined. Tools used by laborers to complete placement and achieve finishing include spreading tools, consolidating or vibrating tools, and screeds. After placement, floats, trowels, and straightedges may be used for smoothing the concrete.
Jointing and edging tools, as well as power saws, may be used to install contraction joints. A broad selection of such tools are pictured, and their use explained, in Chapter 6. Once readers are familiar with placing and finishing tools, CCS-1(10) Slabs-on-
Ground details how the tools should be used, and in which applications.
Considerations such as waiting periods and managing bleed water are included. • Jointing—Concrete slabs are jointed to control cracking associated with the material’s shrinkage as it dries.
CCS-1(10) Slabs-on-Ground describes the basic types of joints used as well as how to install them. The benefits of joint filling, along with sealant types and installation steps, are also covered. • Concrete Curing and Protection—
Curing refers to methods used to keep concrete moist and at the temperature needed to develop the required strength, wear resistance, and durability. Climate conditions— especially temperature—heavily
influence curing procedures and timing. Methods such as ponding, sprinkling, covering with film or mats, and the use of curing compounds are outlined. • Finishing Problems and Solutions—
The final chapter lists common difficulties that can be encountered during concrete finishing. Notable issues include excessive or insufficient bleeding, problems with setting, and surface issues such as crusting, blistering, delamination or stickiness.
Weather-related challenges, such as placing in the rain, are addressed.
Cracking, discoloration, dusting (the development of a powdery material), curling, scaling and more may afflict hardened concrete. Recommendations for mitigating these outcomes are offered in the document.
Information in CCS-1(10) Slabson-Ground should be used as a guide to good practices. The document does not supersede the provisions in the plans and specifications for any project. If provisions in plans and specifications vary from the guidance given in the document, variances should be discussed with the design professional. For more detailed information, ACI 302.1R: “Guide for Concrete Floor and Slab Construction” is a useful reference. Other reference documents are listed in the Concrete Craftsman manual.
• Concrete Fundamentals—
An introduction to concrete and concrete construction.
Sections cover materials, basic construction practices and testing.
Craftsmen in the concrete field also can use this document as a guide for good practice. • Shotcrete for the Craftsman—
Defines shotcrete and describes its proper placement. Chapters cover equipment, materials, environmental conditions, inspection and surface preparation, placement principles and techniques, finishing and tolerances, safety, and testing. • Supported Beams and Slabs—
For the apprentice craftsman, journeyman and foreman involved with cast-in-place elevated slabs and beams. It provides technical background on topics including shoring, reshoring, form removal and reinforcement placement as well as concrete placing, finishing and curing.
• Placing and Finishing Decora-
tive Concrete Flatwork—Details about the materials, equipment and techniques required to successfully install decorative concrete flatwork. Readers should have knowledge of traditional concrete flatwork techniques to fully understand this document.
Michael L. Tholen is the Managing Director, Engineering and Professional Development, American Concrete Institute.
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