Contractor's Guide: Joints and Reinforcement for Slabs-On-Ground-Contractor's Guide - Joints and Reinforcement for Slabs-On-Ground (PDF)

Contractor's Guide - Joints and Reinforcement for Slabs-On-Ground (PDF)

Pdf Summary

Chapter 8 of "The Contractor's Guide to Quality Concrete Construction" discusses the considerations for designing and implementing joints and reinforcement in slab-on-ground construction to manage cracking and load distribution. The proper joint design is influenced by factors like traffic type, load requirements, ground friction, joint spacing, and allowable cracking. Key joint types include contraction (control), construction, and isolation joints, each serving specific functions such as managing shrinkage cracking or accommodating structural movements.<br /><br />Contraction joints are placed to control cracking caused by concrete shrinkage. They allow cracks to occur at predetermined locations, often created by sawing the slab to a specific depth. Proper joint timing is crucial, usually within 4 to 12 hours after concrete placement, and is affected by factors like temperature and mixture characteristics.<br /><br />Construction joints are used to segment concrete placements into manageable sections. A bond breaker should be applied if the construction joint serves as a contraction joint, and load transfer devices are important to ensure stability across these joints.<br /><br />Isolation joints separate slabs from other structural elements, preventing bond and enabling independent movement. These are typically placed at the junctions of slabs and walls, columns, and machinery bases.<br /><br />Reinforcement methods include steel bars, welded wire reinforcement (WWR), and fiber additions. These elements help manage crack widths and enhance structural strength. WWR is used between joints, stopping short to allow joint opening, and reinforced slabs often incorporate dowels to facilitate load transfer. Fiber additions, while not providing structural reinforcement, improve concrete’s tensile strength and reduce cracking.<br /><br />In conclusion, the chapter emphasizes the importance of proper joint placement and timing, as well as reinforcement strategies to minimize uncontrolled cracking in concrete slabs and ensure structural integrity.

Keywords

slab-on-ground

joint design

contraction joints

construction joints

isolation joints

reinforcement

steel bars

welded wire reinforcement

fiber additions

load transfer