Concrete structural elements such as wall sections, bridge abutments and slabs on grade rely on dowels to transfer loads across the joints. Construction joints are formed or placed into slabs to define stopping places or the extent of an individual concrete placement. Using plate dowels that allow horizontal slab movements both perpendicular and parallel to joints lowers the risk of random cracking. Tied construction joints cannot function like contraction joints. When aligned carefully and only bonded to the concrete on one side of the joint, round dowels help carry vertical loads across the joint, maintain vertical alignment of the slabs and allow slab movements perpendicular to the joint. Walker and Holland calculated that a 1/4-inch-thick x 4 1/2-inch diamond dowel spaced at 18 inches on center is equivalent to a 3/4-inch round dowel spaced at 12 inches on center. Technology is changing our options when it comes to deciding whether to repair or replace damaged, cracked concrete. The diameter of All rights reserved. The locked dowels continue to transfer shear, but prevent further movement taking place. Controlling the Frequency of your Concrete Vibrator. Wayne Walker and Jerry Holland, "Plate Dowels for Slabs on Ground," Concrete International, July 1998, pp. Laboratory testing and finite element analyses of dowels embedded in 8-in. Dowels are used in concrete joining to control and prevent the cracking within the concrete slab and to form contraction joints in concrete slabs. Dowels are used to transfer shear across construction and movement joints in concrete. But first, why is a specification needed? the concentration of tensile stress in the concrete around dowels intended for jointed plain concrete pavements (JPCP). Research by Walker and Holland shows diamond and rectangular-shaped plate dowels are more effective than round or square dowels because plate dowels place more steel closer to the joint where the bearing, shear and bending stresses caused by vertical loads are the highest (Ref. The installation of slip dowels is one of the most important steps in the process of constructing slabs on grade. In 1991, PCA suggested using 1.25 in. Dowels and the concrete itself are under the highest stress in the vicinity of joints; thus, in terms of pa … Therefore, construction joints that perform like contraction joints are desirable. Tie bars Tie bars are deformed rebars… Available in lengths of either 9 or 12 inches, the sleeves have been manufactured to provide a precision fit for smooth dowel bars ranging from 5/8 to 1 inch in diameter. [203-mm] concrete slabs have provided the following relationship: rcc = â â ( ) + ( )+1 153 3 2503 153 32. . Using sequestered carbon dioxide, Blue Planet Systems Corp. is developing a construction-grade rock, and ultimately concrete, that would have net-zero or net-negative carbon footprint. These ¾ x 14 x 1 x 16-inch smooth round dowels are often used with 7-8 or 5-6-inch-thick concrete slabs. dowel diameters for concrete slabs less than 10 in. Workers install plate dowels by inserting them into either a precut slot in the concrete forms or cavities in leave-in-place pocket formers that were attached to the forms and cast into the first slab. Using IoT-based concrete testing sensors can keep construction workers safe, encourage remote work on jobsites, and position construction companies well for recovery. ACI 302.1R-04 Concrete Floor and Slab Construction, American Concrete Institute. Save money and use the right concrete saw blade for the season. Installing and keeping round and square dowels aligned properly during the construction process can be difficult and many consider this issue a shortcoming of both round and square dowels. the concrete. Lots of experi-ment results are evidence for limitation of the appearance of this failure criterion on cases, if concrete dowels are placed deeply within the concrete slabs or if thick web plates are used. They are usually either cast or drilled into the concrete. dowels for slabs with higher thicknesses. Typically, one-half of each dowel is greased or sheathed to prevent concrete bonding so dowels are free to slip and accommodate opening of the joint. Purdue Researches Test Concrete Strength Sensors. Consisting of a plastic base and sleeve, this two-component system speeds construction setup and makes possible the installation of as many as 250 perfectly aligned slip dowels per hour. They provide a mechanical connection between slabs but allow for horizontal contraction and expansion of the slab itself. Routine maintenance and daily cleaning will keep your trowels productive and safe. How to Control Early-age Cracking in Concrete, Case Study: Reconstructing a Historical 500-Year Old Bridge, Form-A-Tube Forms - Build Forms of Any Size, Anywhere, Husqvarna Consolidates Surface Preparation Brand Portfolio, Top 10 Construction Stories This Week: Ruling Clarifies Independent Contractor Status, What makes the most-read construction stories of the week includes construction details of the COVID relief bill, how key cement industry players are reducing the industry’s carbon footprint, how to move 50,000 cu yd per week down a 3:1 slope, and more. Using plate dowels that allow horizontal slab movements both perpendicular and parallel to joints lowers the risk of random cracking. Why Does My Blade Dull When Cutting Concrete in the Cold? Sika Speed Dowel is a patented two-component system that is far superior to traditional slip dowel methods for aligning and installing round or square dowels in construction joints. Diamond™ Dowels are plate dowels suited for construction joints in concrete slabs and pavements. Dowels allow horizontal movement of slabs during contraction after laying the concrete and at temperature changes. As the joint width becomes wider, or if the joint is formed, the effect of aggregate interlock to transfer load is reduced and the loads are transferred by dowels. By allowing slab movements perpendicular to the joint, doweled construction joints can act like contraction joints and relieve shrinkage stresses perpendicular to joints. Dowels are located in transverse joints of Jointed Plain Concrete Pavements (JPCP) and they are used to provide load transfer between individual slabs, reduce faulting and improve performance. This can lead to stress concentrations, resulting in subsequent spalling of the concrete. Very heavy and massive pieces of concrete will use heavier gauge rebar, but for typical driveway, sidewalk and step repair, ½-inch rebar is usually adequate. Finding efficient, cost-effective ways to limit sound pollution is a major priority for contractors and hydrodemolition is gaining popularity for noise-restricted jobsites in concrete removal and surface preparation applications. The dowels also allow the slabs to move perpendicularly to your joints. Like round dowels, square dowels must be aligned properly and only bonded to concrete on one side of the joint in order to work. Can we use dowels or keyways for load transfer? On your next slab-on-ground project, consider using plate dowels at construction joints to efficiently transfer vertical loads, maintain vertical alignment of the slabs and help reduce the risk of random cracking. Learn from Rockett’s, schedule a session today. Cortex Composites Inc. was granted a new patent for its geosynthetic cementitious composite mat (GCCM) product, Cortex. Diamond- and rectangular-shaped plate dowels are becoming more popular than round or square dowels at construction joints because plate dowels are more cost-effective, easier to achieve proper alignment and allow movements parallel to the joints. Re published from Permaban. The dowel bars also allow axial thermal expansion and contraction of the concrete slab along the axis of the dowel. The spaces along the vertical sides of the plate dowels are created by: using a compressible material on the vertical sides of the plate dowels, using leave-in-place pocket formers that are slightly wider than the plate dowels, and by letting slab contraction perpendicular to the joint withdraw a diamond-shaped plate dowel from the leave-in-place pocket former as shown in Figure 2. , butt joints, so they do not have any load transfer of between! 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