Otherwise, plate dowels can break out of the concrete from the top or bottom of the slab. Save money and use the right concrete saw blade for the season. But first, why is a specification needed? If not, joints will be mechanically restrained from opening, increasing the risk for random slab cracking. These dowels allow initial shrinkage of the concrete to take place and are then locked in position with a mechanical plate and a controlled amount of epoxy resin. 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. Spaces allow adjacent slabs to move relative to each other in a direction parallel to the construction joint and significantly reduce the risk of random cracking caused by restrained concrete shrinkage. These smooth steel bars are often needed to transfer wheel loads from one slab to the next and to prevent differential settlement between slabs. This results in lower deflections at the joints For a home with a concrete footing, concrete block stem wall, and a … They provide a mechanical connection between slabs but allow for horizontal contraction and expansion of the slab itself. 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. 40 -45. Together with the aggregate interlock, dowels are a solution to improve interaction between slabs at transversal joints (LTE—load transfer e ciency) of concrete … 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. All rights reserved. 2). By allowing slab movements perpendicular to the joint, doweled construction joints can act like contraction joints and relieve shrinkage stresses perpendicular to joints. When workers are ready to make the next concrete placement, dowel bars can be inserted to the full depth of each sleeve. Sika Speed Plate is a patented plate dowel system, which immediately accommodates lateral and axial movement produced by concrete shrinkage at construction joints. Continuous reinforcement through joints can restrict joints from opening freely. Because of the geometry, size of the plates and installation procedures, it is easy to achieve and maintain proper dowel alignment thus reducing the potential of mechanically locking the joint from opening. Like round dowels, square dowels must be aligned properly and only bonded to concrete on one side of the joint in order to work. Dowels are used to transfer shear across construction and movement joints in concrete. One way to minimize these separations is to pin the two sections together with rebar. When the second slab is placed, the second side of the plate dowels for all three systems becomes incased in concrete. Only use butt-type construction joints with or without keyways where vertical load transfer and alignment are not a concern. 2. 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 diameter of Dowels and the concrete itself are under the highest stress in the vicinity of joints; thus, in terms of pa … Using dowels with a compressible material on the vertical sides allows slab movements parallel to the joints. Dowelled control joints (dummy joints) are most commonly used on highway and airport runway constructions, where continuous run concrete trains are used and the dowels can be automatically inserted. Ernest Schrader, "A Solution to Cracking and Stresses Caused by Dowels and Tie Bars," Concrete International, July 1991, pp. If joints can open freely, tensile stresses caused by restrained dry and thermal concrete shrinkage are relieved. Learn from Rockett’s, schedule a session today. Butt-type construction joints are basically free slab edges that deflect under forklift, wheeled traffic or vertical loads. 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. The installation of slip dowels is one of the most important steps in the process of constructing slabs on grade. Therefore, construction joints that perform like contraction joints are desirable. Nox-Crete and JK Thermal have partnered in an exclusive distribution agreement of the domestic TigerLoc products. This reduces restrained shrinkage stresses parallel to joints and significantly reduces the risk of cracking. 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. Plate dowels can accommodate horizontal slab movements parallel to joints by creating spaces along the vertical sides of the plates. 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. However, the third method utilizes the geometry of a diamond-shaped plate and concrete shrinkage to create spaces along the vertical edges. However, concrete shrinkage occurs in all directions causing slab movements both perpendicular and parallel to doweled joints. Measure dust and gas in your construction site in one device, TigerLoc Signs Exclusive Agreement with Nox-Crete. For the first two methods, the space is either created by the compressible material or an oversized leave-in-place pocket former. Why Does My Blade Dull When Cutting Concrete in the Cold? dowel diameters for concrete slabs less than 10 in. 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. This Ground Breakers Podcast episode talks about rebar tying and how the ergonomic design of your tools affects health and safety of workers – as well as the bottom line. The World Cement Association appointed Roland van Wijnen, CEO of PPC Ltd, and Mehendra Singhi, Managing Director & CEO of Dalmia Cement. Also, if the slab reinforcement is continuous through a construction joint, the joint may function more like a tied joint than a contraction joint. 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. [203-mm] concrete slabs have provided the following relationship: rcc = â â ( ) + ( )+1 153 3 2503 153 32. . References 1. Construction joints are formed or placed into slabs to define stopping places or the extent of an individual concrete placement. Relieving shrinkage stresses reduces the risk of random cracking. Dowels and the concrete itself are under the highest stress in the vicinity of joints; thus, in terms of pavement design, the joints are the weakest points of the whole structure. 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. Diamond™ Dowels are plate dowels suited for construction joints in concrete slabs and pavements. 3). As the joint opens because of concrete shrinkage, the ability of the keyway to transfer loads across the joint and maintain vertical alignment are significantly reduced. Aslan™ 600 Fiberglas™ Dowel Bars are used as a “Load Transfer” device between joints in concrete slabs. Cortex Composites Inc. was granted a new patent for its geosynthetic cementitious composite mat (GCCM) product, Cortex. The players driving sustainability and reducing carbon emissions within the cement and concrete industries. thickness, and 1.5 in. If the truck traffic is 80 to 120 trucks per day, then the use of dowels is up to engineering judgement. Dowels can be smooth round or square steel bars or plates. Another method for sizing dowels is based on the bearing stress in the concrete. Dowels are the steel or iron rod which is left according to bar diameter. The dowels also allow the slabs to move perpendicularly to your joints. 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. Lockable Dowels are used at temporary movement joints in post-tensioned concrete frames. Also, concrete cracking and failure above or below the keyway along the joint edge is likely. 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. Re published from Permaban. As the joint opens due to concrete shrinkage, the plate dowel is withdrawn from the cavity in the pocket former creating a space on each side of the plate due to the taper of the iamond-shaped plate. To permit horizontal movement, the dowels must not bond to the concrete on at least one side of the joint.” ACI 224.3R095 (Reapproved 2008) 5.2.4.3 But to function properly, slip dowels must be aligned perpendicular to the construction joint and parallel with each other and the slab surface; if they aren't, the slab may exhibit spalling, cracking, and reduced load-carrying capacity. 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. 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