Affinis Hosts Concrete Pavement and Roundabout EventPosted on Wednesday, May 21st, 2014 by Ryan Fleming
In Materials, Traffic, Transportation Engineering, tagged in Tags: Concrete, Pavement, Roundabouts, Transportation
Concrete pavement is returning to common use in the paving industry. To help our co-workers and clients stay informed we welcomed Todd LaTorella, PE the Executive Director of the Missouri/Kansas Chapter of the American Concrete Pavement Association for a presentation on jointing of concrete pavement.
The presentation included good updates about how the specifications for using concrete pavement have been changing in order to achieve better, longer-lasting, results in the field. Todd’s presentation provided an insight for how concrete joint spacing and locations were previously determined and the lessons learned to arrive at how concrete should be jointed today. In addition to jointing concrete pavement in the traditional rectangular shaped roadways, he discussed various joint patterns for concrete roundabouts.
Jointing pavement is nothing more than controlling where the concrete cracks and putting the load transfer support for the joint types that require the extra strength. Todd presented a number of tools that are located on the ACPA website; http://www.acpa.org/app-library/
Specific to roundabouts, we covered a lot of details about ways to joint the concrete coming into the roundabout to minimize cracking later. Where and how two pieces of concrete come together can make a big difference in the life span of the concrete. This part requires special attention when thinking about roundabouts. This is discussed further in the ACPA publication called “Concrete Pavement Field Reference Pre-Paving”. In the publication it references the following 6 step process.
Step 1: Draw all pavement edge and back-of-curb lines in the plan view. Draw locations of all manholes, drainage inlets, and valve covers so that joints can intersect these.
Step 2: Draw all lane lines on the legs and in the circular portion. If isolating the roundabout circle from the legs, do not extend these through the circle. If using the “pave-through” method, determine which roadway will be paved through. Makre sure no distance in greater than the maximum recommended (15ft (4.5m) is the typical maximum width).
Step 3: In the circle, add “transverse” joints radiating out from the center of the circle. Make sure the largest dimension of a pie-shaped slab is smaller than the maximum recommended slab width. Extend these joints through the back of the curb & gutter.
Step 4: On the legs, add transverse joints at all locations where a width change occurs (at bullnose of median islands, beginning and end of curves, tapers, tangents, curb returns, etc.). Extend these joints through the back of curb and gutter.
Step 5: Add transverse joints beyond and between those added in Step 4. Space joints out evenly between other joints, making sure not to violate the maximum joint spacing.
Step 6: Make adjustments for in-pavement objects, fixtures, and to eliminate L shapes, small triangular slabs, etc. Ensure isolation joints are used surrounding all islands.