N N a a t t i i o o n n a a Technical Services l l , R R o o u u n n d d a a b b o o Vail, Colorado u u t t May 22-25, 2005 Steve Waalkes, P.E. C C o o n n f f e e r r e e Managing Director n n c American Concrete Pavement Association c e e 2 2 0 0 0 0 5 5 TRB National Roundabouts Conference D D Concrete Roundabouts R R Concrete Roundabouts A A F F T T N N a a Flexible Uses liquid asphalt as binder Pro: usually lower cost Con: requires frequent maintenance & rehabilitation t t i i Asphalt o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C Terminology Terminology o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D R R A A Rigid Uses cement as binder Pro: longer lasting Con: higher cost Concrete F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o s n n c f f e i e r r t e e n n e y c c t e h e t 2 2 e 0 0 f s 0 0 aterials onstructability a e conomics 5 erformance (future maintenance) 5 Why Concrete Roundabouts? Why Concrete Roundabouts? D D E C P M R R • • • • •S •A A A F F T T Realize there is a choice N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 What performance characteristics of Where do we typically use concrete pavement? (situations, traffic conditions, applications, etc.) concrete pavement make it the best choice for roundabouts? 5 5 Why Concrete Roundabouts? Why Concrete Roundabouts? D D R R 1. 2. A A F F T T Let’s ask the questions… N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 igh traffic areas 0 reas where future disruption to traffic reas where safety is a priority ituations where we need a “long-term ituations where future maintenance reas with lots of turning movements 5 5 fix” must be kept to an absolute minimum must be kept to a minimum H A A A S S D D R R • • • • • • A A F F T T Answers: Where is Concrete Pavement Used? Where is Concrete Pavement Used? N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c g service life e e 2 2 Doesn’t rut or shove Maintains drainage characteristics No future overlays required (grade issues) 0 0 inimal maintenance requirements esistance to surface deformation ase of construction (constructability) on 0 0 5 5 L R E M D D • • • • R R A A F F Answers: T T Why Concrete for Roundabouts? Why Concrete for Roundabouts? N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e Drainage Skid resistance Lighting n n ore aesthetically pleasing c c uperior safety aspects conomical over long-term (LCC) aster construction e e Why Concrete (cont.) Why Concrete (cont.) S E F M 2 2 0 0 • • • • 0 0 5 5 D D Answers: R R A A F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 Why Concrete Roundabouts? Why Concrete Roundabouts? D D R R A A roundabout applications. F F T T Concrete is the perfect material for N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 Strength Durability Ease of Construction Life Cycle Cost Lighting/Reflectivity Safety Environmentally Friendly Aesthetics 5 5 D D R R A A F F T T Benefits of Concrete Pavements Benefits of Concrete Pavements N N a a t t i i o o n n s a a l t l R R n o o u u e n n d d m a a b t b o o s u u t t u C C j o o d n n f f e e a r r e e n n w c c e e o l 2 2 l ayout locations 0 0 0 0 L 5 5 D • •A D Thickness Design Joint Design Construction R R A A Design of Concrete Roundabouts Design of Concrete Roundabouts F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u software; will be released Fall t t C C o o n n f f e e r r e e n n c c e e Most current Under calibration/implementation 2 2 ew Mechanistic-Empirical Design Guide treetPave 0 0 0 0 2005 S 1993 Pavement Design Guide N 5 5 D • • • D AASHTO PCA (ACPA) Pavement Thickness Design R Pavement Thickness Design R A A F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 ave through, isolate two legs 0 ike normal intersection 0 solate circle from legs 0 0 L P I 5 5 D D • • • Decide on joint layout philosophy Follow 10-step method Joints in circular portion radiate from center Joints in legs are normal (perpendicular) R R A A F F Jointing for Concrete Roundabouts T Jointing for Concrete Roundabouts T Good for small roundabouts or traffic circles? N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 Layout Joints as Normal 0 0 Layout Joints as Normal 5 5 D D R R A A F F T T Ideal for large roundabouts with full detour N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 Isolate Circle from Legs Isolate Circle from Legs 0 0 5 5 D D R R A A F F T T Ideal for roundabouts requiring fast construction under traffic N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o Pave Through Pave Through n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D R R A A F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 ird’s eye view 5 D D B R R • A A Develop a jointing plan Remember rules Follow the steps Be practical! Concrete Roundabout Jointing Concrete Roundabout Jointing F F T T is (~90º (5.0 m) 15 ft > s b Do this by dog-legging joints through curve radius points a N N dd Shapes (keep slabs reating interior corners ngles < 60º labs < 1 ft (0.3 m) wide l a a gs to Avoid wide best) square or pie-shaped) A O S C t t i i o o • •S • • • n n a a l l Thin R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e l r r a e e n c n i c c t e e The Rules of Jointing c The Rules of Jointing 2 2 a 0 0 r 0 0 5 5 P D atch existing joints D nderstand can ut at the proper e lace joints to meet R R gs to Do or cracks time in-pavement structures make adjustments joint location! C P U M A A F F • • • • •B T T Thin N N a a t t i i o unstabilized base (i.e.