Diamond grinding of concrete pavements Geoff Ayton Pavement Structures Section Engineering Technology Branch 8 Sept 2008

Surface profiles & water spray Ride comfort

Surface treatments Three treatments Milling

    Background information: Surface profiles PIARC Roughness Microtexture There are 4 distinct surface profiles (as shown above). The first two are desirable but the third & fourth are undesirable. Microtexture is the main contributor to friction (the sandpaper effect). Macrotexture doesn't (of itself) provide friction but is responsible for dispersing water so that the tyre stays in contact with the microtexture, hence it indirectly contributes to wet-weather skid resistance.  Macrotexture  Megatexture  Roughness

* * Roughness Ride comfort Critical wavelengths change with traffic speed because of frequency influence. * * Roughness Ride comfort

Milling 15mm: coarse milling 8-9mm: fine milling 6mm: micro-milling There are three different grades of "milling" depending on the spacing of the cutters. 15mm: coarse milling 8-9mm: fine milling 6mm: micro-milling

Cumberland Hwy, Wentworthville

Coarse milling * strongly discouraged on concrete surfaces * harsh and noisy ride * unacceptable damage to joints

Diamond grinding

Grooving Pacific Hwy - Wang Wauk

Diamond grinding

Diamond grinding Door plane

Purposes Grinding of concrete pavement improved ride quality * everyday treatment for decades * ~100 grinders * most commonly used as a rehabilitation treatment * also sometimes used on new pavements Purposes improved ride quality reduced tyre noise reduced dynamic traffic impact improved skid resistance

1. Grinding, produces a completely new running surface, hence changing macrotexture and microtexture. 2. Sawblade spacing such that the concrete fins are snapped off thereby producing a new surface

1. By comparison, grooving places sawcuts in the existing surface 2. After grooving, the tyre is still running on the old surface. The macrotexture will be improved but not the microtexture

Grinding Grooving In summary  improves ride quality  improves microtexture  improves macrotexture (albeit longitudinal)  reduces tyre noise Grooving  has no impact on ride quality  has no impact on microtexture (hence no improvement in dry friction)  improves macrotexture, hence improves water dispersion  is likely to increase tyre noise

Summary Distinctly different profiles Milling

Road Noise dB(A) Jeff Parnell. MEngSc thesis. 2006.

Road Noise dB(A) Dash, Bryce, Moran & Samuels. ARRB. Mar 2002

Grinding reduces tyre noise on concrete by removing those texture wavelengths which are responsible for generating the most annoying spectral frequencies. 1/12th Octave, 7.5m offset, F3 near Wyong Jeff Parnell. MEngSc thesis. 2006.

Grinding Megatexture in CRCP Transverse N12 @ 750 c/c Megatexture in JRCP Mesh SL82 * Grinding can remove both roughness and megatexture. * These textures ~2-3 mm deep and so readily removed by grinding.

Grinding Bridgedecks under headlights

Longitudinal grinding followed by transverse grooving.

California - 1989. Grinding on a major overpass.

Florida USA - 2001. An old JRCP after grinding.

USA. Traffic on a pavement during grinding operations.

Grinding in echelon.

Ziming Tu Dr Hans Prem

Effect of grinding (on ride) Enables evaluation of the benefits of targeted grinding on both the ride quality and the resulting incentive value