RUT MIX CHALLENGE

GAUTRANSRPF NOVEMBER 2006

RUT MIX CHALLENGE

• The need arose from increased occurrence of premature failures

• As a result Client bodies want to move away from asphalt to concrete

• Better solution would be a properly designed asphalt that will be:– Rut resistant– Durable at low and high temperatures– “User Friendly” (Manufacturing & Placing)

RUT MIX CHALLENGE

• Role players in asphalt industry to develop 2 asphalt mix designs namely:– Rut resistant intersection mix– Every day highway mix

• Subsequently high modules asphalt included– Shell with low pen binder (French Technology)– Sasobit with 40/50 or Sasoflex (German & French Technology)

These mixes will then be paved on a freeway in Pretoria and tested for rutting, fatigue etc.

• Rules for mix design:– No modified binders (Rut mix & Highway mix)– Any grading (Not limited to Colto Spec.)– Mixes to be verified prior to paving of trials in Pretoria– Reference mix to be paved and tested prior to trials being paved

RUT MIX CHALLENGE

RUT MIX CHALLENGE

WEST RAND

Mix design process

– First plant trials completed– Intersection mix is promising (Performance testing indicates

good rut resistance)• Paving trial planned on R25

– Freeway mix needs refining• Further plant trials planned

RUT MIX CHALLENGE

RUT MIX CHALLENGE

EAST RAND

Performance requirements

Test type utilized

Criteria set Performance Value

Mix 1 Mix 2

Mix 1: WC for highly trafficked roads

Mix 2: WC for highly trafficked intersection

Quartzite Dolerite Quartzite Dolerite

Deformation resistance

MMLS on briquettes at 50°C wet [on cores] (mm)

<1.8 <1.6 1.74 1.4 1.2

Average deformation per cycle in 2 000 – 3 000 range of DCT ()

<0.4 <0.35 0.12 0.33

Gyratory voids at 300 repetition (on a 5% Marshall VIM’s setting)

>2.7 >3.0 2.8 3.2 4.3

Durability Mod Lottman >80% >80% 85 90 84

Fatigue

4 Pt beam fatigue (at 200 micron strain) : Reps to failure

>2 million >2 million To be tested 3.179 m

ITS (kPa) >1 000 >1 000 1368 1222

RUT MIX CHALLENGE

• Verification with Performance Properties

RUT MIX CHALLENGE

AKASIA ROAD SURFACING

Akasia Road Surfacing - Mix design process

– Design in process– Change of aggregate source (From Rooiberg to Granite from

Buffalo quarry Naboomspruit)– Mix type not finalized

RUT MIX CHALLENGE

RUT MIX CHALLENGE

BLACK TOP

NICO WILCOCKS

Mix design process

– TRH8 Coarse– Chrome Slag from Witbank

• High PSV

• Rough surface texture

• Good adhesion

• Varying surface area

• No swell problems

– Mix used successfully on N4 at Tollgate bypass

RUT MIX CHALLENGE

NICO WILCOCKS

RUT MIX CHALLENGE

HIGH MODULUS ASPHALT

(HiMA)

High Modulus Asphalt (HiMA)Mix design process

Sasobit– Soillab busy with mix designs similar to Hamburg International

Airport (40/50 Bitumen + 3% Sasobit)

Shell– Aggregate and bitumen samples sent to Shell Global Solutions

France (Low pen bitumen)

RUT MIX CHALLENGE

ACHIEVING VOLUMETRICS IN ASPHALT

BAILEY METH0D

IS NOT A SPECIFICATION!!!

• What is voids and VMA?

Bailey Method

Volume Voids (3% - 6%)

Volume Binder (10% - 17%)

Volume Aggregate (83% – 90%)

VMA