P di ti fP tS f Skid R Prediction of Pavement Surface Skid R Prediction of Pavement Surface Skid R Effect of Smaller Chip S Effect of Smaller Chip S Birendra Kumar Birendra Kumar Dr Douglas Wilson Dr Douglas Wilson Introduction Results Introduction Research has demonstrated that the road based transport Results Research has demonstrated that the road based transport h i h kid i f d f The DFT (μ) friction results crash rate increases as the skid resistance of road surface surface sample (initial skid r decreases. This research compares the equilibrium skid surface sample (initial skid r accelerated polishing in hour decreases. This research compares the equilibrium skid resistance level of various natural and artificial surfacing accelerated polishing in hour diff l ( resistance level of various natural and artificial surfacing i l di i h hi i d different aggregate samples ( aggregates including varying the aggregate chip size under artificial electric arc furnace) laboratory based accelerated polishing and in response to artificial electric arc furnace) of the materials (greywacke changes in environmental conditions Previous research has of the materials (greywacke ith t diff t hi i changes in environmental conditions. Previous research has h th t t kid it f hi l f i t with two different chip sizes shown that wet skid resistance of chipseal surfaces is not value at which the DFT (μ) l only a function of the polishing resistance of the aggregate, sample is shown graphically but also of its size shape and spacing sample is shown graphically E ilib i Skid R it but also of its size, shape and spacing. Equilibrium Skid Resistance Experimental Methodology Experimental Methodology A lb i d i d h Ui i f A laboratory experiment was designed at the University of Auckland (UoA) to simulate the in-field skid resistance performance of surfacing aggregates The experiment Initial Skid Resistance performance of surfacing aggregates. The experiment i d l td lb t li hi f i ti t ti required accelerated laboratory polishing, friction testing with a Dynamic Friction Tester (DFT) and surfacing samples to be constructed that were compatible with each samples to be constructed that were compatible with each other The testing process and methodological steps are other . The testing process and methodological steps are shown in Figure 1. Figure 2: Friction (μ Figure 2: Friction (μ Step 1: Preparing an Step 3: Friction Testing a Step 1 : Preparing an t l t t t prepared Sample DFT (μ) Figures 3 and 4 respectively aggregate sample to test Figures 3 and 4 respectively greywacke and a South Auc greywacke and a South Auc kid i i skid resistance improvemen chip size from a Grade 4 to chip size from a Grade 4 to demonstrate the effect on m demonstrate the effect on m th dditi f i t the addition of various cont reached (oedometer clay, le powder) with accelerated p Step 2: Polishing with The Dynamic Friction Tester powder) with accelerated p hd Accelerated Polishing Machine The Dynamic Friction Tester and Rubber sliders reached. and Rubber sliders Figure 1: Testing Methodology Figure 1: Testing Methodology R it d th Resistance and the Resistance and the ize ize THE UNIVERSITY OF AUCKLAND FACULTY OF ENGINEERING DEPARTMENT OF CIVIL AND DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING from a newly prepared resistance) through resistance) through rs for three geologically rs for three geologically ( k b l d (greywacke, basalt and an ) are shown in Figure 2. Two ) are shown in Figure 2. Two and basalt) were then tested and basalt) were then tested (G d 4 G d 6) Th (Grade 4 vs. Grade 6). The levelled off for each aggregate and described as the polished and described as the polished (ESR) l l e (ESR) level. Fi 3 Chi Si ff f G k Figure 3: Chip Size effects for Greywacke aggregate Polished Equilibrium Skid Polished Equilibrium Skid Resistance (ESR) level Resistance (ESR) level Figure 4: Chip Size effects for Basalt aggregate μ) vs Polishing Time Research Conclusions μ) vs Polishing Time Research Conclusions 1) Th tifi i l El ti A F t (G d 4) 1) The artificial Electric Arc Furnace aggregate (Grade 4) y for a South Auckland performed the best of the three geological materials and y for a South Auckland ckland Basalt demonstrate the contaminants had very little effect ckland Basalt demonstrate the f d i h contaminants had very little effect 2) The Grade 4 gre acke and basalt aggregates performed nt of reducing the aggregate 2) The Grade 4 greywacke and basalt aggregates performed o Grade 6. The figures also very similarly at ESR level although the basalt had a much o Grade 6. The figures also measured skid resistance with higher initial skid resistance measured skid resistance with t i t ft ESR h b higher initial skid resistance 3) Both the greywacke and basalt aggregate demonstrated a taminants after ESR has been 3) Both the greywacke and basalt aggregate demonstrated a i ifi i h ll G d 6 eighton buzzard sand , emery significant improvement when a smaller Grade 6 polishing after ESR has been aggregate chip was used in comparison to a Grade 6 chip polishing after ESR has been (24% and 35% improvement respectively) (24% and 35% improvement respectively).