High friction surfacing (HFS) is a specialist type of road coating with very high skid resistance. It is used in the UK at locations where there is significant risk of serious or fatal accidents. This paper considers the aggregate used in HFS. Calcined bauxite is the only aggregate that provides the highest levels of skid resistance over the longest period. No naturally occurring aggregate has been found to give a comparable level of in-service performance. This paper reviews the historical development of HFS in the UK relating to aggregate. In-service performance is predicted in the laboratory using the Wear test which subjects test specimens to an estimated 5–8 years simulated trafficking. Examples are given of Wear test data. They illustrate why calcined bauxite performs better than natural aggregate. They show how the amount of calcined bauxite can be reduced by blending with high skid resistant natural aggregates. Data from the Wear test can be related to every HFS laboratory experiment and road trial carried out in the UK for over the last 50 years. Anyone considering the prediction of HFS performance needs to carefully consider the data given in this paper with any other test method currently being considered or used to investigate HFS.

High friction surfacing (HFS), bonded to a road surface at high risk locations, has been shown to significantly reduce road fatalities and serious injuries, i.e., HFS saves lives. Calcined bauxite is the preferred aggregate for use in HFS systems due to its unique ability to resist polishing and abrasion by vehicle tires. Calcined bauxite is expensive, negatively impacts the environment due to mining, production and transporting processes and has come under supply pressures in recent years. This paper investigates the potential for blending natural aggregates with calcined bauxite for use in HFS systems. The experiments involved subjecting HFS specimens to laboratory simulated trafficking and testing for skid resistance, texture depth and mass loss. The testing was carried out in laboratories in Spain and Northern Ireland. The findings suggest that there is the potential to reduce the amount of calcined bauxite used in HFS systems by replacing a percentage of the calcined bauxite with high PSV natural sandstone or volcanic tuff aggregate. The impact of this research could reduce the risks associated with supply issues to the HFS industry, reduce environmental impact by using less calcined bauxite in HFS systems and reduce costs associated with the aggregate component of HFS systems—enabling road authorities to install more systems at high risk locations to further reduce fatalities and serious injuries on their roads.

This article considers semi-flexible composite (SFC) pavement materials made with reclaimed asphalt planings (RAP) and geopolymer cement-based grouts. Geopolymer grouts were developed and used to fill the internal void structure of coarse RAP skeletons with varying levels of porosity. The geopolymer grouts were formulated at ambient temperature using industrial by-products to offer economic and environmental savings relative to conventional Portland cement-based grouting systems. They were characterised on flowability, setting time, and compressive strength. The effect of grout and RAP on SFC material performance was evaluated using permeable porosity, compressive strength, and ultrasonic pulse velocity. SFC performance was significantly influenced by both grout type and RAP content. Improved performance was associated with mixtures of high-flowability/high-strength grout and low RAP content. A practical limitation was identified for combination of grout with low-flowability/fast-setting time and well-compacted RAP skeletons. Solids content exceeding 49% by volume was not feasible, owing to inadequate grout penetration. A suite of SFC materials was produced offering performance levels for a range of practical pavement applications. Preliminary relationships enabling prediction of SFC elastic modulus based on strength and/or ultrasonic pulse velocity test data are given. A pavement design is given using SFC as a sub-base layer for an industrial hardstanding.

This paper details the first assessment of asphalt mixes used in Ireland using the Wehner Schulze test equipment. The mixes assessed were 10-mm SMA, 14-mm SMA, and hot-rolled asphalt (HRA) made with PSV 62 greywacke aggregate. The Wehner Schulze was developed about 30 years ago in Germany and is currently being considered as a European Standard test method. The equipment used was located at IFSTTAR in Nantes, France. Asphalt test specimens (305 mm x 305 mm x 50 mm) were prepared using a Cooper roller compactor. 225-mm diameter cores were then extracted from the slabs for testing on the WS machine. The results found the 10 mm and 14 mm to have higher friction coefficient values compared with the hot-rolled asphalt. Analysis of the data suggests that this is probably due to differing types of contact between the asphalt surface and the Wehner Schulze polishing rollers and rubber pads used for friction measurement. The investigation suggests that the tire-asphalt surface interface needs further research to help explain both the laboratory and on-site measurement of friction.

The Navy's early-stage design tools are integrated with the Leading Edge Architecture for Prototyping Systems (LEAPS) data repository, thus enabling a streamlined, cohesive approach to the creation, storage and access of data pertinent to a ship design. The Smart Ship System Design (S3D) design environment currently under development within the Electric Ship Research and Development Consortium (ESRDC) recently completed development of S3D as a LEAPS application and is extending its capability to include the LEAPS application framework, multi-platform compatibility, and added functionality.