precast concrete bridges and elevated road structures, in which large precast cross-sectional "slices" are post-ten- sioned together to form the final struc- ture a method of particular value where sites are limited in area or ac- cessibility as they normally are in the case of elevated urban roads.
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Three "generations" of segmental design were tested at Wexham Springs for the Hammersmith Flyover in Lon- don, Mancunian Way in Manchester and London's new Western Avenue ex- tension. More recently a "fourth generation", for the approach spans of the West Gate Bridge in Melbourne, Australia, has been the subject of model tests.
Improved skidding resistance
The construction process itself and its significance in relation to the pro- perties of concrete, and the aesthetic, functional and economic quality of the resulting products, is the field of the construction research department.
A particularly important area of re- search is concerned with the skidding resistance of concrete carriageways, and the accelerated wear machine has been an indispensable research tool. It consists of a wheel on which are mounted segments of concrete volving in contact with rubber-tyred wheels.
re-
The effects of long periods of normal road traffic can be simulated in the space of 55 hours, and the effec- tiveness of different mixes, aggregates and surface textures in maintaining high levels of skidding resistance can be assessed. In addition, extensive site testing is carried out on completed concrete roads.
As a result of this research, carried out in conjunction with the Ministry
of Transport Road Research Labora- tory, improved methods of applying a long-lasting skid-resistant surface tex- ture during the construction of new roads have been developed. An exam- ple is the development of a new proto- type texturing machine which uses a specially profiled vibrating beam to apply a deeper and longer-lasting trans- apply a deeper and longer-lasting trans- verse texture to the fresh concrete sur- face than has been possible with the widely-used method of wire brushing.
The continued research on textures has resulted in greatly improved skid- ding resistance on recently-constructed concrete roads and those scheduled for construction in the future. A consider- able mileage of concrete carriageway, however, was built before the value of highly skid-resistant texture was fully appreciated and the skidding resistance of these roads is consequently below present-day standards. Along with the development of improved texturing methods for new roads, therefore, the association has carried out extensive research into methods of economically retexturing existing roads.
A concrete paver
Although motorways and trunk roads are most in the public eye, a large amount of the paving work car- ried out every year is on much smaller projects. In the past concrete roads of this type have been built largely by manual and semi-manual methods.
Mechanisation has been hampered by the lack of concreting plant of suf- ficient flexibility and sufficiently eco- nomical to be suitable for such work; a particular problem has been the com- plex layout of housing estate roads with their many intersections, sharp curves and cul-de-sacs.
One of the most promising de-
Much research has gone into the building of Britain's motorways and other major roads. This picture shows the Harrow road flyover in western London. The roadway carries itself clear of a major congestion area in the heart of London.
velopments in this field of concrete paving is the CPP 60 paver, a slip-form paver with automatic line and level control that does away with the need for expensive side forms. Developed by a consortium of which the associa tion is one of three members, the CPP 60 incorporates a number of unique design features that make it especially suitable for smaller-scale concrete pav- ing contracts.
The machine frame is built with telescoping cross-members so that it can be easily adjusted to paving widths from eight to 15 ft. (2.5 m to 4.5 m) or by substituting longer and heavier telescoping members, up to 24 ft. (7.5 m) two-lane width. The design of the slipforming components, and the auto- matic alignment controls, allow curves as sharp as 33 ft. (10 m) radius to be paved without difficulty.
By replacing the tensioned wire guidance sensors with probes following an existing slab, wider roads or large areas such as lorry parks can be paved as a series of abutting slabs.
The association's research is not confined to the tangible and physical. Operational research carried out in a number of fields is being expanded with the establishment of a depart- ment within the Research and De- velopment Division which will work with other departments, applying mathematical and data-processing techniques to all aspects of research with an ICL 1903A computer as a primary tool.
Communication of results
As important as research itself is communication of its results to indus- try, consultants and other research workers. On a direct, day-to-day level the results of the association's research into all aspects of concrete reach the contractor, the engineer and the archi- tect through the technical advisory ser- vice.
On a more formal level, the as- sociation provides a wide range of training courses for students from Bri- tain and abroad.
The range of courses is wide and covers virtually every field of concrete practice and technology. Some are concerned with a single practical aspect of concrete work pumping concrete, concrete floor finishes, moulds for precast concrete and so on. Others are general introductions to concrete construction or reviews of current practice in broad fields.
Courses are designed for all levels of experience from gangers to archi- tects, engineers and quantity surveyors.
Far East BUILDER, July 1970
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