The Design of Thin, Silica Sand-Asphalt, Wearing Surfaces for Highways and Bridges

This study was performed at the Highway Materials Research Laboratory in Lexington, Kentucky. In this study the various sands were combined with a sphalt cement of penetration 60 to 70 and tested by the Marshall method to determine the physical characteristics of the mixtures. Other variables investigated were the hardness of the asphalt cement and the amount of mineral filler. A coefficient of friction was determined, by means of a laboratory testing device, for each of the mixtures. Due to the promising results of the laboratory testing, and the successful re-surfacing of bridges with silica sand-asphalt mixtures in the New York area; the Research Division of the Kentucky Department of Highways, in June 1958, recommended silica sand-asphalt for the re-surfacing of Clark Memorial Bridge in Louisville. All laboratory testing of sands up to that time had been of crushed sandstones. The lack of sands tone in the Louisville area led to an investigation of the possibility of blending locally available bank and river sands. Various blends of the river and bank sand were tested, with and without mineral filler; and it was concluded that a satisfactory mixture could be manufactured using these sands

Hot-Mix Coal-Tar Concrete Pavement and Multiple, Coal-Tar Seals on Shoulders

It is proposed to construct an experimental section of roadway, 6.6 miles in length, using coal-tar concrete for base and surface, and to use multiple, coal-tar seals (3 seals) with coverstone on the shoulders. A section of pavement, 5.1 miles in length, incorporating the same structural thicknesses and types of courses but containing normal asphaltic binders, to be constructed on the same route will be designated for comparison and control purposes. The use of the coal-tar will be in compliance with Section 201(e) of the Appalachian Regional Development Acts of 1965

Class I Bituminous Mixtures

The attached report reflects the degree of excellence sought in bituminous concrete pavements in Kentucky during the past several years. In the evolvement of the present state of the art, idealized concepts of mixture design have been dutifully tempered with practical considerations, experience factors, and performance features which may not be altogether apparent from this report alone. In substance, the study has been concerned with aggregate gradations, construction operations, and quality of the pavement surface. The achievement of gradation control in the dust of filler sizes has provided opportunities to further optimize mixture requirements. Permissive blending of sands has enabled the utilization of a broader array of materials. Surface appearance has improved; stability has been increased about four-fold; densities are higher; and enhanced durability already seems evident. From these standpoints, the objectives sought are now seemingly replete. Two factors remain sufficiently ominous and formidable to command further attention

A Machine-Laid Surmountable Bituminous Concrete Median

On August 28, 1961, personnel of the Research Division were requested to observe a demonstration of a newly developed Etnyre Median Paver. The demonstration was given at the Lehman-Roberts Company plant in Lexington, and was arranged primarily for the benefit of the paving contractor working on Euclid Avenue in Lexington. The paving contract called for the construction of a surmountable bituminous concrete median which, to our understanding, is the first instance for construction of that type to be machine-laid. Some doubts arose during the demonstration as to the ability of the machine to hold alignment and to give adequate compaction. Following the demonstration, it seemed advisable to examine the finished median from the standpoint of density and stability. Representatives of the Division of Design, present at the demonstration, requested that the Research Division examine and evaluate a short trial-section of the median. The trial-section, approximately 25 ft. long, was laid that afternoon on the lot of the Thompson, King and Tate Ready-Mix Concrete Company in Lexington

Construction and Interim Performance Report of Experimental Salt (NaCl) Stabilization of Plant-Mixed, Dense Graded Aggregate

For some time the Department has been interested in building-up and retaining thicknesses of granular base course on rural roads through the use of various stabilizing additives and(or) the use of light asphalt seals or surfacings (1, 2, 3, 4, 5, 6). These efforts more or less recognize that the stage construction concept is frustrated by weather and traffic erosion of unbound and exposed granular base material. Thus, the motive in experimenting with and in utilizing these treatments is to find economical and effective means by which a granular base can be built and retained until such time that a higher type bituminous surface can be constructed upon it

Kentucky Rock Asphalt Bases and Hot-Mix Surfaces; Experimental Construction

The objectives of this study are disposed toward the development of Kentucky Rock Asphalt for use as a traffic-bound base and surface on rural roads near its source and toward re-development of the material for use as hot-mixed, hot-laid, skid-resistant surface course for higher echelon roads. The material is a natural asphaltic-sandstone which occurs in considerable abundance in Edmonson County and in other outcrops of Pottsville sandstones bordering the eastern rim of the Western Kentucky Coal Fields. From 1900 until the 1950\u27s, rock-asphalt was used extensively in Kentucky and elsewhere for road surfacing and was regarded widely as a premium-grade material -- providing a soft-riding, sand-textured, skid-resistant pavement. The crushed, natural product -- traditionally containing 7.2 percent natural bitumen -- was characteristically tender for a long time after it was spread on the road; consequently, it could not reliably withstand modern traffic. In the past, several attempts were made to process and pre-roast the material to overcome this deficiency, but none proved to be wholly desirable. Production was discontinued in 1956. Re-development began in 1962 with trial uses of lower grade (lean) materials as traffic-bound bases and surfaces on minor roads. These early experiments did not produce favorable performance; in some of the interim experiments, the material was up-graded with additions of liquid and emulsified asphalts; and, in other the raw base courses were sealed, a major development, recently, was the successful production of a hot-mixed, enriched, mixture processed through a conventional dryer, pugmill, etc. The raw aggregate consisted of crushed, graded lean rock -- containing 4 percent or more indigenous bitumen

Class I, Type B, Plant-Mix Initial Treatment, PAC-9

Initial surface treatments of so-called traffic-bound macadam rural secondary roads presents a challenging but frustrating problem in the over-all highway program. In many cases, these roads do not merit the expenditures that would be needed to construct the type of pavement desired, yet there is a need for a dust-free, all-weather type of surface for these roads. It may be argued, for instance, that initial surfacing should be deferred until such time that the construction of a proper base and surface would be justified. On the other hand, one might argue that even a light surfacing would be preferred despite the fact that expensive maintenance might be incurred subsequently. Notwithstanding these or other persuasive arguments, initial treatment work comprises an engrossing proportion of the highway program