802 



SCIENCE 



[N. S. Vol. XLI. No. 1065 



difficulties developed, and it was decided to increase 

 tlie size of tlie briquets to 35 mm. high X 50 mm. 

 diameter. No difficulty is now found in molding 

 the specimens. 



These tests, which the writer has called binding 

 value tests, furnish (o) an easy means of com- 

 paring the adhesive and the cohesive strength of 

 binders, (6) a control of the amount of binder 

 to use, and (c) a quick way of determining the 

 correct amounts of stone, sand and filler to use. 

 The Purchase of Asphalt and Asphaltic Cement 



on the Bitumen Basis: W. H. Beoadhukst. 



To those familiar with the nature and compo- 

 sition of asphalts and asphaltic cements, the ad- 

 vantages from an economic standpoint of pur- 

 chasing these materials on the bitumen basis is 

 obvious. The bitumen, or earbon-bisulphide-sol- 

 nble content of an asphalt, being the eementitious 

 material which binds the mineral aggregate of an 

 asphalt pavement or bituminous concrete together 

 in a compact mass, it follows that, without giv- 

 ing consideration to the character of the insoluble 

 material, or whether the same improves the value 

 of the asphalt as a paving material or is deleter- 

 ious, the greater the percentage of the insoluble 

 material, the less the efficiency of the asphalt in 

 respect of the number of square yards of road- 

 way per ton of asphalt a given asphalt or asphaltic 

 cement will lay. Hence to place all asphalts in 

 competition on an economically sound or even 

 basis, the same should be bought on the basis of 

 the contained bitumen. Specifications for the 

 purchase of asphalt should therefore be drawn 

 outlining the requirements, first as to quality, and 

 secondly, as to quantity of contained bitumen, in- 

 stead of requesting merely bids for refined asphalt, 

 or asphaltic cement, which is a very prevalent 

 custom to-day with many municipalities operating 

 municipal asphalt repair plants and state highway 

 commissions purchasing asphaltic cement for state 

 roads. 

 A Change in the Asphalt Pavement Specification: 



John Martin. 

 Allowaile Maximum Penetration of Various Types 



of Asphalts for Use in the Several Kinds of 



Bituminous Pavements: H. B. Pullar. 



The writer would state that in his own opinion 

 there is no set rule which can be adopted or fol- 

 lowed in setting a maximum penetration for any 

 type of asphalt or any type of bituminous con- 

 struction; that it is necessary to consider the local 

 conditions in conjunction with the various bi- 

 tuminous materials on the market and to incorpo- 

 rate them in such a way into the specifications so 



as to get most satisfactory results. The writer 

 further believes that the maximum penetration is 

 merely one of the many small but important de- 

 tails of construction which must be considered 

 separately for each different piece of work, and 

 that in order to get bids on bituminous materials 

 specifications should be so drawn with limits suffi- 

 ciently open to produce maximum competition 

 with reverting specifications on bituminous mate- 

 rials, these reverting specifications to be drawn up 

 with limits narrow enough to exclude anything 

 but the highest quality of material for that par- 

 ticular type of bituminous material and at the 

 same time not be unjust to the producers of the 

 different kinds of bituminous materials. Under 

 this kind of a specification it is possible to take 

 into consideration all of the local conditions, the 

 different characteristics, and the inherent quali- 

 ties of the different bituminous materials and to 

 incorporate in these specifications the allowable 

 maximum penetration for the particular type of 

 pavement and under the particular conditions it 

 is to be constructed, and the writer believes that 

 it is only by this method that the most successful 

 results can be obtained. 



A Review of the Use of Bituminous Materials in 



Sighway Engineering during 1914 : Abthuk 



H. Blanchard. 



During 1914 the following noteworthy develop- 

 ments have been noted: 



In specifications for bituminous materials there 

 has been a tendency to adopt a group of type 

 specifications in place of a blanket specification. 

 By this method engineers have been able to secure 

 the most suitable grade of a given type of bi- 

 tuminous material for a given method of con- 

 struction, as it is practicable to specify desir- 

 able limits for each type rather than have wide 

 limits, as is necessary in blanket specifications. 

 Another self-evident advantage is that more uni- 

 form material may be secured by this method. 



Bituminous surfaces have been constructed (a) 

 with more attention to the physical properties of 

 the road metal composing the wearing course and 

 the requisite dryness and cleanliness of the surface 

 prior to application of the bituminous material; 

 (6) using to a greater extent bituminous materials 

 which do not require from several days to three 

 weeks to set up; (o) generally employing pres- 

 sure distributors in place of hand methods and 

 gravity distributors. 



In the construction of bituminous macadam 

 pavements there has been a noteworthy tendency to 

 (a) use bituminous cements of a lower penetra- 



