392 



SCIENCE 



[N. S. Vol. XLV. No. 1164 



Concrete foundations should be used on weak sub- 

 soil of clay, etc. Portland cement concrete roads 

 and foundations crack, causing corresponding 

 cracks in the pavement surface, which is retarded 

 by the use of either broken stone or bituminous 

 concrete foundation. Bituminous pavement surfaces 

 are more liable to creep on Portland cement con- 

 crete than on broken stone or bituminous concrete 

 foundations, as in the latter cases the surface and 

 foundation are firmly united to each other. Port- 

 land cement concrete foundations should be used 

 where a maximum rigidity is essential. 



Present Status of Bituminous Surfaces on Gravel 

 Boads: John E. Eablin. 



Value of Physical Tests on Bituminous Aggregates: 

 Pkevost Hubbard. 



Proportions of Ingredients of Bituminous Mortars 



Used for Fillers: Phillip P. Shaeples. 



Bituminous mortars used for fillers in block 

 pavements have been used in the United States of 

 America since 1913. These fillers consist of mix- 

 tures of coal tar pitch and sand, or asphalt and 

 sand. Specifications for both kinds were adopted 

 at the 1916 meeting of the American Society of 

 Municipal Improvements. 



These bituminous mortars are particularly well 

 adapted for use in filling the joints of stone block, 

 brick, lug wood block and Durax pavements. Ob- 

 servation shows that the asphalt-sand mastic does 

 not fill the joints as well as the pitch-sand mortar, 

 owing to the higher melting point of the former 

 and its lower adhesive value. 



Summary. — Those bituminous mortar fillers that 

 have given trouble to date have done so because 

 not sufScient sand was originally mixed with the 

 bitumen. A fine sand gives much better results 

 than a coarse sand, and more of it can be intro- 

 duced in the mastic. By properly heating and ap- 

 plying, a mastic with equal parts, by volume, of 

 sand and bitumen can be forced into the joints of 

 block pavements. For special conditions, special 

 grades of bitumens must be used. Hand mixing 

 is cheaper than machine mixing, and as good. The 

 pouring method should be entirely dispensed with 

 and the flushing and squeegeeing method substi- 

 tuted. 

 Present Status of Physical Tests for Granite 



BlocTcs: C. D. Pollock. 



This paper gives the progress made in tests of 

 granite for paving blocks and reviews the changes 

 made in such tests in standard specifications which 

 have been in very general use. 



Even the latest tests are far from ideal, as the 



conditions which prevail in the tests do not ap- 

 proximate those which exist in actual traffic on the 

 pavements. 



Engineers are now studying this question and 

 undoubtedly will work out some tests which will 

 more nearly conform to the wear and tear of the 

 traflSc on the granite block pavements in the 

 street. 



The service test at the present time is the only 

 sure and reliable test. 



Joint Fillers for Granite BlocTc Pavements: Hee- 



MAN H. Schmidt. 



In this paper the development of the granite 

 block pavement is traced from the first granite 

 pavement laid which resembles our modern granite 

 pavement, up to the present highly improved gran- 

 ite pavement, as laid in our large cities. 



A detailed statement of the requirements of ideal 

 joint fillers is given, followed by a discussion of 

 the various joint fillers used and available. In this 

 discussion the defects in each are pointed out, and 

 the writer suggests what in his estimation would 

 be an ideal joint filler. 



There is also a brief discussion of methods for 

 applying joint filler, and mention is made of the 

 character of the cushion course which will give best 

 results. 



The writer's conclusion is that with slight 

 changes in the methods of work and improvement 

 in the character of joint filler, granite pavement 

 will have reached the highest state of development 

 of which it is capable. 



The Real Sources of Trouble in BricTc Pavements: 



Maurice B. Greenough. 



The most common imperfections in brick pave- 

 ments are caused by non-enforcement of adequate 

 specifications reflecting the best procedure of mod- 

 ern methods. One hundred per cent, construction 

 is not possible of attainment under some specifi- 

 cations in force which are indefinitely worded and 

 incomplete. Few imperfections are caused by 

 brick of poor quality. The American Society for 

 Testing Materials has adopted procedures which, 

 if followed, insure securing the required degree of 

 quality in the brick. Monolithic construction, 

 while not a panacea for all brick pavement 

 troubles, eliminates the hazards of a faultily pre- 

 pared sand cushion and affords a large measure of 

 protection against most brick pavement imperfec- 

 tions. 



A. H. Blanchaed, 



Secretary 

 {To he coivcluded) 



