272 The Philippine Journal of Science 1915 



mand fluxing with petroleum residuum as do the true asphalts. 

 Paraffin, an ingredient which must be low in paving asphalts, and 

 is objectionably high in some of the Leyte bitumens, is remark- 

 ably low in the Leyte rock asphalt, amounting to less than 0.5 

 per cent of the bitumen present. Thus the laboratory investi- 

 gation of samples of the Leyte rock asphalt indicate that it 

 could be used for paving. But the question is one which cannot 

 be definitely answered except by actually laying an experimental 

 pavement and observing its behavior under traffic. 



If the rock asphalt proves to be a good paving material, 

 there would be a market for it in the paving of city streets 

 and important roads in the Philippines. The cost of quarrying 

 the rock asphalt and bringing it to deep water should be small. 

 The scarcity of really superior stone for macadam and the cost 

 of the asphalt pavements which have already been laid in the 

 Philippines make it appear that a suitable rock asphalt could 

 be transported from Leyte to Manila and elsewhere at a profit 

 to the quarry enterprise and with a saving in the cost of asphalt 

 pavements. Consul-General George E. Anderson, at Hongkong, 

 believes ^^ that there is a possible market for asphaltic paving 

 materials in oriental cities outside the Philippines. Such a de- 

 mand might mean the profitable exportation of the Leji;e rock 

 asphalt. 



Rock-asphalt pavements have been employed extensively in 

 Europe, especially in France and Italy. In the latter country 

 the production from 1904 to 1912 ranged between 108,000 and 

 191,000 metric tons, valued at an average of about 6 pesos 

 per ton. In the United States rock-asphalt pavements have 

 found less favor than in Europe, partly, at least, because of 

 the cheapness of artificial asphalt from petroleum. Oklahoma 

 rock asphalt is coming into use, however, and even in California, 

 where artificial asphalt obtained from petroleum is abundant, 

 27,600 metric tons of rock asphalt, valued at 6.18 pesos per 

 ton, were mined in 1913.^- 



Rock asphalt in pavements is laid like sheet asphalt. A con- 

 crete foundation is generally employed, and the rock asphalt, 

 pulverized to maximum diameters of 1 centimeter, is heated to 

 about 150° C. (considerably less than the temperature required 

 for sheet asphalt), spread on the foundation with rakes, and 

 rolled while hot. The wearing coat is about 5 centimeters thick 

 after rolling. 



"Daily Consular and Trade Report, June 9 (1914). 



"Data taken from Min. Resources U. S. Geol. Surv. (1913), pt. 2, 539. 



