SPECIFICATIONS FOR NONBITUMHsTOUS ROAD MATERIALS. 19 



SPECIFICATION Sd-1. 



Natural Sand Clay or Topsail Mixtures for Road Surfacing. 



The sand clay or topsoil shall be composed of a uniform mixture of General. 

 hard durable fragments of sand, together with silt and clay, and may 

 advantageously carry a considerable amount of gravel. The mixture 

 should be free from an excess of feldspar or mica. 



Cementing value of material under | inch shall be not less than 35 Quality. 



The material which will pass a 10-mesh sieve when tested by means of Grading. 

 laboratory sieves shall meet the following requirement for grading : 



Per cent. 



Clay 10 to 25 



Silt - 10 to 25 



Total sand 50 to 80 



Tests of the cementing value and grading of the sand clay or topsoil Methods of 

 shall be made in accordance with the following methods : Testing. 



Cementing value, U. S. Department of Agriculture Bulletin 347, p. 19. 

 Grading, U. S. Department of Agriculture Bulletin 555, p. 33. 



This specification is intended to cover the quality and approxi- 

 mate grading of natural sand clay and topsoil mixtures for use 

 particularly in the South Atlantic States. 



The limits of sizes are drawn so as to exclude only sand clay 

 and topsoil of manifestly inferior grading. Where heavy traffic is 

 to be expected, and likewise in cases where the available mate- 

 rial warrants, the minimum allowable percentage of sand should 

 be increased and the corresponding maximum allowable per 

 centage of both clay and silt decreased. In cases where it is de- 

 sired to construct a sand-clay road by admixing sand and clay in 

 place, the amounts of each to be incorporated should be so 

 gauged that the combined material, after thorough mixing, will 

 grade approximately within the limits here shown. 



The maintenance of a sand-clay road should be continuous. 

 Patching should be done with material as nearly like that used 

 in the original surface as possible. 



