UNITED STATES MINERAL RESOURCES 



LIGHTWEIGHT AGGREGATES 



By A. L. Bush 



CONTENTS 



Page 



Abstract of conclusions 3S3 



Foreword 333 



Structural lightweight aggregates 335 



Introduction 335 



Exploitation 335 



Clays, shales, and slates 338 



Volcanic rocks 341 



Scoria and volcanic cinder 342 



Pumice and pumicite 343 



Diatomite 345 



Other materials 345 



Ultralightweight aggregates 345 



Introduction 345 



Exploitation : 346 



Volcanic rocks 347 



Perlite 347 



Pumicite 348 



Vermiculite 348 



Selected references 351 



FIGURES 



42. 



Graph showing production of materials used as 

 structural lightweight aggregates in the 

 United States, 1940-60 336 



Triangular diagram showing comparative com- 

 position of bloating and nonbloating argilla- 

 ceous rocks 340 



Graph showing production of materials used as 

 ultralightweight aggregates in the United 

 States, 1935-70 346 



TABLES 



66. 



68. 



Classification and properties of lightweight ag- 

 gregate materials 



Comparative composition of expansible clays, 

 shales, and slates 



Comparative composition of volcanic glasses 



Page 



334 



338 

 341 



ABSTRACT OF CONCLUSIONS 



The United States is adequately supplied with both struc- 

 tural lightweight aggregates (scoria, volcanic cinder, pumice 

 and pumicite, expandable clays, shales and slates, diatomite, 

 expanded blast-furnace slag, and fly and bottom ash) and 

 ultralightweight aggregates (expanded perlite, expanded 

 pumicite, and exfoliated vermiculite). The aggregates are 

 low unit value, high place value materials, partly because 

 large quantities are available and partly because normal- 

 weight (sand and gravel) and synthetic aggregates are 

 stiff competition. However, they have high place value, in as 

 much as transportation costs largely determine whether they 

 are used. 



Recoverable reserves of expanded clays, shales, and slates 

 are equivalent to about half the cumulative output needed 

 through the year 2000. For the same period, scoria, cinder, 

 pumice, and pumicite reserves are at least twice the esti- 

 mated demand, and perlite reserves seem to be at least as 

 large, and vermiculite reserves somewhat larger than their 

 respective demands. 



Virtually no export or import markets exist for the light- 

 weight aggregates. Along the eastern seaboard, oceanic 

 freight rates allow competition between pumioe from western 

 domestic sources and pumice imported mostly from the Medi- 

 terranean area, but only a few hundred thousand tons per 

 year are involved. For similar reasons, a few thousand tons 

 of vermiculite are imported annually from the Republic of 

 South Africa. A few thousand tons of domestic perlite are 

 exported to Canada per year. 



The prospects for converting hypothetical and speculative 

 resources of clays, shales, scoria, cinder, pumice, and pumi- 

 cite to recoverable reserves are excellent. For perlite and 

 vermiculite, the prospects are good. 



FOREWORD 



Many materials serve primarily as lightweight 

 aggregates for concretes and plasters, but some of 

 them find even more use as construction materials 

 in their own right, as components in manufacturing 

 processes or in end products, or as aids of various 

 kinds in agriculture. Some are used for their physical 

 properties alone, but for most the chemical prop- 

 erties also are significant. Some are used with only 

 minimal processing, such as crushing and grading, 

 but others require fairly complex and sophisticated 



U.S. GEOL. SURVEY PROF. PAPER 820 



333 



