except as to grading. Importantly, the coarse aggregate should not be 

 susceptible to excessive breakage and attrition during handling and placing 

 in the forms. The void content of the coarse aggregate after placement in 

 the form will customarily range between 38 to 48 percent. For economy, it 

 is desirable to keep the void content as low as possible to minimize the 

 required volume of the intruded grout. A low void content not only results 

 in a saving in cementing materials, but, concomitantly, less volume change. 



The maximum size aggregate depends on availability, type of construction 

 involved, and usual limitations established for thickness of section and 

 spacing of reinforcement bars (King, 1959) . The minimum recommended size is 

 dependent, essentially, on sand grading. Typical aggregate gradations are 

 shown in Table 26. When grout is prepared with sand graded for use in 

 conventional concrete, minimum coarse aggregate size should be 38 millimeters 

 (1.5 inches). When a mason or plaster sand grading is used, minimum coarse 

 aggregate size may be reduced to as low as 13 millimeters (0.5 inches). No 

 limit is placed on maximum size of the coarse aggregate. 



Table 26. Typical aggregate gradations for preplaced aggregate 

 concrete prepared with fine sand grout containing 

 pozzolan and fluidifier 









Typica 



tl fine aggregate grading 











Cumulative 



percentage passing given sieve 







No. 8 



No. 16 





No. 30 



No. 50 



No, 100 



Pan 



FM 





(2.36) 



(1.18 





(600 



(300 



(150 









mm) 



mm) 





urn) 



um) 



um) 









100 



97 





67 



31 



10 







1.95 





100 



98 





72 



34 



11 







1.85 





100 



96 





56 



36 



20 







1.92 











Typical 



coarse aggregate grac 



ing 











Cumulative 



percentage passing given sieve 









4% 





1-3/4 1-1/2 











6 in. 



in. 



3 in. in. 



in. 



7/8 in. 



3/4 in. 



5/8 in. 



h in. 



(150 



(114 



(75 



(45 



(38.1 



(22.4 



(19.0 



(16.0 



(12.5 



mm) 



mm) 



mm) 



mm) 



mm) 



mm) 



mm) 



mm) 



mm) 









100 



97 



45 



9 



2 



1 







100 





62 





4 



2 



1 





100 



78 





40 





10 



2 



1 



100 





67 





40 





6 



2 



1 



The coarse aggregate should be well graded up to and including the 

 largest size which can be placed economically in the forms without excessive 

 segregation. Gap grading, using a ratio of minimum nominal size coarse 

 aggregate to the maximum nominal size fine aggregate of 10:1 without inter- 

 mediate sizes, has been occasionally used to achieve exceptionally low void 



185 



