moist at the time of grout injection. Dry aggregate will absorb water from 

 the grout which thickens the grout within the aggregate mass and may result 

 in ungrouted or honeycombed areas. If more than one size of coarse aggregate 

 is used, the aggregate should be weighed, batched, and mixed in the proper 

 proportions, or discharged at proportional rates onto the wash screen. The 

 wash screen may be either a vibrating deck or revolving type. The latter 

 is effective as a blender, as well as a washer. 



For structural concrete work, aggregate is commonly conveyed to the 

 forms in concrete buckets. A flexible rubber elephant trunk is often used 

 to limit the height of free fall, thus preventing segregation, and for 

 placing in constricted areas. The total fall distance and method of 

 handling should be such that segregation and aggregate breakage are reduced 

 to a minimum. Permissible fall distance depends on aggregate size and 

 soundness. Where coarse aggregate is being placed through water in mass 

 concrete work, as in bridge piers, it may be discharged directly into the 

 forms from bottom dump barges or self-unloading ships. Coarse aggregate 

 has been placed successfully to depths of well over 30.5 meters (100 feet) 

 in water where the possibility of breakage is eliminated (Davis and 

 Haltenhoff , 1956) . While some segregation may occur, segregation itself is 

 not usually objectionable since it tends to result only in a somewhat greater 

 void content and a non-uniform distribution of the void system throughout 

 the aggregate mass, the result being to increase, slightly, the grout require- 

 ments with an insignificant effect on the strength of the mass concrete. 

 However, an accumulation of smaller sizes might reduce the void size suffi- 

 ciently to preclude consolidation within the area by the grout. 



(3) Grout Quality Control . The pumpability of grout is controlled 

 by the consistency test, using a standard flow cone in accordance with Corps 

 of Engineers CRD C611. To maintain uniformity, time of outflow should be 

 limited to between 18 and 22 seconds. However, grouts can be successfully 

 pumped having an outflow of up to 30 seconds, depending on void content of 

 the aggregate. Test cylinders should be made in accordance with Corps of 

 Engineers Specification CRD C84 and tested in accordance with appropriate 

 ASTM standards. 



f . Curing. Curing should be in accordance with accepted conventional 

 concrete practice. As with any concrete, extended periods of wet curing 

 beyond the usual 7 days will be beneficial in improving the quality of the 

 concrete. 



3. Portland Cement Grout . 



a. Types and Characteristics . Portland cement grout has a variety of 

 uses in coastal structures and is similarly varied in its makeup. A simple 

 combination of cement and water, in a flowable consistency, is sometimes 

 used to fill joints and voids in concrete, masonry, or rock. More often 

 other materials are added to improve various properties or reduce cost. 

 These include sand and clay, used as inert fillers, and colloidal clays such 

 as bentonite to stabilize fresh grout placed under water. Also included are 

 special purpose admixtures to increase strength, retard or accelerate set 

 and strength gain, cause expansion of the grout, prevent shrinkage, or 

 improve bond, penetration, impermeability, plasticity, or resistance to 

 freeze-thaw damage or chemical attack. These are discussed more fully in 



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