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7-i4-04; 17:40 ;Lester Building ;3203955376 # 23/ 28 <br /> Article Request Page Page 21 of 26 <br /> more susceptt�le to damage during driliing than are drier cores.While this is just a theory pmposed <br /> by the authors of this paper,it has merit based on the fact that othera(Bungey, 1989;Maholtra, <br /> 1977;Neville, 1996)report that core drilling operations can affect bonds between aggregate and <br /> surrounding paste.Neville states that"however cazeful the driIling,there is a high risk of slight <br /> damage." <br /> Somewhat confi�sing is the significant decrease,with time,in the average compressive strength of <br /> the top footings in t�nks 5 and 6(figure 13).This caa only be partially explained by the fact that <br /> specimens removed later in the study had higher moisture contents.Another possible explanation is <br /> that a small modification in test procedure had a greater than expected affect on test results.While <br /> coring footings for the 28-day tests,the coring bit wore out.During the search for a new bit,the <br /> remaining footings—those from tanks 5 and 6-were exposed to mom conditions for an additional <br /> four hours.When it became clear that a bit could not be obtained until the next day,the footings <br /> were placed in plastic bags to help ma.inta.in their moisture content until coring.W'hile it seems <br /> unlikely that this change in testing proceduze would have affected results,it remains a possibility. <br /> Another possbility is that the new bit caused less damage during coring operations than the old <br /> one. � <br /> Future Work <br /> While the results of this study are interesting,they do little to support the acdial use of,or reliance <br /> on,in-situ hydration in everyday practice. <br /> Like most investigations,this s�dy has raised more questions than it has answered.Some of these <br /> queations follow. <br /> Uniformity of Mix <br /> What impact doea uniformity of mix have on resulting concrete pmperties? <br /> What methods exist for temporary coating of aggregates with dry cement particles juat before <br /> placement so as to maintain a uniform distribution of cement particles during placement7 <br /> What methods exist for permanent coating of aggregates with dry cement particles so as to <br /> maint�in a uniform distribution of cement particles during placement? <br /> Compaction/Confinement: <br /> How does degree of compaction affect resulting concrete pmperties? <br /> Is a confining pressure required during hydration? <br /> Does method of hydration dictate the need for,or the amount of,confining pressure during <br /> hydration? <br /> At what point does compaction and confinin�pressure impede hydration? <br /> Aggregate: <br /> Is there a significant difference in compaction of dry mixes feahuuig natural aggi�egates as opposed <br /> to manufactured(i.e.,more angular)aggregate? <br /> hrip://asae.fiymulti.com/request2.asp7JID=S&AID=140828�CI�1nv2003&v=&i=&T=1 6/4/2004 <br />