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7-14-04; 17:40 ;Lester BUlldin� ;3203955376 # 24/ 28 <br /> Article Request Page Page 22 of 26 <br /> How does aggregate size distribution(aggregate gradation)affect resulting concrete properties? <br /> In an effort to coat aggregate with dry cement particles,will a specific mineral composition of <br /> aggregate be needed? <br /> Hydration <br /> What is the most effective way to hydrate a confined dry mix: (1)water under low pressure, (2) <br /> water under high pressure,(3)steam injection,or(4)vapor diffusion7 <br /> Do high initial flow velocities segregate mix ingredients? <br /> Does flow direction influence particle segregation? <br /> How does hydration method impact confinement of the dry mix? <br /> Conclusions <br /> Based on this study,the following was concluded. <br /> In-situ hydration of a dry concrete mix can produce concrete with a compressive strength <br /> comparable to a noimally hydrated concrete mix. <br /> For a given mix,the closer the aggregate spacing,the stronger the resulting concrete.Closer <br /> aggregate spacing can be achieved by compacting dry ingredients instead of ingredients to which a <br /> minitnal amount of water has already been added. <br /> Confinement of a dry mix prior to hydration helps keep particles together during the hydration <br /> pmcess and this counteracts the hydrostatic pressures that work to drive particles apart when <br /> excessive water is brought into a mix. <br /> The main advantage that normally-hydrated concrete has over in-situ hydrated concrete is that <br /> mixing of ingi�edients after the addition of water helps disperse cement particles more uniformly <br /> throughout the mix.Research is needed to assess methods far pmducing dry concrete mixes that <br /> will be characterized by a uniform dispersion of cement after being compacted into forms/molds <br /> The compressive strength of a concrete specimen is decreased if its moisture content is unifozmly <br /> increased throughout its volume. <br /> Additional research is needed to determine how in-situ hydrated concrete strength is affected by <br /> ag$regate properties,initial compaction,confinement pressure,dry mix unifornlity after placeznent, <br /> as well as conditions related to water movement into the confined mix. <br /> Acknowledgements <br /> Thanks to American Materials Corporation of Eau Claire,WI for donating the concrete mix,aad <br /> Wingra Stone Company of Madison,WI for donating and delivering the sand used in this study. <br /> References <br /> ASTM.2002.ASTM C33-02a. Standard specification for concrete aggregates.Annual Book of <br /> http://asae.&ymulti.com/request2.asp?JID=S&AID=14082&CID 1nv2003&r&i=&T=1 6/4/2004 <br />