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7-14-04; 17:40 ;Lester Bulldlne :3203955376 # �7/ 28 <br /> Article Request Page Page 15 of 26 <br /> compressive strength values between some replicates(i.e.,footings removed on the same day,&om <br /> the level,from tanks subjected to the same water treatments). For this reason,a two-tailed T-test <br /> was use to determine the significance of the average strength differences for each set of replicates. <br /> The results of this analysis are give�n in Table 3.For example: the two footings removed at the four <br /> week mark from the top of tanks 1 and 2 had average compressive strengths of 3107 and 2485 <br /> lbf/in2,respectively.Table 3 lists the level of probability at which the observed d�erence between <br /> these replicates is significant at 5.2%.What this means is that only 5.2 times out of 100 would we <br /> expect to see a difference greater than 6221bf/in2(3107 -2485 1bf/in2)if there indeed was no <br /> difference between how the footings were fabricated and hydrated. Since 5.2 out of 100 is a rather <br /> low probability,one may conclude that the footing pair is significantly different.Note that a color <br /> code is used to identify replicates in Table 3 whose difference is statistically more significant. <br /> Despite statistically significant differences between the cornpressive strength of some footing <br /> replicates,their values were still averaged.These average values aze listed at the bottom of Table 3 <br /> and have been plotted in figure 14. <br /> Normally Hydrated Concrete <br /> Compressive strengths values from cylinder tests on norn�ally hydrated concrete tests are compiled <br /> in Appendix B.Individual values for each consolidation method were average and have becn <br /> plotted against water/cement ratio in figure 15.Also shown in the figure is a plot of an equation <br /> that was fit to data for all rodded specimens. <br /> 5000 <br /> N ❑ Water Treatment A <br /> = p Water Treatment B � � . <br /> n. <br /> ' 0 Water Treatment C � <br /> _ �: - , . <br /> . , . <br /> . .... . <br /> �, 4000 <br /> m -. <br /> � <br /> � 3000 . <br /> � <br /> � . <br /> cg � . :. . . <br /> m 2�� ...- Top Foatings <br /> W � � - Middle Footings <br /> � - Bo�am Footings <br /> ¢' <br /> 1000 <br /> 0 � 10 1� 20 25 <br /> Embedment Time,wee�Cs <br /> Figure 14.Average footing compressive strength as a function of water treatrnent,location,and <br /> embedment time. <br /> http://asae.fiymulti.comhequest2.asp?JTI�S&AIl�14082&CII�1nv2003&v=&i=8cT=1 6/4/2004 <br />