Comparison of 9.5 mm SuperPave and Marshall Wearing I Mixes in ...

63The various Superpave mixes are compared in Table 6.2. The overall comparison of Superpavemixes with and without natural sand indicated the null hypothesis should be rejected,supporting the conclusion that the inclusion of sand increased rutting potential. Howeverfurther examination of the table shows that when the natural sand was limited to 13 percent,the null hypothesis could not be rejected in all but one case. This indicates that no difference inthe performance of the mixes was detected. The case where the null hypothesis was rejectedwas for a mix with 13 percent sand for heavy traffic versus 100Table 6.1 Global Comparisons of Rutting PotentialComparison T-statistic CriticalT-valueReject nullhypothesis(Y / N)Marshall Superpave 2.107 2.074 YHeavy Traffic Medium Traffic 1.013 2.074 NLimestone Sand Natural Sand -2.268 2.074 YSP Heavy SP Medium -0.220 2.228 NSP Heavy SP Low -0.713 2.228 NSP Medium SP Low -0.627 2.228 Npercent limestone for light traffic, Table 5.6 shows the Superpave light traffic, 100 percentlimestone, mix showed very little rutting potential relative to the other mixes. In all cases, thenull hypothesis was rejected when the amount of sand in the Superpave mix was 40 percent orgreater. The null hypothesis was not rejected for the comparison of the Superpave light trafficmixes with 40 and 64 percent sand.Table 6.3 shows the comparisons of the Marshall mixes. The null hypothesis was rejected forthe comparison of the heavy traffic mix designs with 100 percent limestone and 13 percentnatural sand. In this case, the mix with 13 percent sand showed more rutting potential thanother mixes. This mix also showed significantly more rutting potential that the Marshallmedium traffic design with 13 percent sand.Table 6.4 shows the comparisons between Marshall and Superpave mixes. The null hypothesiscould only be rejected for four of the 16 comparisons. The Superpave heavy traffic with 13percent natural sand had significantly more rutting than the Marshall heavy traffic design with100 percent limestone. This Superpave mix also showed more rutting potential than theMarshall medium traffic design with 13 percent natural sand. The Superpave medium traffic