Design and Construction of NDOT PG-Special Test Sections
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In 2000, NDOT constructed three sections on I-15 in Clark county, Nevada, as part ofcontract 3000. The objective ofthe test sections was to evaluate the field performance ofHMAmixtures designed with binders graded with the Superpave PG grading system plus toughness and tenacity, and cold temperature ductility. NDOT added these requirements to ensure appropriate modifications of the asphalt binders and long term field performance ofthe mixtures. The graded binders are referred to as PG-Special binders. The three test sections were constructed in the westbound direction between mileposts 118.50 and 121.50 (each section is one mile long). The constructed layer consisted ofmilling l" ofthe existing HMA layer and replacing it with 2" of dense graded HMA and 3/4" open graded HMA. All three test sections were designed using the NDOT Hveem mix design method. Field samples ofthe binders and mixtures showed that all materials met NDOT's specification with very few exceptions: 4 out of34 samples ofthe PG76-22S binder failed the toughness and tenacity requirements and 1 out of 10 samples ofthe PG76-22S mix failed the stability and air voids requirements. Additional binder and mixtures were sampled during construction and are being evaluated for rutting, fatigue and low temperature properties.