Evaluating Georgia's Compaction Requirements for Stone Matrix Asphalt Mixtures

Abstract

This study determined a compaction level for stone matrix asphalt (SMA) mixes with the Superpave® gyratory compactor (SGC) that would match a 50-blow Marshall compaction using aggregates and mix designs common in Georgia. SMA mix designs were prepared with five aggregate sources using a 50-blow Marshall compaction and using 50, 75, and 100 gyrations with an SGC. Optimum asphalt contents from the mix designs were compared. Aggregate breakdown from each of the compactions was analyzed. Laboratory rutting tests were conducted on each mix design by using the asphalt pavement analyzer (APA). Results of the laboratory mix designs indicated that generally 35 gyrations in the SGC provided the same density as Marshall compaction. At 50 gyrations, the optimum asphalt contents for the SMA mixtures were 0.1% to 0.5% less than when the Marshall hammer was used; however, four of the five mix designs with 50 gyrations met Georgia Department of Transportation (DOT) specifications. Aggregate breakdown was slightly less with the SGC than with the Marshall hammer. APA tests showed that the mix designs were not sensitive to asphalt content, and all passed Georgia DOT requirements. Testing with plant-produced SMA mixtures confirmed that 34 gyrations in the SGC yielded specimen densities equivalent to the Marshall compaction. For the plant-produced mixtures, compaction in the SGC caused less aggregate breakdown than with the Marshall hammer. The field mixtures also performed well in APA testing. On the basis of results from the laboratory and field mixes, 50 gyrations are recommended with the SGC to replace 50-blow Marshall compaction for SMA mix design in Georgia.

Evaluation of High Los Angeles Abrasion Loss Aggregate in Stone Matrix Asphalt

“…West et al ( 14 ) conducted a study to evaluate Georgia DOT’s design compaction requirements for SMA. Five aggregate sources were selected for the study with a range of LA abrasion loss values from 16% to 44%.…”

“…Based on Georgia DOT’s successful use of aggregates with relatively high LA abrasion loss values (45% max.) to produce SMA, a 50 gyration N design value is recommended for designing SMA with the SGC ( 14 ).…”

Rutting analysis of 100 mm diameter polypropylene modified asphalt specimens using gyratory and Marshall compactors

“…In the study by Roberts et al, a review of the past, present, and future trends in asphalt mixture design are presented 53 . The very beneficial effects for the realistic simulation of the compaction on site in the laboratory environment by Superpave gyratory compactors is known and once more can be seen in the studies by various researchers that have been published in the last 13 years [54][55][56][57][58][59][60][61][62][63][64] . In all through these and the similar vast literature about the gyratory compaction studies published till date, limited studies about the 100 mm diameter specimens cored from 150 mm diameter gyratory compacted specimens for the preparation of laboratory prepared specimens have been discussed [19][20][21][22][23][24][25][26] .…”

Estudo de misturas asfálticas tipo Stone Matrix Asphalt (SMA) à luz dos compactadores Marshall e Superpave

“…A partir da densidade aparente dos corpos de prova (Gmb) obtidos da dosagem Superpave (em vários giros) e a densidade aparente dos corpos de prova (Gmb) compactados com 50 golpes por face no Marshall foi criada uma correlação. Mesmo tendo havido grande variabilidade nos resultados, estimouse que, em média, 78 giros no CGS proporcionariam a mesma densidade de 50 golpes com o martelo Marshall, para a realidade dos agregados comuns na Geórgia, EUA(WEST & MOORE, 2006). A seguir são apresentadas algumas recomendações quanto à compactação de misturas SMA oriundas de diferentes instituições.Na Geórgia, EUA, considerado um dos estados pioneiros no uso desse tipo de mistura, as especificações recomendam compactação Marshall (50 golpes por face nos corpos de prova) ou compactação no CGS (50 giros por face nos corpos de prova).…”

“…No estudo que forneceu a base das recomendações, foram utilizados agregados típicos do estado da Geórgia e em todos os casos foi utilizada uma granulometria com TMN de 12,5 mm. Alguns estudos prévios recomendavam níveis -26 -de compactação no CGS de 70 a 100 giros para projeto de misturas SMA(WEST & MOORE, 2006). Maryland, que junto com Geórgia, esta na vanguarda do uso de SMA nos Estados Unidos, vem utilizando a compactação de 100 giros para as misturas SMA há vários anos.…”