Verification of Superpave Number of Design Gyration Compaction Levels for Georgia

Abstract

The objective of this project was to evaluate the performance of Georgia's mixes designed by using the Superpave® gyratory compactor. Mixes designed with numbers of design gyrations that are too high would be rut resistant but may be difficult to compact adequately in the field and may lack sufficient durability because of reduced asphalt binder content. The following conclusions were made on the basis of an evaluation of field projects and from laboratory volumetric and performance testing with various aggregate sources and gyration levels: (a) It is unlikely that Superpave mixtures will reach the design air voids of 4.0% during the life of the pavement. After nearly 5 years, the average air voids measured in the wheelpaths were 5.7% for Superpave projects and 3.8% for Marshall projects. On the basis of volumetric comparisons, 66 gyrations with the laboratory-produced mix gave approximately the same density achieved on the Superpave projects in the field. (b) The difference between 4-in.-diameter Marshall samples and 6-in.-diameter gyratory samples for moisture susceptibility was not statistically significant enough to assign a relationship between the tensile strength ratio (TSR) for samples with a diameter of 4 in. and the TSR for samples with a diameter of 6 in. (c) Although the asphalt binder content was an important factor in extending fatigue life, aggregate source and strain level were the most significant variables affecting fatigue results.

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] .…”

Avaliação do comportamento mecânico de corpos de prova de misturas asfálticas a quente resultantes de diferentes métodos de compactação.

“…Tal situação, em campo, gera superfícies de agregados não ligadas que tornam a mistura mais suscetível ao dano por umidade e acelera a deterioração do pavimento (WATSON et al, 2008).…”

“…O primeiro representa a resistência intrínseca do material ou a parcela da resistência que existe independente de qualquer tensão aplicada e o segundo representa a capacidade do material de desenvolver resistência sob o carregamento externo aplicado (FOSTER, 1982;HEAD, 1986). Nesse contexto, sabe-se que a água não transmite esforços de cisalhamento, ou seja, as tensões de cisalhamento em qualquer plano são independentes da pressão neutra (PINTO, 2006 (HABIB et al, 1998;PROWELL, 2001;MOORE, 2005;VITILLO et al,2006;WATSON et al, 2008;KABIR et al, 2011;KHOSLA;AYYALA, 2013 Após a definição das misturas de teste (nível 0 do método), esse ainda é dividido em outros quatro níveis variando do mais simples (nível 1) ao mais completo (nível 4).…”

“…3.1, Watson et al (2008) alterou a especificação quanto ao número de giros de projeto para 65, independentemente da condição de tráfego.…”

Validation of Ndesign in Iowa

“…The levels of gyration is critical in design because overcompaction in the laboratory design can lead to higher air voids in the field due to undercompaction during the compaction process, which consequently leads to durability issues in pavement [11]. Similarly, undercompaction in the field will cause higher ultimate pavement density which leads to bleeding or rutting [17]. A desirable, stiff asphalt mixture consists of a good aggregate skeleton and/or low asphalt content and generally compacts to 4% air voids after the pavement has been densified by traffic; whereas a weak asphalt mixture with the same compaction effort overcompacts to 2% air voids [12].…”