What is asphalt matrix?
Stone-matrix asphalt (SMA) is a gap-graded asphalt pavement designed to improve rut resistance and durability through the use of a stable stone-on-stone skeleton held together by a rich mixture of asphalt cement, along with stabilizing agents such as fibers and/or asphalt modifiers.
What kind of stone is used in asphalt?
Medium and low-volume roadways, such as county roads and city streets, typically are made of crushed gravel from open-pit mines or limestone, a sedimentary rock. Gravel and limestone aggregates typically cost less than granite and trap rock because they are less durable, locally available and hauled shorter distances.
What size of stone is used for asphalt?
Superpave base courses typically use 1.5-inch or 1-inch rock. Superpave surface courses typically use 3/8-inch rock. In the field, a mix that has 3 percent or less air voids may be susceptible to rutting and shoving. And mixes designed with more than 5 percent air voids are susceptible to raveling and oxidation.
Is SMA an asphalt?
SMA is a relatively thin (12.5–40 mm) gap-graded, densely compacted, HMA that is used as a surface course on both new construction and surface renewal. It is a mixture of asphalt cement, coarse aggregate, crushed sand, and additives.
What is SMA concrete?
Stone Mastic Asphalt (SMA) is a gap-graded mix laid between 30mm and 40mm thickness. SMA is used in the construction of new roads and overlaying existing roads and offers superior durability and resistance to deformation.
What is BC in road construction?
BITUMINOUS CONCRETE (BC) ❖ BC is a Dense Graded Bituminous. Mix used as Wearing Course for. Heavily Trafficked Roads.
What is 6mm DBM?
6mm Dense Bituminous Macadam / Asphalt Concrete 6 Normally used on footpaths, playgrounds and drive ways. A fine close textured material that can be laid as a thin surface course often used to overlay an existing surface with a new surface course.
What are gravel sizes?
Gravel is classified by particle size range and includes size classes from granule- to boulder-sized fragments. In the Udden-Wentworth scale gravel is categorized into granular gravel (2–4 mm or 0.079–0.157 in) and pebble gravel (4–64 mm or 0.2–2.5 in).
What is #1 stone used for?
Crushed Stone Grade 1-10 #1 – The # 1 crushed stone grade is the largest of the crushed stone grades and includes stone between 2-4 inches long. This material is great for larger jobs or for filling in larger holes.
What are the properties of stone matrix asphalt?
Stone matrix asphalt (SMA) is a gap-graded HMA (Figure 1) that is designed to maximize deformation (rutting) resistance and durability by using a structural basis of stone-on-stone contact (Figures 2-6). Because the aggregates are all in contact, rut resistance relies on aggregate properties rather than asphalt binder properties.
Why is SMA more expensive than dense graded asphalt?
SMA is generally more expensive than a typical dense-graded HMA (about 20 – 25 percent) because it requires more durable aggregates, higher asphalt content and, typically, a modified asphalt binder and fibers. In the right situations it should be cost-effective because of its increased rut resistance and improved durability.
Why is stone on Stone Better Than Asphalt?
Because the aggregates are all in contact, rut resistance relies on aggregate properties rather than asphalt binder properties. Since aggregates do not deform as much as asphalt binder under load, this stone-on-stone contact greatly reduces rutting.
Which is better asphalt SMA or asphalt binder lift?
Rut Depth String Line, Williams St. Intersection Surface SMA asphalt binder was oxidized more than the binder lift of SMA as shown by the lower penetration values and higher Performance Grade(s). Observations, cont.