Water Damage and Prevention of Asphalt Pavement

Water Damage and Prevention of Asphalt Pavement

For nearly two years, soon built many highways, asphalt pavement early damage will occur. These damages are mainly as follows: water permeable pavement mixture and water are common, in many areas the rainy season or spring thaw season, loose, pit road slurry, become a serious failure. Effective analysis and measures to prevent water damage is significant.

Analysis of causes of asphalt pavement water damage:

Asphalt pavement is attached to the aggregate of asphalt-aggregate glued together. Asphalt pavement, asphalt and aggregate adhesion and peeling resistance is to keep pavement performance is one of the basic conditions.

So-called asphalt pavement water damage refers to in the presence of moisture on asphalt pavement conditions, subjected to repeated traffic loading, while moisture gradually penetrated into the asphalt and aggregate interface, and because of hydrodynamic effects, asphalt membrane gradually split from the aggregate surface, and led to the loss of bond strength between aggregate and road damage. Due in asphalt pavement material choices, hard choices of high quality stone, using coarse grain size, appropriate measures such as reducing asphalt content, creates problems, namely lack of water stability of asphalt pavement in the spring melt season and rainy season, part of road pock marks, loose and even the pit gradually appear. Water damage has become a major mode of pavement damage.

Asphalt pavement water damage mechanism and characteristics, you can see from the development course of destruction:

It should be noted that is, water damage may be start from beneath the asphalt surface layer. Due to water entering the asphalt pavement, stranded on top of grass-roots, asphalt surface layer layer is larger voids of asphalt macadam or type II asphalt mixtures, voids filled with water, poses a potential threat to asphalt pavement water damage. So in set material and asphalt film stripping, and occurred loose Hou, asphalt mixed material no longer into a overall, set material in load contains role Xia on grass-roots surface produced impact, grass-roots of powder quality part as cement, and lime, and fly ash and soil part will became dilute pulp, through road of gap up extrusion, in asphalt road Shang can see white of Jack pulp, surface layer visible local of tortoise shell-like crack, this is asphalt road water damage most obviously of logo. When asphalt pavement on pieces of Pan-white network of cracks that occurred when bottom layer has become loose aggregates of bituminous membrane completely detached, pothole is unavoidable.

Prevention of asphalt pavement water damage:

As mentioned above, the water damage of asphalt pavement is derived from bitumen membrane from the surface of the Strip which is water involved on the interface between bitumen and aggregate, changing the relationship between asphalt, aggregates and water caused by. So, the key to prevent water damage is to be resolved through three ways: ① prevention or reduction of water entering the asphalt mixture, not intrusive to the asphalt-aggregate interface to ② improve the adhesion of asphalt and aggregates, improving bond strength between aggregate c control of pavement cracks and water infiltration.

First, asphalt mixture gradation is the most important factor, in particular reduced porosity. However, this is limited. Ordinary gradation asphalt mixtures, largely suspended in the asphalt of coarse aggregate in mortar, and porosity of void fraction is less than the detection limit (2%-4%), the asphalt in the summer when thermal expansion without proper clearance to go, it is easy to float (oil pan), jostle, push the rutting liquidity deformation of mixture.

Problem now is the voids of asphalt mixtures are often larger, providing water to places within the asphalt mixture. Most of our current terms of Expressway asphalt pavement, and voids has two levels: 1.First is the antiskid surface, for anti-sliding surface structure depth needs necessitated the gap had increased to 4%-8%, whether under heavy rain, always within the asphalt mixture is soaked with water, which is now graded against sliding of Achilles. One way to solve conflicts between anti-sliding performance requirements and water stability is that the use of stone matrix asphalt mixture (SMA) structure, SMA is a filling of gap-graded broken stone matrix asphalt mixtures composed of skeletons. Because of gap-graded gravel formation skeletons at the surface caves, texture depth, and had good antiskid performance. And because the fully populated matrix asphalt, asphalt mixtures voids within the very small (2%-4%). SMA is basically impervious advantage can significantly improve the water stability of asphalt pavement; the same problem also happens on the bottom floor, now universal design for voids larger type II asphalt mixtures, such as AC-25 or AC-30 structures of type ⅱ is currently adopted. Surface layer for type ⅰ in dense graded asphalt mixtures, although more difficult to enter from the upper layer of water surface, but in fact there is always a small amount of infiltration, sometimes pavement with cracks, water is inevitable, not to mention the moisture from the grass-roots up into the asphalt mixture. Especially in winter frozen in the process of accumulation of moisture by capillary action up, until the spring thaw season, melting of excess moisture naturally stuck in the holes of the bottom layer mixture. Type II asphalt mixture of pore water in the long-term under traffic loading, dynamic water pressure to asphalt membrane adherence of aggregates is a very big threat. So, actually, for asphalt pavement Water damage destroyed lots from the layers below to begin. We see loose, pit in the surface layer, layer already loose. Local cracks of intensive excavation from the surface, one can often see, bottom layer of asphalt mixtures have stone is stone, asphalt bitumen, clearly, this is the spring melt season often large cause of pothole damage.