Defects of asphalt concrete pavement: types, methods of elimination

Pavements made of asphalt concrete are frequently seen on parking lots, driveways, and highways. They are prized for being strong and having a smooth surface that offers both cars and pedestrians a safe route. But just like any material, asphalt concrete can get flaws over time from a variety of sources, including bad installation, harsh weather, and high traffic.

Maintaining the quality and safety of asphalt concrete pavement requires an understanding of the various types of defects that can arise. Cracks, potholes, and surface distortions are common problems that each have their own set of difficulties and solutions. The pavement’s lifespan can be increased by effectively addressing these issues at an early stage.

This article will examine the various kinds of flaws that can impact asphalt concrete pavements and go over workable solutions for their removal. Whether you are a contractor overseeing a major roadway or a homeowner with a cracked driveway, this guide will offer helpful tips to help you maintain sturdy and smooth pavement surfaces.

Causes and classification of damage to roads

Any disparity between the properties of the asphalt concrete pavement and the anticipated or necessary attributes compromises the object’s integrity and technically sound operation, which ultimately results in the roadway’s destruction.

Numerous factors are linked to various types of defects in asphalt concrete pavement:

1. Structural (design) defects appear as a result of erroneous calculations during design, violation of technical specifications and incorrect application of regulatory documentation.
2. Manufacturing defects are associated with discrepancies in the actual technical solutions (road slope, roadbed width, etc.) and the requirements of the developed design documentation.
3. Technological – caused by violations of the technological instructions, non-compliance with the rules and procedures for performing work.
4. Operational – arise during the operation of the roadway and are the result of natural aging of the coating, wear, the influence of weather and climatic conditions, the impact of transport loads, etc.

A defect coefficient, which is the average weighted volume of damage per square meter of surface, is used to calculate the scale of violations.

Classification of possible structural violations

Two types of road destruction and plastic deformations can be distinguished: coverage defects and damage that leads to the overall destruction of road clothes.

The most typical harm to the structure of the road’s surface:

• subsidence — distortion of the road profile in the form of depressions with gentle edges;

• rut — deformation of the transverse profile of the road surface along the rolling line;

• breaks — thorough destruction of the structural layers of the pavement with a sharp deformation of the transverse profile;

• chipping — damage to the pavement due to the loss of parts of the mineral material;

• edge damage — collapse of the outer cut of the road surfaces at the junction with the shoulders;

• open cracks — linear untreated damage with a gap width of 3 mm or more.

The following flaws are regarded as damages to the pavement’s surface:

• shifts — displacement of the structural layers, usually on steep descents or at braking points;

• waves – alternation on the surface of elevations and hollows in the longitudinal direction relative to the central axis of the road;

• peeling — sequential destruction of the surface as a result of peeling off thin flakes of material;

• potholes — defects in the form of depressions with sharply defined edges (depth of 3 cm or more);

• cracks (single, mesh) — longitudinal, intersecting, transverse breaks, randomly located on the surface without any pattern.

Poor construction techniques, severe traffic, and weather can all cause asphalt concrete pavement to deteriorate over time, resulting in cracks, potholes, and surface wear. Maintaining safe and long-lasting roads requires an understanding of the various types of these flaws and an understanding of efficient repair techniques. In order to ensure longer-lasting pavement and better driving conditions, this article examines common pavement problems and provides workable fixes.

Methods for eliminating damage to road surfaces

Defects are classified as hidden, obvious, critical, etc. depending on their importance and position in the chain of events that determines the state of the road. Furthermore, each of these infractions falls into one of two broad categories: irreversible or removable damage.

Removable: This is an irreversible defect that only needs major repairs; it is a breach of the road surface’s integrity that is technically and financially justified to remove without international intervention. When the strength of the road surface has reached the lowest levels allowed and surface repairs are not financially viable, that is the condition under which a complete road repair should be performed.

Replacement of road surface

The primary goal of major repairs is the full restoration of the road surface’s operational functions, allowing for the maintenance of standard safety values under conditions of heavy vehicle traffic while taking this category of road’s requirements into consideration.

The asphalt concrete pavements and bases must be removed, a new underlying layer must be installed, a better new road surface must be laid, and the highway must be moved to a higher corresponding category if the current category of the route does not meet operating standards.

Prior to commencing repairs, it is imperative to ascertain the precise cause of the road surface damage. Only then can a technological map of the repair be created, along with the quantity of materials required, the number of workspaces, and equipment needed.

The cost of rebuilding an existing facility and the viability of carrying out this kind of work are established based on the findings.

The process of removing the asphalt concrete pavement starts after the calculations and design of the road are finished. Soil cutters or jackhammers are used for dismantling.

Dump trucks carry the removed asphalt to the plant where it is heated and put to further use.

The underlying layer and soil are inspected following the removal of the road pavement. If needed, steps are taken to make it stronger. Subsequently, the new coating is applied in compliance with the approved design choices.

Regeneration of the road surface

Hot regeneration is a less expensive and labor-intensive method of capital repairs for asphalt concrete pavements.

Road structural layer hot regeneration involves the following technological processes:

• heating existing layers of road pavement to the required temperature;
• milling the surface;
• adding, if necessary, skeletal material or binder, additional volume of asphalt concrete mixture, necessary modifiers with subsequent mixing of all components;
• uniform distribution of finished asphalt over the road base, compaction of the mixture with the implementation of all technological procedures at the place of laying the material.

Extra ingredients needed to make restorative concoctions:

1. Road bitumens GOST 22245-90
2. Mixture reunifiers – modifiers, plasticizers, petroleum solvents. Usually used in the form of bitumen emulsion. Reduce the viscosity of old asphalt and provide a flash point when heated above 230 ° C.

Hints: You can achieve a plastic and more homogeneous asphalt granule concrete mixture without local overheating by using reunifiers in the form of bitumen emulsion.

1. Skeletal materials – additional volume of aggregates.
2. Mineral binders: Portland cement, Portland slag cement.

1. Asphalt granuloconcrete (GOST 9128-2009) acts as a new additional mixture. Grain size 20–40 mm.

Using a watering machine, the existing base needs to be thoroughly cleaned of dirt right before work is done. In the event that the old asphalt has a surface treatment layer, the surface is milled to a depth that matches the treated surface layer.

There are several ways to use the hot regeneration method to eliminate defects in asphalt concrete pavement:

• work is carried out without adding new asphalt granuloconcrete;
• restoration of road pavements using additional mixtures;
• hot regeneration with simultaneous laying of asphalt concrete and the creation of a new top layer from an asphalt granuloconcrete mixture.

Asphalt heating units, complete with thermal mixers, are utilized as the primary equipment during restoration projects (see the video in this article).

The thermal mixer follows the asphalt heater at a 5-meter distance, moving at the heater’s speed.

Some guidance: the degree of softening of the asphalt concrete determines the visual depth of heating of the structural layer, which is measured with a metal probe.

Using the thermal mixer’s vibrating plate, the mixture is first compacted. Self-propelled rollers weighing 8–16 tons are the last.

Bitumen road materials age due to mechanical, atmospheric, and solar radiation effects. Over time, the oxidation or evaporation of certain components causes voids to appear in the structure of the canvas, a decrease in its plasticity, and the appearance of cracks and other defects.

To fix damage to asphalt concrete surfaces, there are two primary repair methods available:

• pothole repair;
• crack rehabilitation.

Pithole method for asphalt restoration

The purpose of pothole repair is to remove surface imperfections like combs, bumps, and potholes.

There are three ways to remove damage, depending on the materials used:

• jet-injection method;
• repair technology using cold organomineral mixtures;
• pothole repair with hot asphalt concrete.

Jet-injection scheme for eliminating defects

This technique typically fixes damage in the early stages of destruction with a defect diameter.

Take note! Repair work should not be done during precipitation as this makes priming and cleaning potholes more difficult.

The technology is very helpful in fixing large open cracks and potholes on extra-urban highways and is characterized by increased productivity.

This method’s equipment for small-pit repair includes the following primary components:

• receiving bin for fine aggregate;
• heated emulsion tank;
• diesel engine;
• compressor;
• emulsion pump;
• pneumatic jet pump;
• boom-manipulator with pipeline and nozzle for spraying the mixture;
• control panel.

This particular kit is mounted on a car trailer and functions in tandem with a dump truck to guarantee continuous fine aggregate or screenings loading into the unit hopper.

Procedure for work, guidelines:

1. The surface is cleaned of dirt.
2. Using a cord rubbed with chalk, mark the contour of the area to be repaired. The dimensions of the contour should exceed the actual dimensions of the damage by 5 cm.
3. Using a milling cutter or "grinder", cut the contour of the marked defect. Then cut out the damaged layer with a jackhammer.
4. Clean the hole with compressed air, wash with water and prime with emulsion.
5. The finished mixture is introduced, leveled and then covered with a reservation (finishing layer).
6. The material gains strength within 1.5–2 hours from the moment of laying.
7. Remove excess gravel remaining along the edges of the hole with your own hands or with a sweeping machine.

Technology of repair with hot asphalt concrete mixtures

Depending on the state of the road surface and the current weather, pothole repair with hot mixtures typically starts in early spring and ends in late autumn. When the finished mixture is laid, it should be as close to the manufacturing temperature as feasible, but not any lower than 100°C.

The superior performance of the following technological processes determines the caliber of repairs and the longevity of the road:

• repairs should be carried out at an ambient temperature not lower than that recommended for a given material and on a clean, dry base;
• When cutting down an existing coating, it is necessary to carefully remove the weakened material from all problem areas of the pothole (scraping, peeling, etc.);
• the prepared area (map) must be cleaned and dried;
• the map must have a regular geometric shape – the bottom is flat, the walls are vertical;
• the entire surface of the area must be primed with bitumen;
• the repair mixture must be laid at the optimum temperature corresponding to a specific type of mixture;
• the thickness of the laid layer must be greater than the prepared depth of the area, taking into account the value of the compaction coefficient for this type of mixture;
• the repair mixture, after laying and compacting, must be flush with the existing pavement.

Both mechanical and manual methods can be used to lay hot asphalt concrete material.

By using a rotary chute to feed the repair mixture directly into the prepared pothole and level it evenly along the entire length of the damaged area, the mechanized method eliminates the need for a thermos. To prevent a cold seam from forming between the old and new coating in this instance, the entire volume of the solution is applied to the card in a single pass.

Asphalt concrete compaction is initially performed with manual rollers or mechanized rammers. Fine compaction of asphalt concrete is performed with heavy rollers weighing 10-18 tons and up to 15 passes are made in one track.

Repair with cold organomineral mixtures

The use of cold mixtures for pothole repair has become common in road construction because of its low weather requirements and cost-effectiveness.

It is important to consider that cold asphalt concrete has 2-3 times less strength and water resistance than hot asphalt concrete when deciding between the two types of technology. As a result, category III and IV roads are the only ones that can be repaired using cold mortar without modifiers.

The technique of working with organomineral mixtures and all related preparatory steps is comparable to the hot asphalt concrete repair method. The pothole is filled with a repair composition that is 30–35% thicker than the depth of the cut potholes after the preparatory work is finished.

Shovels, rakes, and specialized trowels are used to level the laid solution. Depending on the depth of the prepared pothole, the mixture is compacted using self-propelled or manual rollers to form a solid seam with the current road surface.

It is advised to use sand, cement, or granite screenings to the surface of recently laid asphalt. Take out the waste asphalt mixture and dispose of it after the repair is finished.

Sealing of cracks

A series of technological procedures known as sealing or rehabilitation of cracks in asphalt concrete pavement guarantee the use of polymer or rubber-bitumen repair compounds for high-quality sealing of joints and cracks.

Joint bitumen-polymer strips, specifically made for this kind of task, can be used to sanitize small, non-functioning cracks and joints without expanding.

The entire process consists of the following operations:

• cleaning and blowing out the crack cavity with compressed air;
• laying out the roll along the crack;
• removing the protective film from the inner layer of the tape;
• heating the adhesive side of the patch with a building hair dryer or gas burner to a temperature of 130-140°C.
• fixing the repair strip along the axis of the gap;
• sprinkling the glued tape with fine sand.

In other situations, cracks are sealed using either hot or cold repair mixtures.

Guidelines for using liquid sealants to repair cracks up to 5 mm in diameter:

• cleaning the gap cavity with compressed air;
• heating the crack to a temperature of at least 80°C;
• filling the damaged area with ready-made mastic or bitumen emulsion;
• drying the laid mixture.

Type of Defect	Methods of Elimination
Potholes	Clean the hole, apply a tack coat, fill with asphalt mix, compact the material.
Cracks	Seal with crack filler, overlay with new asphalt layer.
Rutting	Remove the deformed layer, replace with new asphalt mix, ensure proper compaction.
Surface Wear	Apply a new asphalt overlay, use seal coating for protection.
Edge Breaks	Rebuild the edges, apply new asphalt, ensure proper drainage.

Maintaining safe and long-lasting roads requires an understanding of the different types of defects that can arise in asphalt concrete pavement. Early detection of common problems like potholes, cracks, and rutting allows for the prompt application of the proper repair techniques to stop further deterioration.

Different flaws call for different fixes. While more extensive damage, such as potholes and rutting, may require more involved repairs, like patching or overlaying, simpler cracks may be sealed. For asphalt concrete pavements to function at their best and last a longer time, regular maintenance and prompt intervention are essential.

All things considered, being vigilant about spotting and fixing pavement flaws can ultimately save a lot of time and money. It is possible to maintain smooth, safe, and dependable roads for many years to come by using the appropriate repair methods and performing regular maintenance.

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