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Analysis of factors affecting road compaction
Time:2015-5-7 8:27:43                  Click:1518


1 Introduction

Compaction is the last step of the road pavement construction, but also affect the key process of asphalt pavement construction quality. Practice shows that: Most diseases are associated with road pavement compaction inadequate related, such as: water damage, compaction type rutting. Therefore, the road compaction has gradually been attention. Materials, equipment, technology, and environmental factors: Pavement compaction many factors, in simple terms, including the impact. In this paper, various factors affecting road Compactness a comprehensive in-depth analysis, pointed out that the impact of the mechanism of the effect of road compaction and improve technical measures related Compactness, relevant conclusions for the actual construction of reference.

2 in the material properties

2.1 Aggregate

Aggregates and asphalt compaction will affect the mix, frictional resistance between the aggregate particles are compacted important impact resistance, it is also an important factor affecting the stability ply compaction. This frictional resistance is the aggregate result of the interaction of the surface texture structure, but also all the aggregate effect of the shape and angle of results. Having a rough interface between the aggregate difficult to move each other, generating frictional resistance between the high particle. This causes those particles angularity good mix better than those compacted mix requires more energy to compaction. In effect roller, shape smooth aggregate friction resistance is small, easier to move closer together. This type of mix A lower compaction effort, sometimes light compactor can be applied. Aggregate surface texture and level of impact varies with the friction between the particles, but a great amount of influence through 9.5mm sieve. Generally speaking, crushed aggregate by crushing surface will increase the surface texture structure, broken aggregates have more angularity, which is very beneficial to improve the strength of compacted pavement.

Aggregate stability and water absorption is also an important factor affecting compaction, soft or hard is not good in the role of aggregate drum compactor will be broken, making it difficult to achieve good compaction, water absorption aggregate make bitumen from the aggregate surface into the interior of the particles, thus allowing the mixture to dry, making it more difficult compaction. Aggregate gradation, particle shape and volume of the nature of the mix also affected the compaction, a good mix of grading should always uniform, which mixes for various properties are good, this is compacted using conventional procedures Density of the easiest ways to obtain. Gradation of coarse aggregate in excess can cause coarse mixture. As mentioned above, the rough mixes require larger power to compaction, especially for the initial pressure or re-pressed.

Mix has too much sand round the construction process more difficult to operate. Excessive sand acting as ball mix, workability is good, but it is difficult rolling. If the middle of the mix of fine aggregate too much, especially near the 0.6mm sieve aggregates too, will mix brittle, and therefore a lower mix of stability, and it is easy to over-voltage, it is necessary to adopt lightweight rollers and lower rolling temperatures, sand application will reduce or eliminate this problem. Mixture means a mineral filler compound by partial 0.075mm sieve. Enough to improve the adhesion of asphalt filler is necessary. If the cohesion is low, the aggregate particles move closer to each other after rolling difficult, if the filler is too high, the mixture will harden, this mix is difficult to compaction. Asphalt binder and filler combined into, it would be set in the rolling material bonded together, binders provide cohesion, which forms the tensile strength in the mix, when the mixture is cooled, the mixture stick cohesion substantial improvements, the rapid growth of bitumen cohesion. Recommended pink gum usually is between 0.6 to 1.6.

2.2 asphalt binder

Asphalt binder viscosity serious impact compaction, when the mixture compacted asphalt high viscosity limits the movement of aggregate particles. If the viscosity is too low, the compacted particles tend to move, but once compaction is completed, there is not enough power to keep the particles in place. When temperatures rise, mastic asphalt as a lubricant, so that frictional resistance between the particles is reduced. Once the mixture is cooled, asphalt cement binder becomes so aggregate particles bonded together. Determine the viscosity grade bitumen binder mix, usually speaking, high viscosity asphalt mix makes it difficult compaction, especially when the temperature is low. Therefore, in order to reduce the viscosity of the mastic asphalt compaction process requires the use of high rolling temperature, or shall softer asphalt to facilitate compaction. E.g. containing more natural sand mixes, especially those with less filler mixture, have low adhesion and poor stability. We need to adjust the level of the asphalt cement, or adjust the compaction process to enable it to provide sufficient force to prevent the roller under the action level of aggregate particles to lapse. Mix with a lower VMA or less difficult asphalt compaction, low levels of lubrication asphalt mixture aggregate between the poor form of dry, hard mix, not only difficult to compaction, and cementation material can make aggregate stick knot long, high porosity can cause a bad mix durability. Too many will mix asphalt content in precarious roller action. Too many asphalt mixture will reach zero gap, mainly due to the asphalt mastic filled all the gaps reason, between too much clay would mix aggregate particles from the larger, reducing the friction between the particles and reduce the stability of the pavement.

3 in paving thickness

Generally speaking, the thicker ply easy to achieve a predetermined degree of compaction, plies thick insulation for a long time, so there is enough time to rolling. The thin layer of cooling fast, you need as quickly as possible compaction roller, so thin (4cm or less) mixture of the initial pressure temperature should be high to ensure there is enough time to compaction, a thick layer (7cm or more) may be slightly lower initial pressure temperature. Usually not allowed paving asphalt surface layer on weak bearing layer. But the actual work of weak bearing layer may be difficult to avoid. Then increase the useful thickness of thick layer protects the bearing layer, and allows the pavement compaction, you can use lightweight rollers.

The thickness of the structural layer of asphalt pavement should be called the greatest common mix to match the particle size, to conventional asphalt mixture, mixing layer thickness should not be less than three times the maximum aggregate nominal particle size. Pawnshop thick through hours, the road will produce segregation, difficulties arise compaction, aggregate crushing situation. Compactness is not guaranteed, it is one of the main early asphalt pavement water damage.

4 mixture temperature

Mix temperatures may affect important indicator of HMA compaction, which affects the stiffness of the asphalt cement, in turn, it controls the compaction characteristics of the mix. Too high a temperature will lead to action under the roller mixture flows, low temperatures will cause the mixture is too stiff and difficult to compaction. Suitable compaction temperatures should be: there is enough time to complete compaction temperatures. Table 4-1 lists the recommended minimum temperature compaction, which is based on the thickness and temperature of the laminate. Digital table below lists the rolling after the start time of paving.



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