Micro-Surfacing: HighTech Road Maintenance Technology at Low Cost

Rainer Wiegmann,
Consulting Engineer for Equipment
for Bituminous Road Construction
Special Collaboration


Nowadays, precautionary assessments are taken for granted for every responsible citizen. So forward-looking road maintenance should only serve one goal: to prevent larger, non-foreseeable consequences, such as increased costs and increased risks resulting in reduced road safety!

German cities and municipalities have increased the use of modern and environmentally friendly road maintenance technologies which offer lower costs – Micro-Surfacing.

The Micro-Surfacing mix of cold polymer bitumen emulsions, aggregate, cement, water and dope is produced directly on the paving machine and immediately applied to the road surface. The cold application process has very low power consumption and this results in very low CO2 emissions.

The on-site application of Micro-Surfacing is carried out by specially-designed electronically-controlled laying machines. Depending on the condition of the existing substrate the aggregate size of the mixture is determined as well as the possible requirement for a second layer. The latter is usually needed when reprofiling is advised.

The installed thickness of Micro-Surfacing averages about 1 cm. This eliminates extra work such as milling-off the old surface layer, regulating or raising manholes, etc. So Micro-Surfacing not only conserves resources but also minimizes costs of disposal.

Micro-Surfacing application causes only very minor impairment for both the flow of traffic, as well as for residents, because the newly laid surface can be reopened to traffic within about 30 minutes.

For all those reasons, Micro-Surfacing is considered to be the most efficient and cost-effective method of road maintenance.

Standard Micro-Surfacing Process
First, visual inspection of the road section to be maintained and repaired to ensure that it is suitable for treatment by Micro-Surfacing and that no preparatory works are needed for possible major road damages if needed.

Proper cleaning of the road surface by means of a road sweeper and/or of a high-pressure water cleaner (pmax 150 bar).

Marking and taping of all street furniture such as manhole covers or gullies.
Then, application of the first Micro-Surfacing layer – for reprofiling the road surface, a maximum aggregate size of 8 mm is applied. If there are signs of a lack of bitumen content in the existing road surface an additional tack-coating of bitumen emulsion is strongly recommended, as this will act as a bonding agent. A machine with an integrated spraybar enables spraying and the application of the first layer of Micro-Surfacing in one pass.

Finally, installation of a second Micro-Surfacing layer. About 45 minutes after applying the reprofiling layer, a second layer can be laid. Its maximum size of aggregate is 5 mm. A correct application needs to be made of this homogeneous Micro-Surfacing mix. A good surface finish will be obtained with the aid of a variable width distributor box with augers.

Micro-Surfacing Machine with integrated tack-coating spraybar
This special Micro-Surfacing method – tack-coating and simultaneous application in one pass – requires the latest machine technology, such as the SCHAEFER SMS 12.000.

This offers the advantage that prior to the application of the micro-surfacing mix a tack coat ensures that dirt and dust will not affect the adhesion of the composite layers. The dosage of the emulsion is variable – corresponding to that of the Micro-Mix. Furthermore, when changing the width of the distributor-box, the width of the spraybar can hyraulically be adapted.

The modern control system of the Schaefer SMS 12.000 includes a PLC control together with a touch screen display allowing input of mix specification and display of real time operating data with production output data and input of any operating data. A sequence control enables a precisely timed starting and stopping of the various components.

The input of the recipe of the mix is carried out in percentages, based on the amount of the aggregate required.

All these facilities guarantee an exact dosage of the mix right from the start - resulting in a constant homogeneous mix. The advanced onboard control system and feedback monitoring is easy to use and helps to eliminate operator errors.

Micro-Surfacing Asphalt is suitable for repair of road surfaces of all load classes under running traffic and characterized by their high daily performance at low traffic impairment. The repaired road can be reopened for traffic a short time after application of Micro-Surfacing. Practical experience has shown that the life-time of such a Micro-Surfacing can approximately last between 8 to 14 years – the best proof of high efficiency of this advanced road maintenance technology!

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