The Physical Research Section of the Minnesota Department of Highways has developed and constructed a device to measure the retro-reflective characteristics of pavement marking materials. The device can be operated at highway speeds and during normal daytime working hours with a minimal disruption to traffic.
The device is a useful research tool and has been used mainly in this capacity. However, with the recent increase in materials cost of pavement marking and the reduced availability of these materials, ERMA can and should be used as a maintenance management tool. This will enable us to paint when it is necessary rather than according to a time schedule.
This is only a portion of the final report and is not intended to give a complete description of the development of the device and proof that it works and results are repeatable. The complete final report will show the data which was obtained and prove the value of the device.
This report is intended to show how the device is constructed and operated and a description of the method used to correlate the device to what drivers observe as reflectivity level under nighttime driving conditions.
This report describes the work done by Mn/DOT during the past ten years to develop and evaluate a durable yet economical striping material. Discussed in the report are: the development of equipment capable of applying a two-component epoxy resin, the evaluation of the epoxy, polyester and thermoplastic resins and the cost effectiveness of such materials. Field evaluation of the
various materials consisted of visual observations, photographs, macrophotographs, retro-reflectivity measurements and chipping surveys. The available data suggests that epoxy can be placed on a high volume bituminous or Portland cement concrete roadway, at a thickness of 10 mils, and provide adequate delineation for 12 months or longer, while remaining as economical as paint. It was also found that; the polyester material did not adhere well to Portland cement concrete and the aggregate in the bituminous pavement, and thermoplastic is generally unacceptable because it is too susceptible to removal by traffic and snowplows when placed at the manufacturer's recommended minimum thickness of 30 mils , and also does not bond adequately to Portland cement concrete.
This report describes a laboratory evaluation of the physical characteristics of shrinkage compensating cements when additives are used. Two admixtures were studied, Dow Corning 777B, a reactive polysiloxane, which increases the durability or resistance to weathering, and Sika Set, a low-shrinkage, final set accelerator. The concrete used was a standard Minnesota Highway Department bridge deck design mix (3Y43).
The two additives generally improved the physical characteristics of the ChemComp shrinkage compensating cement but greatly reduced the durability of the concrete in the freeze-thaw tests.
It is recommended that Sika Set and Dow Corning 777B not be used in ChemComp cement concrete due to the low durability which results. The use of other additives with ChemComp cement should be evaluated before use in the field.
Coating reinforcing bars with epoxy was assumed to be the answer to corrosion problems in highway structures when it was developed. In the last few years, this assumption has been seriously questioned. Cases of damage to structures resulting form corrosion of epoxy coated steel have been reported in Florida, New York and Ontario. In 1992, the Physical Research Section was asked by the Office of Bridges and Structures at the Minnesota Department of Transportation to conduct a limited field survey to determine if a problem existed in Minnesota.
The first bridge built with epoxy coated rebars in Minnesota shows no signs of distress almost 20 years after construction.
The corrosion of epoxy coated rebars that has been observed elsewhere was not discovered by this survey.
The prestressed girder bridges included in this survey· showed fewer transverse cracks than the steel girder bridges.
The life of the various types of cutting edges for use on Motor Graders and Snowplows varies with the type of steel and its treatment by the manufacturer. This is an evaluation of the wear characteristics of five types of cutting edges, both Motor Patrol and Snowplow, used in the maintenance of gravel roads.
Comparing the two sets of data (gravel and snow) excluding the Carbide edges, the Carbon is best on snowplows and second best but only slightly lower in durability than flame hardened on gravel blading. Gravel blading is about three times more severe than snowplowing on cutting edges other
than Carbide Insert.
