Field Trials of Anti-corrosion Paint Using Full-size Specimens
Bridges and sluice gates must, as valuable structures indispensable for the life of the people, be appropriately maintained. Many of these structures are made of steel, so measures to counter corrosion (rusting) of the steel (anti-corrosion measure) must be taken. Painting is the method now most widely used as a bridge or sluice gate corrosion prevention measure.
But no matter how high the quality of the paint used, if painting is not executed appropriately in an environment suited to the paint, the paint will fail to fully display its essential performance or external appearance, with the result that the structure must be repainted far earlier than expected. If, for example, the air temperature is low when the painting is done, the paint will cure slowly, either causing sagging (paint appears to have run down the surface) or a rise of its viscosity, making it difficult to paint large surfaces. If the humidity is high, condensation occurs easily, so that if paint is applied to a surface where moisture has condensed, the paint film either has mottled appearance or the moisture mixes with the paint, resulting in a low quality finished surface.
Recently developed types of paint in particular, may display properties that differ sharply from conventional paint, so before applying such paint to a real structure, it is vital to perform repeated field trials to fully clarify the characteristics of the paint and precautions needed during its application.
So, in characteristic environments in Fujinomiya, Shizuoka Prefecture (PWRI, Asagiri Environment Material Observation Facility, elevation is high and it is cool all year) and in Ogimi, Okinawa Prefecture (Okinawa Construction Material Durability Test Facility, located on the seacoast in a subtropical climate), the PWRI conducts trial executions of new paints as they are developed. At these locations, large specimens simulating actual bridges are used for testing. Actual structures are constructed by combining members with varying shapes, creating uneven surfaces at welds and bolted connections etc., and other narrow places difficult to paint. The workability and the time required to complete it differ greatly from those of the work of painting simple flat plates. And according to the shape of a structure, some members are easily subjected to moisture, or the surface temperature varies between members, so it is important to perform trials on shapes and surface areas as similar as possible to actual structures.
Through trial painting, a variety of categories of data are collected, including air temperature, humidity, surface temperature of steel, temperature and viscosity of the paint, ease of painting and adhesive properties, paint curing properties, appearance of the finished paint, impact of member shape and so on. And painted specimens are exposed for long periods (10 to 15 years) under natural meteorological conditions (sunlight, wind, rain, etc.) to confirm the durability of the paint. Based on the knowledge obtained in this way, materials are being improved and developed as execution standards etc. are studied.
(Contact: Advanced Materials Research Team)
Evaluation of slipperiness on roads and spreading of anti-icing agents
-Toward improved spreading of anti-icing agents -
The Studded Tires Regulation Law was enacted in 1990 to regulate the use of studded tires. Since its enactment, there have been problems with highly slippery road surfaces in cold snowy areas such as Hokkaido, resulting in traffic jams and accidents.
Road administrators strive to secure a safe, comfortable flow of road traffic in winter by spreading anti-icing agents (*1) and anti-slip agents (*2) using spreader vehicles, but there is now increased concern over rising maintenance and management costs and the heavy load placed on the environment due to excessive spreading.
There are two methods of spreading anti-icing and anti-slip agents: pre-freeze spreading, which spreads anti-icing agents beforehand in areas where freezing is expected, and post-freeze spreading, which spreads them on frozen roads.
The need for post-freeze spreading is judged based on visual observations by road patrols and the experience of spreader vehicle operators. However, as the slipperiness of actual roads cannot be easily determined in some places, frozen areas may be overlooked, or anti-slip agents may be spread in locations where no freezing is seen.
The Machinery Technology Research Team develops techniques to allow fast, accurate spreading of anti-icing agents in the exact areas where they are needed using a continuous friction tester (CFT) installed on a spreader vehicle and monitoring slipperiness in order to evaluate road surface conditions during vehicle movement.
In FY 2010 we practically evaluated the spreading locations by visual observation and the slipperiness by CFT as well on national highways in Fukagawa City,Hokkaido.
From the results, it can be inferred that it is possible to clarify the slipperiness of places where anti-icing or anti-slip agents are spread and identify areas where spreading is needed.
We plan to conduct field surveys and carry out studies and tests to develop a system that enables automatic spreading of the following anti-icing or anti-slip agents when slippery roads are detected:
※ *1: Salt and other materials serving to reduce the freezing point of water and reduce freezing risk
※ *2: Crushed stone/sand and other materials for spreading on frozen roads to prevent slipping
(Contact: Machinery Technology Research Team, CERI )