2020 all weather element project in Shandong construction date: July 13, 2020

Reflect Visible Light and Infrared Light Markings Currently the road markings in the world are almost based on the reflection of visible light. These markings can be easily identified by video analysis and other methods in automatic driving. But when in rainy, snowy and icy days, these identifications become blind areas. In order to identify the road markings better without blind areas. It becomes true to have the infrared reflection function in road marking, under the premise of having visible light. Traffic signs and markings which adapt to automatic driving road should be cleaned and maintained frequently to ensure the visibility. The signs and markings should avoid to be blocked by trees and be affected by road light. Digital traffic signs and markings adapted to automatic driving road can be divided into two types base on their number. The two types’ classification as below sheet Classification of digital signs and markings Category Definition I One facility is only used to convey individual traffic signs and marking information. II Within a certain road section, one facility conveys multiple traffic signs and marking information Reflect Infrared Light Glass Beads In 2016, reflect infrared light glass beads have been used on the monitoring of vehicles exhaust. Following the increase of vehicles and the policy of vehicles’ annual survey every six years, it makes monitor the vehicles real-time on the road with remote sensing method more important. Moreover, the newly issued “Atmospheric” in 2015 clearly stipulates that real-time telemeter can be used without affecting the driving of vehicles on the road. Tradition vehicles exhaust telemeter just can detect one car every time. If there are two cars pass through the telemeter at the same time or overlap, it is impossible to identify which ones’, and the detection data is invalid. And tradition vehicle exhaust telemeters use mirror emission to emit light. When use gantry-type to fix the telemeter, the way of installing plane reflectors on the ground is basically inadvisable. At present, the measurement of the concentration of the main pollutant vehicles exhaust uses the principal of retro-reflection. There are two methods of tradition retro-reflection: the first one is optical angle reflector which has good retro-reflective function, but is expensive and requires high processing accuracy. Its reflective angle is almost 0 degree and the angle of incidence is also around 0 degrees which limit its application in many fields. The second one is glass microbeads retro-reflective materials which are mostly used for road marking lines. Its life span is generally only about 3 months, and the wavelength is limited to the visible light range. For example, the patent publication No.CN104461169A provides an infrared return, but the reflection film wavelength can only reach 940mm.

The refractive index is the ratio of the light speed in a vacuum to the light speed in the medium. It is mainly used to describe the material's ability to refract light. The material with higher refractive index, the ability to refract incident light is stronger. In China, the standard of refractive glass beads for pavement GB/T24722-2009, according to the refractive index of glass beads, glass beads can be divided into three types: low refractive index glass beads, medium refractive index glass beads, and high refractive index glass beads, the refractive index (RI) is 1.50≤RI <1.70, 1.70≤RI <1.90, and RI≥1.90. 1.5 Refractive index glass beads: It is mainly made by crushing, sieving and melting recycled glass, the main component is silica. 1.7 Refractive Index Glass Beads: It adopt a matching method, first melting 1.7 refractive index glass, then furnacing glass beads.The main component is titanium dioxide, with a density of ≥3.0.The technical requirements and melting process are complicated, but the maximum retro reflective of 1.7 index glass beads can reach more than 1000mcd, and it has a good reflectivity in rainy night condition.Drop on the 1.7 beads on road without paint, it can reach about 200mcd.Particle size range: 0.212 ~ 2.0mm. （1.7 index beadsdrop onthermoplastic paint with 2% Titanium, the reading is 582mcd）

Project requirements: -1. Initial retro-reflective is≥450mcd, -2. Retro-reflective during the application period not less than 150-200mcd. Using glass beads with a size propotion of 0.3~0.85mm, if the thermoplastic temperature control is not good, it is easy to settle inside the paint, cause a bad retro-reflectivity in initial. If floating on the paint surface, the retro-reflectivity maybe not bad, but only stay for 3 months. Add the glass bead grade with 0.85-1.4mm (type3) to extend the glass bead grading to 0.3~1.4mm. See the surface of the line marking: Uniform distribution Good subsidence The large size beads sink into paint with 2/3 All of the small size sink to the inside of the paint, there is a connection with the premix glass beads Tips: Beads size of 0.85-1.4mm work for the first half of the year’s retro-reflectivity, size of 0.6-1.18mm will work for the middle period, the premix beads 0.3-0.85mm have a continuous retro-reflectivity. Continuous reflection is no longer a problem. What is the retro-reflectivity we can achieve? See below pictures: Retro-reflectivity in wet weather after 1 week:

Reflective element applied in Seoul City, South Korea.

HR glass beads applied in Beijing.