Factors Influencing the Backreflection Luminance Coefficient of Markings in Road Construction by Measuring the Backreflection Coefficient Tester of Markings
12 10 月, 2023
The function of road markings is to convey rules, warnings, and guidance related to road traffic to road users through traffic markings on highways, separating motor vehicles, non motor vehicles, and pedestrians, improving road utilization, reducing or preventing traffic accidents, and using them in conjunction with traffic signs and signals to increase their effectiveness, providing legal basis for law-abiding and law enforcement personnel. According to GB5768.3-2009 “Road Traffic Signs and Markings”, road markings are divided into indication markings, prohibition markings, and warning markings according to their functions; Divided into vertical markings, horizontal markings, and other markings according to settings; Divided into lines, characters, raised road signs, and contour signs according to their morphology.
The colors of the markings are divided into white, yellow, blue, or orange. White and yellow are commonly used in highways, with yellow for the central line and white for the side lines.
Inspection and statistics of existing road markings have been conducted. Some markings have fallen off and have insufficient thickness. Drivers can recognize markings drawn on the road during the day, but at night, they cannot clearly see the markings through their headlights. The contour of the road surface is not clear enough, and the brightness value of the reverse reflection coefficient detected is too small, which poses certain risks to the safety of driving on the road. The main factors affecting the brightness coefficient of retroreflection are as follows:
1. The qualification of raw materials for road markings is a prerequisite: When selecting materials, select products from qualified and legitimate manufacturers, and send samples to qualified units for quality testing to ensure that the product quality is qualified.
(1) Selection of coatings: The prices of coatings vary and there are various varieties. Materials should be selected based on the model of road markings. The reflective type of hot melt markings must use coatings with a glass bead content of 18-25% in the coating, and cannot be replaced by ordinary coatings to ensure its reflective effect.
(2) Selection of glass beads: Glass beads are colorless and transparent small balls that have the functions of refracting, focusing, and directional reflection of light. Glass beads should be selected with uniform transparency, consistent size, and color. The higher their roundness, refractive index, and transparency, the better their reflective performance. Poor quality glass beads should not be used.
2. The surface of the road surface needs to be clean: After the road is rolled by vehicles and polluted during construction, the road surface needs to be carefully cleaned before marking construction. If necessary, the contaminated debris on the road surface should be removed and cleaned to ensure that the road surface is clean and effective adhesion of the markings.
3. The application of primer requires drying: there are fewer social vehicles on newly built roads, fewer intersections, and less obvious road surface pollution. Generally, primer is not applied during the construction of asphalt pavement markings. In construction areas or mixed traffic areas with high pollution, the primer must be applied evenly. Only when the primer is completely dry can road marking construction be carried out to ensure good adhesion between the markings and the road surface.
4. Avoid a large number of bubbles during marking construction: During the construction of asphalt pavement markings, certain bubbles may appear, mainly due to the following reasons: in sections where the asphalt pavement separates, after the marking machine passes through, the melted coating will fill the gaps in the separated sections, and bubbles may appear locally on the surface; The surface of asphalt pavement is damp, and the base glue is not dry. When high temperature meets low temperature water vapor, it vaporizes, and the water vapor evaporates upwards; The road surface is not cleaned thoroughly, resulting in particles and debris on the markings, as well as air gaps. The generation of bubbles can cause the glass beads scattered on the coating surface to fall off, the thickness of the markings is insufficient, and the brightness value of the retroreflection coefficient of the markings is weakened.
5. Uneven distribution of glass beads: Glass beads are the main indicator that affects the retroreflective brightness coefficient. Excessive or insufficient distribution of glass beads can affect the retroreflective brightness coefficient of the marking line, and the optimal dosage is generally around 0.35kg/. According to relevant test certificates: When the embedding degree of the glass bead is below 50%, the effect of regression reflection that can be formed is extremely poor, and the light almost completely penetrates the glass bead and refracts; when the embedding degree of the glass bead is about 60%, the effect of regression reflection is better; as the embedding degree increases, the effect of regression reflection gradually decreases, because the amount of light entering the glass bead also decreases with the increase of the embedding degree of the glass bead. It is crucial to master the depth of glass beads embedded in the coating.
6. Insufficient thickness: Thickness is the main indicator for road marking control and is directly related to the retroreflective brightness coefficient. The insufficient thickness of the marking results in a decrease in the number of glass beads embedded in the coating, poor light reflection and refraction effects, and a weakening of the reverse reflection brightness coefficient. GB16311-2009-T “Quality Requirements and Testing Methods for Road Traffic Markings” stipulates that the thickness of hot-melt markings is 0.7-2.5mm, and the design generally adopts a range of 1.5-2.0mm. During construction, the requirement of a thickness error of ≤ -0.1mm for hot-melt markings must be strictly controlled to ensure that the thickness meets the standard requirements.
7. Poor temperature control of the coating: the construction temperature of the coating is 180~210 C., When the temperature is low during construction, the glass beads scattered on the surface of the coating will fall off and cannot be effectively embedded into the interior of the coating, resulting in a weakened retroreflection value; If the construction temperature is too high, it will cause the glass beads to completely embed into the interior of the coating, and the reflection effect will be poor after light irradiation, which will also cause a decrease in the reverse reflection value.