CN106644914A - Method for evaluating snow-melting effect durability of snow-melting asphalt mixture - Google Patents

Abstract

The invention discloses a method for evaluating the durability of snow-melting asphalt mixture. Firstly, a rut plate test piece is formed, and the length and width of the test piece are measured. The volume of rainwater in the area of the rut plate; then use a measuring cylinder to measure the volume of water flowing out of the hood within a certain period of time, and calculate the flow rate of the hood; then carry out a simulated rainfall test, sprinkle the water in the hood to the rut plate, so that The surface of the rutting slab is evenly scoured, and the rainwater after the shower is collected every 5 minutes with a glass and the conductivity is measured, and the effective years of the durability of the snow-melting asphalt mixture snow-melting effect are calculated according to the shower time corresponding to the required minimum conductivity . The invention can accurately and conveniently evaluate the snow-melting durability of the snow-melting asphalt mixture, and provides important help for the quantitative evaluation of the snow-melting durability of the snow-melting asphalt pavement.

Description

A method for evaluating the durability of snow melting effect of snow melting asphalt mixture

technical field

The invention belongs to the technical field of road engineering, and in particular relates to a method for evaluating the durability of the snow-melting effect of a snow-melting asphalt mixture.

Background technique

Three-quarters of my country's land belongs to winter snow-covered areas, and some areas have snow-covered periods as long as 3 to 4 months. Snowfall and icing will directly lead to the decline of the anti-skid performance of the road surface, causing the brakes of the car to fail and the direction to be out of control, thus easily causing traffic accidents. Relevant data show that the adhesion coefficient of dry asphalt pavement is about 0.6, while the adhesion coefficient of snow-covered pavement is 0.2, and the adhesion coefficient of icy road is 0.15, which is reduced to 1/3 and 1/4 of dry asphalt pavement. Therefore, on ice and snow roads, cars are prone to skidding and deviation, and the braking distance is significantly prolonged, which seriously affects the operational stability and safety of the vehicle, and the incidence of traffic accidents is high.

The effective freeze-inhibiting components of salinity are mainly soluble salts (sodium chloride, calcium chloride, etc.), which are processed into granules or powders through different processing techniques, and added to the asphalt mixture. Salts are precipitated through the pores of the porous structure. When it reaches the hole of the mixture, it spreads to the road surface, interacts with the ice and snow on the road surface, lowers the freezing point of the snow on the road surface, and turns the ice and snow into liquid water or water vapor to discharge the road surface, achieving the effect of melting ice and snow. After sodium chloride is precipitated, the volume of the porous material remains unchanged, avoiding the hazard of voids caused by the precipitation of effective components in the mixture.

An important performance of salt-melting snow-melting asphalt pavement compared with ordinary asphalt pavement is the ice-melting ability. How to accurately evaluate the snow-melting durability of salt-melting snow-melting asphalt pavement is an important part of the design of salt-melting snow-melting asphalt pavement.

At present, there are few researches on ice and snow melting evaluation at home and abroad, and they are only in the exploratory stage. (1) The most common qualitative evaluation method is to directly compare the ice-melting snow pavement with the ordinary asphalt pavement after snowing in winter. This method needs to pave the pavement with antifreeze asphalt mixture, which is costly and not suitable for the experimental research stage (2) After freezing, observe the scratch phenomenon on the surface of the test piece to evaluate the effect of melting ice and snow. This method can intuitively feel the effect of melting ice and snow on the sample added with antifreeze, but it cannot accurately evaluate the effect of melting ice and snow on the road surface ; (3) Deicing test is carried out by applying static load to the square disc specimen. This method uses static pressure head to simulate the actual road conditions poorly. Moreover, this method is only suitable for analyzing the ice breaking effect under the condition of road surface icing. (4) The so-called road surface exposure rate refers to the ratio of the exposed road surface area (anti-freezing road surface area) to the area of the detection section within the range of vehicle driving, and the road surface exposure rate is only applicable to outdoor tests. This index cannot be used to evaluate the effect of ice and snow melting indoors. Moreover, the road surface exposure rate is greatly affected by the traffic flow, the greater the traffic flow, the greater the road surface exposure rate.

Contents of the invention

The purpose of the present invention is to provide a method for evaluating the durability of snow-melting asphalt mixture, which simulates the influence of rainfall on the durability of snow-melting asphalt mixture, and evaluates the snow-melting durability of snow-melting asphalt mixture accurately and conveniently.

The technical scheme adopted in the present invention is: a method for evaluating the durability of snow-melting asphalt mixture, comprising the following steps:

Step 1: According to the method in "Test Regulations for Asphalt and Asphalt Mixtures in Highway Engineering JTG E20-2011" T0703-2011, form the rutting plate specimen, and the length and width are a (mm) and b (mm);

Step 2: Determine the flow rate of the awning used for sprinkling water. The specific method is to use a container to collect the amount of water V (L) sprayed within a certain period of time t (min), then the flow rate of the awning is V/t (L/min);

Step 3: Obtain the local average annual precipitation p (mm) from the survey, and calculate the rainfall falling on the area of the rut plate within a year as a*b*p (mm ³ );

Step 4: Carry out a simulated rainfall test, so that the water in the awning head is sprinkled vertically on the surface of the rut plate from a certain height, so that the surface of the rut plate is evenly scoured. During the test, the rainwater is collected with a glass at the bottom of the rut plate, and collected every five minutes once;

Step 5: Use a conductivity meter to measure the conductivity of the collected rainwater that showers the rut plate, and obtain the trend curve of the conductivity of the rainwater leaching out of the rutted slab with the leaching time at different periods;

Step 6: Select the minimum conductivity required for leaching rainwater according to the demand, and obtain the rinsing time T (min) corresponding to the conductivity through the relationship curve of conductivity-leaching time, then the snow-melting asphalt mixture can keep snow melting The effective service life of the performance is: n=T*(V/t)*10 ⁶ /(a*b*c).

As preferably, in the simulated precipitation test described in step 4, the sprinkling height is 1m.

As a preference, the minimum electrical conductivity required for leaching rainwater described in step 6 is 1.5 times the electrical conductivity of flushing water.

The invention can be used to analyze the influence of simulated rainfall on the durability of the snow-melting effect of the snow-melting asphalt mixture, and evaluate the service life of the snow-melting performance of the snow-melting asphalt mixture.

Beneficial effects of the present invention:

Compared with the evaluation method of snowmelt durability of conventional snowmelt asphalt mixture, the present invention has obvious advantages in the following aspects:

(1) Economy. The most common method for evaluating the snowmelt durability of snowmelt asphalt pavement is to directly compare the snowmelt pavement with the ordinary pavement. In the test and research stage, the invention provides an indoor test evaluation method for the snow-melt durability of the snow-melt asphalt mixture, the test is simple and easy, and the cost is low.

(2) Time limit. It generally takes several years to evaluate the snowmelt durability of snowmelt asphalt pavement with traditional methods and can make a proper evaluation of the snowmelt durability of snowmelt asphalt pavement according to the actual use of the asphalt pavement. The method provided by the invention can be based on local The actual situation simulates the rainfall, and evaluates the snow-melting durability of the snow-melting asphalt mixture according to the electrical conductivity of the rainwater, which greatly shortens the test time.

The invention can accurately and conveniently evaluate the snow-melting durability of the snow-melting asphalt mixture, and is of great help to the quantitative evaluation of the snow-melting durability of the snow-melting asphalt pavement.

Description of drawings

Fig. 1 is specific embodiment of the present invention conductivity-time curve;

Fig. 2 is the conductivity-scouring time relationship curve of the specific embodiment of the present invention.

Specific implementation method

The content of the present invention will be further clarified below in combination with the detailed description and accompanying drawings.

A method for evaluating the durability of snow-melting asphalt mixture, comprising the following steps:

Step 1: Form the rutting plate specimen according to the method of wheel rolling in "Test Regulations for Asphalt and Asphalt Mixtures in Highway Engineering JTG E20-2011" T0703-2011. The length and width of the rutting plate are a (mm) and b ( mm);

Step 2: Determine the flow rate of the awning used for sprinkling water. The specific method is to use a container to collect the water sprayed within a certain period of time t (min), and use a measuring cylinder to measure the volume of the received water as V (L). The flow rate is V/t(L/min);

Step 3: Obtain the local average annual precipitation p (mm) from the survey, and calculate the rainfall falling on the area of the rut plate within a year as a*b*p (mm ³ );

Step 4: Carry out a simulated rainfall test, so that the water in the awning head is sprinkled vertically on the surface of the rut plate from a certain height, so that the surface of the rut plate is evenly scoured. During the test, the rainwater is collected with a glass at the bottom of the rut plate, and collected every five minutes once;

Step 5: Use a conductivity meter to measure the conductivity of the collected rainwater from the rutted slabs, and obtain the trend curve of the conductivity of the rainwater leached out in different periods with the leaching time, and the abscissa of the curve is the rainwater leaching time , and the ordinate is the conductivity of rainwater, as shown in Figure 1;

Step 6: Select the minimum conductivity required for leaching rainwater according to the demand, and obtain the rinsing time T (min) corresponding to the conductivity through the relationship curve of conductivity-leaching time, then the snow-melting asphalt mixture can keep snow melting The effective service life of the performance is: n=T*(V/t)*10 ⁶ /(a*b*c).

Example

The assay method of the present invention has obtained good experimental verification. The snow-melting durability of the snow-melting asphalt mixture was evaluated by the method of the present invention.

The instruments and materials needed for this embodiment include:

(1) The rutting plate specimen formed according to the method in "Test Regulations for Asphalt and Asphalt Mixtures in Highway Engineering JTG E20-2011" T0703-2011; (2) The head used for sprinkling water; (3) The measuring cylinder with a measuring range of 200mL ; (4) timer, accurate to the second; (5) glass; (6) conductivity meter, which can measure the conductivity of the solution within the range of 0-100 ℃, accurate to 0.001mS/cm.

According to the method in "Test Regulations for Asphalt and Asphalt Mixtures in Highway Engineering JTG E20-2011" T0703-2011, the rutting plate specimens are formed. The length of the rutting plate specimens is 300mm and the width is 300mm; The average rainfall is 1100mm, so the average amount of rainwater falling on the rut plate in one year is 300mm×300mm×1100mm=9.9×10 ⁷ mm ³ .

Use a glass to collect the amount of water that flows out of the top within a certain period of time, use a measuring cylinder to measure the volume of the water, and calculate the flow rate of the top to be 3.9L/min. Fix the awning head at a position 1m above the rut plate, open the awning head, and sprinkle water on the rut plate, so that the surface of the rut plate can be evenly washed.

During the process of scouring the rut plate, use a glass cup to collect rainwater at the bottom of the rut plate, collect a certain amount of water flowing down from the test piece with a container every 5 minutes, and measure its conductivity. The test results are shown in Table 1 and Figure 2 shown.

Table 1 Changes in electrical conductivity during the process of scouring rut plates

time/min Conductivity/(mS/cm) time/min Conductivity/(mS/cm) 0 0.142 65 0.229 5 0.193 70 0.210 10 0.236 75 0.198 15 0.253 80 0.180 20 0.268 85 0.175 25 0.292 90 0.171 30 0.324 95 0.158 35 0.378 100 0.155 40 0.433 105 0.152 45 0.45 110 0.15 50 0.335 115 0.147 55 0.278 120 0.145 60 0.239 125 0.142

The conductivity of the flushing water is 0.10mS/cm. It can be seen from Figure 2 that the conductivity in the early stage is relatively small. This is because the salt dissolution in the surface layer of the road in the early stage is relatively small, and the conductivity is relatively small; after 10 minutes, the conductivity gradually increases. , this is due to the effect of ion migration with the continuation of rainwater erosion, more salt dissolution, and the measured conductivity is larger until it reaches the peak value at the 40th minute. With the continuous precipitation of antifreeze components, the antifreeze components contained in the flushing solution gradually decrease. Taking 1.5 times the conductivity of flushing water, that is, 0.15mS/cm as the critical value, and the corresponding time is 110min, the service life of the snowmelting durability of snowmelting asphalt mixture is:

n=110*3.9*10 ⁶ /(9.9*10 ⁷ )=4.33 years

It should be pointed out that those skilled in the art can make some improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention. All components that are not specified in this embodiment can be realized by existing technologies.

Claims (3)

1. a kind of evaluation method of snow melt asphalt snow melt effect durability, it is characterised in that：Comprise the steps：

Step 1：According to《Highway engineering pitch and Asphalt Mixture Experiment code JTG E20-2011》Side in T0703-2011 Method is molded rut plate test specimen, long and wide respectively a and b；

Step 2：It is determined that the flow velocity of watering fluffy head used, concrete grammar is, with the water sprayed out in container collection certain hour t Amount V, then the flow velocity of fluffy head is V/t；

Step 3：Investigation obtains mean annual precipitation p of locality, and calculates drop in 1 year in the range of rut plate suqare accordingly Rainfall be a*b*p；

Step 4：Rain test is simulated, the water in fluffy head is vertically spilt to rut plate surface from certain altitude, make rut plate Surface is uniformly washed away, and rainwater is collected with glass in rut plate bottom during test, collects once per five minutes；

Step 5：Using conductivity meter, the shower rut plate rain electrical conductivity of water collected is measured, obtain different periods and drench rain The conductance of water is with the change trend curve for drenching the time；

Step 6：The minimum conductivity drenched needed for rainwater is selected according to demand, by the relation curve of electrical conductivity-drench time, The corresponding shower time T of the electrical conductivity is obtained, then snow melt asphalt to be kept for effective service life of Thaw performance be： N=T* (V/t) * 10⁶/(a*b*c)。

2. a kind of evaluation method of snow melt asphalt snow melt effect durability according to claim 1, its feature exists In：Simulated precipitation test described in step 4, watering height is 1m.

3. a kind of evaluation method of snow melt asphalt snow melt effect durability according to claim 1, its feature exists In：The minimum conductivity drenched needed for rainwater described in step 6, to wash away 1.5 times with water conductivity.