2. Multiple-choice questions
1. When filling embankments in deep valleys and steep slopes, it is impossible to fill them in layers from bottom to top. [A] can be used
A. Vertical filling; B. Layered filling; C. Mixed filling.
2. Layered filling in embankment filling refers to [C]
A. Horizontal layered filling B. Vertical layered filling C. Both of the above are correct .
3. When the soil foundation is compacted, the rolling speed should be [ A ]
A. Slow first and then fast B. Fast first and then slow C. Consistent in sequence
4. For the same type of soil, its optimal water content and maximum dry density change with () [ B ]
A. Number of compactions B. Compaction work; C. Thickness of soil layer
5. When the cross slope of the ground is 1:5~1:2.5, the original ground should be dug into steps, and the width of the steps should not be less than [C]
A.2.0m B.0.5 m C .1.0m D.1.5m
6. The hot mix asphalt mixture should be compacted according to ( ). [ A ]
A. Initial pressure, re-pressure, and final pressure; B. Initial pressure, final pressure; C. One-time compaction by a large-tonnage roller.
7. When constructing asphalt pavement, rolling with the road roller should be carried out from ( ). [ A ]
A. Both sides are toward the center; B. The center is toward both sides; C. One side is toward the other side.
8. For hot-mix asphalt pavement, its transverse joints should be aligned with the road center line ( ). [ B ]
A. Oblique; B. Perpendicular; C. Parallel.
9. ( ) is a thin-layer pavement surface layer that is coated with asphalt and mineral materials, with a thickness of no more than 3cm. [ A ]
A. Asphalt surface treatment; B. Asphalt penetration; C. Asphalt gravel.
10. The asphalt penetration pavement is to pour asphalt through the preliminary compacted gravel or rolled gravel, then spread the caulking material and pour the asphalt in layers, and pass through the divided A thicker pavement surface layer formed by compacting layers. Its thickness is usually ( )cm. [ B ]
A.4～6; B.4～8; C.5～7
11. The asphalt pouring temperature should be selected according to the construction temperature and asphalt grade. The spreading temperature of petroleum asphalt is (). [ B ]
A. 30～70℃; B． 130～170℃; C230～270℃; D. 330～370℃
12. Asphalt concrete pavement is used ( ). [ B ]
A. Layer laying method B. Mixing method, C. Stir up and down D. Penetration method
13. Asphalt gravel has a ( ) type structure. [ C ]
A. Dense; B. Stable; C. Embedding; D. Semi-dense semi-embedded extrusion
14. Asphalt concrete pavement mainly contains ( ), which greatly increases the bonding force. [ B ]
A. Fine granular material B. Mineral powder; C. Gypsum D. Asphalt with low consistency
15. Asphalt penetration pavement belongs to the ( ) type of pavement. [ A ]
A. Embedded extrusion type B. Compact type; C. Semi-embedded and semi-dense type; D. Grading type
16. The factory temperature of bulk cement in summer should not be higher than ( ) in the south and not higher than ( ) in the north. [ A ]
A. 65℃, 55℃; B 55℃, 45℃; C 75℃, 65℃
17. For concrete strength grades greater than C60, grade () coarse aggregate should be used.
[ A ]
A. Grade I; B. Grade II; C. Grade III
18. The concrete strength grade is C30~C60 and has frost resistance and anti-seepage requirements. Use grade () coarse aggregate [B]
A. Grade I; B. Grade II; C. Grade III
19. The lateral spacing of the vibrator rods should not be greater than 45cm. Should be evenly arranged () [ B ]
A. 20m; B. 45m; C.60m
20. The distance between the edge vibrators on both sides and the paving edge should not be greater than ( ) [ C ]
A. 100m; B. 400m; C.250m
21. The maintenance time of the previous cement concrete pavement on one side of the slipform paver track should be controlled to be above ( ), and the minimum should not be less than ( ). [ A ]
A 7d, 5d; B28d, 7d; C10d, 8d
22. The vacuum dehydration process is suitable for the construction of concrete pavement with a thickness not greater than (). [ A ]
A 24cm; B 30cm; C48cm
23. The best time to cut joints in cement concrete pavement is ( ) [ B ]
A. Reach When 4MPa; B. When it reaches 8MPa; C. When it reaches 15MPa
24. The loading sequence of the mixer should be ( ) [ A ]
A. Sand, cement, crushed (gravel) ) stone, add water while stirring; B. Cement, sand, stir while adding water;
C. Crushed (gravel) stone, sand, cement, stir while adding water
< p>25. When the construction temperature is between 10 and 20°C, the maximum allowable time from the discharge of concrete from the mixer to the completion of pouring [B]A.2h; B.1.5h; C.1.0 h
Soil with a liquid limit greater than ( ), a plasticity index greater than ( ), and a moisture content exceeding the specified limit shall not be used directly as roadbed filler.
[ B ]
A. 40%; 25 B.50%; 26 C.45%; 27 D.50%; 16.
27. When the cross slope is steeper than ( ), steps should be dug on the original ground, and the width of the steps should not be less than 1m. [ C ]
A. 1:10; B. 1:10～1:5; C. 1:5; D.1: 2.5
28. The crushing value of semi-rigid base material is not greater than ( ) for general highways and not greater than ( ) for high-grade highways. [ D ]
A. 35%; 30%; B. 40%; 35%; C. 40%; 30%; D.35%; 30%
29. The maximum particle size of coarse aggregate for cement concrete pavement is not greater than ( ). [ B ]
A. 35mm; B． 40mm; C. 45mm; D. 30mm
30. A settlement joint in a culvert is generally provided with a plume ( ). [ B ]
A. 4～8; B． 4～6;C. 5～6; D.5～8
True or False Questions
1. During the compaction process of soil, the more times it is compacted, the denser the soil becomes. ( B )
2. In the standard compaction curve of soil, the optimum moisture content corresponds to the maximum dry density. (A)
3. When the ground cross slope is not steeper than 1:10 and the embankment height does not exceed 0.5m, the base does not need to be treated.
(A)
4. Different soil qualities should be considered when filling embankments. The original ground should be filled layer by layer and compacted layer by layer. The thickness of each layer of filling soil can be determined by the effective compaction of the compaction machine. Depth and compaction determined. (A)
5. The relationship between the layout of the spur dam and the direction of the flow is different, but the function is the same. (B)
6. Gabion protection is a permanent building, with two types: tile type and stacked type. (B)
7. During the construction of riprap protection, it will not be affected by the season. (B)
8. When laying turf bricks, only the grass side should be upward, and all layers should be consistent. (B)
9. Clay soil with a plasticity index of 15 to 20 is suitable for stabilization with lime. (A)
10. Longitudinal joints should be avoided during the construction of cement-stabilized soil layer. When construction must be divided into two parts, the longitudinal joints must be mitered. (B)
11. When paving the mixture with a paver, it should not be interrupted. If the interruption time exceeds 4 hours for any reason, transverse joints should be set up. (B)
12. When the central station centralized mixing method is used for construction, before the mixture is officially mixed, the plant mixing equipment used must be debugged to ensure that the particle composition and moisture content of the mixture reach the stipulated requirements. (B)
13. Class C asphalt is suitable for all grades of highways and is suitable for any occasion and level (B)
14. Hot mix asphalt mixture should be of smaller tonnage When transporting dump trucks, their trunks should be clean. (B)
15. Hot mix asphalt mixture, since the mixture has been heated during mixing, the truck does not need to be covered with tarpaulin. (B)
16. The compaction of hot mix asphalt mixture should be carried out in three stages: initial pressure, re-pressure and final pressure. ( A )
17. The strength of dense asphalt pavement is mainly composed of internal friction resistance, supplemented by bonding force. ( B )
18. The strength of dense asphalt pavement is mainly composed of bonding force and internal friction resistance. (A)
19. In order to improve the technical performance of cement concrete, appropriate admixtures can be added during the preparation of concrete (A)
20. Sliding paver paving There is no need to erect formwork when constructing cement concrete pavement. ( B )
21. Dowel rods must be installed at all expansion joints. (B)
22. The material mix ratio when mixing concrete refers to the construction mix ratio. (A)
IV. Term explanation questions
1 Segmented excavation method
If the cutting to be excavated is very long, the cutting can be placed at the appropriate position of the cutting Lateral digging is done to divide the cutting into several sections, and each section is excavated longitudinally. This method of digging the cutting is called the segmented excavation method. This excavation method can increase the construction working surface and reduce the distance between the working surfaces. mutual interference and increase the discharge port, thereby greatly improving the work efficiency, and is suitable for excavation of deep and long road cuttings near mountains.
2 Optimum water content
Under the compaction of a certain function, changes in water content will cause the dry density of soil to change accordingly. At a certain water content (optimal (moisture content), the dry density reaches the maximum value (maximum dry density)
3 Falling water rapid chute
Falling water - set up where the height difference is large and the distance needs to be drained. A stepped structure on a short or steeply sloping site.
Its main function is to reduce the flow rate and reduce the energy of water.
Rapid trough - a trough with a very steep slope. Its main function is to drain water within a short distance and under a large drop in the water surface.
4 Lime stabilized soil
Add sufficient amounts of lime and water into crushed or originally loose soil (including various coarse, medium and fine-grained soil), and mix , compaction and curing of the mixture obtained, when its compressive strength meets the specified requirements, it is called lime stabilized soil. Lime stabilized soil includes lime soil, lime gravel soil, and lime gravel soil.
5 Dense asphalt pavement
Dense asphalt pavement requires the gradation of mineral materials to be designed according to the principle of maximum density, and the strength and stability mainly depend on the mixture
Cohesion and internal friction resistance.
6 Longitudinal layered filling method
Longitudinal layered filling is suitable for bulldozers or scrapers to take soil from road cuttings to fill embankments with short transportation distances. The fill side should be excavated manually according to the requirements, and then the soil steps should be excavated in layers according to the direction of the longitudinal slope, and the fill should be bulldozed and compacted layer by layer. This method is commonly used in sections where the original ground longitudinal slope is greater than 12%.
7 Stone-filled seepage trenches
Stone-filled seepage trenches are also called blind trenches. They are generally used in road sections with low flow and short seepage trenches. They are a commonly used seepage trench on highways. During construction, attention should be paid to siltation failure. Due to the large resistance of the drainage layer, its longitudinal slope should not be less than 1%, and generally 5% can be used. The depth should not exceed 3m, and the width is generally 0.7~1.0m.
8 Highway base layer
As an important part of the highway, the roadbed is the foundation of the road surface. It not only bears the load of the soil itself, but also bears the repeated action of the driving load. It is the load-bearing main body of the highway.
9 Gap-filling gravel
Use single-size coarse gravel as the main aggregate to form an interlocking structure, which can bear and transmit the wheel load, and use stone chips as gap-filling The material fills the pores between gravels to increase density and stability. This material is called interstitial gravel. The gap-filling gravel can be used as the base layer of highways of all grades and the base layer of highways below grade 2
10 Asphalt pavement
Asphalt pavement uses asphalt materials as binders to bind mineral materials. The pavement structure consists of the built surface layer and various base layers and cushion layers.
11 Route centerline construction stakeout
Use measuring instruments and equipment to accurately place the "centerline" of the highway according to the various elements and control point coordinates in the design drawings. On-site, guide construction operations. Staking out method: 1. Use control points along the line to stake out; 2. Use route control points (intersection points, straight circle points, straight circle points, etc.).
12 Single-layer cross excavation method
The cross excavation method is to excavate forward from one or both ends of the road cutting within the full width of the cross section. It is mainly suitable for short and shallow road cuttings. . When the cutting depth is not large, the excavation method of digging to the design elevation in one go is called the single-layer cross excavation method.
13 Direct measurement method
The direct measurement method is to calculate the distance between each pier and platform based on the pile numbers of the bridge positions on both sides and the center number of the known bridge piers and platforms. The distance is controlled by the bridge piles on both sides of the bank, and the center position of the bridge pier and platform is directly measured.
14 Compaction degree
Let the actual measured dry bulk density at the construction site be , and the relative value of its ratio to the value obtained by the indoor standard compaction test is called the compaction degree K.
15 Positive circulation rotation
Use mud to pass through the hollow drill pipe at high pressure and shoot out from the bottom of the drill pipe. When the drill cone at the bottom rotates, the drilling residue is suspended by the mud and overflows to the mud pool outside the well, where it is precipitated and purified before being recycled.
16 Offset
It refers to the vertical height difference between adjacent panels at the joints.
17 Compactness of Soil
The compactness of soil is also called theoretical compactness, which refers to the tightness of arrangement of solid particles within unit volume. That is, the greater the solid volume ratio of soil, the The dry density of soil is also greater, so dry density is sometimes used to express the compactness of soil.
18 Embankment load forced replacement method
The embankment load forced replacement method relies on the embankment load to force out part of the soft soil layer and replace it with good filling materials. During construction, filling should be started from the center line and gradually toward the outside. However, for wide embankments, due to inconsistent settlement, some soft soil remains under the embankment. Unfavorable uneven settlement will occur after completion, which should be paid attention to.
19 Permeable layer and adhesive layer
The permeable layer is made by pouring emulsified asphalt, coal asphalt or liquid asphalt on the base layer in order to make the asphalt surface layer and the non-asphalt surface layer well combined. A thin layer formed that penetrates the surface of the base layer.
The adhesive layer is a thin layer of asphalt material spread to strengthen the bond between the asphalt layer of the road surface and between the asphalt layer and the cement concrete pavement.
5. Questions and Answers
1 How to use a level to measure a known slope?
As shown in the figure, A and B are the two ends of the design slope line. It is known that the elevation of point A is HA and the design slope is iAB. Then the design elevation of point B can be calculated by the following formula
< p> HAB = HA + iAB * DABiAB——The designed slope between two points A and B. When the slope rises, i is positive, otherwise it is negative;
DAB—— The horizontal distance between points A and B.
Steps to use a level to measure a known slope:
First, measure the design elevations HA and HB of the two endpoints A and B of the design slope line on the ground based on the leveling points, and Drive the stakes.
Place the level at point A and measure the height i of the instrument. When installing, make the general foot screw in the AB direction, and the connection line of the other two foot screws is roughly perpendicular to the AB direction line.
Rotate the foot screw or slight tilt screw in the AB direction so that the scale reading on scale B equals the height i of the instrument, then the line connecting the tops of each pile is the design slope required for measurement. If the actual reading of the scale on the top of each pile is bi, the filling and digging value of each pile can be calculated according to the following formula
Filling and digging value = i – bi
Where, i = bi When , do not fill or dig; when i>bi, dig is required; when i 2 Briefly describe the main methods of measuring the plane position of points and the main instruments used? The measurement of the plane position of a point can be divided into: Cartesian coordinate method, polar coordinate method, angle intersection method, distance intersection method, etc. Rectangular coordinate method: steel ruler or distance measurement Theodolite, theodolite Polar coordinate method: theodolite, distance meter Front intersection method: two theodolite Distance intersection method: steel ruler 3 What are the commonly used treatment methods for soft soil foundation? Plastic drainage board Sand well drainage method Filling method Lime soil compaction pile Geotechnical Synthetic material reinforcement 4 What are the specific methods of replacement and filling? 1) Excavation and replacement method That is, the soft soil is excavated within a certain range, replaced with non-erosive low-compression bulk materials, and compacted in layers. According to the distribution pattern of the soft soil layer and the excavation location, there are two types: comprehensive excavation and replacement and partial excavation and replacement. Forced replacement method (1) This method relies on the embankment load to force out part of the soft soil layer and replace it with good filling materials. During construction, filling should be started from the center line and gradually toward the outside. However, for wide embankments, due to inconsistent settlement, some soft soil remains under the embankment. Unfavorable uneven settlement will occur after completion, so attention should be paid. (2) Blasting and filling method This method is to load explosives into the soft soil layer and squeeze out the soft soil through blasting. This method has a great impact on the surroundings and can only be used in areas where blasting has no adverse effects on surrounding structures or facilities. And generally, it takes several blasts to make the embankment gradually sink, and the bulging soft soil on both sides must be excavated in time to ensure that the blasting effect is not reduced. 5 What are the commonly used construction methods in drainage consolidation method? 1) Plastic drainage board The principle of using plastic drainage boards to treat soft subgrade is to use drainage boards inserted deeply into the soft subgrade to prevent the surface and groundwater outside the subgrade from entering the subgrade range. When building a roadbed, the load acts on the soft foundation, and the groundwater rises along the plastic drainage board into the sand cushion due to extrusion and capillary action, and is discharged from the sand cushion to both sides, thus improving the bearing capacity of the base. 2) Sand well drainage method This method is to set up vertical drainage wells in the soft soil layer, usually composed of medium sand or coarse sand, and cardboard is also used in China. The method is to use a steel pipe equipped with a buried pile shoe at the lower end to drive into the soil, then pour sand from the upper end, tamp it layer by layer, and at the same time pull up the pipe until the pile hole is filled with sand to form a sand well. 6 Try to describe the types, functions and applicable conditions of roadbed protection 1) Slope protection is divided into plant protection engineering protection Function: used to protect vulnerable Soil and rock slopes damaged by natural factors Plant protection: Mainly planting grass, laying turf and planting trees on the slopes of roadbed soil suitable for plant growth, using vegetation to cover the slope, and its root system Consolidate topsoil to prevent soil erosion, regulate slope humidity and temperature, ensure slope stability, and play the role of greening roads and protecting the environment. Engineering protection: It is suitable for steep slopes that are not suitable for the growth of vegetation. Sand, cement, lime and other mineral materials are used for surface protection. Generally, plastering, hammering, shotcrete, shotcrete, jointing and Slope retaining walls, etc. 2) Scouring protection is divided into direct protection (plant protection, gas slope protection, riprap protection, gabion protection, etc.) and indirect protection (gross dams, parallel dams, etc.) Function: Used to protect the roadbed from scouring and scouring by water flow 7 Try to describe the types of roadbed scouring protection Scouring protection is divided into direct protection (plant protection, gas slope protection, riprap protection, Gabion protection, etc.) and indirect protection (gross dams, parallel dams, etc.) 8 Describe the construction method and construction process of the central plant-mixed cement stabilized base layer (1) Cement Stabilized soil can be mixed centrally using factory mixing equipment at the central station, and then transported to the construction site for paving, rolling and other processes. (2) Mixing equipment. Stabilized soil mixer, forced cement concrete mixer and asphalt concrete mixer. (3) The mixing of centralized plant mixing should meet the following requirements: ①The soil clods should be crushed, and the maximum size should not be larger than 15mm; ②The ingredients should be accurate, Mix evenly; ③The water content should be slightly greater than the optimal water content; ④Crushed stone or gravel of different sizes and fine aggregates (such as stone chips and sand) should be isolated , stacked separately; (4) Transportation of mixed materials. If necessary, the mix on the truck should be covered during transportation to reduce moisture loss. (5) Paving of mixture ①Asphalt concrete paver or stabilized soil paver A. The current bearing layer is stable fine particles When removing soil, first roughen the top surface of the lower bearing layer and then spread the mixture. B. A dedicated person should be assigned behind the paver to eliminate the segregation of coarse and fine aggregates. In particular, local coarse aggregate "nests" should be eradicated and filled with fresh mixture, and the paving thickness should be checked. ②Paver box, automatic grader or manual paving mixture A. Calculate the density of each truck of mixture based on the thickness of the paving layer and the required compacted dry density. Paving area, B. Unload the mixture evenly in the center of the road width. When the road width is wide, the mixture can also be unloaded into two rows; C. Use flat ground The machine will spread the mixture evenly according to the loose paving thickness, and check the paving thickness; D. Have a dedicated person carry a trolley containing fresh mixture to follow behind the grader, and eradicate the rough accumulation in time. The material "nest" and the coarse aggregate "belt" are replenished with freshly mixed homogeneous mixture, or replenished with the mixed and uniform fine mixture, and mix evenly with the coarse aggregate. (6) Shaping and rolling (7) First use a light two-wheel roller to follow the paver for rolling in time, and then use a heavy-duty vibratory roller and a three-wheel roller Or the tire roller will continue to compact it until there are no obvious wheel marks and the specified compaction degree is reached. (8) Transverse joints ① When paving the mixture with a paver, it should not be interrupted. If the interruption time exceeds 2 hours for any reason, transverse joints should be set; ② Tidy up the mixture at the end, and place two square logs close to the mixture. The height of the square logs should be the same as the compacted thickness of the mixture, and the mixture close to the square logs should be leveled; ③The other side of the square log is backfilled with gravel or gravel about 3m long, and its height should be a few centimeters higher than the square log; ④Crush the mixture to make it dense;
⑥ Return the paver to the compacted layer At the end, start paving the mixture again;
⑦ If the transverse joints are not processed according to the above method after the paving is interrupted, and the interruption time has exceeded 2 hours, the area near and below the paver should be unpressurized. The solid mixture should be shoveled away, and the end that has been compacted and whose elevation and flatness meet the requirements should be dug into a section perpendicular to the center line of the road and vertically downward, and then new mixture can be paved.
(9) Try to avoid longitudinal seams.
(10) Paving mixture
(11) Health maintenance
9 What are the factors that affect the compaction effect of roadbed?
Answer: For the subgrade of fine-grained soil, the factors that affect the compaction effect include internal factors and external factors. Internal factors refer to soil quality and humidity, and external factors refer to compaction functions (such as mechanical properties, compaction time and speed, soil layer thickness) and other external natural and man-made factors during compaction.
1) The effect of moisture content on compaction
1) The relationship between moisture content ω and density (measured by dry bulk weight/measurement)
2) Content The relationship between the amount of water added and the water stability of the soil
2) The impact of soil quality on compaction effect
3) The impact of compaction function on compaction
4) The impact of compaction thickness on compaction effect
10 How to deal with joints and U-turns during pavement base construction?
Answer: The connection between the two working sections should be overlapped and mixed. After the first stage of mixing, leave 5-8m without rolling. During the construction of the second section, add some cement to the part left in the previous section, mix it again, and grind it together with the second section. pressure. a) Cut the end of the compacted section into a vertical plane, and push the next section of crushed soil away from the joint;
b) Place a square log at the end of the compacted section, And use a piece of thick construction paper to protect it, and cover the paper with soil (or lay wooden boards);
c) Spread the crushed soil until the joints, and sprinkle water on the new section to make its moisture content meet the requirements. value, and push the cement;
d) Mix the cement and soil completely, and add some water if necessary;
e) Push the mixed mixture away from the joints , cut off the thick paper and remove the square wood;
f) Spread the mixed mixture back to the joints, and use paper to separate the cement-soil mixture from the covering soil;
< p> g) The new section has been compacted, leaving only a small amount of work at the joints. Remove the covering soil and paper, and then scrape the raised parts flat.11 Briefly describe the steps of measurement and setting out for culvert construction.
Answer: 1) Determine the central pile position of the culvert; 2) Determine the axis of the culvert; 3) Set out the hole body; 4) Set out the hole entrance; 5) Set out the elevation.
12 What measures should be taken during the construction of cement concrete pavement in low-temperature seasons?
Answer: When the ambient temperature for construction operations and health care is ≤5cC or the lowest day and night temperature may be lower than -2℃, it is considered low-temperature construction. During low-temperature construction, the strength of concrete increases slowly due to the reduced hydration rate, and it may be damaged by freezing. Therefore, process design for low-temperature construction must be proposed. A. Increase the concrete mixing temperature; B. Pavement insulation measures; C. During low-temperature construction, the design mix ratio of concrete should generally not exceed 0.6.
13 What are the grades and labels of road petroleum asphalt? How to choose road petroleum asphalt?
Asphalt grade Scope of application
Grade A asphalt various grades of highway, suitable for any occasion and level
Grade B asphalt 1. Expressway, first-class highway The lower layer of asphalt and the layers below, and all layers of secondary and secondary highways
2. Used as the base asphalt for modified asphalt, emulsified asphalt, modified emulsified asphalt, and diluted asphalt
C-grade asphalt, all levels of grade three and below highways
14 What types of mixing machinery are there for hot mix asphalt gravel? What is the mixing procedure?
Classification of mixing machinery:
According to the process flow, it can be divided into intermittent forced type and continuous drum type.
It is divided into large, medium and small according to production capacity.
Mixing procedure
Conduct trial mixing according to the mix ratio of the asphalt mixture, and determine the mixing quality control indicators through trial mixing and sampling tests.
① For intermittent forced mixing equipment, the mix ratio of each hot material bin should be determined; for continuous drum mixing equipment, the size of the various mineral material feeding ports and the feeding of asphalt and mineral materials should be determined. Material speed.
② Take samples of the trial-mixed asphalt mixture and conduct Marshall test, asphalt extraction and screening tests to verify whether the various technical indicators of the asphalt mixture, asphalt t and mineral gradation are in compliance with Specifications and design requirements; if any indicators do not meet the specifications and design requirements, appropriate adjustments should be made.
③Determine the appropriate mixing time.
④ Determine the appropriate mixing and leaving factory temperatures.
Strictly control the amount of various materials and heating temperature according to the ingredient list. The color of the mixed material after mixing should be uniform, and there should be no whitening, segregation, agglomeration, etc. Each shift takes samples to test the performance of the asphalt mixture, the gradation of mineral materials and the amount of asphalt.
15What is the rolling process of hot mix asphalt gravel? What is the rolling temperature?
(1) Initial pressure
(2) Re-pressure
(3) Final pressure
Temperature
Construction process No. of petroleum asphalt
No. 50 No. 70 No. 90 No. 110
Asphalt heating temperature 160～170 155～165 50～160 145～155
Ore material heating temperature Gap forced mixer The aggregate heating temperature is 10~30% higher than the asphalt temperature
Continuous drum mixer │The mineral material heating temperature is 5~10% higher than the asphalt temperature
< p> Asphalt mixture discharge temperature 150～170 145～165 140～160 135～155Storage temperature of the mixture storage bin The temperature should not drop more than 10 during the storage process
The waste temperature of the mixture is higher than 200 195 190 185
The temperature when transported to the site is not lower than 150 145 140 135
135The paving temperature of the mixture is not lower than normal construction 140 135 130 125
Low temperature construction 160 150 140 135
The internal temperature of the mixture at the beginning of rolling shall not be lower than normal construction 135 130 125 120
Low temperature construction 150 145 135 130
Surface temperature after rolling,
not lower than steel wheel roller 80 70 65 60
tire roller 85 80 75 70
p>Vibratory roller 75 70 60 55
The road surface temperature open to traffic shall not be higher than 50 50 50 45
16 Construction procedures for top-mix and bottom-penetration asphalt pavement What is it?
17 What are the main materials of cement concrete pavement? What are the technical requirements for these materials?
The main materials of cement concrete pavement are cement, coarse aggregate, fine aggregate and water, as well as admixtures and mineral admixtures added to improve process performance and mechanical properties.
1 Cement should be made of cement with high strength, small shrinkage, strong wear resistance and good frost resistance. The compressive strength, flexural strength, stability and setting time of cement must be inspected and qualified.
2 Coarse aggregate should be hard, durable, clean, well-graded, and should meet certain technical requirements. When selecting coarse aggregates for pavement and bridge deck concrete, aggregates of 2 to 4 particle sizes should be blended according to the maximum nominal particle size. The synthetic gradation must meet the "Technical Specifications for Construction of Highway Cement Concrete Pavement" (JTG F30-2003) requirements. The maximum nominal particle size of pebbles should not be greater than 19. 0mm; the maximum nominal particle size of crushed pebbles should not be greater than 26.5mm; the maximum nominal particle size of gravel should not be greater than 31.5mm.
3 The fine aggregate should be clean in texture with low content of harmful impurities, hard and wear-resistant, rough and angular in surface, and comply with the prescribed grading. Its grading requirements and technical requirements should comply with the "Highway Cement Concrete" Technical Specifications for Pavement Construction)) (JTG F30-2003). When selecting fine aggregates, both fineness modulus and gradation should be considered.
Natural sand for pavement and bridge decks: medium sand (fineness modulus 2. 3 to 3. 0) is suitable, but sand with a fineness modulus of 2.0 to 3.5 can also be used. The variation range of the fineness modulus of sand used in the same mix ratio should not exceed 0.3, otherwise it should be stacked separately and the sand rate in the mix ratio should be adjusted before use.
4. The water used for cleaning aggregates, mixing and curing concrete should not contain harmful impurities such as oil, acid, alkali, salt and organic matter that affect the normal setting and hardening of concrete. Drinking water should be used as the should.
5 Admixtures that improve the flow properties of concrete mixtures, such as water-reducing agents, air-entraining agents, pumping agents, etc. Admixtures that adjust setting time and hardening properties include retarder, accelerating agent, and early strength agent. Admixtures that improve the durability of concrete, such as air-entraining agents, waterproofing agents, and rust inhibitors. Admixtures that improve other properties of concrete, such as expansion agents, antifreeze agents, alkali-aggregate reaction inhibitors, etc.
When using admixtures, the suitability test must be carried out with the cement used, and the type of admixtures that are compatible with the cement should be used. The quality of admixtures used in pavement concrete should meet the requirements of first-class products.
6 When fly ash is mixed with concrete pavement, it should be mixed with electrostatic precipitator I and II dry discharge or finely ground fly ash whose quality indicators meet the requirements. Class III fly ash shall not be used. There should be a grade inspection report when purchasing goods, and bulk ash should be used. Silica fume and ground slag should be tested before use to ensure that the technical indicators such as flexural tensile strength, abrasion resistance, and frost resistance of road and bridge deck concrete are qualified.
18What are the steps for cement concrete mix proportion design?
1) Calculate the preliminary mix ratio
(1) Determine the strength of the preparation
(2) Calculate the water-cement ratio (W/C)
(3) Calculate unit water consumption (W0)
(4) Unit cement consumption per cubic meter of C0 concrete mixture
(5) Calculate sand and gravel material units Dosage
2) Adjustment of mix ratio
1) Trial mixing inspection in laboratory
2) Trial mixing inspection in mixing building
3 ) Fine-tuning during construction