I. Overview

The UV-22 contract section of Quiet Salt expressway starts from the northwest of Ruanjia Village in Daduo Town and ends at the border of Xingtai Township in Jiangyan City. Lime-flyash macadam includes the main line K46+ 100-K69+850 and the Daduo-Guzhuang interchange, with a thickness of 20CM-36CM. According to the high index requirements of provinces and cities, 20% of the quantity of lime-fly ash macadam base must be completed by the end of June, and all the assessment targets of lime-fly ash macadam base must be completed by the end of September. On may 18, the management office carried out the paving work of the test section of lime-fly ash macadam in K56+782-K57+0 10 on the right. Through the construction of trial paving section, the construction technology is further verified and formed.

Second, the construction mixture ratio

My department * * * selected three kinds of mixture ratio to carry out the test, and compared the test results, and selected the mixture ratio of lime-fly ash macadam construction:

Lime: fly ash: crushed stone =5.5: 12:82.5

Through the construction of trial paving section, the mixture ratio completely meets the specification and design requirements.

Third, the preparation before construction

Before construction, first organize technicians, front-line construction workers and mechanical operators to seriously study the relevant specifications and the spirit of the document "Guiding Opinions on Lime-fly Ash Macadam Base Construction" issued by relevant provincial and municipal departments, familiarize themselves with the construction drawings, formulate work instructions, and hold a technical disclosure meeting with the supervision team to make each employee clear the quality requirements. According to the local construction characteristics and the specific conditions of this bid, the project department scientifically formulated the construction technical scheme suitable for this bid. Through the trial paving section construction, the shortcomings in the construction technical scheme are further improved.

Fourth, the process handover

From the completion of lime-fly ash soil subbase construction to lime-fly ash macadam subbase construction, it is one of the key process handover control points in the whole pavement construction. Under the leadership of the Municipal High Index, the project to be inspected for lime-fly ash soil subbase shall be inspected jointly with the supervision team, subbase and grass-roots construction unit, and handed over after passing the inspection, so as to ensure the construction quality of lime-fly ash macadam subbase.

Verb (abbreviation for verb) raw material control

The quality of all kinds of raw materials should fully meet the technical specifications and design requirements, and the lime-fly ash macadam adopts qualified materials.

1, all kinds of raw materials need to be stacked in the warehouse with partition walls to ensure that the materials are not polluted.

2. The lime shall be Grade II ash produced in Yixing (the content of available calcium and magnesium oxide in quicklime is not less than 80%, and the content of hydrated lime is not less than 60%). Lime that does not meet the quality requirements shall not enter the material yard, and the digestion time shall be strictly controlled at not less than 7- 10 days, especially for thorough digestion. The digested lime should maintain a certain humidity, and no dust is allowed, but it should not be too wet and caked. The amount of ash in each pile is suitable for one day's production. When lime is stacked for a long time, it should be sealed. The digested lime should pass through the 1CM vibrating screen first, and it should pass through the 1CM vibrating screen when feeding. 3. Through experiments, the high-quality fly ash from Yangzi Petrochemical Company is selected, with Fe2O3+Al2O3+SiO2 > 70%, ignition loss less than 20%, specific surface area more than 2500CM2/g and water content less than 35%, but the fly ash transported to the site should have enough water to prevent dust. In the dry and windy season, the surface of the material pile should be kept wet or covered. If a block is formed when stacked, the ash block should be broken when used. Fly ash piled up in the yard should be covered to prevent the rain from getting too wet.

4, all kinds of gravel choose Yixing limestone stone or Zhenjiang Chuanshan stone ore, the maximum particle size of stone shall not exceed 3 1.5MM, and particles smaller than 0.075MM shall be close to zero. Stones with different particle sizes should be stacked in different warehouses, and the stone grading should meet the requirements. The crushing value is not more than 30%, and the silt content and needle content should be lower than the specified value.

Six, the construction technical scheme

1, preparation of lower bearing layer

The surface of lime-fly ash soil shall be smooth and solid, and there shall be a specified road arch. The elevation, width, compactness and flatness of the lower bearing layer should meet the specification requirements, and it should be rolled by a roller to check whether there are wheel tracks and spring phenomena. Unqualified road sections should be rectified by measures such as supplementary rolling and replacement of granular materials. Low-lying areas and potholes should be carefully filled and compacted. Debris on lime fly ash soil should be thoroughly cleaned to make its surface smooth and free of debris. After cleaning, properly sprinkle water on the surface of lime-fly ash soil, so that the water content of the lower bearing layer after sprinkling is close to the optimal water content of lime-fly ash macadam, and then roll it with a rubber tire roller.

2, vertical steel mold

Before laying lime-fly ash macadam, steel formwork should be erected in time to ensure the edge is dense and prevent the rolling displacement from affecting the edge elevation and causing material loss.

3. Mixing and transportation of lime-fly ash macadam

There are five hoppers, a mixing drum and a discharge hopper for lime-fly ash macadam mixing. The flow rate of aggregate is controlled by the speed of screw motor and the opening of feed door. According to the construction mixture ratio, before the lime-fly ash macadam is formally mixed, the speed of screw motor and the opening of feed door of each hopper are determined according to the gradation and the output of mixer. The laboratory will assign special personnel to monitor the mixing building, check the water content and aggregate gradation of the mixture, ensure the quality of the mixture, and deal with the problems immediately when found. The water content of the mixture should be slightly greater than the optimal water content, so that the water content of the mixture can be close to the optimal value when it is rolled after being transported to the site for paving. (Attached is the flow chart of centralized mixing of lime-fly ash macadam). After the rain, the water content of various materials should be measured again, and the mixture ratio should be adjusted by adjusting the opening of the hopper door. In the process of batching, the deviation of measured mixture ratio should be controlled within the following range: aggregate 2%, fly ash 1.5%, lime 1% and water +2%.

Five kinds of aggregates are collected in the mixing tank through the conveyor belt, and then stored in the storage bin through the conveyor belt after mixing. When the material storage is full, loading begins. When loading the car, install the rear of the car first, and the car should move back and forth. A certain amount of mixture is left in the storage bin to prevent the separation of coarse and fine aggregates. Trucks should be driven to the paving site from the sidewalk as far as possible to reduce the wear and tear of the surface layer. After arriving at the construction site, stop in front of the paver 10-20M, and dump the materials accurately to avoid hitting the paver. In the process of unloading, the truck should be placed in neutral position and pushed forward by the paver. Leave the paver immediately after unloading. Before paving the mixture in the paver hopper, the next truck should stop in front of the paver and start unloading, so as to ensure that there is 10CM thick mixture in the paver hopper (there should be five trucks in front of the paver) to avoid ups and downs.

4. Paving and rolling of lime-fly ash macadam

(1), lime-fly ash macadam paving

Before laying lime-fly ash macadam, construction lofting should be carried out. As two pavers are used for step operation, two paving datum lines are drilled by total station every 10M during lofting, and the paving leveling is automatically leveled by wire walking method. Steel wire should leave the paving edge (lime line) 10CM, and the steel wire should be tightened with a tightener, and the pulling force should not be less than 100Kg, so as to prevent sag deflection from exceeding the limit. Before paving, start with the board with the same thickness as the loose paving thickness calculated on the screed bottom pad. When paving, rely on the paver on one side of the middle belt to find the steel wire on the middle belt, and use the cross slope meter to control the cross slope of the screed on the other side. Surveyors should track and measure the paving cross slope, and adjust it in time if any deviation is found. On the shoulder side, the paver follows the first paver (about 10M) to find single-sided steel wire, and on the other side, the thickness is controlled by the skid. The two pavers overlap about 10CM to avoid longitudinal joints during construction. Combined with the actual output of the mixer, the paving speed is relatively continuous. Sensors on both sides of the paver shall be supervised by special personnel, and whether the paving elevation is consistent with the baseline shall be checked at any time and recorded. If elevation deviation is found, the operator of automatic level shall be notified in time for correction. Considering that the lime-fly ash macadam is paved with cold material, and the weight of the screed is heavy, in order to ensure the accuracy of the transverse slope during paving, the screed should be adjusted to 0. 1% inverted arch.

(2), lime-fly ash crushed stone rolling

When the paving mixture can reach the rolling length (more than 50M), the surface moisture has not evaporated in large quantities, and the water content is at the optimal water content of 65438 0%, it can be rolled. When rolling, it should be light before heavy, and rolled from the edge to the middle. First, use VV 170 vibratory roller to stabilize the pressure slowly twice, then gently vibrate once and then re-vibrate, then gently vibrate and re-vibrate once with Ingersoll Rand SD 175 vibratory roller, and then cover it with steel three-wheel roller for four times. When rolling, each compaction machine will press the two edges of the road again to ensure the edge compactness. If peeling occurs during rolling, a rubber-tyred roller can be added in the middle to make it stable. When rolling, the speed should be strictly controlled. The last wheel track and the previous wheel track should overlap by half, and the rear wheel paving should repeat the full width. The roller shall not stop on the pavement base that has not been pressed or is being rolled, and shall not suddenly brake, turn sharply and turn around. After rolling, if it is partially low-lying, it can be turned loose and added with fresh mixture before rolling.

Construction technology of paving and rolling with lime-fly ash macadam.

5. Combined therapy

(1), longitudinal joint

Because this experimental section adopts two pavers for echelon operation, in order to avoid longitudinal joints, the first paver can be rolled after paving for a certain length, and 50CM is reserved for longitudinal overlapping with the paving belt of the second paver without rolling. When the paving belt of the second paver is connected with the first paving belt, it will be rolled together to ensure that the two paving belts are well bonded and avoid longitudinal joints. When paving the upper base, the paving belt joints of two pavers should be staggered with the lower base by 50- 100cm.

(2), transverse joint

In order to reduce transverse joints, try to choose two or more structures as a construction section during construction. If the paving can't be completed at one time due to the long working face, before the next paving, the broken lime-fly ash macadam end should be chiseled along the full width of the paving layer and directly to the top surface of the lower bearing layer. The section should be perpendicular to the surface of the lower bearing layer and the road center line, and the connecting surface should be cut into a vertical plane. Before paving, it is best to brush cement slurry on the chiseled section to ensure good adhesion between the old and new mixture. Oblique seams are prohibited.

6. Health

After the lime-fly ash crushed stone is rolled and formed, it must be moistened with sprinkler, and the curing period is usually 7 days. During the curing period, the surface should always be moist and the traffic should be closed. In order to protect the road surface from damage, heavy vehicles are prohibited from passing except sprinklers.

7, in the whole construction process, should pay attention to the following aspects:

(1), the water content should be grasped from the source and strictly controlled in the mixing station to prevent too much and too little during paving and rolling. The mixing station focuses on controlling the water content of fly ash, lime and fine aggregate, so that it can cover colored strips in rainy days. If the weather is dry and the water content is low, water should be sprinkled on the coarse aggregate. Before each mixing, the water content of the material should be determined, so as to adjust the mixture ratio and water content in time.

(2) The feeding of the mixer should be accurate, the rotating speed of the screw motor and the opening of the feeding gate should be well controlled, and the feeding amount of each bin should be regularly checked on the feeding conveyor belt.

(3) Mixing shall be uniform, and segregation of coarse and fine aggregates shall not occur. The finished material pile should be leveled with a loader at any time to avoid the formation of a cone and the coarse and fine aggregates slipping to the bottom of the cone.

(4) The mixture shall be paved and rolled in time, and the whole construction process from mixing to rolling shall be controlled to be completed on the same day, and no later than 48 hours. In case of rain during mixing and paving, the mixture should be covered with striped cloth in time.

(5) The paver should first adjust the screed into a straight line, and then repeatedly adjust the vibration level and amplitude of the screed to determine its loose paving coefficient. Strictly control the elevation and flatness. The compaction thickness of each layer shall not exceed 20cm, and the minimum compaction thickness shall not be less than 10cm. Bad phenomena such as thin-layer repair are strictly prohibited.

(6) After the rolling, enter the maintenance stage. At this stage, sprinkler is used to spray water, so that the surface of the base is always wet. The curing time is usually 7 days. For the lower layer of the base, the upper layer can be paved immediately after the rolling is completed, and no special maintenance is needed. If it cannot be paved immediately, it shall still be maintained according to the regulations.

Seven, quality assurance system

1, organize all members involved in grass-roots construction to make technical disclosure, study construction technical specifications seriously, master grass-roots construction technology, technical indicators and quality control points, and ensure that each working procedure is strictly controlled and carried out smoothly.

2, the implementation of total quality management

(1), the quality and technology are controlled by the management department, and the construction scheme, method and technology are formulated by the chief project engineer and the engineering department of the joint venture company; During the construction, the central test is responsible for the mixture ratio, test frequency, random sampling and material test to ensure the accuracy and reliability of the test data; The survey team is responsible for the plane position and elevation control of the route to ensure the accuracy of the plane position and elevation; Mechanical equipment shall be inspected by mechanical engineers one by one, and all relevant measuring instruments shall be inspected and calibrated by the national measuring system. Testers and surveyors regularly check the instrument to ensure accuracy.

In the whole construction process, implement total quality management and post responsibility system. The project manager pays attention to quality personally, the chief engineer is responsible for quality management, and full-time quality inspectors and technicians are responsible for quality inspection. Every construction link, every working procedure and every quality control point are checked by professional engineers, technicians and skilled employees.

(2) The person in charge of the construction site is responsible for the overall scheduling of equipment and personnel, directly grasping the implementation of process quality standards, implementing the construction plan, and checking the quality indicators of each process on site.

3. Quality control methods

(1), strictly control the mixture ratio, adjust the mixture ratio repeatedly on the mixer according to the design before batching, and check it regularly to ensure it is correct.

(2) Measure the water content of materials before mixing and the water content of mixture during mixing in time to ensure that the mixture is in the best water content during mixing and rolling, thus ensuring the compaction quality.

(3), the uniformity of the mixture directly affects the strength of the base, so in the process of mixing, transportation, paving, try to reduce segregation.

(4) Compaction process is an important link in the formation of base strength. According to the equipment configuration, VV 170, Ingersoll Rand DS 175 and steel are used in the static pressure-vibration pressure-static pressure process until the degree of compaction reaches over 98%.

Mechanical equipment of lime-fly ash macadam base comes into play.

Project order

Prepare to enter

name

model

amount

situation

1

300T/h 1 mixer is good.

Mixer 400T/h 1 good 2

spreader

WLTL8500

2

okay

three

mechanical loader

ZL30

1

okay

mechanical loader

ZL50

six

okay

four

Digger

R200

1

okay

Digger

R290

1

okay

five

vibratory roller

VV 170

2

okay

Ingersoll rand PPS 170

1

six

Three-wheel roller

18-2 1T

four

okay

seven

Rubber wheel roller

YL 16T

1

okay

eight

bulldozer

TY 120

1

okay

nine

sprinkler

5T

2

okay

10

vibrating screen

20 tons/hour

2

okay

1 1

Dump truck

10T

20

okay

Author: anonymous