What is the mixture ratio of graded macadam (subgrade graded macadam mixture ratio specification)
2) Process overview
After the yard structure and site leveling are completed and accepted, the graded macadam cushion can be constructed. Graded macadam mixture is mixed by centralized factory and transported to the site by dump truck, paved by paver or loader, leveled by grader and rolled by roller.
What is the mixture ratio of graded macadam (subgrade graded macadam mixture ratio specification)
3) Process flow
What is the mixture ratio of graded macadam (subgrade graded macadam mixture ratio specification)
Second, the construction preparation
1) material preparation
(1) coarse aggregate
Adopt clean, hard, wear-resistant and impurity-free hard rock, and crush the gravel with a large combined crusher. The crushing value is not more than 30%, the needle-like particle content is not more than 20%, the maximum particle size of crushed stone is not more than 37.5 mm, and the aggregate specifications meet the design and specification requirements.
(2) Fine aggregate
The content of stone chips processed with gravel below 0.075mm is not more than 20%, and the specifications of fine aggregate meet the design and specification requirements. All mobilization materials shall be used after passing the self-inspection, and submitted to the supervision engineer for inspection and approval, and materials shall be reserved in advance to meet the requirements of site construction progress.
(3) Water
Use clean, pollution-free and qualified water sources.
2) Mix proportion design
The mixture ratio design of (1) graded macadam should take the materials used in practical work as the object, construct 3-4 experimental gradation curves according to the gradation range recommended by the design or specification and previous engineering experience, and optimize the gradation through the mixture ratio test.
(2) The mixture ratio should be tested by heavy compaction or vibration molding to determine the optimal water content and maximum dry density.
(3) CBR strength test and modulus test shall be carried out according to the gradation and optimum water content determined by the test and the compaction standard of standard specimens for field construction.
(4) The gradation with the highest CBR intensity should be selected as the target gradation for engineering use, and the corresponding optimal water content should be determined.
3) Selection of mechanical equipment
(1) factory mixing equipment
Stabilized aggregate mixing station is usually used for graded macadam plant mixing equipment. The main models of stabilized aggregate mixing station are WCB series and WCZ series, and a corresponding number of loaders are equipped for loading.
Graded macadam mixture can be purchased directly from professional manufacturers, and its graded macadam mixing equipment and mixture ratio should meet the construction requirements.
(2) Selection of paving equipment
When graded macadam is used as cushion, it is generally paved with stable material paver or asphalt concrete paver, or it can be paved with loader and leveled by grader according to the field equipment.
What is the mixture ratio of graded macadam (subgrade graded macadam mixture ratio specification)
(3) Rolling equipment
According to the previous construction experience, the graded macadam cushion can be rolled by vibrating roller with excitation force greater than 35t, three-wheel roller with 18-2 1t or tire roller with excitation force greater than 25t.
4) Determination of loose laying coefficient
The loose paving coefficient of graded macadam is determined by experiments, and the loose paving coefficient of grader should be controlled between 1.25 ~ 1.35.
Third, the construction steps
Step 1: Site cleaning and leveling.
1. After the structural construction, the site within the construction scope shall be cleaned;
2. The site should be flat.
Step 2: Mixing and transportation
1, graded macadam mixing;
2. Graded macadam transportation.
Step 3: Pave the road
1. Measure the elevation to determine the paving width and loose paving thickness;
2, according to the paving area of each car mixture, equidistantly piled up;
3, after the loader paving, with grader ChuPing;
What is the mixture ratio of graded macadam (subgrade graded macadam mixture ratio specification)
4, with a grader or tire roller quickly rolling again;
5, grader leveling, shaping.
Step 4: Scroll.
1, sprinkling water to adjust water content;
2, roller rolling;
3. 1 ~ 2 t small vibratory roller is used for edge compaction;
4, before the end of the rolling, with a grader leveling time, its slope should comply with the design requirements.
Step 5: Combined therapy.
1, longitudinal seam treatment;
2, transverse joint processing.
Fourth, the construction points
Site cleaning and leveling
1. Before the graded macadam is laid, the site shall be cleaned and rolled by a heavy roller for 3-4 times. In the process of rolling, when the surface layer is found to be loose, water should be sprinkled appropriately; When the phenomenon of "spring" is found, measures such as digging dry, changing soil, mixing lime or cement should be taken to deal with it.
What is the mixture ratio of graded macadam (subgrade graded macadam mixture ratio specification)
2. Strictly control the elevation and flatness of the top surface of the lower bearing layer. Within the allowable error range of design, low is better than high. At the same time, the top elevation of graded macadam is controlled to make full preparations for paving at the grass-roots level.
Mixing and transportation
1, solid and clean aggregate is selected, and the aggregate gradation meets the design and specification requirements; Accurately control aggregate gradation according to the approved proportion.
2. The graded macadam is factory mixed, and the plant mixing equipment adopts stabilized soil mixing station. All kinds of aggregates are accurately controlled by electronic metering equipment, and the discharge door of finished product warehouse adopts air pump timing control switch to discharge into the hopper regularly, so as to reduce the segregation of finished products when discharging. The valve at the outlet of the water storage tank is adjusted according to the paving conditions and weather conditions on site. The feeding, mixing and discharging processes are continuous.
3, according to the weather conditions in the process of mixing, arrange someone to detect the water content of the material, and adjust the water consumption in time according to the change. , to ensure that the water content of the mixture is uniform, and the water content is generally controlled to be about 65438 0% higher than the optimal water content.
4. Testers should check the gradation and water content of graded macadam at required frequency; Mixed graded macadam should be uniform.
5. Graded macadam is transported by dump trucks, and its transportation capacity should be adapted to the mixing and pouring capacity and the specific situation of the warehouse surface. Drive slowly during transportation to avoid segregation during transportation.
6. The top surface of granular material transport vehicles should be covered with tarpaulin to prevent granular materials from scattering and losing water.
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