Compaction: sand filling method
Flatness: 3m ruler
Thickness: core
Strength: 7 days unconfined compressive strength (check the construction self-inspection report)
Cement stabilized macadam is generally suitable for base or subbase, and its thickness is generally 15 ~ 22 cm. In order to ensure its quality and standardize the construction process, the technical disclosure of cement stabilized macadam construction is specially formulated. This technical disclosure is only a supplement to the chapter "Cement Stabilized Soil" in JTJ034-2000 "Technical Specification for Highway Pavement Base Construction", the technical specifications in drawings and tenders, and the annex to the contract, so all units are requested to jointly implement it.
1.0 material
1. 1 Materials such as cement, gravel and sand used for roads must be approved by the supervision engineer. Unauthorized entry and use are not allowed.
1.2 cement: the final setting time is long (preferably more than 6 hours), so 325# slag and ordinary portland cement should be adopted. It is strictly prohibited to use quick-hardening cement, early-strength cement and cement deteriorated by moisture. The choice of cement brand should consider its quality stability, production quantity and transportation distance. Cement should have a certificate of approval before entering the site every time, and the setting time and label of cement should be sampled every 200T t.
1.3 crushed stone: the crushing value is required to be no more than 30%, the maximum particle size is no more than 30 mm, and the particle composition of crushed stone should comply with the provisions in the first paragraph of JTJ 034-93.
2.2. 1.6 2# gradation requirements. For the convenience of construction, 10-30 mm coarse aggregate, 5- 10 mm medium aggregate and 0-5 mm fine aggregate should be used. The crushing value of coarse aggregate, the screening of various granular materials (mainly to check the particle grading deviation of feed), the plasticity index of fine soil below 0.5mm and the particle content below 0.075mm should meet the requirements in JTJ 034-93. After the above materials enter the site, two samples shall be inspected every 2000m3.
1.4 water: the drinking water of people or livestock can be used for the construction of cement macadam.
2.0 Composition Design of Mixture
2. 1 Composition design principle: ① The powder content should not be too much. (2) On the premise of reaching the strength, adopt the minimum cement dosage, but not less than 4.0%. (3) improve aggregate gradation, reduce the cement dosage, so that the cement dosage does not exceed 6%.
2.2 The dosage of cement can be prepared in five ways: 4%, 4.5%, 5%, 5.5% and 6%.
2.3 Make 9 samples for each dose (minimum quantity).
2.4 The specimen must be kept wet at the specified temperature (20 2℃) for 6 days, and the unconfined compressive strength test shall be conducted after soaking 1 day, and the average value and deviation coefficient of the test results shall be calculated, and whether RX( 1- 1.645Cv) is greater than Rd (the design strength of this project is
3.5 MPa). The design dose should be the minimum dose to meet the strength, not exceeding 6%.
2.5 According to the designed dosage, do experiments on the influence of delay time on the strength of mixture, and determine the delay time to be controlled through experiments.
2.6 The amount of cement actually used in the construction site increased by 0.5% compared with the designed amount.
3.0 Quality control standard of cement stabilized macadam.
3. 1 Specific detection technical indicators:
3.2 After the rolling of each operation section is completed, the indicators shall be tested immediately, and the information in the industry shall be collated and submitted to the supervision and inspection (within 24 hours), and the strength indicators shall be submitted for inspection separately. Supervisors should go to the site to conduct spot checks in time, and notify them in time when problems are found.
3.3 Each subdivisional work shall be graded according to the Standard for Quality Inspection and Evaluation of Highway Engineering in Hebei Province and the Measures for Quality Supervision, Inspection and Evaluation of Highway Engineering in Hebei Province. Engineering scores must be above 97. Those who fail to meet this requirement are not allowed to complete.
4.0 Key points of construction technology
4. 1 Cement macadam construction technology can be found in 2.5-2.7 of JTJ034-93 Technical Specification for Highway Pavement Base Construction.
4.2 Sub-base detection and soil-raising mold
4.2. 1 Before paving the cement stabilized macadam base, the subbase must be comprehensively inspected, including plane position, elevation, cross slope, width (strength and thickness have been inspected) and surface cleaning. If it fails to meet the requirements, reasonable measures should be taken to deal with it (especially the thickness is insufficient), especially the loose and peeling materials at the grass-roots level should be thoroughly removed, and no weak interlayer should be left. Sprinkle water on the subbase before paving the subbase to keep the surface moist (without water).
1. The extreme degree of compaction is 98% and 94%, with 2 places per lane every 200m. According to mathematical statistics, 100%
2. Flatness (mm) 83m ruler 100ft100 m 95%.
3. Width (cm)≥ 1200 feet, around every 200m 100%.
4. Elevation of longitudinal section (mm)+5,-10 elevation, 85% for every 200m 4 section (left, middle and right elevation) (including unqualified points within+10mm-20mm).
5. The transverse gradient (%) is 0.3, with 95% in 4 sections every 200m.
6. The representative value of thickness is-10mm-20mm, and the extreme value of 100% is calculated by mathematical statistics.
7. The strength (MPa) is greater than the design 1 group (9 specimens) per 2000m2. According to mathematical statistics, it is 100%.
8. Cement dosage +0.5% ~ 2% 65438+0 group per 2000m2, 6 samples 100%.
9. The first few sets of sloping must be done within the specified range, and then it should be done at a time according to 2000 square meters 100%.
10. The delay time shall not exceed the specified time.
Answer supplement
4.2.2 Before paving cement stabilized macadam, the soil on both sides must be ploughed. The width of soil model is wider than the design width 10-20 cm, and the height of soil model is the same as that of water-stabilized virtual paving. The soil must be cut vertically with a stay wire, and the soil should have a certain density, generally around 80%. The specific data depends on the test section.
4.3 The person in charge of cement macadam site (foreman, operator and quality inspector) shall be a person with strong ambition, skilled business and strong management ability. The person in charge of the construction site should always keep an eye on the construction site and must not leave temporarily.
4.4 Selection of benchmarks
4.4. 1 Before lofting, the surveyors of the joint management department and the technicians of the internal supervision section shall disclose the control points and leveling points, control the measured data must be the data approved by the supervisor, and sample the measured lofting data.
4.4.2 Choose φ (2-3 mm) steel wire as the baseline.
4.4.3 The tensioning length is 100-200m, and both ends must be tensioned at the same time with tightener, so as to avoid deflection caused by steel wire loosening, and the tensioning force is 1KN.
4.4.4 Steel bars shall be brazed with φ16-18 round steel with relatively high rigidity, and equipped with a fixing frame. It is best to use threads for the fixing frame, which is convenient for disassembly and elevation adjustment; Generally, the rebar spacing is 5- 10m (straight line segment is not more than 10m, curve segment is not more than 5m). Drill pipes should be placed at a distance of 30cm-40cm from the laying width.