Construction & Materials

I. Classification and selection of road materials

1. Asphalt pavement materials

1) Ordinary hot mix asphalt (HMA)

● Composition: petroleum asphalt + aggregate (crushed stone, sand) + mineral powder, applicable to all grades of road surface layer.

● Characteristics: flexible road surface, low noise, good leveling, can be quickly opened to traffic after construction (can be passed after cooling).

● Innovation upgrade:

modified asphalt: add SBS, rubber powder and other modifiers to improve high-temperature rutting resistance (softening point increased by 10-20 ℃) and low-temperature anti-cracking performance (brittle point decreased by 5-10 ℃), for heavy traffic sections.

Warm Mix Asphalt (WMA): through the addition of foaming agent or organic viscosity reducer to reduce the construction temperature, reduce energy consumption and carbon emissions, suitable for urban centers and environmental protection construction.

2) Asphalt horseshoe crushed stone (SMA)

● Characteristics: Skeleton dense structure, coarse aggregate proportion ≥70%, excellent anti-skid performance, suitable for highway, airport runway and other anti-skid requirements of the scene.

2. Cement concrete pavement materials

1) Ordinary concrete (C30-C50)

● Application: rural highway, industrial area road, high strength, long life (design life 20-30 years), low maintenance cost but long repair cycle.

2) Specialty Concrete

● Fiber Concrete: blended with steel fiber and polypropylene fiber, 30%-50% increase in crack resistance, used for bridge paving layer and heavy traffic section.

● Pervious concrete: porosity 15%-25%, water permeability rate ≥20mm/s, alleviate urban flooding, commonly used in sidewalks, parkways.

● self-compacting concrete: vibration-free self-leveling, suitable for the construction of complex structures (such as tunnel arch), reducing labor costs.

3. Environmental protection and recycled materials

1) Recycled asphalt mix (RAP)

● Old asphalt pavement recycled materials are crushed and screened, and then mixed with new materials proportionally (base layer ≤50%, surface layer ≤30%) to reduce cost and carbon emission.

2) Industrial Waste Utilization

● Fly ash and slag powder replace 30%-50% of cement and are used in road base layer (e.g. cement stabilized gravel) to improve strength and reduce cement consumption.

Construction technology and technological innovation

1. Asphalt pavement construction

1) traditional process

● process: acceptance of grass-roots level → measurement and sampling → spraying penetrating oil → asphalt mixture paving (temperature ≥140℃) → rolling (initial pressing, re-pressing, final pressing) → maintenance.

● Key equipment: paver (width 4-12m), double drum roller (10-14 tons), rubber roller (more than 25 tons).

2) new technology

● Thermal regeneration construction:

On-site thermal regeneration: using heating equipment to soften the old pavement, adding regeneration agent and then re-paving, retaining the original pavement structure, construction efficiency increased by 50%.

Factory Mixed Thermal Regeneration: old materials are transported back to the factory for regeneration, suitable for large-scale pavement renovation.

● Ultra-thin Abrasion Layer (UTAC)

paving thickness of 1.5-2.5cm, adopting high-viscosity modified asphalt + basalt aggregate, repairing pavement diseases and improving anti-skid performance, and the road can be opened to traffic in 2 hours after construction.

2. Cement concrete pavement construction

conventional process

● formwork installation → reinforcement bar tying (if necessary) → concrete pouring → vibration → marking (anti-skid) → maintenance (covering film ≥ 7 days).

Mechanized construction

● Slipform paver: one-time completion of paving, vibration and molding, with an efficiency of 200-500 m/day, suitable for highways and airport road surfaces.

● Three-roller unit: commonly used in small projects, with low equipment cost, suitable for construction of rural roads and parking lots.

3. Special pavement construction

color pavement

● Spraying type: spraying color polymer coating (such as MMA methyl methacrylate) on the original road surface, drying in 2 hours, used for bicycle paths and landscape roads.

● Paving type: paving colored ceramic particles + special adhesive, thickness 3-5mm, anti-skid performance up to BPN65+ (international standard ≥60).

Anti-ice road surface

● ready-mixed type: slow-release snow-melting agent (such as sodium chloride particles) is mixed into asphalt mixture and released by vehicle rolling, with snow-melting efficiency up to 200g/m²・times.

Third, construction quality control key points

1. Inspection of raw materials

● asphalt: test the needle penetration, softening point, ductility and other indicators to ensure compliance with the Technical Specification for Highway Asphalt Pavement Construction (JTG F40).

● Aggregate: control mud content (≤3%), crushing value (base layer ≤30%, surface layer ≤26%), grading uniformity.

2. Process control

asphalt temperature monitoring:

● mix factory temperature 140-165 ° C, paving temperature ≥ 130 ° C, end of rolling temperature ≥ 70 ° C (depending on the asphalt grade adjustment).

Concrete slump control:

● pavement concrete slump should be 10-30mm, summer construction add retarder to prevent early condensation.

3. Testing and acceptance

● compaction: asphalt pavement is tested by core drilling method, compaction ≥ 97% (surface layer); concrete pavement bending and tensile strength ≥ design value (e.g. C30 concrete ≥ 3.5MPa).

● flatness: detected by 3m straightedge, asphalt pavement flatness deviation ≤3mm, concrete pavement ≤5mm.

IV. Construction equipment and efficiency improvement

1. Intelligent equipment

● paver automatic leveling system: real-time adjustment of paving thickness by ultrasonic or laser sensor, error ≤±2mm.

● Unmanned Roller Group: Equipped with GPS positioning and automatic control system, it rolls evenly according to the preset trajectory, reducing labor cost and improving consistency.

2. Modular construction

● Prefabricated concrete curb and gutter components are quickly installed on site, shortening the construction period by more than 30%;

● assembled steel trestle bridge is used for temporary right-of-way, which can be disassembled and reassembled repeatedly, and is suitable for the construction of cross-river and soft-base sections.

V. Typical application scenarios

1. New construction of highway

Material combination:

● top layer: 4cm SMA-13 (modified asphalt)

● middle layer: 6cm AC-20 (ordinary asphalt)

● Bottom layer: 8cm AC-25 (ordinary asphalt)

● Base layer: 36cm cement stabilized gravel (cement dosage 5%)

Process Highlights:

● Multi-machine paving (2 pavers working in echelon) to reduce longitudinal joints;

● rubber wheel rollers follow the paver closely to ensure the initial compactness of the asphalt mixture.

2. urban road white to black (cement to asphalt)

Process:

● old concrete pavement testing → broken plate repair → spraying adhesive oil → laying stress absorption layer (such as 1cm synchronized gravel sealing layer) → paving asphalt surface layer.

Advantages: Reduces noise by 5-8dB, improves driving comfort, and shortens construction period by 50% compared with full excavation and reconstruction.

3. Low-cost program for rural roads

material:

● Surface layer: 3cm emulsified asphalt gravel (emulsified asphalt dosage 1.2-1.5kg/m²)

● base layer: 15cm graded gravel + 10cm natural gravel

Construction: manual with small machinery (e.g. 10 tons vibratory roller), the cost per kilometer is 30%-50% lower than that of asphalt concrete.

Summing up

Road construction and material solutions need to balance performance, cost and environmental protection, with core trends:

● Material decarbonization: recycled aggregates, warm mix asphalt and other green materials accounted for more and more every year;

● Intellectualization of process: unmanned equipment, intelligent monitoring technology to reduce manual intervention and improve construction accuracy;

● Maintenance front-loading: extend the life of pavement through preventive maintenance (e.g. micro-surface treatment, fog sealing layer) to reduce the full-cycle cost.

Flexible selection of materials and processes according to project positioning (e.g. heavy traffic, landscape roads, rural roads) can realize the construction goal of “technically applicable, economically reasonable, green and sustainable”.