PFC Asphalt Mixture Modeling

Use this skill to build the load-ready digital specimen for asphalt concrete in PFC2D/PFC3D 5.0. It distinguishes physical phases from DEM objects: aggregate may be explicit balls/clumps, mastic may be homogenized into contact laws or partly resolved by fine particles, and air voids remain pore space. This skill produces the specimen only; the parent route is pfc5-asphalt-workflow.

When To Use

Use this skill when the user needs to:

• Build a PFC asphalt-mixture specimen from scratch (2D or 3D), including a source-defined wheel-tracking slab or a standard/large Marshall specimen formed by the selected current method.
• Convert an aggregate gradation (AC-13/16/20 级配曲线) into particle counts / clump templates.
• Decide how to assign different contact models across 集料-集料、集料-砂浆、砂浆-砂浆、集料-墙 contact pairs.
• Choose coarse aggregate as clump versus ball, declare the resolvable fine fraction, and set a target air-void content from the selected mix design/standard.
• Prepare a reproducible, staged specimen (00_setup → 01_particles → 02_settled → 03_compacted → 04_burger) before any mechanical test.

Do NOT use this skill for loading tests themselves — route those to pfc-rutting-test, pfc-marshall-test, or pfc5-standard-tests.

Required Inputs

Ask for these if missing:

• Dimension: 2D or 3D; specimen size and provenance. For current Chinese methods, record the JTG 3410-2025 forming method separately from the performance method (for example T 0702 before T 0709, or T 0703 before T 0719).
• Gradation: AC-13 / AC-16 / AC-20, with sieve passing percentages (or a gradation_*.csv).
• Binder content with an explicit convention (binder/aggregate or binder/mixture); never convert mass to volume without constituent densities.
• Contact-model plan: which pairs use linear / Hertz / Burger (see references/overview.md).
• Target air-void content and the sieve/size boundary between resolved and homogenized fractions.
• Measured constituent densities and whether coarse aggregate uses clump templates.
• Aggregate test provenance from JTG 3432-2024 or the applicable project/laboratory record, including sieve, density/absorption and any shape metric used to justify the DEM representation.

Three-Phase Characterization

Asphalt mixture = 三相复合材料. Model each phase distinctly:

Keep the physical gradation classification separate from the DEM resolution boundary. Any sieve value below is project/specification data, not a universal switch that forces one PFC object type.

相	物理组成	PFC 表示
项目定义的粗集料	按所选级配/规范定义	clump、ball 或其他已验证形状表示；由形状目标和分辨率决定
项目定义的细集料+矿粉	按所选级配及可分辨尺度定义	可解析为 ball/clump，或并入均质砂浆/接触抽象；必须声明截断边界
沥青砂浆	沥青 + 细料 + 矿粉的均质化胶浆	可由接触模型等效；这不是显式砂浆体积
空隙	项目/试验/规范给定的目标空隙率	颗粒间剩余孔隙（压实控制并做质量-体积闭合）

Two common modeling routes:

• Route A (homogenized mastic): explicit aggregate plus a calibrated contact law. It is economical, but binder/mastic mass is not automatically represented by object volume.
• Route B (resolved fines): add resolvable fine/filler particles and define aggregate-fine/fine-fine interfaces. Binder may still be homogenized at contacts, so do not call this a literal three-particle-phase model unless binder objects exist.

Gradation Conversion

Convert sieve passing percentages into retained-bin mass/volume fractions, then into resolved objects only after applying constituent densities and the declared DEM cutoff. See references/gradation.md for the user-input schema and conversion procedure. It deliberately does not bundle standard gradation tables. Key rule: 各档留存比例 = 相邻筛孔通过率之差；object type follows the declared shape/resolution abstraction rather than a fixed sieve; target volumes must satisfy the selected binder convention, constituent densities, air voids and mass-volume closure.

Contact-Model Assignment

接触对	推荐模型	说明
集料-集料	linear 或经论证的 bonded law	linear 表示无黏结摩擦；contact bond 不能标成“无黏结”
集料-等效砂浆界面	Burger 或标定的界面模型	只有相应对象/分组存在时才能分配
细料-细料/砂浆等效接触	Burger	需由宏观蠕变/动态响应反演
集料-墙/压头	经标定的 linear 或适用界面模型	钢模、压头、橡胶轮及润滑条件分别标定；不预设“高摩擦”

Details and PFC command templates in references/overview.md and the sibling skill pfc-burger-viscoelastic.

Default Modeling Pipeline (Staged, Resumable)

Use this as a default auditable route. Stage names may be renamed, merged or skipped for imported specimens or alternative preparation methods if the same state provenance, checks and restart points remain explicit.

1. setup: create the domain and dimensionality-appropriate specimen boundaries, save 00_setup.
2. particles: generate the declared resolved fractions with the selected ball/clump/shape abstraction, save 01_particles.
3. settle: use the declared deposition/compaction preparation; identify and treat floaters with a stated criterion rather than deleting them automatically, save 02_settled.
4. compact: top-wall downward compaction to target porosity/height, save 03_compacted.
5. contacts: audit existing contacts and future cmat defaults, install final contact models with a PFC5-verified procedure, re-equilibrate, save 04_contacts.
6. Hand off the load-ready specimen to pfc-rutting-test / pfc-marshall-test / pfc5-standard-tests.

Working Rules

• Use PFC 5.0 cmat semantics and reject unsupported newer-major command families. This package does not maintain a cross-version migration route.
• Fix the random seed and record it — asphalt specimen generation must be reproducible.
• Select the generator intentionally: PFC5 ball/clump distribute targets an overlap-uncorrected porosity and can create large overlaps, while ball/clump generate rejects overlaps but may stop at its tries limit before the requested count. Neither command alone proves the achieved post-compaction voids.
• Use the user's measured/project gradation and name the governing specification edition. Do not reconstruct or supply a standard gradation table when the user has not provided legally sourced project inputs.
• Keep aggregate characterization, mixture forming and performance testing as separate source records. A T 0302/T 0327 sieve result, a T 0702/T 0703 forming procedure and a T 0709/T 0719 performance result are not interchangeable provenance fields.
• Prefer validated non-spherical representations when aggregate shape/interlock is a target; balls are acceptable when the simplification is declared and its effect is checked.
• Preserve logically distinct milestone states and their checks. The example names are 00_setup, 01_particles, 02_settled, 03_compacted, 04_contacts; a project may combine or rename them if restartability and audit evidence are retained.
• Verify mass/volume closure and achieved air-void content; neither a remembered 3–5% range nor specimen height alone is a universal acceptance criterion.

Output Contract

A complete specimen handoff should include:

• Dimension, gradation table, resolved/homogenized cutoff, representation choice, and object counts by group.
• The staged save list with file names and what each stage achieved.
• Contact-model assignment table (which pair → which model + key properties).
• Achieved porosity vs target porosity (压实验证).
• A clear note that loading tests continue in pfc-rutting-test / pfc-marshall-test / pfc5-standard-tests.

Local Contents

• references/overview.md: three-phase characterization, contact-model strategy, and the staged pipeline with a transactional contact-switch rule.
• references/gradation.md: user-supplied gradation schema and the volume-to-object conversion procedure; no standard data tables.
• ../pfc5-asphalt-workflow/references/standards-method-map.md: reviewed standard roles and the aggregate-to-performance method chain.
• scripts/minimal_specimen_smoke.p3dat: complete six-wall PFC3D 5.0 command-flow smoke test; not a production asphalt specimen.
• dependencies.json: package-level links to the PFC5 parent and Burger specialist.
• agents/openai.yaml: agent interface metadata.