39 lines
1.5 KiB
Markdown
39 lines
1.5 KiB
Markdown
# Material Passport — Rapid-Set Cement Mortar
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**File:** `mp-rapid-set-cement-mortar.md`
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**1. Material Name**
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Rapid-set cement mortar (e.g., “Cement All”).
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**2. Source Type**
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☑ Perennial Secondary Market (building trades, hardware stores).
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☑ Industrial Junk Stream (construction sites often discard partial bags).
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**3. Physical Specs**
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- Type: pre-mixed hydraulic cement with additives.
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- Form: dry powder, grey or off-white.
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- Bag sizes: typically 5–25 lbs (2–11 kg).
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- Compressive strength: ~4000–6000 psi (brand-dependent).
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- Set time: 15–60 minutes; practical handling after ~1–2 hours; fuller cure ~24 hours.
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**4. Substitute(s)**
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- Plaster of Paris / Perfect Cast (lighter, weaker, faster).
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- Standard Portland cement mortar (slower, stronger, heavier).
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- Lime plaster (softer, brittle, low strength).
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**5. Known Limitations**
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- Brittle under impact.
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- Shrink cracks possible if cast too thin.
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- Moisture sensitive before curing; absorbs water after curing.
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**6. Hazards**
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- Alkaline dust: skin/eye irritant; gloves and goggles recommended.
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- Exothermic curing; prolonged skin contact may cause burns.
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- Store sealed: absorbs humidity and hardens in bag.
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**7. Visual Reference**
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*(Add a photo of a typical retail bag with label visible.)*
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**8. Declared Use in Design**
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Acts as structural bulk fill for the **Sag-Mesh Plane v0.1**. Provides stiffness and flatness; PLA mesh provides geometry and keying. Central compromise: chosen because it’s cheap, plentiful, and globally ubiquitous—at the cost of brittleness and lack of tensile reinforcement.
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