good-enough/projects/sag-mesh-plane-v0u1/mp-rapid-set-cement-mortar.md

Material Passport — Rapid-Set Cement Mortar

File: mp-rapid-set-cement-mortar.md

1. Material Name Rapid-set cement mortar (e.g., “Cement All”).

2. Source Type ☑ Perennial Secondary Market (building trades, hardware stores).
☑ Industrial Junk Stream (construction sites often discard partial bags).

3. Physical Specs

• Type: pre-mixed hydraulic cement with additives.
• Form: dry powder, grey or off-white.
• Bag sizes: typically 5–25 lbs (2–11 kg).
• Compressive strength: ~4000–6000 psi (brand-dependent).
• Set time: 15–60 minutes; practical handling after ~1–2 hours; fuller cure ~24 hours.

4. Substitute(s)

• Plaster of Paris / Perfect Cast (lighter, weaker, faster).
• Standard Portland cement mortar (slower, stronger, heavier).
• Lime plaster (softer, brittle, low strength).

5. Known Limitations

• Brittle under impact.
• Shrink cracks possible if cast too thin.
• Moisture sensitive before curing; absorbs water after curing.

6. Hazards

• Alkaline dust: skin/eye irritant; gloves and goggles recommended.
• Exothermic curing; prolonged skin contact may cause burns.
• Store sealed: absorbs humidity and hardens in bag.

7. Visual Reference (Add a photo of a typical retail bag with label visible.)

8. Declared Use in Design 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.