Concrete Mix Recipes

Category: The Marble Method (casting Pearl-Method aggregate into concrete) Research Date: April 12, 2026 (v2 — pearl-aggregate rewrite) Status: Test pour required for final validation

Portland cement formulations for the four flat-priced Stream A products. The aggregate comes from the Pearl Method (sodium-silicate granulation of cremains into BB-sized pearls). The casting + finishing of those pearls into concrete is the Marble Method — named for the marbled visual signature the pearls produce when the cured surface is sanded or polished. v2 fully decouples product size from cremains volume.

What changed in v2 (read this first)

The original v1 recipe doc treated cremains as a 17%-by-volume sand substitute and used 3 parts pea gravel as the structural aggregate. That model was inconsistent with the Pearl Method, which produces a true mineral aggregate (the pearls). v2 rewrites every recipe so that the customer's cremains pearls ARE the aggregate, not an additive on top of one. The pearls are then cast into concrete via the Marble Method, producing the marbled visual effect on the finished surface.

Three structural changes flow from this:

1. Stone size is decoupled from pet weight. Every Stream A product is the same size regardless of whether the cremains came from a hamster or a Great Dane.
2. No "17% inclusion ratio." That rule belongs to v1 and is obsolete. Pearls go in at whatever volume the customer's pet produced.
3. Backfill, never excess. If the customer's pearls don't fill the aggregate volume of their chosen product, the remainder is supplemented with standard pea gravel (matched in size to the pearls) so the structure holds. The customer's pearls remain visible and dominant in the cast. No customer's pearls are ever held back, discarded, or pooled. Pillar 2 (Integrity).

If a pet produces more pearls than one product can hold, the order spills over into a second unit of the same product, gifted to the customer at no charge. There is no scenario where pearls leave the customer's order.

Cremains chemistry — unchanged from v1

Cremains are calcium phosphate (hydroxyapatite) — already calcined by the crematory. Calcining bone separately adds labor for no measurable gain. Use cremains as shipped. Sieve to a uniform particle size before granulation:

• 20-mesh for garden stones, candle holders, and the planter
• 40-mesh for worry stones (smoother hand-feel)

Store in food-grade lidded containers labeled with the pet's name, intake date, and order number. No exceptions, ever.

Step 1 — The Pearl Method (granulation, mandatory before any mix)

Before any of the four recipes below, the customer's cremains must be granulated into pearls. This is the step the v1 recipes skipped entirely.

1. Load the sieved cremains into a 304 stainless laboratory disc pelletizer (400–500mm pan, 20–50 RPM, ~45° tilt).
2. Mist the tumbling cremains with the binder (see Binder Selection below) using a hand spray bottle.
3. Grow — within ~5 minutes the cremains snowball into uniform BB-sized pearls (roughly 3–5mm diameter, comparable to fine pea gravel).
4. Cure in open air on a tray for 24 hours. The binder cures by drying into rigid mineral aggregate — chemically waterproof and structurally sound.
5. Weigh and label the pearl yield. This number drives whether the recipe needs pea gravel backfill (small yield) or whether the order will spill into a bonus unit (large yield).

Binder selection (Phase 1 bench-test deliverable)

The Pearl Method binder is being finalized empirically in Phase 1 bench testing. Two candidates are running in parallel:

• B1 — Colloidal silica (primary candidate). Industrial mineral binder, ~$30/quart from US Composites / Smooth-On / ceramic suppliers. Drop-in workflow replacement: same pan granulator, same hand spray bottle, same cure cycle. Contains no free sodium, eliminating the alkali-silica reaction (ASR) and efflorescence risks identified during Phase 0 chemistry due diligence.
• B2 — Dilute Portland Type II cement slurry (secondary candidate). A watery slurry of the same Portland cement used in the final cast, sprayed onto the cremains in the pan granulator. Pearls cured this way are chemically identical to the matrix they will eventually be embedded in — no foreign alkalis, no bonding interface mismatch. Trickier timing (cement slurry sets faster than colloidal silica) but zero new materials in the supply chain.

Phase 1 bench protocol: parallel batches with each candidate, compressive strength + freeze-thaw + 90-day surface inspection, pick the winner empirically. See Research/Pearl_Method_Binder_Selection.md for the full chemistry analysis, the three alternatives that were considered (Path A — geopolymer cement; Path B — alternative binder; Path C — sintered ceramic), and why Path B was selected.

The original sodium silicate (Type N water glass) binder from the Pearl Method v1 documentation remains in the equipment inventory as a Phase 0 reference. It cures the pearls into rigid mineral aggregate quickly and cheaply, but introduces sodium ions that react with Portland cement over the 5–10 year outdoor lifetime of the Garden Stone and Cement Memorial Planter products. It may retain limited use for indoor-only product variants (Worry Stone Set) where the matrix-compatibility risk does not apply, but it is not the binder of record for outdoor catalog products.

Yield reference (rough — needs validation by test runs):

• 1 lb cremains → ~1.2–1.5 cups of pearls
• 0.05 lb hamster cremains → ~1 tablespoon of pearls
• 3 lb large dog cremains → ~4–5 cups of pearls
• 5–7 lb human cremains → ~6–10 cups of pearls

Stream A is a cremains business — species-agnostic. Pearl Method chemistry, recipes, molds, and finishing are identical regardless of whether the input is from a hamster, a large dog, or a human. The only variable is volume, which feeds the intake fee tier (Tiny / Small / Medium / Large / XL — Human). Stream B (memorial soil via NOR) remains pets-only because whole-body NOR for humans is not legal in Georgia; that constraint does not apply to Stream A because casting cremains into stone is a long-established and broadly permitted use.

Why a mineral binder, not epoxy: non-toxic, no fumes, no PPE escalation, very low per-unit cost, and the chemistry produces a real mineral bond instead of a polymer glue. Epoxy was considered and rejected on cost, fume, and bonding grounds.

Step 2 — The Marble Method (casting the pearls into concrete)

The four recipes below are the casting protocols for incorporating Pearl-Method aggregate into concrete and producing the marbled visual signature on the finished surface. Each recipe is a complete dry mix → wet mix → cast → cure → finish protocol for one of the four catalog products.

Recipe 1 — Worry Stone Set (3 stones, indoor/intimate)

Use case: held in the hand, carried in a pocket, rubbed with the thumb. Surface quality and hand-feel dominate every other criterion. Pearls visible at the surface for emotional resonance.

Base mix per set, by volume:

• 1 part white Portland cement (creamier, lighter finish than gray Type II)
• 1.5 parts fine silica sand, ~100 mesh
• Customer's pearls (40-mesh granulation) — go in as the aggregate
• Backfill if needed: white silica fines or finely crushed white marble chips, matched to pearl size, to bring total aggregate volume to ~1 part by volume of the mix
• Water: 0.38 water-to-cement ratio (lower water = harder, tighter, smoother surface)
• Optional pigment: 2% iron oxide (raw sienna or burnt sienna) for a warm cedar-tone match to the brand palette

Sizing & spillover:

• Standard set = 3 stones, ~1.5–2" oval, palm-sized
• If the customer's pearls fill more than the 3 stones can hold → set expands to 4 or 5 stones at no extra charge
• If the customer's pearls fill less → backfill with white silica fines; the customer's pearls stay visible at the cast face

Finishing — microcement overlay: After 48 hours of initial cure, apply a 1–2mm microcement topcoat pigmented to match the core. This is the step that takes the stone from "rough concrete blob" to "earned object." Final polish with 600-grit then 1200-grit wet sandpaper for a glass finish.

Cure schedule:

• 48 hours under plastic
• Microcement overlay
• 5 days air-dry
• Final polish

Molds: silicone, 1.5–2" flat oval, $25–60 each, reusable for 50+ casts.

Recipe 2 — Candle Holder Set of 4 (outdoor-capable, thermal-rated)

Use case: holds tea-lights or standard tapers. Repeated thermal cycling. Must withstand the candle's heat without cracking. Set of 4 matched holders.

Base mix per set, by volume:

• 1 part Portland Type II cement (moderate sulfate resistance, lower heat of hydration)
• 2 parts fine sand
• Customer's pearls (20-mesh granulation) — distributed across all 4 holders
• Backfill if needed: 1/4" pea gravel matched to pearl size, to bring aggregate volume up
• Pozzolanic additive: 5% silica fume or fly ash by cement weight — improves thermal resistance and reduces microcracking under heat
• Water: 0.42 water-to-cement ratio

Sizing & spillover:

• Standard set = 4 matched holders, mix of 2 tea-light + 2 taper, ~3" × 3" footprint each
• Spillover → 5th holder at no charge
• Insufficient pearls → pea gravel backfill, customer's pearls visible on the rim

Critical thermal safety specs (non-negotiable):

• Minimum wall thickness: 3/8" (10mm) at every point. Thinner walls crack under repeated thermal cycling.
• Embedded metal candle cup: standard tea-light cup or 22-gauge steel taper insert embedded in the cast so the flame never touches concrete directly. The concrete is the holder; the metal is the candle interface.
• Cure duration: 14 days minimum before first lit use. Green concrete cracks under heat.
• Permitted candle types: standard tea-lights, standard tapers. Do not use for pillar candles, 3-wick candles, or anything over 4" diameter — the thermal load exceeds what a 3/8" concrete wall can manage safely.

Finishing: microcement overlay on the outer surface for the "pretty" finish. Optional 2% iron oxide pigment for warm tone.

"How do you make concrete thin and pretty?" — Phase 6 research thread. The standard high-end answer is GFRC (glass fiber reinforced concrete), which lets wall thickness drop to ~1/4" with alkali-resistant glass fibers in the mix. v2 candle holders use the conservative 3/8" Portland recipe; a GFRC variant is on the research shortlist for v3.

Molds: custom silicone or 3D-printed PLA, $40–150 per cavity. One single-cavity tea-light mold + one single-cavity taper mold covers the full set.

Recipe 3 — Garden Stone (single, mid-size, outdoor freeze-thaw)

Use case: placed in a garden, permanently outdoors, exposed to North Georgia winters (light freeze-thaw cycles, not arctic). One stone per order, mid-size, "nothing major."

Base mix per stone, by volume:

• 1 part Portland Type II cement (sulfate resistance for soil contact)
• 2 parts washed masonry sand (no clay content)
• 3 parts aggregate total = customer's pearls (20-mesh granulation) + 3/8" pea gravel backfill as needed
• Air-entraining admixture: Sika AEA-15 or equivalent, 1 oz per 100 lbs cement — essential for freeze-thaw durability, this is what prevents the stone cracking when winter water inside the concrete expands on freezing
• Water: 0.45 water-to-cement ratio

Sizing & spillover:

• Standard stone = ~6–7" diameter, rounded shape, ~3 lbs finished weight
• Spillover (large pet) → second stone gifted, same size
• Insufficient pearls → pea gravel backfill, customer's pearls visible on the cast face

Cure schedule:

• 7 days under damp burlap
• 21 days slow air-dry
• Optional surface seal with concrete penetrating sealer for extended outdoor durability

Strength: standard 1:2:3 Portland Type II mix with the specified water-cement ratio reaches ~3,500 psi at 28-day cure. Far above what a garden stone needs.

Molds: silicone, 6–8" diameter, rounded river-stone shapes, $40–120 each, reusable for 50+ casts.

Recipe 4 — Cement Memorial Planter (NEW — outdoor, drainage, plant-capable)

Use case: outdoor cement planter that holds soil and a living plant. Must drain. Must survive North Georgia freeze-thaw. Must look pretty enough to live in someone's garden for decades. The largest cast in the Stream A catalog.

Base mix by volume:

• 1 part Portland Type II cement
• 2 parts fine sand
• 3 parts aggregate total = customer's pearls (20-mesh granulation) + 3/8" pea gravel backfill as needed
• Air-entraining admixture: Sika AEA-15, 1 oz per 100 lbs cement — essential
• Pozzolanic additive: 3–5% silica fume by cement weight — improves crack resistance and surface density on the larger cast
• Water: 0.45 water-to-cement ratio

Sizing (starter spec — needs final mold decision):

• ~10" diameter × 10" deep, cylindrical or gently tapered
• ~25 lbs finished weight
• Wall thickness: 1" minimum for outdoor freeze-thaw at this size
• Drainage: 1–2 holes molded or drilled at the bottom, ~1/2" diameter, before pour. Bottom 1" of the interior is filled at use-time with a drainage layer of pea gravel or pearl rejects.

Pearl handling:

• Customer's pearls embedded in the wall mix — pearls visible on the upper rim where they show, pea gravel backfill in the body where they don't
• Spillover (large pet or human cremains) → second smaller planter gifted, same finish
• Insufficient pearls (small pet) → pea gravel backfill in the body, customer's pearls concentrated visibly at the rim

Finishing:

• Direct cast against a smooth silicone mold for the visible exterior face
• Microcement topcoat on the rim for the rim-pearl visibility
• Optional 2% iron oxide pigment for warm cedar-tone or stone-charcoal finish
• Surface sealed with concrete penetrating sealer for outdoor longevity

Cure schedule:

• 7 days under damp burlap
• 28 days slow air-dry before outdoor exposure
• 60 days before first plant (allows full hydration and prevents pH burn on plant roots from green concrete)

Pretty / thin: the same Phase 6 GFRC research applies here. Standard Portland mix at 1" wall thickness is structurally safe but visually heavier than a GFRC equivalent at 1/2". v2 ships with the conservative spec; v3 may upgrade to GFRC after test pours.

Molds: custom silicone with a 3D-printed master, ~$200–400 for a starter mold. Cylindrical shapes are simplest; tapered or organic shapes are a v3 design exercise.

What's the same across all four recipes

• Customer's pearls always go in the cast. Always. No exceptions, no held-back portions, no pooling.
• Backfill aggregate is standard pea gravel (or white silica fines for worry stones), matched in size to pearls so the structural ratios stay consistent.
• Spillover → free bonus unit of the same product, never held back or sold separately.
• Microcement overlay is the consistent finishing technique for the "pretty" surface. GFRC is the v3 upgrade path.
• All products are documented and customer-visible. Bob Ross standard.

Equipment delta from v1

Recipe-to-COGS impact (preview)

These numbers go into the next round of Line_One_Financial_Analysis.md rewrites. Preview only:

• Cement per stone: drops by ~50–80% because every product is now small (3–25 lbs) instead of scaling up to 35 lbs
• Pea gravel: drops by ~70% (backfill only, not primary aggregate)
• Sodium silicate: new ~$0.05–0.10 per stone
• Shipping per unit: drops dramatically (USPS Priority Mail Small Flat Rate likely replaces UPS Ground for everything except the planter)
• Estimated revised gross margin on Stream A: ~85–90% (up from 76%)

Full COGS rewrite per product is the next phase.

Sources and validation status

Standard concrete proportioning: ACI 211 (standard practice for proportioning normal-weight concrete), Portland Cement Association Design and Control of Concrete Mixtures 15th edition. Both are well-established literature.

Pearl-aggregate concrete specifically: Not in the ACI literature. This is our adaptation of pan granulation of calcium phosphate (cremains) into a structural aggregate, then cast into Portland Type II concrete. Test pours are required to validate:

1. Binder selection (primary Phase 1 deliverable): Empirical comparison of colloidal silica (B1) vs dilute Portland cement slurry (B2) as the Pearl Method granulation binder. Compressive strength at 28 days, freeze-thaw cycling on a garden stone cube, surface inspection for efflorescence at 7/14/28/90 days. See Research/Pearl_Method_Binder_Selection.md for the chemistry analysis and decision rationale.
2. The cement-to-pearl-aggregate ratios produce the strength predicted by analogous gravel-aggregate calculations.
3. Air entrainment behaves correctly with pearl aggregate (it should — pearls are inert mineral, not organic).
4. Thermal cycling on the candle holders does not induce pearl-cement interface cracks.
5. Freeze-thaw cycling on garden stones and the planter does not cause delamination at the pearl surface.

Test pour plan goes in Operations/Line_One_Test_Pour_Protocol.md (to be written).

Microcement application: Topciment and Pandomo manufacturer documentation — both well-established commercial products with cure data and substrate prep guidance.

Colloidal silica as pelletizing binder: standard industrial practice for binding calcium phosphate ceramics in fields outside memorial work (catalyst supports, refractory aggregates, mineral processing). Chemistry is well-known and contains no free sodium, eliminating the alkali-silica reaction (ASR) and efflorescence concerns that arise from sodium silicate binder in a Portland cement matrix.

Sodium silicate as pelletizing binder (Phase 0 reference): standard industrial application, used in iron ore pelletizing and several mineral aggregate processes. Works correctly in isolation but introduces sodium ions into the Portland cement matrix that cause efflorescence (cosmetic) and alkali-silica reaction (structural) over a 5–10 year outdoor lifetime. Phase 0 chemistry due diligence identified this risk and Research/Pearl_Method_Binder_Selection.md documents the decision to switch to colloidal silica.

v2 supersedes the v1 recipes (pea gravel + 17% sand-substitute model) entirely. Anywhere v1 recipes are referenced in other docs (Line_One_Process.md, Line_One_Financial_Analysis.md, the proposal documents, marketing copy), those references need to be updated to match v2. See the cascade audit log for the current status of each downstream file.