Mechanism: Three-Phase One-Pass Fabrication
The disclosed fabrication flow proceeds through three temporally adjacent phases executed at a single pour station. Phase one, form preparation, establishes the fixed geometry of the eventual structural element. Reusable outer formwork is set; sacrificial inner formwork defining the cavity volume is positioned within the outer mold; reinforcing steel (rebar) is threaded between the two, terminating short of the sacrificial form so that no bar penetrates the eventual cavity wall. The sacrificial formwork is hollow and is fitted with at least one access port that remains accessible from above the pour. The formwork wall itself is impermeable to the cementitious slurry over the cure interval but is removable post-cure through burnout, dissolution, or biodegradation, depending on the formwork material selected.
Phase two, cementitious pour, places structural concrete into the annular volume between the outer formwork and the sacrificial inner formwork. The pour proceeds by conventional means: gravity placement, pump placement, or tremie placement for deeper sections. Because the sacrificial formwork wall is impermeable to slurry, the cementitious binder is fully contained on its outer face and does not enter the interior cavity volume. This containment is essential to the disclosed primitive: any binder migration into the cavity volume would contact the active material and contaminate it, defeating the purpose of the cavity-bath architecture.
Phase three, active-material introduction, delivers the active material through the formwork interior. Delivery may be by gravity feed (for free-flowing powders or slurries), by pumped delivery (for thick slurries or pastes), or by inert-carrier transport (for moisture-sensitive active materials carried in dry gas or non-aqueous fluid). Phase three may begin during phase two, concurrent loading, or may follow phase two with a brief delay short of cementitious initial set. In either case, the active material occupies the cavity volume defined by the sacrificial formwork's interior wall, while the cementitious matrix occupies the volume defined by the formwork's exterior wall. The two volumes are physically separated by the formwork wall throughout cementitious cure. The active material does not contact the binder during the alkaline, exothermic cure interval, which preserves both the reactivity of the active material and the integrity of the binder.
Operating Parameters
Pour timing is governed by the cementitious mix's initial-set window, typically 45 to 240 minutes from water addition depending on cement chemistry, admixture package, and ambient temperature. Active-material introduction must complete before initial set so that the formwork wall remains supported by uncured surrounding slurry rather than by green concrete. Loading rates are governed by the active material's flow rheology: dry powders pour at near-gravity rates limited only by Janssen-effect bridging in the formwork throat; aqueous slurries pour at rates governed by viscosity and the formwork port cross-section; pastes and gels require pumped delivery at pressures of 20 to 200 kPa typical.
Cavity dimensions are constrained at the small end by the practical minimum diameter for sacrificial-formwork retention of slurry pressure during pour, approximately 12 mm for thin-wall polymer formwork, smaller for thicker-wall materials, and at the large end by the structural element's cross-section after deducting the rebar cage, cover, and minimum wall thickness for the structural concrete. Aspect ratios of cavity length to diameter from approximately 1:1 to 50:1 are admitted by the disclosed primitive, with the upper bound governed by formwork buckling under hydrostatic slurry pressure during pour. Active-material fill fractions of 60 to 95 percent of cavity volume are typical, with headspace reserved for thermal expansion, gas evolution during operation, and (in active-fill embodiments documented elsewhere) refresh-fluid exchange.
Post-Cure Formwork Removal
After the cementitious matrix achieves its release strength, typically 24 to 72 hours from pour for ordinary Portland systems, faster for accelerated mixes, the sacrificial formwork is removed through the mode appropriate to its material. Burnout removal applies to thermally decomposable formwork (paraffin wax, thermoplastic polymers with decomposition temperatures below the cementitious matrix's heat tolerance) and proceeds by elevated-temperature exposure that volatilizes the formwork without damaging the surrounding concrete. Dissolution removal applies to water-soluble formwork (PVA, salt-bound binders) and proceeds by flushing the cavity interior with the appropriate solvent. Biodegradation removal applies to enzymatically labile formwork and proceeds over a longer interval at ambient conditions.
Following removal, the cavity walls present as the cured cementitious matrix and the active material is in direct contact with that wall. No interface layer, no liner, no secondary container intervenes. The cavity wall serves simultaneously as structural compression member, electrochemical confinement boundary, and (in embodiments incorporating ionically conductive cement chemistries) a participating component of the cell's ionic transport network.
Alternative Embodiments: Deferred Two-Phase Flow
An alternative embodiment defers active-material introduction until after formwork removal. This two-phase flow separates structural fabrication from active-material loading in time and, optionally, in place. Phase one, structural fabrication, proceeds through pour, cure, and formwork removal at a precast facility, yielding a structural element with empty cavities ready for loading. The cavities may be sealed at the precast facility with temporary closures (removable plugs, peelable membranes) to prevent contamination during transport and storage. Phase two, active-material loading, proceeds at the installation site or at a regional loading depot, with active material introduced through the same access ports that served the formwork during pour.
The deferred flow admits factory-fabricated structural elements that are field-loaded with active material at installation time. This embodiment offers logistic advantages for active materials that are sensitive to transport conditions, that have shelf lives shorter than the structural element's procurement-to-installation interval, or that are subject to regulatory regimes that constrain bulk shipment of pre-loaded electrochemical assemblies. The embodiment also admits inventory pooling: a single inventory of empty structural elements may be drawn against multiple active-material chemistries selected at the time of installation based on grid-service requirements, regional climate, or end-of-life recovery economics. The choice between concurrent (one-pass) and deferred (two-phase) loading is therefore a function of logistics economics, the active material's storage requirements, and regulatory constraints, rather than a constraint of the disclosed primitive itself.
Composition
The structural pour admits any cementitious system compatible with the cavity-bath architecture's structural and electrochemical requirements: ordinary Portland cement, blended cements incorporating supplementary cementitious materials (fly ash, ground granulated blast furnace slag, silica fume, calcined clays, natural pozzolans), calcium aluminate cement, calcium sulfoaluminate cement, geopolymer binders, and magnesium-based cements. Aggregate selection follows conventional structural concrete practice with the additional constraint that aggregate near the cavity wall must not introduce contaminants incompatible with the active material's electrochemistry.
The sacrificial formwork material is selected from thermally decomposable polymers (paraffin, polyethylene, polypropylene, polylactic acid), water-soluble polymers (polyvinyl alcohol, polyvinylpyrrolidone), enzymatically degradable polymers (cellulose esters, starch composites), and salt-bound or sugar-bound binder systems. Selection balances slurry impermeability during pour, dimensional stability through cure, removability post-cure, and absence of residue species that would contaminate the active material. Active-material composition is unconstrained by this primitive and is documented in companion disclosures covering carbon-bound, lithium-ion, sodium-ion, flow-cell, and other electrochemistries that the cavity-bath architecture admits.
Prior Art
Conventional structural concrete fabrication uses formwork purely as a shape-defining element, with no functional role for the formwork interior beyond providing a void to be either filled with structural material or left as a duct for post-tensioning, plumbing, or electrical service. Prior art in concrete-encapsulated battery systems (Meehan et al., Tan et al.) addresses cells fabricated separately and subsequently embedded in concrete during pour, with the concrete contacting only the cell housing rather than the active material itself. Prior art in slip-form casting and lost-wax casting uses sacrificial inner forms but does not load functional material through the form's interior during the structural pour.
The disclosed primitive is distinguished by the temporal coincidence of structural pour and active-material loading at a single pour station, by the use of the sacrificial formwork as both shape-defining element and active-material conduit, and by the maintenance of a non-contact relationship between binder and active material throughout the cementitious cure interval. The inventor is unaware of prior art that combines all three of these elements in a single fabrication flow.
Disclosure Scope
Provisional 64/050,895 claims the cavity-bath architecture inclusive of both the concurrent (one-pass) and deferred (two-phase) loading flows documented in this article. The disclosure scope extends to all combinations of pour-material chemistry, formwork material, formwork removal mode, cavity geometry within the stated aspect-ratio envelope, and active-material composition compatible with the architecture. The disclosure does not claim any specific cementitious mix design, formwork polymer, or active-material chemistry as such; rather, it claims the architectural primitive of fabricating structural element and electrochemical cell volume in one pour, with the sacrificial formwork mediating the interface. Subsequent continuations are anticipated to address specific active-material chemistries, automated pour-station tooling, and quality-assurance instrumentation for verifying cavity-wall integrity and active-material fill homogeneity.
