Structural reinforcement and technoeconomic optimization of cementitious matrices incorporating hydroxyapatite nanorod biopolymer composites

Abstract The integration of advanced nanomaterials into cementitious matrices frequently encounters severe particle agglomeration in alkaline pore solutions and prohibitive processing costs that hinder commercial adoption. Here, we synthesize an electrosterically stabilized hydroxyapatite–chitosan (HAp-CS) nanocomposite (approx. 5:1 weight ratio) via in-situ co-precipitation to accelerate hydration kinetics and enhance compressive performance at trace addition levels. HAp-CS nanorods were incorporated into ordinary Portland cement at dosages from 100 to 2000 ppm, alongside standalone 1000 ppm HAp and chitosan controls to isolate biopolymer–nanorod synergy. Dynamic light scattering and solid-state phosphorus EDS mapping verified that chitosan encapsulation prevents nanorod flocculation at high alkaline pH. Isothermal calorimetry revealed that the 1000 ppm dosage advanced the primary hydration peak by 6.4 h (a 37.2% acceleration) and increased cumulative heat release at 72 h from 248.1 to 316.5 J/g, corresponding to an increase in degree of hydration (α 72 h) from 52.8% to 67.3%. Thermogravimetric analysis confirmed an associated 31.7% enrichment in portlandite content (14.2 to 18.7 wt%) and a 28.1% gain in chemically bound water, verifying accelerated C-S-H gel nucleation. Consequently, the 1000 ppm formulation achieved a maximum 28-day compressive strength of 57.0 ± 1.6 MPa (+ 42.5% over the 40.0 MPa control), substantially exceeding the individual additions of HAp (+ 15.0%) and chitosan (+ 6.3%). A bottom-up technoeconomic analysis incorporating precursor and pilot-scale lyophilization energy costs (25.50 USD/kg HAp-CS) established that 1000 ppm optimizes the unit binder cost (109.81 USD/m 3 ) and maximizes the Cost-Performance Index to 0.519 MPa/USD (+ 36.6% over control). While the laboratory findings demonstrate pronounced early-age kinetic and strength gains, commercial viability and structural service life remain subject to multi-regime durability verification and cradle-to-gate life cycle assessments.