Two Unpublished Tests on the End-of-Life Artificial Turf Field: Recovered Infill Sand as Concrete Fine Aggregate, and Aged Turf Crumb as Asphalt Modifier — Open Research Proposals

A full-size artificial turf field leaves roughly 120 t of silica sand and 60 t of ground tire rubber (crumb infill) when removed, against 18 t of polymer carpet. Dry mechanical separation recovers sand and rubber at 99 % purity, yet neither recovered stream has been tested in the application that would absorb it, and in the United States removed fields go to landfill at USD 30,000–60,000 each. Two go / no-go research proposals, written so that any civil or environmental engineering laboratory with a partner recycler can run them: Proposal 1 — Sand. Recovered turf infill sand as fine aggregate in concrete and pressed pavers. Three field-age lots; ASTM C33 characterisation including residual rubber/polymer by sink–float and TGA; 0–100 % replacement mortar and concrete strength series; SPLP and monolithic tank leaching of hardened concrete for 6PPD-quinone (draft EPA Method 1634) and zinc; factory paver trial against ASTM C936 / EN 1338. ~14 months. Proposal 2 — Rubber. Aged turf-infill crumb as crumb-rubber modifier in asphalt. Fresh tire crumb in rubberised asphalt has been shown (2023) to release 6PPD-quinone far below the coho salmon LC50 of 0.095 µg/L; decade-old, sand-laden infill — whose loose-phase release does not decline with age (2025) — has not been tested. The proposal replicates the 2023 protocol on three aged lots alongside a fresh control, adds binder and mix performance, 52-week dosed rainfall leaching, a sorption arm, a 6PPD / 6PPD-Q mass balance through the 175 °C wet process including fume capture, which has not been reported, and (rev. 2) two further arms: a treatment train — bioretention soil media, biochar-amended media and granular activated carbon columns run on real crumb-stockpile leachate, with a bioassay on a 6PPD-Q-sensitive salmonid — and leaching under saturated, anaerobic, landfill-like conditions, so that the routing comparison (bound matrix vs lined landfill vs unlined) rests on a measurement. Field strip gated on a laboratory GO. ~14 months laboratory phase. Both proposals fix decision thresholds before the first specimen is cast and commit either outcome to publication with open data. A background article sets out the mass arithmetic, what is already proven (separation, fresh-crumb encapsulation, end-of-life LCA) and what is not. Every figure is tagged computed or cited. Standards designations are from working knowledge and must be confirmed against current editions; budgets are scoping ranges. Licence CC-BY-4.0. Anyone may run, adapt, or fund these proposals. v1.3.0 — adds a closing list of every stream in the series, each marked published, designed or open question, so a reader arriving by DOI sees the whole of the work rather than only this stream. No figure, source or conclusion in the article changed. v1.4.0 — expands the acronyms a general reader needs in order to judge the sources: PFAS, PE and PP. The companion research-proposal document is unchanged: its ASTM, SPLP and ICP-MS vocabulary is the working language of the laboratories it addresses. No figure, source or conclusion changed.