How the service life and the life-cycle impacts are calculated
Service life. The tool solves Fick’s second law of chloride diffusion through the concrete cover, exactly as the Life-365™ software (v2.2.3) does. Every mixture starts from the same 28-day diffusion coefficient, D₂₈ = 10^(−12.06 + 2.40·w/cm), because the water-to-binder ratio is fixed at 0.40 for all teams. Your binder choices then change how chlorides move: fly ash and slag slow diffusion progressively over time by raising the aging exponent m = 0.20 + 0.4·(FA/50 + SG/70) (they refine the pore structure as they react: a long-term effect, capped at m = 0.60 and at 25 years of hydration), while silica fume cuts the diffusion coefficient immediately by the factor e^(−0.165·SF) (it densifies the paste from day one). The concrete warms and cools with Tampa’s monthly temperatures (diffusion speeds up when warm), and surface chlorides build up linearly to 1.0% over 10 years, as in the marine spray zone definition. Corrosion initiates when the chloride content at the 50-mm rebar depth reaches 0.05% by mass of concrete; the predicted service life adds a 6-year corrosion propagation period. This is the “time to first repair,” t.
Life-cycle impacts. Producing 1 m³ tells you the upfront impact. But a slab must serve for 100 years, and every time corrosion initiates, the cover (50 of 200 mm = 25% of the volume) must be replaced with the same mixture. So the total material demand over 100 years is the reference flow RF = 1 + 0.25·(100/t): a mixture lasting 12 years needs RF ≈ 3.1 slab-volumes of concrete, one lasting 78 years only ≈ 1.3. The ratio Z = RF(BCS)/RF(ACS) is the amplification factor that converts your upfront saving in each category into the life-cycle saving: σᶠᵁ = 1 − (1 − σᴰᵁ)/Z. This is why durability is worth so much: a mixture with a modest upfront saving (or even a small upfront penalty of up to Z − 1) can still deliver a large life-cycle saving if it lasts much longer.
Full derivation with equations: “EcoConcrete Calculation Tool V3.0: Instructions for Teams,” Sections 3 and 4.
Why fly ash and slag carry an environmental footprint: economic allocation
Fly ash is a by-product of coal power generation and slag (GGBFS) of pig-iron production. Neither is produced for its own sake. So how much of the power plant’s or the blast furnace’s emissions should they carry? If we assigned them zero burden (treating them as waste), replacing cement would look almost impact-free and the incentive to use them wisely would vanish; if we split emissions by mass, they would carry nearly as much burden as the main product, which ignores that nobody operates a power plant to make fly ash. LCA practice resolves this with economic allocation: the processes’ total emissions are divided among its products in proportion to their economic value. Because fly ash and slag sell for far less than electricity and pig iron, they carry a small but non-zero share: in this tool’s database, slag carries 19.4% of the impacts of pig-iron production and fly ash 12.4% of the impacts of hard-coal electricity (Chen et al., 2010); silica fume carries 13% of ferrosilicon production (Van den Heede et al., 2014). That is why substituting cement reduces (but does not eliminate) the binder’s footprint, and why different SCMs have different intensities per kilogram.
Full explanation with references: “EcoConcrete Calculation Tool V3.0: Instructions for Teams,” Section 5. Sources: Chen et al. (2010), Resources, Conservation and Recycling 54(12); Van den Heede et al. (2014), Construction and Building Materials 67A.
1Define your mixtures (kg per m³ of concrete)iEnter the constituents of both mixtures in kg per m³ (SSD basis for aggregates). The BCS binder is 100% portland cement; the ACS may substitute up to 40% of binder mass with SCMs. Transport distances for cement and aggregates are yours to research (show a travel map in your report); SCM distances are fixed by the rules and locked. See Instructions, Section 2.
Enter both mixtures. The Base-Case Scenario (BCS) binder must be 100% portland/hydraulic cement. The Alternative-Case Scenario (ACS) may replace up to 40% of binder mass with SCMs. w/b is fixed at 0.40; the tool checks all rule constraints live. Enter real, documented transportation distances for portland cement and aggregates (a travel map is required in your report); SCM transport distances are fixed by the rules (Table 1) and locked automatically.
Base-Case Scenario (BCS)
Alternative-Case Scenario (ACS)
2Service life (computed automatically)iTime to first repair, predicted with the same model and defaults as Life-365™ v2.2.3 for the standardized Tampa marine-spray exposure. Fly ash and slag slow chloride ingress over time; silica fume cuts it immediately. See Instructions, Section 3, or the explainer at the top of this page.
The tool predicts time to first repair for the standardized exposure: 200-mm slab, 50-mm cover, black steel (6-year propagation), Tampa FL marine spray zone, 100-year analysis period (the same model and defaults as Life-365™ v2.2.3). Fly ash, slag cement, and silica fume are the only SCMs permitted by the rules (they are the materials modeled by Life-365™). Service lives at or beyond the 100-year analysis period are reported as “>100 years”.
3Environmental results: upfront and life cycleiUpfront = comparing 1 m³ of each mixture as produced (declared unit). Life cycle = charging every future cover repair over 100 years of service (functional unit). Durable mixtures need fewer repairs, so the ratio Z amplifies their savings. See Instructions, Sections 3–4.
Upfront (declared-unit) reductions compare 1 m³ of ACS vs BCS as produced. Life-cycle (functional-unit) reductions charge every future cover repair over the 100-year analysis period: RF = 1 + 0.25·(100/t); σFU = 1 − (1 − σDU)/Z.
4Score previewiFinal score = 0.40 × life-cycle score + 0.10 × upfront score + 0.20 × written report + 0.30 × presentation & interview. Eligibility requires a mean upfront reduction of at least 15%. See Instructions, Section 6, and rules Section 3.
Final score = 0.40 × life-cycle score + 0.10 × upfront score + 0.20 × written report + 0.30 × presentation & interview. Environmental scores are the mean percentage reductions (clamped to 0–100). Eligibility requires a mean upfront reduction of at least 15%.
5My saved calculations
Every calculation you save is stored on the competition server under your team account. Load any earlier design to continue from it. Judges see the same records, so save the run that matches your report.
6SubmitiExport the results file and attach it to your submission with the report, slides, and video link. Judges reload the file in this same tool to verify your numbers: every input must be real and documented. See Instructions, Section 6.
Your saved calculations are already on the competition server: make sure the design described in your report is saved with a clear label. You may also download a local results file for your own records.