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The embodied carbon of mastic asphalt is typically ~0.12–0.22 kgCO₂e per kg (A1–A3). This is roughly 5–10 kgCO₂e per m² for a 20 mm layer (using a density of ~2.25–2.45 t/m³). The precise figures for embodied carbon content of mastic asphalt depend on bitumen fraction (≈10–20%), aggregate/filler sourcing, plant energy, melt temperatures, and transport. Site installation (A4–A5) can add ~1–4 kgCO₂e/m². In EN 15804 and Environmental Product Declaration (EPD), A4–A5 describes the construction stage. A4 covers transport of the product from the factory gate to the site (e.g., lorry/rail/ship emissions based on distance, vehicle type, load factor, and return trips), and A5 covers on-site installation impacts. The embodied carbon content will depend on kettle fuel, haul distance, and on-site heating time. Measures like warm-mix processing, recycled aggregates/filler, and lower-carbon binders reduce impacts, while polymer modification and long logistics routes increase them. For projects, use the product’s EPD and thickness to calculate a project-specific value.
Embodied carbon is the greenhouse gas footprint associated with making, transporting, installing, maintaining, and disposing of a product or building—everything other than in-use energy. It’s reported as kilograms of CO₂-equivalent (kgCO₂e), often per kilogram of product or per square metre at a stated thickness. Manufacturers disclose it in Environmental Product Declarations (EPDs), which use standardized rules so results are comparable. Its scope is organised into life-cycle modules: A1–A3 (raw materials and manufacturing), A4 (transport to site), A5 (installation), B (use/maintenance), C (end-of-life), and optional D (reuse/recycling benefits beyond the system boundary).
Embodied carbon differs from operational carbon, which comes from running the building (heating, cooling, lighting) over time.
It matters because much of a project’s total climate impact is “locked in” at design and procurement, long before operations begin.
You can reduce it by choosing lower-carbon materials and binders, increasing recycled content, sourcing locally, right-sizing quantities, extending service life, and designing for reuse. In practice, teams total embodied carbon by multiplying product-specific EPD values by the quantities used within the chosen life-cycle boundary and summing across the project.
The embodied carbon content of mastic asphalt matters because embodied carbon captures the mastic asphalt’s climate impact before the building is even used—driven largely by bitumen content, high-temperature manufacturing, and on-site heating. Given the high density of mastic asphalt, the per-m² impact of a 10–20 mm layer is non-trivial, so choices about mix design, thickness, and sourcing meaningfully shift totals. A durable, well-detailed system spreads that impact over decades, lowering carbon per year of service and avoiding early replacement. Design teams can cut it with warm-mix processing, reclaimed aggregates/filler, lower-carbon binders, local supply, efficient site melting, and right-sizing—verified with product EPDs to meet client and regulatory requirements.
Embodied carbon accounts for the emissions released before the building is even used—raw materials, manufacturing, transport to site, and installation. For mastic asphalt, the biggest contributors are bitumen production, high-temperature mixing, haulage, and kettle heating during laying. This makes it impossible for the product to be genuinely “zero carbon” without external offsets. Knowing this number lets teams prioritize reductions where they matter most.
Your choices materially change the footprint per m²: thickness scales emissions almost linearly, and higher binder fractions usually mean higher carbon. Binder grade/modifiers, aggregate and filler type, and haul distances can all swing results. Warm-mix processes and recycled/locally sourced constituents typically lower impacts. Treat embodied carbon as a design variable, not a fixed property.
A long service life spreads the upfront footprint over more years, reducing carbon per year of use. Well-detailed systems that avoid early failure or frequent resurfacing outperform “thin but short-lived” options in whole-life terms. Preventive maintenance—renewing protective finishes, fixing defects early—extends life and saves carbon. Design for repairability so small areas can be patched instead of full-scale replacements.
EPDs give verified, like-for-like data so you can select lower-carbon products and specify realistic targets. Compare A1–A3 values across suppliers and check A4–A5 for site impacts you can control. Prefer mixes with lower binder intensity, recycled/secondary materials, local sourcing, and warm-mix processing where viable. Write these requirements into specifications and submittals to lock in the gains.
You can minimise embodied carbon by right-sizing thickness to actual loads and using high-density boards or plates to spread point loads instead of overspecifying depth. Binder-related emissions can be cut with lower binder content and warm-mix processing, only adding polymers if performance truly requires it. Specifying recycled inputs (reclaimed mastic asphalt, recycled aggregates/filler) and sourcing locally can reduce A1–A4 impacts. Whilst running site works efficiently (insulated/electric kettles, tight pour sequencing) can trim A5. Designing for longevity by incorporating robust detailing, protective/reflective finishes, and planned maintenance also helps to minimise embodied carbon by ensuring the initial footprint is spread over decades.
Embodied carbon scales almost linearly with layer thickness, so only specify the depth needed for actual loads. Map point loads (plant legs, pedestals, trolley paths) and use high-density boards or plates to spread contact pressure instead of thickening the whole area. Where extra capacity is required, apply local thickening at hotspots rather than a blanket increase. Verify adequacy with indentation/creep criteria and ensure the substrate is continuously supported to avoid stress concentrations. Document the load paths and protection layers in the spec so installers don’t default to over-thick sections.
Bitumen is the most carbon-intensive part of the mix, so keep binder content at the lower end of the specification while still meeting performance. Use warm-mix processing to reduce production and installation temperatures, cutting fuel use without compromising workability. Only specify polymer modification when it is genuinely required (e.g., high heat or heavy duty); polymers raise both footprint and cost. Where possible, select binders with recycled or lower-carbon constituents and confirm performance with supplier test data. Cross-check EPDs to ensure the chosen mix actually delivers the expected reductions.
Use reclaimed mastic asphalt (RMA) and recycled aggregates/fillers to displace virgin materials without compromising performance. Set clear limits and acceptance criteria—grading, moisture, contaminants, and binder compatibility—and prove compliance with indentation/creep and workability tests. Start with conservative percentages in critical areas (roofs, tanking) and use higher levels in less sensitive zones (walkways, steps) once validated. Document traceability and declare actual recycled content in submittals so the carbon benefit is real, not assumed. More information can be found here: What Is The Recycled Content Percentage Of Mastic Asphalt?
Prioritise nearby plants and quarries to trim A4 transport, consolidate deliveries, and arrange backhauls where possible. On site, use insulated or electric kettles with tight-fitting lids, minimise hold times, and avoid repeated reheating that wastes fuel and ages the mix. Plan pour sequences so material arrives hot and is laid immediately, reducing idling and offcuts. Track fuel use per tonne laid to drive continuous improvement and verify that procedures actually cut A5 impacts.
Long life spreads the upfront carbon over decades, so detail for durability at upstands, penetrations, thresholds, and drainage points. Use finishes which increase the solar reflectance index (SRI) of mastic asphalt (e.g., stone chippings or coatings). By using these finishes heat gain and surface wear can be reduced. Establish simple maintenance: periodic inspections, prompt patching of scuffs or blisters, and timely renewal of the wearing/sand-rub finish in high-traffic paths. Where loads are concentrated, add local thickening or load-spreading boards to prevent early damage that would force carbon-intensive replacements.