Case study · Membertou, NS · Sand Replacement
Access Nova Scotia Building
ΔC was used in 70 m³ of sidewalk and curb air-entrained concrete for a new office building, reducing embodied carbon by 13% and storing approximately 40 kg CO₂e per cubic metre, while all batches exceeded the 35 MPa strength target.
Mix
4%ΔC-SR
Volume
70 m³
GWP reduction
13%
Strength target
35 MPa @ 28 days (C2 exposure)
ΔC sidewalk and curb pours, NS · 4%ΔC-SR · 13% GWP reduction
Project overview
alterBiota's ΔC admixture was deployed in 70 m³ of concrete for sidewalks and machine-extruded curbs surrounding a new 1,700 m² timber office building at the Mi'kma'ki Place development in Membertou, Nova Scotia. Officially opened on November 12, 2025, this project represents one of the first full-scale field implementations of ΔC under standard ready-mix production conditions. The mix was designed using the Sand Replacement (SR) strategy, where biochar solids volumetrically replace a portion of fine aggregate. This is a low-risk approach that preserves the cementitious volume while introducing engineered biochar-based carbon storage.
- Volume placed
- 70 m³ (12 truckloads)
- Application
- Sidewalks and machine-extruded curbs
- Specified strength
- 35 MPa @ 28 days (C2 exposure)
- Mix design technique
- SR (Sand Replacement)
- ΔC dose
- 4% biochar by weight of cement
Fresh-state performance
Across all 12 field-produced truckloads, ΔC integrated seamlessly into standard batching, transport, and placement practices with no adjustments required to admixture systems or batching procedures. Sidewalk (10 trucks): 170 mm avg slump at plant, 6.9% avg air content. Curb (2 trucks): 37 mm avg slump, 7.5% avg air content. The material performed well in both hand-finished sidewalks and machine-extruded curbs.
GHG reduction analysis
The Sand Replacement method enabled carbon storage through biochar, achieving a 13% reduction in total embodied carbon:
- ΔC carbon storage (biochar)
- −40 kg CO₂ e/m³
- Max savings per truckload
- −320 kg CO₂ e
- Total project GHG savings
- −2,775 kg CO₂ e (13%)
- Embodied carbon of ΔC mixes
- 265 kg CO₂ e/m³ (sidewalk) | 272 kg CO₂ e/m³ (curb)
Hardened-state results: Sidewalk mix
All 10 field-produced sidewalk batches exceeded the specified 35 MPa at 28 days, with an average of 45 MPa. Bulk electrical resistivity increased consistently from 7 to 28 days, indicating continued microstructural enhancement. Modulus of rupture results at 28 days ranged from 5.6 to 7.1 MPa, well above the 3.7 MPa expected per ACI 318 for a 35 MPa target.
- · MOR based on 6 of 10 trucks with available flexural specimens. All 28-day MOR values exceeded the ACI 318 expected value of 3.7 MPa.
| Day | f'c (MPa) | BER (Ω·m) | MOR (MPa) |
|---|---|---|---|
| 7 | 39.1 ± 3.5 | 68.6 ± 7.4 | 5.7 ± 0.4 |
| 28 | 45.0 ± 3.4 | 90.9 ± 11.7 | 6.1 ± 0.5 |
Hardened-state results: Curb mix
Both curb truckloads exceeded the 35 MPa target, with consistent strength gain from 7 to 28 days. Bulk electrical resistivity values above 80 Ω·m at 28 days indicate a refined microstructure under the lower w/c ratio required for machine extrusion. Flexural performance was satisfactory, meeting the capacity typically required for curb durability.
- · MOR based on 1 of 2 trucks with available flexural specimen.
| Day | f'c (MPa) | BER (Ω·m) | MOR (MPa) |
|---|---|---|---|
| 7 | 41.5 ± 4.9 | 68.6 ± 14.8 | 5.1 ± 0.3 |
| 28 | 45.6 ± 3.3 | 89.6 ± 10.9 | 5.4 ± 0.3 |
Key benefits
- All 12 truckloads exceeded 35 MPa at 28 days, with an average of 45.0 MPa
- 13% reduction in embodied carbon through biochar carbon storage, with 40 kg CO₂ e stored per m³
- 2,775 kg CO₂ e total project savings, with up to 320 kg CO₂ e stored per truckload, equivalent to offsetting the emissions of an additional concrete truck delivery
- No operational changes required, since ΔC was dosed using standard ready-mix pumping systems with no modifications to batching, transport, or placement
- Versatile application that performed reliably in both hand-finished sidewalks and machine-extruded curbs
- Higher reductions achievable: since all ΔC mixtures surpassed specified strength, a cement replacement strategy could push GWP savings beyond 20%
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