Enter your conditions
Example data table
| Temp | Humidity | Mix | Curing | Light foot | Soil load | Near full cure |
|---|---|---|---|---|---|---|
| 20°C | 50% | Standard | Wet | ~1–2 days | ~6–9 days | ~28 days |
| 30°C | 40% | Standard | Plastic | ~12–24 hr | ~4–6 days | ~18–25 days |
| 10°C | 70% | Standard | Wet | ~2–4 days | ~10–14 days | ~35–45 days |
| 20°C | 50% | Rapid | Wet | ~6–12 hr | ~2–4 days | ~10–20 days |
| 25°C | 30% | High early | Compound | ~12–24 hr | ~4–7 days | ~20–30 days |
Formula used
The calculator estimates a strength fraction over time using a simple maturity-style model. It starts from an equivalent-age curve and adjusts it using site factors.
- Strength model: f = 1 − e^(−k · t_eq), where f is the fraction (0–1), k depends on mix, and t_eq is equivalent days.
- Rate adjustment: t_eq = t · R, where R multiplies temperature, humidity, wind, curing, thickness, and w/c effects.
- Solving for time: t = −ln(1−f_target) / (k · R).
This is a planning model, not a lab test. When the project is structural or safety-critical, follow supplier guidance and local standards.
How to use this calculator
- Pick the mix that matches your bag or ready-mix label.
- Enter temperature, humidity, and wind for your work area.
- Set thickness and curing method you will actually follow.
- Use the milestones to plan walking, planting, or sealing.
- In hot or dry weather, extend moist-curing for durability.
Curing milestones for garden concrete
Garden concrete is usually safe for light use once it reaches about 25% of its design strength. At that point, careful foot traffic will not distort edges or leave deep impressions. Heavier activity, like wheelbarrows or compacted soil, is better planned near 50–70%. Near full cure is often discussed around 28 days, yet weather and curing protection can shift that timetable.
Weather effects on strength gain
Temperature strongly influences early hydration, so a warm day can shorten set time while a cold night stretches it. This calculator uses a rate factor that increases as temperature rises above 20°C, then slows below it. Relative humidity and wind matter because they control evaporation. Dry air and steady breeze can pull moisture from the surface, reducing effective curing and raising cracking risk. For cool, shaded sites, consider insulating blankets overnight to reduce temperature swings.
Moisture management on outdoor slabs
Maintaining moisture helps concrete form denser paste and stronger surface durability. Wet curing and tight plastic cover generally keep the surface from drying prematurely, especially on thin garden paths and stepping stones. Curing compounds reduce evaporation, but coverage must be continuous. If you choose no protection, expect slower strength gain and higher shrinkage, so extend timelines and limit early loads. Start curing as soon as finishing permits, and avoid ponding water that can mark the surface.
Planning loads and finishes
Use “Backfill / soil load” when you plan to place soil against a curb, planter wall, or edging strip. Use “Sealer or coating” when applying decorative sealers, stains, or waterproofing. If you need to drill anchors, wait for higher milestones to reduce spalling. For frequent irrigation nearby, protect fresh concrete from direct spray during early set and finishing.
Recordkeeping and repeatable mixes
Consistent results come from logging conditions and repeating practices. Save your CSV or PDF with notes like project type, batch size, and curing method used. Water–cement ratio is a simple indicator of mix wetness; higher values can reduce surface hardness and increase bleed. When you adjust thickness or exposure, rerun the calculator to update milestones before scheduling planting or traffic.
FAQs
How long before I can walk on new garden concrete?
Many garden pours allow careful foot traffic after the “Light foot traffic” milestone. Protect edges, avoid twisting steps, and keep pets off until the surface is firm and no longer marks easily.
Does watering the surface help curing?
Yes, gentle moisture helps maintain hydration and reduces shrinkage. Begin after finishing is complete, keep the surface damp, and avoid strong spray that can erode paste or leave marks.
What if temperatures drop at night?
Cold slows strength gain and can extend timelines. Cover with plastic and insulating blankets, and avoid loading the slab early. If freezing is possible, postpone the pour or use approved cold-weather measures.
Can I backfill soil against a curb or planter wall quickly?
Backfilling too early can crack green concrete. Use the “Backfill / soil load” estimate as a planning minimum, and compact soil gently in thin layers to reduce lateral pressure.
When should I apply a sealer or coating?
Wait until moisture has reduced and strength is adequate. Use the “Sealer or coating” milestone as a guide, then follow the product label for dryness tests, prep steps, and weather limits.
Why do results differ from bag labels or contractor advice?
Materials, admixtures, sun exposure, and curing practice vary widely. This tool estimates a schedule from inputs, but supplier data and field testing can override it, especially for specialty mixes.