Concrete Mix Design Calculator
Mix Recipe · w/c Ratio · Cement Content · Compressive Strength · Consistency Class
Concrete Mix Calculator
Formulas & References
f_c = A · f_c0 · 2^(−B·w/c) [MPa]
Simplified: f_c ≈ f_c0 / (1 + 2.5·w/c) or f_c = k·(f_c0 − f_c0·w/c)
m_Water = w/c · m_Cement
m_Aggregate = m_Concrete − m_Cement − m_Water − m_Air
d_max → Water content (ACI 211, BS 8110, DIN 1045-1)
Defined by consistency class (slump) and maximum aggregate size
c_min [kg/m³] per EN 206 / ACI 318
X0: 160 | XC1: 240 | XC2: 260 | XC3: 280 | XC4: 300 | XS: 320–340 | XF: 300–320
Reference Table: Cement Strength
| CEM I 32.5 R | f_c28 = 32.5 MPa, early: 2d ≥ 10, 7d ≥ 20 |
| CEM I 42.5 N | f_c28 = 42.5 MPa, normal: 2d 10–20, 7d 20–40 |
| CEM I 42.5 R | f_c28 = 42.5 MPa, rapid: 7d ≥ 30 |
| CEM I 52.5 N | f_c28 = 52.5 MPa, high: 2d ≥ 20, 7d ≥ 40 |
• Cement: 320 kg/m³ (CEM I 42.5 N)
• w/c ratio: 0.55 → Water: 176 L/m³
• Aggregate: ~1800 kg/m³ (sand + gravel)
• Compressive strength 28d: ~30 MPa
Technical Background
Concrete Mix Design – Fundamentals
Concrete mix design is the engineering discipline of determining the correct proportion of cement, water, sand, gravel, and optional admixtures to produce concrete with desired properties: strength, durability, workability, and economy.
w/c Ratio (Water-to-Cement Ratio)
The w/c ratio is the ratio of water to cement and is the most critical parameter for concrete quality:
- Low w/c (0.3–0.45): Higher strength, better durability, but poor workability
- High w/c (0.60–0.75): Easy placement, but lower strength and durability
- Optimal (0.45–0.60): Balance between strength and workability
Abrams' Law
The famous Abrams' Law states that concrete compressive strength is inversely proportional to the w/c ratio:
where K ≈ 2–2.5 depending on cement type
Consistency Classes (DIN EN 12350-2)
| Class | Slump [cm] | Application |
|---|---|---|
| F1 Stiff | 0–1 | Foundations, rigid concrete (shot concrete) |
| F2 Plastic | 2–4 | Road concrete, parking lots, industrial floors |
| F3 Soft | 5–9 | Columns, deck slabs, walls (standard) |
| F4 Flowing | 10–15 | High-rise, pump concrete, surface finish required |
| F5 Very Fluid | 16–20 | Shot concrete, self-compacting concrete (SCC) |
Exposure Classes (EN 206 / ACI 318)
The exposure class describes environmental conditions and determines minimum cement content, w/c limit, and concrete cover:
- X0: No corrosion (indoor, dry) → c_min = 160 kg/m³
- XC: Carbonation-induced corrosion (humidity) → c_min = 240–300 kg/m³
- XS: Chloride-induced corrosion (seawater) → c_min = 320–340 kg/m³
- XF: Freeze-thaw cycling → c_min = 300–320 kg/m³ + entrained air 3–5%
Concrete Compressive Strength Classification (EN 206 / ACI 318)
| Class | Strength [MPa] | Application |
|---|---|---|
| C12/15 | 15–18 | Lean concrete, slopes, minor components |
| C20/25 | 25–30 | Standard for simple structures, roads |
| C25/30 | 30–37 | Standard concrete for high-rise buildings |
| C30/37 | 37–45 | Bridges, parking structures, higher demands |
| C40/50 | 50–60 | High-strength concrete, tunnels, hydraulic structures |
| C50/60 and higher | ≥60 | Ultra-high-strength concrete, special applications |
• Precise aggregate grading and bulk densities
• Batching proportions and compatibility
• Admixture dosages (fly ash, silica fume)
• Placement losses and curing effects
• Temperature effects on early strength
Consult a concrete specialist or cement supplier for final mix designs!
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