Professional Permeable Concrete Mix Proportion Calculator 2026
Pervious concrete mix design creates permeable concrete allowing water infiltration through interconnected void networks within the hardened matrix. This sustainable paving solution manages stormwater runoff, reduces urban flooding, recharges groundwater, and improves water quality by filtering pollutants. Mix design balances permeability requirements with structural strength, durability, and placement characteristics for parking lots, pedestrian paths, cycle tracks, and low-traffic roadways throughout the UK.
Pervious concrete contains little to no fine aggregate, using single-sized coarse aggregate coated with cement paste forming interconnected voids allowing water passage. Target void ratios typically range 15-25% providing permeability rates 100-1000mm per hour compared to conventional concrete effectively impermeable at under 1mm per hour. Higher void content increases permeability but reduces strength, requiring careful balance between drainage performance and structural requirements for intended applications.
Typical compressive strengths reach 10-25 MPa sufficient for light vehicle traffic, pedestrian areas, and residential driveways but lower than conventional concrete at 30-40 MPa. Aggregate size selection influences void structure and strength, with 10-20mm single-sized aggregates standard. Cement content typically 270-400 kg/m³ provides adequate paste coating aggregate particles without filling voids. Water-cement ratios of 0.27-0.35 ensure proper hydration and paste consistency achieving target strength while maintaining void network integrity.
Coarse aggregate comprises 85-90% of pervious concrete mix volume compared to 60-75% in conventional mixes. Single-sized aggregates 10-20mm create consistent void networks, with smaller sizes providing higher strength but lower permeability, while larger aggregates increase permeability at reduced strength. Aggregate must meet durability standards including freeze-thaw resistance, abrasion resistance, and chemical stability ensuring long-term pavement performance in demanding exposure conditions.
Cement content ranges 270-400 kg/m³ depending on target strength and void ratio. Higher cement contents increase strength and durability but risk filling voids reducing permeability if paste consistency proves too fluid. Portland cement CEM I provides reliable performance, while blended cements incorporating GGBS or PFA enhance sustainability and cost-effectiveness. Fine aggregate typically comprises 0-10% of total aggregate mass, with zero fines maximizing permeability while minimal fines improve workability and strength for higher traffic applications.
Mix design begins with target void ratio selection based on drainage requirements and traffic loading. Pedestrian areas tolerate 22-25% voids maximizing permeability, while car parks specify 18-20% balancing drainage with vehicle support. Target compressive strength determines cement content and water-cement ratio, with typical specifications 15 MPa for light traffic, 20 MPa for parking areas, and 25 MPa for access roads and heavier applications.
Proportioning calculations determine aggregate, cement, and water quantities achieving target void ratio and strength. Aggregate volume typically 1500-1650 kg/m³ with cement paste coating particles without excessive void filling. Trial mixes verify design assumptions, with adjustments addressing workability, void ratio, and strength development. Admixtures including hydration stabilizers extend workable life for transport and placement, while retarders compensate for hot weather or extended placement durations.
Pervious concrete placement requires specialized techniques ensuring proper compaction without void closure. Delivery within 60-90 minutes of batching maintains workability, with hydration stabilizers extending this window for distant sites or phased placement. Spreading occurs with minimal material handling preventing segregation, achieving target thickness typically 100-200mm for pedestrian areas and 150-250mm for vehicle traffic.
Compaction using roller screeds or plate compactors achieves target density and surface level without closing surface voids. Excessive compaction closes voids reducing permeability, while inadequate compaction compromises strength and ravelling resistance. Surface finishing leaves exposed aggregate texture providing slip resistance and maintaining infiltration capacity. Edging and jointing follow conventional practice with proper detailing ensuring durability and crack control throughout service life.
Pervious concrete requires prompt covering with polyethylene sheeting maintaining moisture for hydration without premature drying. The open structure loses moisture rapidly demanding immediate protection after finishing. Minimum 7-day curing under sheeting ensures adequate strength development and surface durability. Light water misting supplements moisture without flooding or washing cement from aggregate surfaces.
Traffic restrictions during curing prevent damage to immature concrete. Pedestrian access typically allowed after 3 days, with vehicle traffic delayed 7-14 days depending on strength development. Protective measures prevent sediment loading during construction blocking voids and compromising permeability. Regular vacuum sweeping removes accumulated debris maintaining infiltration capacity throughout pavement service life typically 20-30 years with proper maintenance.
Car parks represent primary pervious concrete applications, managing stormwater at source eliminating traditional drainage infrastructure. Typical thickness 150-200mm over compacted aggregate sub-base provides structural support and additional infiltration capacity. Pedestrian paths and cycle tracks use 100-150mm thickness for lighter loading. Tree surrounds in urban streetscapes allow water and air exchange supporting tree health while providing durable pedestrian surfaces.
Permeability testing verifies installation quality using falling head or constant head infiltrometers measuring water infiltration rates. Properly installed pervious concrete achieves permeability 100-1000mm per hour, vastly exceeding typical rainfall intensities ensuring effective stormwater management. Long-term performance monitoring confirms sustained permeability with periodic vacuum sweeping maintenance preventing sediment accumulation. Service lives of 20-30 years match conventional concrete when properly designed, installed, and maintained.
| Parameter | Typical Range | Notes |
|---|---|---|
| Cement Content | 270-400 kg/m³ | Strength and void dependent |
| Water-Cement Ratio | 0.27-0.35 | Low for paste consistency |
| Coarse Aggregate | 1500-1650 kg/m³ | Single-sized 10-20mm |
| Fine Aggregate | 0-10% of total aggregate | Minimal or zero fines |
| Void Ratio | 15-25% | Application dependent |
| Compressive Strength | 10-25 MPa | At 28 days |
| Permeability | 100-1000 mm/hr | Void ratio dependent |
| Typical Thickness | 100-250mm | Loading dependent |
| Application | Void Ratio | Strength | Thickness |
|---|---|---|---|
| Pedestrian Paths | 20-25% | 10-15 MPa | 100-150mm |
| Cycle Tracks | 18-22% | 15 MPa | 120-150mm |
| Residential Driveways | 18-20% | 15-20 MPa | 150-180mm |
| Car Parks | 15-20% | 20 MPa | 150-200mm |
| Access Roads | 15-18% | 20-25 MPa | 200-250mm |
| Tree Surrounds | 20-25% | 10-15 MPa | 100-150mm |
Pervious concrete achieves permeability 100-1000mm per hour through 15-25% interconnected voids, managing stormwater at source eliminating traditional drainage.
Uses 10-20mm coarse aggregate with little to no fines creating consistent void networks. Aggregate comprises 85-90% of mix volume.
Typical strength 10-25 MPa sufficient for light traffic but lower than conventional concrete. Void ratio determines strength-permeability balance.
Cement content 270-400 kg/m³ with low water-cement ratio 0.27-0.35 coats aggregate particles without filling voids maintaining permeability.
Requires controlled compaction and immediate moisture protection. Excessive compaction closes voids while inadequate compaction reduces strength.
Reduces urban flooding, recharges groundwater, filters pollutants, and eliminates traditional drainage infrastructure with 20-30 year service life.
Pervious concrete mix design creates permeable paving using single-sized coarse aggregate with minimal fines and cement paste coating, forming interconnected voids allowing water infiltration. Typical mixes contain 270-400 kg/m³ cement, 1500-1650 kg/m³ coarse aggregate (10-20mm), water-cement ratio 0.27-0.35, and target void ratio 15-25%. This achieves permeability 100-1000mm per hour and compressive strength 10-25 MPa suitable for light traffic applications.
Pervious concrete typically achieves compressive strength 10-25 MPa at 28 days, lower than conventional concrete at 30-40 MPa due to high void content. Strength depends on void ratio, cement content, and aggregate size. Pedestrian areas use 10-15 MPa, parking areas 15-20 MPa, and access roads 20-25 MPa. While adequate for intended applications, pervious concrete proves unsuitable for heavy traffic or high structural loading requiring conventional mixes.
Pervious concrete uses single-sized coarse aggregate typically 10-20mm with little to no fine aggregate. Common sizes include 10mm for higher strength lower permeability, 14mm for standard applications, and 20mm for maximum permeability. Aggregate must meet durability standards including freeze-thaw resistance and abrasion resistance. Single sizing creates consistent void networks essential for water infiltration, while aggregate comprises 85-90% of total mix volume.
Properly designed pervious concrete achieves permeability 100-1000mm per hour depending on void ratio and aggregate size. Higher void ratios (22-25%) produce permeability 500-1000mm per hour, while lower ratios (15-18%) yield 100-300mm per hour. This vastly exceeds typical UK rainfall intensities under 50mm per hour, ensuring effective stormwater management. Conventional concrete permeability under 1mm per hour proves effectively impermeable requiring surface drainage systems.
Pervious concrete applications include car parks, pedestrian paths, cycle tracks, residential driveways, access roads, tree surrounds, and overflow parking areas. Thickness ranges from 100-150mm for pedestrian areas to 150-250mm for vehicle traffic. It manages stormwater at source eliminating traditional drainage infrastructure while providing durable trafficable surfaces. Not suitable for high-speed roads, heavy industrial loading, or areas requiring impermeable surfaces like building foundations or liquid containment.
Pervious concrete costs £100-150 per square metre installed in 2026 including materials, placement, and finishing. While material costs prove comparable to conventional concrete, specialized placement techniques and equipment increase installation expenses. However, elimination of traditional drainage infrastructure including pipes, gullies, and storage tanks often offsets installation premiums. Total project costs prove competitive with conventional paving plus drainage, while providing superior stormwater management and environmental benefits.
For pervious concrete suppliers, visit Hanson Concrete | CEMEX UK | For specifications, check The Concrete Centre