Why Premcrete Must Approve Your Concrete Mix Before Using Hydrocrete

When specifying Hydrocrete, Premcrete's high-performance waterproof concrete additive, we require formal sign-off on your proposed mix design - even if it's already been developed by the structural engineer and ready-mix supplier. That's because achieving truly watertight concrete is not jut about what you add to the mix - it's about the mix itself. 

Hydrocrete Mix Requirements - Explained 

1. Minimum 350kg/m³ Cementitious Content 

This ensures a dense, durable matrix that supports low permeability and effective waterproofing. 

• Well-graded aggregates are essential
• The sand content must contain at least 10kg/m³ of fines <75 microns

2. Blended Cements Permitted (e.g. GGBS, PFA)

Hydrocrete is compatible with blended cementitious materials, including:

• GGBS (Ground Granulated Blast-furnace Slag) – improves long-term durability
• PFA (Pulverised Fuel Ash) – enhances workability and reduces heat of hydration
  Up to 70% GGBS is permitted within the cementitious content.

3. Maximum Water-to-Cement Ratio: 0.43 

A low w/c ratio is essential for waterproof concrete. Ratios above 0.43 increase porosity, cracking, and reduce long-term performance. 

4. Consistence Class S3 (BS EN 206)

S3 workability ensures balance between flow and stability, ideal for watertight concrete with complex reinforcement and limited segregation risk. 

5. Crack Width Limitation : ≤ 0.3mm (BS EN 1992 Eurocode 2) 

Even the best waterproof concrete won't perform if cracks are uncontrolled. 
Your rebar design must limit crack widths to 0.3mm max, especially in large pours or water-retaining structures. 

Mix Submission Process

To maintain full compatibility with Hydrocrete and meet BS 8102:2022 standards: 

• Contractors must email the Concrete Mix Design Certificate from the ready-mix supplier to technical@premcrete.com
• Premcrete will review and provide written confirmation
• Any changes to the mix must also be resubmitted for sign-off

Why We Take This Seriously 

As the manufacturer of Hydrocrete, Premcrete assumes design liability when it's used as part of a project-specific waterproofing strategy. That means we stand behind:

• The performance of your watertight concrete
• The long-term durability of your structure
• Compliance with all relevant UK and European standards

Quick Summary – Hydrocrete Mix Design Criteria

If you’re a contractor, supplier, or engineer — here’s the short version you need to follow:

• Min 350kg/m³ cementitious content with well-graded aggregates
  (Sand must include ≥10kg/m³ fines <75 microns)
• Blended cements allowed (e.g. GGBS, PFA, OPC)
• Max water/cement ratio: 0.43
• Consistence class: S3 (BS EN 206)
• Crack width ≤ 0.3mm (BS EN 1992)
• Submit your mix certificate for approval to technical@premcrete.com before works begin

Want it watertight? Let's get the concrete right.