ISO 18650-2:2025

Overview

ISO 18650-2:2025 - "Building construction machinery and equipment - Concrete mixers - Part 2: Procedure for examination of mixing efficiency" defines a standardized test procedure to evaluate the mixing efficiency of batch-type and continuous-type concrete mixers (as defined in ISO 18650-1). It is applicable to mixers with a rated capacity ≥ 0.5 m3 and is the third edition updating the 2014 version. The standard specifies concrete mix preparation, sampling locations and volumes, test methods, evaluation criteria and reporting requirements for a reproducible assessment of mixer performance.

Key topics and technical requirements

• Scope and applicability: batch and continuous mixers ≥ 0.5 m3.
• Mix design and conditions: typical test mix uses coarse aggregate up to 20 mm or 25 mm, slump (80 ± 30) mm, air content (4.5 ± 1.5) %, nominal compressive strength (25 ± 5) N/mm². Constituent materials weighed within ±3% uncertainty.
• Mixing times:
  • Batch-type gravity mixers: 60 s for ≤ 1.0 m3; add 5 s per 0.5 m3 increase above 1.0 m3.
  • Batch-type compulsory mixers: 30 s for ≤ 3.0 m3; add 15 s per 1.5 m3 increase above 3.0 m3.
  • Continuous mixers: mixing time equal to residency in chamber, minimum 10 s.
• Sampling protocol:
  • Two portions sampled immediately after prescribed mixing time.
  • Minimum sample volume: 20 L for batch mixers, 100 L for continuous mixers.
  • Sampling positions defined for different mixer designs (e.g., concentric zones for pan/turbo mixers, front/rear/centre for paddle mixers, beginning/end of discharge for gravity mixers).
• Variance tests and measured parameters:
  • Air content, mortar content (per unit volume), coarse aggregate content (per unit volume), and consistency (slump).
  • Compressive strength testing of specimens (cubes or cylinders).
  • Efficiency quantified by variance ΔX = (X1 − X2) / ((X1 + X2)/2) × 100, where X1 and X2 are paired portion results.
• Performance evaluation and reporting: criteria for acceptable variances, test-report structure and required manufacturer/mixer verification checks (e.g., RPM conformity, restart capability, discharge design, loss < 0.5%).

Practical applications - who uses this standard

• Mixer manufacturers: validate and demonstrate mixing performance for product development and commercial specifications.
• Testing laboratories and certification bodies: perform standardized mixing-efficiency tests for compliance, type approval and quality control.
• Contractors and concrete producers: select appropriate mixers and verify on-site performance for consistent concrete quality.
• Procurement and equipment auditors: assess mixer capability and acceptance criteria during purchase or tender evaluation.

Related standards (normative references)

• ISO 18650-1 (Concrete mixers - Commercial specifications)
• ISO 1920 series (Testing of concrete - sampling, fresh properties, making/curing specimens, strength)
• ISO 3310-1 (Test sieves)
• ISO 11375 (Terms and definitions)
• ISO 20290-1 (Aggregates test methods)

Keywords: ISO 18650-2:2025, concrete mixers, mixing efficiency, batch-type mixer, continuous mixer, mixing performance test, sampling, variance test, slump, air content, compressive strength.