Overview
ISO 18650-2:2014 - Building construction machinery and equipment - Concrete mixers - Part 2 - specifies the standardized procedure to examine the mixing efficiency of batch-type and continuous-type concrete mixers (as defined in ISO 18650-1). It applies to mixers with a rated capacity greater than or equal to 70/50 and defines the test program, sampling, measurements and evaluation criteria used to quantify how uniformly a mixer produces concrete.
Key topics and requirements
- Mixing performance test: Determination of uniformity by measuring variances in key mix parameters and compressive strength of sampled specimens.
- Measured parameters:
- Air content (pressure method referenced)
- Mortar content per unit volume
- Coarse aggregate content per unit volume
- Consistency (slump)
- Compressive strength of cubes/cylinders
- Variance calculation: The standard provides a formula to calculate percentage variance (ΔX) between two sampled portions against their average, used for evaluation of uniformity.
- Concrete mix preparation: Typical target values are provided (e.g., coarse aggregate up to 20 mm or 25 mm, slump 80 ± 30 mm, air content 4.5 ± 1.5 %, compressive strength 25 ± 5 N/mm2). Weighing tolerance for constituents is ±3 %.
- Mixing time guidance: Manufacturer’s specified mixing time is preferred; when unavailable, the standard gives recommended approximate mixing times for gravity, compulsory (pan/paddle) and continuous mixers (examples include ~60 s for small batch gravity mixers, 30 s for small compulsory mixers, minimum 10 s residence for continuous mixers).
- Sampling rules: Minimum sample volumes - 20 L for batch mixers, 100 L for continuous mixers; sampling locations and timing are specified for different mixer types and for hoppers.
- Equipment verification & operational checks: Mixer geometry, RPM, discharge, and restart capability (drive should restart after 5 min) must conform to manufacturer’s instructions; permitted loss of mix before discharge is limited.
Applications and users
- Quality assurance and performance testing of concrete mixer equipment
- Mixer manufacturers for design verification and claims substantiation
- Testing laboratories conducting mixing-efficiency certification and acceptance tests
- Construction contractors, plant operators and QA/QC engineers who need objective criteria for mixer selection, commissioning and site acceptance
- Certification bodies and procurement teams evaluating mixer uniformity and consistency
Related standards
ISO 18650-2:2014 provides a practical, reproducible framework for measuring and reporting concrete mixer performance, enabling consistent acceptance testing, product comparison and reliable field operation.
Open preview (PDF)Building construction machinery and equipment — Concrete mixers — Part 2: Procedure for examination of mixing efficiency
