ISO 23945-1:2022

Overview

ISO 23945-1:2022 defines a standardized test method for evaluating the setting time of cement paste containing flash setting accelerating admixtures used in sprayed concrete (shotcrete). The standard specifies sampling, apparatus, environmental conditions, specimen preparation and the procedure-using Vicat apparatus-to determine initial and final setting times for both powdery and liquid accelerating admixtures. It also provides related terms and normative flow charts for paste preparation.

Key topics and technical requirements

• Scope and purpose
  • Tests the effect of a particular cement + flash setting accelerating admixture combination on setting time.
  • Intended for sprayed concrete / shotcrete applications; includes regional test conditions for tropical/subtropical climates.
• Test environment
  • Standard: (20 ± 2) °C and relative humidity > 50 %.
  • Alternative for tropical/subtropical: (27 ± 2) °C and 65 ± 5 % RH.
• Apparatus & specimen
  • Vicat apparatus and Vicat mould (top Ø 65 ±0.5 mm, bottom Ø 75 ±0.5 mm, depth 40 ±0.2 mm).
  • Flat trowel, mixer, glass graduates, balances (accuracy ±1 g / ±0.5 g), 50 ml syringe for liquid admixtures.
• Materials
  • Portland cement conforming to ISO 22965 series with specified fineness, C3A and alkali ranges and ≥ 42.5 28‑day strength.
  • Distilled/deionized water recommended for validation.
• Preparation & procedure
  • Typical test batch: 400 g cement with 140 g water (including water in liquid admixtures).
  • Powdery admixture: dry pre-mix 10 s, add water and mix 5 s (low) + 15 s (high).
  • Liquid admixture: pre-mix cement + water 30 s (low), add liquid admixture and mix 5 s (low) + 15 s (high).
  • Moulding within 50 s after final admixture addition; measure setting time immediately with frequent checks near initial set.
• Safety and applicability
  • The standard does not replace site safety practices; users must ensure regulatory and health compliance. Laboratory results may not exactly replicate field shotcreting conditions.

Applications and who uses it

• Admixture manufacturers: product validation and technical data sheets for flash setting accelerating admixtures.
• Shotcrete and sprayed concrete contractors: selecting and qualifying admixtures for tunnelling, mining, repairs, and rapid stabilization.
• Materials testing laboratories: routine quality control and conformity testing of cement–admixture combinations.
• Specifiers and engineers: assessing suitability of admixtures for fast-setting applications and establishing mix controls.

Related standards

• ISO 679 (cement strength test methods)
• ISO 9597 (setting time and soundness)
• ISO 22904 / ISO 22965 (additions / concrete)
• ISO 29581‑1 / ‑2 (cement chemical analysis)
• EN 196‑2, EN 196‑6; ASTM C187

Keywords: ISO 23945-1, sprayed concrete, flash setting accelerating admixture, setting time, shotcrete testing, Vicat, cement paste.