A Comprehensive Study on Non-Proprietary Ultra-High-Performance Concrete Containing Supplementary Cementitious...

Area of Science:

• Materials Science
• Civil Engineering
• Concrete Technology

Background:

• Ultra-high performance concrete (UHPC) offers superior mechanical and durability properties.
• Silica fume, a key component, is costly in North America; fly ash is a common substitute but faces uncertain future availability.
• There is a critical need for cost-effective and sustainable alternatives to silica fume and fly ash in UHPC.

Purpose of the Study:

• To investigate the feasibility of replacing cement, fly ash, and silica fume in UHPC with ground granulated blast-furnace slag (GGBFS), metakaolin, and pumicite.
• To identify acceptable UHPC mixtures meeting specific strength criteria (28-day compressive strength > 120 MPa).
• To evaluate the workability, mechanical properties, and durability of UHPC mixtures incorporating these alternative supplementary cementitious materials (SCMs).

Main Methods:

• UHPC mixtures were designed with varying proportions of GGBFS, metakaolin, and pumicite as replacements for traditional SCMs.
• Standard tests were performed to assess workability, compressive strength, and flexural strength.
• Durability was evaluated through shrinkage, frost resistance, and chloride ion permeability tests (rapid chloride permeability and surface resistivity).

Main Results:

• Acceptable UHPC strengths were achieved with up to 75% fly ash replacement by pumicite, 100% by metakaolin, and 40% by GGBFS.
• All tested mixtures exhibited flexural strengths exceeding 14.20 MPa.
• UHPC mixtures demonstrated excellent durability, with shrinkage strains below 406 μstrain, durability factors above 105, and very low chloride ion permeability.

Conclusions:

• Ground granulated blast-furnace slag (GGBFS), metakaolin, and pumicite are suitable replacements for fly ash and partially for silica fume in non-proprietary UHPC.
• These alternative SCMs enable the production of high-performance concrete with comparable or superior mechanical and durability characteristics.
• The findings support the development of more sustainable and cost-effective UHPC formulations.