Abstract
In this study, ultra-fine spherical particles of silica fume and reactive ultra-fine fly ash were added to a mixture of commercial ultra-high-performance grout (UHPG) with the aim of enhancing the rheological properties, compressive strength, compactness, and permeability. This commercial UHPG study was conducted in collaboration with Triaxis Corporation (Changsha city, Hunan province, China). A water-to-binder ratio of 0.21 and a binder-to-fine aggregates ratio of 1.17 were used as fixed parameters, and the binders were a combination of type-II Portland cement, sulphoaluminate cement, silica fume, and reactive ultra-fine fly ash (RUFA). Polycarboxylate superplasticizer powder was used to control the rheology. The results revealed excellent compressive strength, volume stability, and resistance to chloride penetration. Mercury intrusion porosimetry and scanning electron microscopy tests revealed that the medium-sized RUFA particles with small silica fume particles completely filled the spaces between large cement particles to achieve optimal densification. This mixture also produced dense hydration and calcium-silicate-hydrates colloids, which filled the microstructures of the UHPG resulting in excellent engineering properties and durability. This commercially available UHPG mix responded to excellent compressive strengths approaching 120 MPa and exhibited good workability with a loss of slump-flow rate up to 33% after 60 min. It also exhibited very low abrasion resistance (0.5%), stable shrinkage and expansion rates (stabilization over 10 days), very low chloride diffusion coefficient (less than 0.1 × 10−14 m2/s) with a denser microstructure. This commercial UHPG (UHPG-120) has been developed to meet the needs of the market.
Highlights
Ultra-high-performance concrete (UHPC) is an innovative cement-based material with a minimum specified compressive strength of 120 MPa [1,2,3,4]
The binders used in this study consisted of four materials: ordinary Portland cement, rapid hardening sulphoaluminate cement, silica fume, and reactive ultra-fine fly ash (RUFA), all sourced from Triaxis Corporation(Triaxis, Changsha, China)
The inclusion of ultra-fine particles, such as silica fume and RUFA, had a positive effect on the densification of Ultra-high-performance grout (UHPG), which corresponds to the results described in the previous section
Summary
Ultra-high-performance concrete (UHPC) is an innovative cement-based material with a minimum specified compressive strength of 120 MPa [1,2,3,4]. UHPC has increasingly been used in road and bridge engineering, repair and rehabilitation, and surface decoration in a variety of engineering fields. This material is relatively new (less than 30 years) and has been applied to a relatively small proportion of cement grouting composites. Ultra-high-performance grout (UHPG) materials are an ideal use of UHPC for use in precast construction, structural rehabilitation, soil stabilization, crack injection, and filling holes in concrete structures [14,15]. These research and engineering applications imply a bright future for UHPG
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