The following collection of videos are to give the viewer a better understanding of common procedures when placing silica fume concrete, which are in line with high-performance, and good concreting practices.
Silica fume imparts special properties on plastic concrete due to its sub-micron particle size. Being over 100 times finer than cement particles and spherical in nature, silica fume’s unique particle structure will affect viscosity of concrete in specific ways allowing the design team to manipulate the plastic concrete properties to suit specific applications.
Increased viscosity in plastic concrete translates into higher resistance to flow, which is used to clear advantage in this video showing reconstruction of the domed roof of a wastewater treatment plant, preventing the concrete flowing downslope, yet enabling delivery of a well workable 8” slump concrete which benefits both pumpability during delivery and consolidation upon placement.
A high percentage silica fume inclusion often allows the concrete to achieve SCC (self-consolidating concrete) consistency with conventional mix design proportioning; i.e. conventional S/A (sand-to-total aggregate ratio), lower total cementitious quantities and low w/cm (water-to-cementitious ratio) can be maintained as used in conventional high performance concrete designs and unlike SCC proportioning with higher total cementitious quantity, higher S/A, and elevated w/cm, elements that promote increased drying shrinkage. High silica fume content increases the concrete’s viscosity to allow for cohesive, non-segregating, high flow concrete that can be discharged rapidly, fill formwork efficiently with little or no consolidation or other labored input, and maximize the density of the concrete-in-place for maximum durability and concrete service life..
Small diameter pumping and simple manual tools accommodated by high performance, 12,000 psi, silica fume-viscosity-modified concrete designed to endure abrasion-, impact- and chemical- exposure in this industrial rehabilitation project.
An identical concrete mix design as in the previous video (industrial flooring) to produce a long service life access road to truck scales. The viscosity of this highly workable concrete enabled simple and rapid placement technique with minimal finishing efforts required.
A large scale flatwork application of corrosion-resistant silica fume concrete at a new parking garage facility demonstrates specific details, tools and methods preferably employed for any high-performance concrete placement operation, but essential for successful silica fume concrete construction.
Many US State Department Of Transportation agencies specify silica fume concrete for its superior engineered characteristics to resist corrosion and increase service life. These types of projects use a more automated process for concrete placement, specifically tailored for high performance concrete placement.
