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The Pozzolanic Reaction

As one of the two key technologies that fuel the exceptional performance of US Grout’s cementitious grouts (the other: an ultrafine particle size), the pozzolanic reaction ignited by pumice counteracts the problematic conditions inherent in hydrated Portland cement paste. The beauty of a pumice-fueled pozzolanic reaction is that it does so much more than simply mitigate deleterious junk. It takes that junk and literally transforms it into the very chemical binder that makes concrete concrete. Think of the pozzolanic reaction this way: a molecular reclamation project.

pumice, portland cement, and an ultrafine particle size mean superior grout performance

A Secondary Reaction that Amplifies the Primary Cement/Water Reaction

The science behind that amazing pozzolanic reaction is this: the particle-binding glue of concrete—Calcium Silica Hydrate (CSH)—is the result of combining water and Portland cement. But that same hydration reaction also produces Calcium Hydroxide (CH) by-products (up to 25% of the hydrated Portland cement) that not only do nothing to contribute to grout strength and density, but actively work against it. This CH-induced porosity introduces a host of ills...poor strength, weak resistance to chemical attacks, high permeability, and thus, shorter life.

Replacing some of the Portland cement with a pure natural pumice pozzolan ignites a pozzolanic reaction within the hydrated paste that, via a molecular-level reclamation process, reacts to and melds with the trouble-causing CH, ultimately converting it into additional CSH. This consumptive transformation of the CH mitigates or completely eliminates the problems it spawns. And that newly-created CSH does what you’d expect: it further densifies and strengthens the grout, welding the grout particles into a dense, durable, virtually impermeable matrix.

And, whether used to seal fractures or to improve soil structure, the enriched CSH presence helps bind the grout tightly to whatever it is injected into.

Technospeak Version: How the Pozzolanic Reaction Ignited by High Amorphous Silicon Dioxide Content Pumice Improves Cured Grout Performance

The following comes directly from the patent application document prepared by scientists at Sandia National Laboratories for the ultrafine cementitious grout they developed (and subsequently licensed to US Grout) to seal the microfractures in the underground confinement chambers at the U.S. Department of Energy’s Waste Isolation Pilot Plant in New Mexico:

“The ultrafine particle sizes enable the superior penetration characteristics of this grout and also enhance the beneficial chemical interaction between the Portland cement and the amorphous silica in pumice due to the increased surface area of the ultrafine particles. The chemical interactions between the two main constituents successfully combat the main degradation mechanism for cementitious grouts. With ordinary cementitious grouts there is always some permeability. Water from external sources or bleed water produced during hardening collects on the exterior surfaces of the grout and in the interconnected porous spaces in the grout and begins to dissolve the Portlandite phase (calcium hydroxide) of the grout. This produces an excess of calcium and hydroxyl ions in solution. Mass transfer drives these ions from areas of high concentration to areas of low concentration. This predominately means that the ions exit the external interface between the grout and the host rock, degrading this interface and creating a fluid pathway through the grouted rock. The grout of this invention employs the high amorphous silicon dioxide content pumice to prevent this chemical reaction from occurring. The amorphous silicon dioxide reacts with the calcium and hydroxyl ions in the fluid grout to form calcium tri-silicate (replacing the Portlandite) which has very low solubility. The relatively high fraction of pumice pozzolan decreases the relative amount of Portland cement, thereby reducing hydrational heat during hardening. The ultrafine pozzolan also results in smaller pores in the grout (average diameter is one micron) and causes the pores to be more disconnected as evidenced by mercury porosimetry and the extremely low hydraulic conductivity exhibited by this grout.”

inforgraphic about the pozzolanic reaction taking place within US Grout Cementitious Grouts

Unique Among Cementitious Grouts

No other cementitious grout on the market can claim the life-span, rheologic superiority, and exceptional performance specs that US Grout products can. The secondary chemical reaction ignited by the carefully-balanced pumice pozzolan component in the mix design contributes significantly to that effectiveness.

Expert Support

As the world-wide distributor for US Grout products, Avanti International ( • 800-877-2570) provides the customer service, objective professional advice, material estimates, and the caliber of world-class technical support that comes only from 35 years of geotechnical experience.


Research Study on Pumice Pozzolan

Summary of research done by the University of Utah on the effectiveness of Hess pumice as a pozzolanic material to improve concrete (including cementitious grout) performance.

Research Report Summary done by University of Utah on Pumice Pozzolan

Key Excepts from the Grout R&D Report

Sandia National Laboratories commissioned an “Optimization and Determination of the Physical Parameters of Ultrafine Cementitious Grouts” Research Study from AECL (Atomic Energy of Canada Limited) Whiteshell Laboratories on the critical-use grout they were developing for U.S. Dept. of Energy's underground waste isolation site in New Mexico. Some of the key language describing the observations and conclusions are excerpted and gathered.

Key Excerpts from the R&D Report of an Ultrafine Cementitious Grout

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