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ASR Mitigation with Pumice-Blended Cement

skate park being destroyed by ASR

ABOVE: This public skate park in Idaho Falls, an area known for its reactive aggregate, is being slowly and relentlessly destroyed by ASR. BELOW: Close up of the ASR-infected concrete.

pumice sand (Hess Grade 1/8MN) PDF: scorecard of ASR mitigation materialsPDF: scorecard table: ASR mitigation materials

PDF document—Score Card: ASR-Mitigating SCMs—details how pumice pozzolan stacks up against various supplementary cementitious materials used to mitigate the alkali-silica reaction.

ALKALI-SILICA REACTION (ASR) fuels a relentless, slow-motion explosion within cured concrete that shatters both the concrete and the aggregate, significantly shortening the engineered lifespan of the infected structure.

The ASR Train Wreck Explained

Researchers have defined a causal triangle that sets off the chemical ASR train wreck within concrete. The stew of water, Portland cement, and reactive aggregate generate the four essential ingredients of expansive ASR gel—alkalis, silica, free calcium hydroxide (CH), and moisture. Starving the concrete of one of those components can effectively flatline ASR.

insulated concrete forms

Simple Explanation: the alkali compounds within Portland cement react with the silica in the aggregate forming a chemical compound with a thirsty affinity for water. As water is absorbed, the resulting gel swells, cracking both concrete and aggregate, opening the concrete to further attack from outside elements—sulfates and chlorides, marine salts, and freeze-thaw—which accelerate the death-march of the structure.

Deep Dive: the primary chemical reaction (hydration) between Portland cement and water creates a deleterious compound know as Calcium Hydroxide (CH)—radical free calcium—that, unabated, reacts with alkali and aggregate-contributed silica to form a hydrophilic (water-attracting) gel that expands relentlessly. The reaction will go dormant when starved of moisture, only to swell and expand again when sufficient water is again present.

Defeating ASR

Where concrete engineers have had success combating and defeating ASR is with preventative mix designs. Various ineffective and often impractical methods have been identified and used since the alkali-silica reaction was first identified in the late 1930s, including using low-alkali cement, trucking in non-reactive aggregate, specifying low W/C ratios, using less cement, even air entrainment.


—Download a Summary of the Pumice Pozzolan Research (including the effectiveness of pumice pozzolan to flatline ASR) from the University of Texas-Austin and the University of Utah.

—Download the Whitepaper: Flatline ASR With Pumice-Blended Cement.

—Download the Knowledge Brief: Score Card: ASR-Mitigating SCMs.

—Visit the ASR MitiGator website.