Sources: Hess Pumice Products, Malad City, Idaho; CP staff
By Don Marsh
Family-owned Hess Pumice has developed 3-micron and 15-micron gradations of its amorphous aluminum silicate product, each with pozzolanic properties well suited to concrete mixes. A sister business to Hess Ready Mix, it recently doubled capacity at its Wright Creek Area mine in southeast Idaho, announcing availability of the HessPozz product to concrete producers across the country.
Formal rollout took place at the 2012 Precast/Prestressed Concrete Institute Convention in Nashville—on the heels of a white paper reflecting University of Utah testing on HessPozz infused concrete. “How Pumice Pozzolans Super-Charge Concrete Performance” details the agent’s potential to a) lower heat of hydration 10-40 percent in a mix’s first 100 hours; b) resist sulfate attack and alkali-silica reactivity development; and, c) to replace up to 40 percent of portland cement as a supplementary cementitious material. The latter finding is indicated in four 0.48 water-cement ratio specimens exhibiting 3,300- to 4,600-psi and 4,800- to 7,000-psi compressive strength characteristics, respectively, in 7-day and 28-day tests.
Hess Pumice Vice President of Research & Development Joseph Thomas notes that HessPozz is lightly colored, thus suited to architectural or decorative slabs and structures; chemically inert outside of a calcium hydroxide environment, the raw material differing only in gradation from powder the company supplies for dental toothpastes; and, measures up well against fly ash, silica fume and metakaolin in reacting with free lime to form a denser calcium silicate hydrate concrete matrix. The non-crystalline silica agent comprises 80 percent SiO2 and 14 percent Al2O3. It ships in 50-, 1,200- and 2,000-lb. bags. — www.hesspozz.com; www.hesspumice.com