About Pumice: Questions and Answers About Pumice 2

page title: questions and answers about pumice

The unique, nature-crafted, frothed-glass character of the pumice stone finds application in a variety of consumer goods and industrial processes.

Uses and Applications of Pumice

What makes pumice such an excellent abrasive?

In short, a complimentary relationship of form factor and chemical composition. The pumice form factor is that of an amorphous foamed stone, which gives it friability, meaning it gives rather than gouges under pressure. The chemical composition makes pumice glass-like, which brings cutting edges and just-right hardness. Pumice also combines readily with various fluids to make abrasive compounds, which, along with pumice grade size selection, add even more control to cutting rates.

Another valuable combination that comes into play with the Hess pumice deposit in particular is a natural hardness and purity combined with additional process purification: Hess has an entire plant designed to remove the trace amounts (less than 2%) of heavier, harder igneous minerals that are in with the pumice.

Download Knowledge Brief: Pumice: A Full-Featured Abrasive for Circuit Board Preparation

NOTE: Over 30 of our standard grades and grade blends have application for industrial abrasives. Please contact us for recommendations.

Can pumice be used to improve poor or damaged native soils?

What roles does pumice play in the construction industry?

Several. Pumice is arguably most famous as the lightweight aggregate in Concrete Masonry Units (CMUs)—so called cinder blocks. Pumice also finds utility as aggregate and sand in formed-and-poured lightweight concrete structures, precast concrete products (including pipe, tanks, tilt-up walls), and lightweight stuccos and bonding mortars. Pumice aggregate also fills a role as a lightweight geotechnical fill for infrastructure projects.

In fine-powdered form, pumice is a natural and highly effective concrete pozzolan, providing a host of benefits to standard (and problematic) Portland cement concretes. Also, pumice pozzolans combine with slaked lime to form Pozzolanic Hydraulic Lime (PHL) plasters and binders. Pumice is inter-ground with Portland cement to create ultrafine, ultra-enduring cementitious injection grouts.

Pumice also finds use as a soil amendment, improving the functional structure, drainage, and water-retention profile of poor native soils beneath landscaped cover plantings. Pumice is also a lightweight and functional component in functional urban landscaping: engineered green roof soils, ecology embankments, storm-surge bioswales (rain gardens), and filtration strips protecting waterways from runoff.

Microfine pumice powders are used as safe, functional fillers in paints and coatings, epoxies and caulks. Pumice grits are used to provide dimensional texture and holding grip to non-slip floor paints and plaster-holding primers.

See the Where can I find more detailed information on the various uses for pumice? question/answer below for links to sites with more information on the uses mentioned above.

Can the use of pumice in construction and landscaping processes contribute to LEEDS certification?

Indeed it can. Pumice finds a role in the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) certification program in the following areas: Brownfield Redevelopment and Remediation (rehabilitating damaged sites to reduce pressure on undeveloped lands). Rainwater Management and Storm Water Design: Quality and Quantity Control (replicate and limit disruption of natural water hydrology and water balance of the site). Heat Island Reduction (minimize impacts of microclimates and human and wildlife habitats). Outside Water Use Reduction and Water Efficient Landscaping (limiting or eliminating use of potable water resources for landscaping). Minimum Energy Performance and Optimized Energy Performance (incorporating thermal mass to reduce heating, cooling, ventilating and realize energy cost savings). Use of Regional Materials (use of local materials and reduced transportation distances). Reduce Cement Content (use of a supplementary cement material).

Download the white paper: Pumice and LEED Certification

How does pumice improve concrete?

The improvement pumice imparts to standard concrete is directly related to the grade size used. When used as the aggregate component⁰¹, pumice lightens the dead load weight, improves the R-value, sound dampening, freeze-thaw resistance, and fire resistance (against spalling). Pumice aggregate (rock and sand) grades directly replace common sand and rock and are mixed, handled, transported, and placed using the same equipment and methods.

When used in fine powder form as a percentage of cement replacement (functioning as a pozzolan⁰²), pumice improves final cure strength, density, and freeze-thaw resistance, while mitigating sulfate attacks, alkali silica reaction (when reactive aggregate is present), and efflorescence. In short, pumice can greatly improve the longevity and functional life of the concrete structure.

01—Website: More information on pumice in concrete, including mixing instructions and some base mix designs.

02—Website: More information on pumice as a pozzolan.

Download Whitepapers: How Pumice Pozzolans Super-Charge Concrete Performance and Flatline Alkali-Silica Reaction for Pennies a Yard

Natural pumice pozzolans not only replace a percentage of the cement in the mix design, they prevent this kind of premature structural concrete failure.

Is pumice absorbent?

Does pumice make a good filtration media?

The foamed-stone nature of even tiny pumice particles makes for an effective filtration media filtering culinary water, cleaning water for drip irrigation, produce washing and other processes. The rough and pitted surface area of a pumice particle provides aggressive filtration, being especially effective in capturing slippery organics. Pumice media back flushes readily: the lightweight particles are easily animated during the flush cycle. The range of pumice grade sizes available also allow the filtration media to be more effectively customized to the filtration task, load, and back flushing cycle frequency. Pumice can replace sand media or be used with sand in dual media setups. It can be used in tank systems, cartridge systems, and open bed systems.

Download Knowledge Brief: Pumice as Filtration Media.

Order Samples: Hess Grade #5 and Hess Grade #7 (Filtration Media)

Does pumice have application in engineered soils?

Are there really animals that bath in pumice dust?

Does pumice work as a mechanical insecticide?

Can pumice be used as a reusable growing media in hydroponic and aquaponic systems?

What types of personal care products use pumice?

Creams, soaps, gels, and tooth pastes and polishes. Pumice has efficient abrasive properties, and in fine-grit form, makes an excellent exfoliant. When added to cosmetic creams and exfoliating gels, frothy pumice grit stays in suspension and spreads evenly. When worked lightly across the skin, the microscopic edges cut loose, bind, and sweep away dead skin. Pumice adds grime cut-and-capture strength to heavy duty hand soaps and gels without the need for chemicals. Pumice powders combine beautifully with soaps and moisturizers. Grade choice and concentration dictate aggressiveness.

Download Knowledge Brief: Pumice in Cosmetics and Personal Care Products.

Pumice powders are used widely as the functional exfoliant agent in commercial products, but can also be stirred into a favorite liquid soap, gel, or moisturizer to create an exfoliant. (See Hess Pumice’s Magma brand.)

Is pumice good for scrubbing away hard water stains?

Are there other pumice-like materials in the marketplace?

Can pumice be used as an economical replacement for expanded perlite to improve soil structure and function?

Yes, pumice can directly replace expanded perlite as a soil amendment/component. Research studies, like the one from the Department of Horticulture, University of Illinois⁰³, find pumice to be the physiochemical and in-soil function equivalent of expanded perlite. The downside of expanded perlite, of course, is the fiery energy it takes to expand it, which contributes significantly to its cost. For engineered soils at volume—green roof grow beds, commercial greenhouse production, palleted bags of retail potting soils—pumice is the economical choice. Same for large-scale projects faced with the need to amend poor native soils—landscaping, turf fields, construction site remediation, and engineered storm water control/filtration constructs. Economical because pumice is naturally calcined (expanded) and need only be minimally processed for use as a soil amendment. The soil-amending pumice grades are sold by the ton, grade-prepped, and truck-loaded directly at the mine. Process-wise, it doesn’t get more economical than that.

03—Evaluation of Pumice as a Perlite Substitute for Container Soil Physical Amendment. Noland, Spomer, Williams; Dept. of Horticulture, University of Illinois.

Order a Sample: Hess Grade 1/8 Fines (Soil Amendment)

Close-up images of pumice (left) and expanded perlite (right).

Where can I find more detailed information on all of the various uses for pumice?

Hess Pumice Products publishes extensive information on the various processes and end-use products that use pumice. A wide and detailed overview is found on the primary Hess Pumice website, including suggested grades for each use. White papers, knowledge briefs, research summaries, infographics and other informational publications are available (in PDF file format) from that site’s Downloads Library.

Additionally, Hess has websites built around specific pumice-use topics and branded products, including:

Pumice as a Concrete Pozzolan, including tightly focused sites on ASR Mitigation and Pumice as a Replacement for Fly Ash.

Pumice in Agriculture (crops, livestock care, waste management).

Micronized, Non-Crystalline (NCS) Functional Fillers.

Pumice as a Soilless Grow Media (hydroponics and aquaponics systems).

Pumice as a Soil Amendment (gardens, landscaping, and turf)

Pumice in Concrete (both as a lightweight aggregate and as a pozzolan).

Pumice Aggregate and Sand in Lightweight Stuccos and Bonding Mortars.

Pumice-Enhanced Ultrafine Cementitious Injection Grouts.

The Branded Pumice Products directory site features use and ideal grade selections for several applications: wood finishing, exfoliant grit, cleansing scrub powders, texturizing grits for paints and primers, soilless grow media for succulents and bonsai, compost amendment, pet care, insect control, and more.