Pumice Concrete

There’s nothing new about pumice concrete. The Romans were using it 2000 years ago. Roman engineers and builders have been celebrated for their enduring wonders—especially for the most well-preserved of all Roman architecture, the Pantheon of Rome. The dome itself is a world-class wonder. It was expertly cast using a concrete consisting of hydrated lime cement, fine-grained pumice pozzolan (critical!) and lightweight pumice aggregate.

Modern scientists have determined that the manageable weight of the Pantheon’s huge, unreinforced concrete dome is attributed to lightweight pumice aggregate, while the secret to Pantheon’s (and other Roman structures) longevity is pozzolan: fine-grained pumice (known as pozzolana to the Romans).

Advantages of Lightweight, Insulating Pumice Concrete

Modern pumice concrete formulations are composed of Portland cement, pumice rock, pumice sand, and water. In critical precast or special-duty infrastructure applications, a ultrafine pumice pozzolanic powder (Hess UltraPozz) is also added. Pumice concrete is proportioned, mixed, and placed in a similar manner as conventional sand-and-gravel concrete, is used in the same applications, and is screed, troweled and finished with the same equipment.

Lightweight Concrete

One of the most significant of the advantages of pumice aggregate concrete is its lightweight quality—up to one-third lighter than conventional sand-and-gravel concrete. This trait contributes to a decrease in structural steel costs and, consequently, job costs. Larger volumes of concrete can be handled by lighter equipment with less wear and tear on the equipment.

The reduction of dead load on structural supports, trusses, girders and slabs can allow extra stories on buildings where dead load is a governing factor.

 Lightweight Hess pumice concrete also reduces the live load on formwork and falsework. And of course, the inclusion of fine-ground pumice pozz adds the proven advantages of a pumice pozzolan.

Low Thermal conductivity CONCRETE

The lower thermal conductivity of pumice concrete provides less heat loss. Hess pumice concrete has 4X the R-value of typical sand-and-gravel aggregate concrete. This significant R-value increase both slows heat transfer and eliminates or reduces moisture condensation on walls and ceilings. For those seeking the super-insulating benefits provided by insulated concrete forms (ICF), pumice concrete is the ideal concrete for ICF block walls and decks.

Pumice concrete delivers a higher fire rating that standard concrete and will not spall under contact with direct flame.


Another key factor is workability, particularly in nailing, sawing, and drilling. As for appearance, pumice concrete has a uniform color and texture.

Acoustical ratings are higher for pumice concrete as well.

durability of pumice concrete

Pumice concrete has superior resistance to harsh weather conditions like freezing and thawing. This, plus its inherent high R-value, makes pumice concrete desirable for colder climates and dramatic changes in weather.

Hess pumice concrete is also more elastic, for reduced brittleness under earthquake or high-wind conditions.

The superior water absorption/desorption characteristics of the pumice means that the moisture held in the interior of the pumice aggregate is not immediately available for chemical interaction with cement, so is extremely beneficial in maintaining longer periods of curing, resulting in better strength and reduced permeability in the final concrete. [ASTM Technical Publication 169C]


Lightweight aggregates are reactive, and if used with ordinary Portland cement without the mitigating effects of a reactive pozzolan, the concrete inevitably develops a nasty ASR problem—a reaction between the high silica content in the aggregate and the alkali in the hydrated cement paste. The alkali-silica reaction forms expansive gels that generate a sort of slow-motion explosion, map-cracking and eventually destroying concrete structures from the inside out. Adding a high-quality pozzolan—interestingly—made from the same pumice as the aggregate, but milled to a fine powder, ignites an immediate (secondary) reaction within the hydrated lime paste, consuming the deleterious calcium hydroxide (CH) generated by the primary cementitious reaction and effectively removing one of the needed components to fuel ASR.

The pozzolanic benefits go well beyond ASR mitigation—pumice pozzolan predictably and effectively fortifies against sulfate attack, strengthens and densifies to add incredible longevity, and even reduces heat of hydration cracking. [MORE ON PUMICE POZZOLAN; SEE ALSO: WWW.HESSPOZZ.COM]

Pumice Concrete Products and Applications

Lightweight pumice concretes are ideally suited in applications where 3500 psi or less is acceptable and where thermal and lightweight properties are desired.

•Structures. Homes, industrial facilities, and commercial buildings—especially those located in extreme temperature locations—benefit from the inherent insulative properties (4x R-value; reduced or eliminated moisture condensation) and resistance to freeze/thaw cycles afforded by pumice aggregate concrete.

•Oil Well Cements. Oil and gas wells need to deliver under the harshest of conditions—from deep under the North Sea to the sands of Arabia—and the well cement has to be equal to the challenge.

For over 15 years, Hess Pozz and pumice aggregate has been used by leading oil field service companies to formulate strong, lightweight, flexible, and enduring well annulus concrete.

Our DS-325 Pozz and DS-200 lightweight aggregates are specifically engineered for use in the oil well cementing industry. They provide a superior composite of lightweight slurry, high-strength concrete and a low permeability shield. Additional benefits are imparted by the pozzolanic nature of pumice, providing long-term durability, and up to 4X the insulation value possible with standard aggregates or a straight cement mix.

Hess Standard Pozz DS-325 Hess DS-200 Aggregate
Dx Micron Size Dx Micron Size
D90 0-45 D50 0-45
  ASR Miti•Gator TM D95 0-75

•Synthetic Fracking Sand. Hess produces a carefully refined pumice powder used to make a high-performance synthetic fracking sand.

•PUMICE-BLENDED CEMENT TO MITIGATE ASR. Research done by the University of Utah quantifed the mechanism and effectiveness of pumice-blended cement on creating concrete resistant to alkali-silica reaction (ASR). This resulted in the development and release of the ASR Miti•Gator™ product.

•Manufactured Stone. Pumice aggregates and pumice pozzolan are used extensively in the production of stone and brick veneer products, glass fiber reinforced panels, architectural elements, statuary, and other precast concrete products. Pumice makes the ideal aggregate: it can be economically sized for any needed mold shape, provides bulk and strength yet results in a lightweight product that can be used as interior and exterior finishes without additional supporting ledges. And the consistent clean white color of Hess pumice means the color of every manufactured stone or brick starts and finishes rich and vibrant. [ MORE ]

•Pumice concrete blocks are lighter to lift and place and mean less deadweight loads...and still meet compressive strength requirements. Blocks made with Hess pumice produce a lightweight concrete structure that is the whitest masonry available. This block is popular for commercial, professional, and residential buildings and for decorative uses such as fireplaces, planters and walls.

•Block Fill. Pumice concrete, or even the dry pumice alone, is used as an insulating cavity fill for concrete block walls.

•pumice pozz vs. fly ash. A two-year University of Texas-Austin study (done for the Texas DOT) compares the perfomance of pumice pozzolan with Class F fly ash in concrete over a two-year period.

Mixing and Placing Pumice Concrete

All pumice aggregate should be uniformly prewet to reach total saturation, then be allowed to sit while excess water drains out. This will fill the internal voids of the pumice with water. Prewetting the mix will prevent its drying out on the way to the placement site and slump will be uniform throughout the load, and from load to load. The concrete will also pump well if prewetted.
1 • Handling pumice concrete is very similar to handling normal-weight concrete, and follows the same basic rules for producing quality finished concrete.
2 • Pumice concrete has about two inches less slump than normal-weight concrete for the same consistency and workability. Low-slump pumice concrete will flow when vibrated, and finishers can get on it much sooner when the slump is held to two-to-three inches.
3 • Avoid over-vibrating or over-finishing pumice concrete. When using normal-weight concrete, segregation and over-finishing cause the paste to come to the top. With pumice concrete, it’s the coarse pumice particles that float to the top.
4 • Pumice concrete is cured in the same method as is normal-weight concrete.
5 • Form removal should be delayed for an additional 24 hours for pumice concrete as compared to normal-weight concrete. This applies only if sharp corners are formed, as they are softer for a few days.


•If you’d like to run tests and trials using our pumice in your commercial product formulation or industrial process, please contact us at salesteam@hesspumice.com with your request. We look forward to answering your questions, helping you select the best grade for your process, or helping you explore the fit of pumice for your needs. PLEASE include your name, your company or organization, pertinent project details, ship-to address, and preferred contact information in the sample request email.

pumice store logo

•If you’d like a bit of pumice for personal use, we have a nice selection of pumice grades available to purchase via our Pumice Products Store.


We know pumice. We’ll be glad to answer your questions, join you in your lab for tests, or simply supply a sample for testing—whatever you need.

•SALES: If you need to talk availability, grades or grade blends, logistics, costs...contact Jason Kimberling, Sales Manager, at extension 142 or email salesmgr@hesspumice.com

•RESEARCH: Perhaps you are exploring the possibilities—thinking pumice concrete may fit your particular need, thinking you’d like to see the existing research data, thinking you’d like to do some testing of your own—then we invite you to contact Brian Jeppsen, VP Research and Development, at (208) 766-4777 x111 or email: rd@hesspumice.com

Modern pumice concrete formulations are composed of Portland cement, pumice rock, pumice sand, and water.

Concrete TrucksPumice concrete is proportioned, mixed, and placed in a similar manner as conventional sand-and-gravel concrete.


sunset concrete pour Pumice concrete is proportioned, mixed, and placed in a similar manner as conventional sand-and-gravel concrete. sunset concrete pour Hess pumice concrete has 4X the R-value of typical sand-and-gravel aggregate concrete. offshore drilling rig Well cements made from Hess Pumice aggregates have performance advantages in strength, durability, elasticity, permeability and insulation value over standard concrete.

Concrete Products Magazine CONCRETE PRODUCTS magazine ran an article on our expanding pumice pozzolan processing capabilities and national distribution.

placing concrete The high R-value of pumice concrete makes it ideal for exterior wall applications. pumping concrete Pumice concrete is lightweight and can be pumped over long distances.
Pumice and Concrete Website
Additional information about the various applications of pumice in concrete at the Pumice and Concrete website.
Hess Pozz Website
Extensive pozz information over on the HessPozz.com website. 208.766-4777  •  Malad City, Idaho 83252