Lighter and better: new technologies and products can lighten concrete

Concrete Producer, The, July, 2004 by Rick Yelton

Like the weight-conscience public, designers and architects are interested in innovative approaches and ingredients to help lighten concrete. Whether the goal is to provide more sustainable structures or longer, sleeker bridges, designers and architects are embracing new ways to use concrete, especially when the elements weigh less, yet perform similarly to standard concrete.

Their quest isn't new. Producers have traditionally satisfied this demand with concretes batched with lightweight materials, such as scoria or expanded shale and slate, as replacements for normal coarse aggregate. Contractors added foam to the cement mortar in some special flatwork applications such as roofing and elevated floors.

Now, the concrete design community will have even more opportunities to lighten up, as a number of new products and services have recently been made available in North America. Several were introduced at World of Concrete in February and at BAUMA in March in Munich, Germany.

For concrete producers interested in expanding their product offerings and operations, here are some new systems and products.

Better forming with foam

Not new in the true sense of the word, ready-mixed producers of commercial concrete have used cellular concrete to tighten controls on entrained air levels at 5% to 10%. And at higher concentrations, mix design engineers used the admixture to batch economical flowable fill. But Dallas-based Miracon Technologies reports that since the Miracon foaming process was introduced three years ago, precast producers have used it in more applications. This is an effective way to increase casting-bed productivity and cast lighter, more durable products.

Producers can lighten products in most of their sales categories. For example, the system can be used to reduce the weight of non-structural lightweight concrete elements, like controlled vaults or manhole risers, where weight reduction of 30% to 50% is desired, and ultimate 28-day compressive strength needs to be in the 2000 psi to 4000 psi range. Some producers have also used the system to cast structural, high-strength, lightweight concrete, with final product densities of 100 pcf to 120 pcf while achieving ultimate strengths of 2500 psi to more than 7500 psi. Producers say the foam system also is an economical alternative to lightweight aggregate.

Designers have engineered the foaming system to be a plant-dispensed product. The producer installs the manufacturer's automated technology in the production sequence. During installation, the dispenser's controller is integrated into the producer's automatic hatching system. The integration ensures proper proportions of chemical concentrate and water are hatched so they are mixed with consistent accuracy, regardless of run time.

The system produces repeatable, stable results. The foam generation device handles typical production ranges found in a plant, pumping out high production volumes, with a foam generation capacity of 22 cubic feet per minute, or accurately dispensing 0.5 cubic feet for small jobs.

Along with the specially designed plant dispensing equipment, the manufacturer supplies a foam chemistry that results in strong bubbles that have at least a one-hour life in wet concrete, even in a truck's mixer drum. The patented chemical is a formulation of specially blended polymers. Producers find the foam produces a cellular concrete that is stable even with high slumps producing high-flow characteristics. This is even true when concrete is hatched at water-cement ratios as low as a 0.25 for precast operations or 0.30 for ready-mixed concrete.

To learn more about the Miracon foaming system, visit www.miracontech.com, telephone 972-387-3099, or circle 2 on the reader service card.

From the source

Old World quality has a new meaning as North American producers can now buy aggregate mined from the site that was the world's initial source of lightweight pumice. Introduced to producers at World of Concrete, Pumex is a lightweight pumice that has been widely used in Europe. Visitors to the Pumex booth were enthusiastic about the introduction, says Timo Puig, the Italian manufacturer's international sales manager.

Puig believes the lightweight aggregate has great potential in the U.S. market. The manufacturer plans to sign large aggregate suppliers for distribution. They ship in bulk internationally. While they primarily target block producers, Puig also hopes to encourage using the lightweight pumice in geotectonic applications and lightweight precast concrete.

To learn more, visit PUMEX S.p.A. at www.pumex.it, e-mail Timo Puig, sales manager, at pmxcomm@tin.it, or telephone 39 02 6671 0195.

Bubbles for ecology

Developed by a Hungarian research scientist, Geofil is a new lightweight material introduced in North America at World of Concrete by Geofil Holding Schweiz AG of Switzerland. The product is a manufactured filler that uses recycled glass as its source. It comes in five different sizes to fit a wide range of mix design needs. The material is carefully ground and shaped to meet tight product parameters.