Left: Sand-lime blocks are similar to standard gray blocks in the United States. Right: Most presses can manufacture sand-lime blocks in sizes ranging from face brick to much larger blocks.

While concrete is the most utilized building material in the world, what do you think is number two? Some might suggest wood. Others, especially business executives from the United States and Canada, might suggest brick or masonry block. But after visiting bauma in Germany in April, I realize that there are many materials with which to build a structure.

One item that caught my attention was the European material called calcium silicate, commonly called sand-lime block. At first glance, it's difficult to distinguish these units from our familiar concrete block. Sand-lime blocks are very similar in size and shape to the standard gray block used in the United States.

But on closer examination, I discovered sand-lime block has some superior qualities compared to standard grays. The units can be produced to very tight dimensional tolerances. Their facings show a very consistent grain. And the process is versatile, as the material can be cast as either hollow or solid units for structural applications or facades. And sand-lime blocks have one key advantage over concrete blocks. Lacking any soluble salts, they don't suffer from efflorescence.

Calcium silicate units are made from a mixture of sand, lime, and water. Properly mixed, the mortar is pressed into molds using high-speed rotary presses. The green units then are conveyed into an autoclave where they are pressure-heated until cured. The same mold presses can form units ranging from the size of face brick to large blocks. Most plants are very automated with production rates very high, thus requiring fewer employees.

Convincing producers

This white block has been a tough sell to producers, says Mike Gill, president of Lasco Engineering of Detroit. His firm represents one of Europe's largest sand-lime block machine manufacturers in the United States. Producers are skeptical of the process, especially when they learn of the autoclave. “I try to explain that the autoclave is nothing more than an advanced curing system, but there's still some reluctance to invest in the technology,” he says.

But Gill cites three reasons why there has been renewed interest in sand-lime production outside of Europe. First, the turnkey plants that have recently been introduced in Europe are very labor efficient and easy to operate. Second, many newer plants in Europe have successfully incorporated a large percentage of fly ash into the mix recipes, radically reducing unit costs. Third, many producers find the exacting production process effective in casting architectural quality units that can earn high sales prices.

Sand-lime units aren't exactly unknown in North America. There are a few producers casting product that conform to the ASTM C 73-05 Standard Specification for Calcium Silicate Brick (sand-lime brick), usually as cast stone elements.

One producer who many recognize as the leader in domestic sand-lime production is Arriscraft. Headquartered at Cambridge, Ontario, Arriscraft operates two plants in Canada and one in Fort Valley, Ga. Due to an increase in demand for architectural elements for residential construction, the producer recently announced it will add a second production line toward the end of the year.

Visit Lasco Umformtechnik,or telephone Lasco Engineering at 313-579-7169.