Consumers hold business owners to a high standard. You wouldn't go to a hair stylist with a bad haircut, and you've probably heard the saying "never trust a skinny chef." That's the theory commercial construction company Tri-North Builders kept in mind when building its national headquarters in Madison, Wis. The company set out to create a showcase of the latest in green building technology, and in August of this year the $8 million, 53,000-sq.-ft building achieved a LEED Gold rating.

Green features at the Tri-North headquarters include recycled denim insulation, bamboo and cork flooring, day-lighting, a green roof with indigenous plants and low-water irrigation system, and no-water urinals. The company also recycled 261 tons of construction debris and strove to utilize regional materials whenever possible.

The headquarters parking lot also includes 8,500 sq. ft. of pervious concrete, working in conjunction with asphalt and non-pervious concrete. Tom Geary, head of Tri-North's Concrete Division, explains original plans included the use of porous pavers in the parking lot. Geary saw the project as a chance for him to experiment with pervious concrete, which is a relatively new concept in Wisconsin.

"I went to the owner and pushed for him to allow us to self-perform this aspect of the project. He agreed, and I went to work learning as much as I could about pervious concrete," Geary recalls. Geary got certified as a Pervious Concrete Technician through the National Ready Mixed Concrete Association (NRMCA) and teamed with his local ready-mix supplier, LYCON Inc. in Janesville, Wis., to nail down a mix that worked well. A few test jobs were laid, and Geary was ready for the parking lot project.

On the project
With the pervious slabs at Tri-North, Geary used an air-entrained, no-sand mix with 3⁄8-in. aggregate and 600 lbs. total of cementitious material with a percentage of fly ash. A retardant and VMA (viscosity-modifying admixture) were also used. The mix has a very low water/cement ratio and a zero slump.