Siegel substitutes fly ash for cement in about half of the firm's concrete installations. “We started using it because it was green, and we use more of it now because it slows the curing time, leading to less porous and stronger concrete,” he says. Fly ash comes from waste produced by coal-fueled power plants. “Plus,” says Siegel, “most local concrete suppliers carry it and contractors like working with it more.” Headwaters Resources, 800.236.6236;


Henry Siegel, FAIA
siegel & strain architects
emeryville, calif.