Trade war! What is it good for? Whether absolutely nothing or something else, construction will start to find out March 23 when a 25% tariff on imported steel and a 10% tariff on aluminum proposed on March 8 by President Donald Trump takes effect.

Trump had to act by April 11 and April 19, respectively, to impose them under national security provisions in Section 232 of the U.S. Trade Expansion Act based on U.S. Commerce Dept. reports sent to the White House in January. Of proposed options that included quotas and tariffs on all foreign imports, Trump chose tariffs on all countries, with the exception of Canada, the largest exporter of steel into the U.S., and Mexico, the fourth-largest steel exporter. The result could simply divert steel from high-tariff countries to North American producers.