Many CalPortland drivers are unionized, and he expects a tax cut to produce demands for the wage increases that Republican sponsors said the tax plan would generate. Mr. Regis said he would like to oblige, but wasn’t sure which of the company’s priorities would win out.

Mr. Regis, who says he “leans to the right,” said he believed in the economic logic of cutting corporate taxes to 20 percent from 35 percent. Yet he’s worried about how the Republicans in Congress are pushing through their tax bills, quickly and without the support of Democrats. Can a business count on the provisions of a law that the other side might try to rewrite in a couple of years?

“I think it’s bad news for the country to have one side make the rules,” Mr. Regis said. “It was bad when they passed the health care bill; it’s bad now if they pass the tax bill.”

The uncertainty is particularly frustrating for a company like CalPortland, since its biggest spending commitments often have to be made far in advance. And the tax bills have fleeting components, like the idea of allowing companies to take the entire cost of equipment off their taxable income the year they start using it. In the House bill, that provision expires after five years. In the Senate version, it phases out gradually after five years and ends by the 10th year, 2027.

In Washington, five or 10 years may be a lifetime. But CalPortland probably could not even get the permits for a new cement plant in that amount of time. The company, Mr. Regis noted, is not popping out iPhones — it is blowing up rocks in the desert.