ZURICH--LafargeHolcim Ltd. (LHN.EB) Chief Executive Eric Olsen said Thursday that proposals for massive U.S. infrastructure spending, as well as other projects around the world, should help maintain a healthy flow of demand for the world's largest building materials company by sales, but cautioned that questions remain over the potential funding for such projects.

"Infrastructure is a real theme and the U.S. is certainly a part of that theme," Mr. Olsen said in an interview at the company's headquarters near Zurich. "I'm convinced good infrastructure investment pays off three times what you put into it but you need to have the capital up front and debt levels are high in many governments."

In a speech to Congress on Tuesday, U.S. President Donald Trump repeated his pledge to rebuild America's roads and bridges through a $1 trillion infrastructure program. "To launch our national rebuilding, I will be asking Congress to approve legislation that produces a $1 trillion investment in infrastructure of the United States--financed through both public and private capital--creating millions of new jobs," he said.

"You see the commitment, you see the need, now we need to make sure that the funding is in place to be able to do it," said Mr. Olsen.

Shares in LafargeHolcim rose Thursday after it said that it returned to profit last year despite a drop in revenue, helped by cost-cutting and the absence of impairment charges that weighed on the combined performance of component companies Lafarge and Holcim when they merged in 2015.

LafargeHolcim posted net profit of 1.79 billion Swiss francs ($1.81 billion) in the year to Dec. 31, a turnaround from a pro forma net loss of CHF2.12 billion the previous year.

The company said net sales last year were CHF26.9 billion, down 8.7% from the previous year. The combined group's closely watched operating profit before interest, taxes, depreciation and amortization, rose 13% to CHF5.8 billion.

"Earnings momentum remains strong and valuation attractive," said analysts at Vontobel Research, which confirmed its buy rating on the stock. LafargeHolcim shares were up 3.5% at 1130 GMT.

Separately, the company disclosed the findings of an internal review of Lafarge's operations in Syria in 2013 and 2014 related to alleged dealings with some armed groups to ensure the safety of plant employees.

"It appears from the investigation that the local company provided funds to third parties to work out arrangements with a number of these armed groups, including sanctioned parties, in order to maintain operations and ensure safe passage of employees and supplies to and from the plant," LafargeHolcim said.

"In hindsight, the measures required to continue operations at the plant were unacceptable," it said, adding that the reported allegations aren't expected to have any material financial impact on the company.

-Write to Brian Blackstone at brian.blackstone@wsj.com