The Aug. 7 completion of the world’s largest concrete-arch railroad bridge, which reaches 384 meters, at the Alcantara reservoir in western Spain adds another link in the nation’s big and growing high-speed network. But as the pace of new construction at home slows in hard economic times, Spanish contractors, such as Madrid-based FCC Construcción S.A., are searching overseas for more opportunities.

“Due to economic constraints, the [Spanish] projects are now focused first to improve conventional lines,” says Pedro Cavero, head of railroad work at FCC. That firm and Spain’s other big contractors now aim to export their expertise to markets including the U.S. and U.K.

FCC, reporting $2.2 billion in 2015 revenue and ranking at No. 83 on ENR’s Top 250 International Contractors list, is putting finishing touches to the Almonte arch bridge on the Madrid-Extremadura line. The newly completed crossing rises some 70 m from abutments to straddle the entrance of the Alcantara reservoir between Plasencia and Badajoz. It is now the world’s longest in steel or concrete built for high-speed trains, according to the national railroad infrastructure manager ADIF. It is also the world’s third-longest concrete arch for any use.

ADIF considered various options for the crossing, including steelwork and cable stays, says Pablo Jimenez, the owner’s project manager. In terms of whole-life cost, the concrete arch is the most economical, he says, explaining that it is “much better than a cable-stayed bridge.”

Pairs of octagonal sectioned legs of the arch rise from each abutment and merge 90 m away into a single box forming the central span. The arch depth reduces from 6.9 m at abutments to 4.8 m at the crown.

ADIF and its design joint venture— Arenas y Asociados, Madrid, and IDOM Ingeneria y Consultoria, Bilbao—ruled out using a temporary pier in the river to ease arch erection. The shape and depth of the riverbed and variable water levels were too difficult, says Jimenez.

So, the joint venture, 85% owned by FCC, built the arch with cast-in-place concrete. As it grew, the arch was tied back to the abutment piers with stay cables. The upper cables were anchored to a 54.6-m-tall temporary tower at either abutment.

To meet long-term design requirements, the arch’s concrete strength had to exceed 80 MPa at 28 days. It also needed to be self-compacting to flow around the densely packed rebar, says Cavero, who was the original project manager. “We had no experience … with this kind of concrete in Spain,” he adds.

And the challenge intensified with the need to achieve sufficient short-term concrete strength of around 40 MPa for the required 10- to 12-hour formwork striking time to fit the 10-day casting cycle, he adds.

Fortunately for the contractor, Cementos Portland Valderrivas Group, an FCC affiliate, had developed but not yet launched a sulphate-resistant, high-strength cement called UltraVal.

“We told them, ‘OK, let’s test it,’ ” says Cavero. Laboratory tests and a full-scale trial pour confirmed the mix design.

While the contractors overcame early technical challenges, the project fell victim to Spain’s austerity economy following the global banking crisis. Construction initially was due to last 32 months, starting in February 2011. But the schedule was tailored to available funding, extending the completion date to August 2016.

In addition to delays, design changes that required complicated temporary works also contributed to a roughly 30% hike in the viaduct’s cost, says Cavero. Originally, the whole contract covering 6.3 kilometers of line was valued at $91.5 million, including $51.3 million for the Almonte viaduct. The need to include around 2,000 tonnes of extra rebar in the structure to accommodate temporary load was a major inflationary factor, he adds.

Logistics were more troublesome on another high-speed project, about 320 km northeast of the viaduct on the Madrid-Galicia line. FCC is in an equal joint venture with Acciona Infraestructuras S.A. to build roughly 6-km-long twin bores of the Bolaños Tunnel. ADIF bid each bore separately and combined both contracts after their award, says Juan Margareto, FCC’s deputy project director.

“There was nothing here,” says Margareto, speaking of the remote spot near Campobecerros in Ourense province. Instead of setting up polluting diesel generators, the contractor built, at a cost of $4.5 million, a 35-km line to the main grid, with a third underground; it also installed a 95-cu-m-per-hour water-recycling plant to preserve the small local river. The company has effectively become the local highway authority, maintaining and improving local routes.

A Strong Track Record

Having been at the birth of Spain’s high-speed system in the late 1980s, FCC is among a handful of large local contractors to have developed the network into one of the most extensive in the world.

Now exceeding 3,000 km, the Spanish system carries 31 million passengers a year at 310 km per hour and accounts for more than half of all national rail travel, according ADIF.

In the decade to 2014, Spain invested about $40 billion in high speed at a total cost per km of $10.5 million to $24.3 million. Of this, civil construction accounts for $6 million to $16.3 million.

European Union grants account for about a fifth of the investment, with ADIF raising debt and receiving government capital to make up the balance.

“The big market in Spain forced our companies to operate at the top level,” says an ADIF spokesman. A policy of awarding relatively small contract packages to encourage small and medium contractors has inadvertently protected the market from big foreign rivals.

Spanish contractors “are so strong, there is no way foreign companies will come in,” says Cavero.

While the home markets seem secure, Spanish contractors are exporting their expertise. In the U.S., FCC is teamed with compatriot firm Corsan-Corviam Construccion S.A. in one of five consortiums bidding for a 35.4-km section of California’s high-speed project. Spain’s Ferrovial Agroman S.A. is among rival bidders for the $400-million to $500-million Central Valley contract.

Last year, FCC joined an existing joint venture of two U.K. contractors that is short-listed for three packages on the planned high-speed London- Birmingham line, HS2. Together, the contracts are valued at $3.2 billion to $5.3 billion. Spanish contractors Acciona Infraestructuras S.A., Dragados S.A. and Ferrovial Agroman also are bidding in different teams.