The railway of the future is built on pillars. The high-speed line based on InfraMag trains, is available as an add-on.
Here, the underlying bridge building and especially between concrete and steel are compared.
 

There are three options for buildings as well.

1 heavy traffic with an axle load of 35 tons.
2 ordinary train traffic with an axle load of 18 tonnes
3 light traffic with axle pressure < 10 tonnes widespread loa d

The comparison below is based on version 2

There are only three conceivable materials for building the bridge paths: concrete, steel and wood. But, unfortunately, the wood lacks the required strength properties. The bridge decks on pillars that are built around the world are in most cases cast in concrete. Here we present the pros and cons of using steel or concrete for train bridge tracks, where Steel = steel bridge tracks and Concrete = concrete bridge tracks

Amount of material in one meter of bridge track without pillars ,
Steel:                                       Approx. 5 tons of steel
Concrete:                                Approx. 3.5 tons of steel + approx. 19.7 tons of concrete, total weight 23.2 tons

The calculation is made for high-speed trains with an axle pressure of 18 tons.

Environmental impact in the manufacture of steel or concrete.
Steel: Steel production has large carbon dioxide emissions today, but SSAB currently develops a fossil-free manufacturing of steel expected to be operational in a few years. This provides significant environmental benefits. The amount of steel needed to build train bridge tracks on pillars is a fraction of the amount of concrete.
Concrete: It is well known that cement production is one of the biggest contributors to CO2 emissions in Sweden. The cement industry is also making efforts to reduce carbon dioxide emissions .

Can the material be reused?
Steel:  Steel bridge tracks can be dismantled and re-assembled at another location. The bridge tracks can also be melted down to new steel material.
Concrete: The reinforcement in the concrete can be released and melted down. The concrete can be reused as building/filling material, but is associated with a high cost .

Noise from the train
Steel:  The steel bridges are a noise nuisance if no measures are taken. They can be filled with noise dampening material that removes resonant sounds. A thin layer is laid between the pillars and the bridge girders, which effectively breaks the transmission of sound. The rails are laid in a thin liquid layer that breaks the sound transmission. Thus, the noise level is considerably much lower
Concrete: The concrete bridges with their great weight dampen the sound. However, SKANSKA assesses that the noise level is higher than from trains on embankments.

Handling of the steel/concrete modules
Steel:  The steel bridge girders are 30 meters long and have a maximum weight of 35 tonnes. The production of modules can take place at several locations by already existing producers. The transport from the factory can be done with trucks and ordinary railway wagons, and lifted on site with a mobile crane. No reinforcements of roads or tunnels are needed. All necessary personnel and equipment are available in the country.
Concrete: The concrete bridge girders are 40 meters long and have a total weight of about 925 tons. SKANSKA intends to set up temporary concrete factories along the track. In order not to have to blow up large tunnels for passage with the special machines, factories will be needed on both sides of the tunnel. Special machines and some personnel are brought from China.

Maintenance
Steel: The steel bridge track will need to be repainted every 40 years and today there are paint materials that protect the steel from external influences. The painting work can continue without disturbing the trains. Snow removal in winter is minimal because the snow falls freely to the ground between the beams.
Concrete: Moisture can enter micro-cracks in the concrete and damage the reinforcement. One example is the Öland Bridge, where the problem was solved by adding a completely new layer of concrete to the entire bridge at great expense. The need for snow removal on the bridge track is similar to that for a normal track embankment.

Replacement of damaged bridge track parts
Steel:  The steel bridge deck is composed of modules that can be replaced relatively easily, and in a short time. Thereby, traffic stops will be limited.
Concrete: The concrete bridge deck is built in 40 meter long modules weighing 925 tons. These can only be cast in place with special machines. The repair time risks being long.

Dynamic calculations and resonant frequencies
Steel: The light steel bridge deck is exposed to, among other things, self-oscillations that must be counteracted with an effective damping system. Furthermore, the pillars are provided with support legs where curves or wind conditions require.
Concrete: The concrete bridge deck is inherently heavy enough to dampen the impact of dynamic oscillations.

Seats in the train track
Steel:  The steel bridge girder rests on a column and is attached with a screw connection. By loosening the screw connection and lifting the bridge girder (each bridge girder weighs a maximum of 35 tons), it is easy to put in a spacer that corresponds to the settlement. This can be done quickly and have little impact on traffic flow.
Concrete: The concrete bridge deck rests on roller bearings. By lifting up the 925-ton bridge module, the attachment can be corrected. This requires a special machine for the lift and is a complicated job.

If an accident happens
Steel: The steel bridge track has a space along the track (between the bridge girders) where the train will slide down in the event of a derailment. The train will tilt and rush forward on the bridge track, but it cannot fall off the bridge track. This is what happened to the Shinkansen during an earthquake in Japan.
Concrete: The concrete bridge deck has a design similar to an embankment. In the event of a derailment, the train risks leaving the track area. No guardrail can prevent the train from going through the guardrail and falling to the ground.

Can the bridge track be provided with an alternative future technology with magnetic bearing?
Steel:  Steel bridge tracks can handle the precision of the flat surface that the magnets need to support. Then trains can be run virtually friction-free at low operating costs. Speeds up to 450 - 600 km/h are possible.
Concrete:  Magnetic bearing can be built into concrete bridge decks, but at significantly higher costs than for steel bridge decks.