Concrete (2031)

Drill core replaced by grass.

Many older residents of Malmö talk about the floods on August 31, 2014 as the moment when the city inhabitants started to look upon water as both foe and friend. The city experienced immense downpours, resulting in large-scale flooding. Everything was affected — buses were stuck in newly formed urban lakes and family photo albums perished when basements filled with water. For decades, the city had built hard surfaces of concrete and asphalt, which stopped the water from reaching the soil beneath.

After the floods in 2014, much work has been done to adapt the city to a changing climate. House owners avoid using asphalt and concrete, streets and squares are covered with trees and ponds and rivers collect rainwater.

One of the more visible changes is the holes that have appeared in many of the city’s concrete structures. The core on display here was extracted from a square in 2028. By drilling holes in the concrete and planting grass in these, the square turned green! The cores were then recycled and used in new buildings in the city to meet rules for circularity in construction.

Concrete did not just increase the risk of flooding, its production also had a big environmental impact. In 2019, two-thirds of all buildings in the world were built using reinforced concrete. This required vast amounts of sand extracted from sea, lake and riverbeds, as not all sand is fit for this purpose—for instance, grain size and shape disqualify desert sand.

Accessible sand is still in short supply, and sand mining was very damaging to marine ecosystems and caused erosion in coastal areas. On top of that, the production of cement released a lot of greenhouse gasses, up to eight percent of the world’s total emissions when the Paris Agreement was signed.

The fact that the chemical reaction in cement production was the cause of the majority of emissions made the transition harder than when it came to the energy system—instead, the production and consumption of cement had to be drastically reduced.

Today, we exclusively use recycled cement, bio-cement and some CCS cement—but in substantially reduced quantities. Instead, wood buildings have experienced a renaissance. Skyscrapers in wood have popped up in most large cities!

Circularity: Economic models where materials are reused and recycled, rather than extracted and disposed. Such models try to create more value and less waste by “closing the loop”.

Bio-cement: Building material made from microorganisms, similar to how corals build their reefs.

Reinforced concrete: Concrete cast around a grid of iron bars, which increases the strength of the material.

CCS cement: In traditional cement production, limestone and sand is heated in a cement kiln to a thousand degrees Celsius. Here, a chemical reaction produces a so-called clinker that is then broken down into cement. This chemical process emits carbon dioxide, about half of which originate directly from the chemical reaction and the other half from the fuel used to heat the kiln. In CCS cement, the carbon dioxide is separated and stored underground, see CCS.

(Coastal) erosion: A natural process where sediment is transported by waves, streams and wind to accumulate at another location. This process has been accelerated due to sea level rise caused by climate change. Coasts in southern Swedish are particularly affected since the ground is not rising, as in the rest of Sweden. Sand mining also accelerates erosion.

This text is part of the future scenario and study material Beyond the Fossil Era.

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