While aviation and ground transport get lots of well-deserved attention, in terms of their climate change impact, the concrete industry seems to get a lot less scrutiny. In a way, this is unsurprising; concrete is hardly glamorous stuff. At the same time, concrete production accounts for about 5% of all greenhouse gas emissions: mostly from the process of manufacturing clinker by heating limestone and clay. This is usually done using coal. The average tonne of concrete produced generates about 800kg of carbon dioxide: both as a result of the coal burning and the product of the chemical reaction involved (CaCO3 -> CaO and CO2, ignoring silicates). This figure does not include emissions relating to quarrying rock or transport.
Cement manufacture can be incrementally improved in three ways: by reducing the ratio of clinker to other additives, by making kilns more efficient, and by using fuels other than coal for the heating. All of these can make contributions, to a certain degree, but only a complete shift to biomass heating could have a terribly significant effect on greenhouse gas emissions (and that effect could be moderated by the emissions from transporting the biomass).
Demand for cement is growing at about 5% a year, and is partially driven by the construction of new hydroelectric dams and nuclear power plants. At present, the rate of demand increase exceeds the rate of efficiency improvements. As such, greenhouse gas emissions associated with concrete are increasing every year. The average North American home uses about 25 tonnes of concrete, mostly in the foundation.
George Monbiot discusses concrete in his book, focusing on geopolymeric cements as a solution. Carbon capture and storage (CCS) is theoretically possible, but with an added problem. Concrete plants must be sited near limestone quarries. These are not necessarily near the salt domes or aquifers where CCS can probably be most effectively deployed. Geopolymeric cements are similar to the pozzolan cement used by the Romans to build the roof of the Pantheon. They are made from clay, certain kinds of sedimentary rock, and industrial wastes. Producing them generates 80-90% less carbon dioxide. This is because they require a lot less heating and the chemical reaction that produces them does not generate CO2 directly.
The modern version of this material was only developed in the 1970s and has yet to be widely adopted. Partly, that is because of the cost of refitting existing cement works or building new ones. Partly, it reflects the hesitation of the construction industry to use new materials. Such objections can probably be most efficiently addressed through carbon pricing. If the concrete and construction industries were paying for those 800kg of CO2, the incentives they face would probably change decisively and fast.