British engineers have developed a new environmentally friendly cement that is carbon-negative | Environment | guardian.co.uk

Now this looks really potenially a kind of win-win thing: read about it here British engineers have developed a new environmentally friendly cement that is carbon-negative . And the reason for optimism is, in a nutshell: "Novacem's cement, based on magnesium silicates, not only requires much less heating, it also absorbs large amounts of CO2 as it hardens, making it carbon negative."
Now this is worth putting in a broader perspective: "Making the 2bn tonnes of cement used globally every year pumps out 5% of the world's CO2 emissions - more than the entire aviation industry. And the long-term trends are upwards: a recent report by the French bank Credit Agricole estimated that, by 2020, demand for cement will increase by 50% compared to today."
It'll all come down to cost and availability, I guess. And it may also be worth keeping an eye open for the particular material qualities of the 'crete compared with other materials. One commenter on the article mentions the conservatism of the building industry as a likely retrogressive force...

Climate Engineering Is Doable, as Long as We Never Stop

"Climate scientists Damon Matthews of Concordia University and Ken Caldeira of Stanford ran the numbers on atmospheric geo-engineering through a climate simulation and found that while cranking out carbon dioxide at business-as-usual rates we can geo-engineer our way back toward pre-industrial temperatures in short order, reaching 1900 levels in about five years. Not only that, it would be fairly cheap and easy to do. Pumping 20 to 25 liters of aerosols per second to keep enough particles in the stratosphere would cool temperatures, causing the planet's carbon sinks to suck more carbon dioxide out of the atmosphere. 'That kind of flow rate can be handled by a single fire hose,' said Caldeira. 'For something like $100 million a year you could probably keep a hose in the stratosphere suspended by an array of balloons with pumps along the way. The problem is what happens if we stop short or screw it up."
Climate Engineering Is Doable, as Long as We Never Stop: