Cement

What is important about Cement

Cement is the active ingredient that goes into making concrete. Cement along with water, sand and aggregates of varying ratios is used to make the construction material, concrete. Concrete, invented in Roman times, is used extensively in buildings, bridges and roads. Growth in the developing world is expected to increase the demand for more and more cement. Given its CO₂ emissions from both the burned fuel used in cement kilns and the decomposition of calcium carbonate rocks to lime (calcium oxide), it's a problem. There is progress in alternatives to cement, different chemistries and reducing usage.

Worldwide, cement manufacturing currently generates 8% of global warming CO₂ emissions as reported in:

Making Concrete Change: Innovation in Low-carbon Cement and Concrete - Chatham House - June 2018

"To bring the cement sector in line with the Paris Agreement on climate change, its annual emissions will need to fall by at least 16 per cent by 2030."

Reducing CO2 Emissions

Solar Cement Processing (5% anthropogenic C0₂ Source, also George Washington University, 2012)

"Solar thermal process produces cement with no carbon dioxide emissions" - Phys.org - Lisa Zyga - April 10, 2012

Reinventing Cement report

"The Race to Reinvent Cement" - Anthopocene Magazine - Akshat Rathi - 2017

Reducing Cement Usage

Environmentally friendly concrete is discussed in:

"In Pursuit of Environmentally-Friendly Concrete" - Building Enclosure - August 2, 2019

where alternative mixes (recipes) are reviewed.

Green Cement

From Wikipedia on Cement

“Green cement is a cementitious material that meets or exceeds the functional performance capabilities of ordinary Portland cement by incorporating and optimizing recycled materials, thereby reducing consumption of natural raw materials, water, and energy, resulting in a more sustainable construction material.

New manufacturing processes for producing green cement are being researched with the goal to reduce, or even eliminate, the production and release of damaging pollutants and greenhouse gasses, particularly CO₂.

Growing environmental concerns and the increasing cost of fuels of fossil origin have resulted in many countries in a sharp reduction of the resources needed to produce cement and effluents (dust and exhaust gases).

A team at the University of Edinburgh has developed the 'DUPE' process based on the microbial activity of Sporosarcina pasteurii, a bacterium precipitating calcium carbonate, which, when mixed with sand and urine, can produce mortar blocks with a compressive strength 70 % of that of conventional construction materials.”

Innovative Cement Technologies in Development

Brimstone

Brismtone a California startup, claims to make cement from carbon-free calcium silicate rocks, eliminating these process emissions from the start. Calcium silicate rocks are abundant and voluminous at the surface of every continent in the world.

Cement industry accounts for about 8% of CO2 emissions. One startup seeks to change that. - CBS News - January 2023.

Sublime Systems Electrochemical Cement

Sublime Systems are developing an electrochemical process to produce lime (CaO) at room temperature using renewable energy and no carbon emissions.

Cement made at ambient temperature, using renewable electricity, for a decarbonized future - Ellis and Chiang - Medium, January 18, 2023

Swinburne University

Bendable concrete goes cement-free to cut environmental footprint - New Atlas - Michael Irving - March 03, 2020

Bendable, Green, and Cement-Free Concrete Created to Better Withstand Earthquakes - Interesting Engineering - Loukia Papadopoulos - March 05, 2020

Solida Technonogies

URL: https://solidiatech.com/

“At scale, each year Solidia’s Technologies will be able to reduce:

• the carbon footprint of concrete by up to 70%, equaling 1.5 gigatonnes or ~4% of the world’s CO₂ emissions, with the potential to do more;
• water usage up to 100%, avoiding the consumption of 3 trillion gallons of fresh water…enough to fill 1 million Olympic swimming pools;
• energy consumption at cement plants equal to ~260 million barrels of oil/year (or 67 million tonnes of coal); and
• landfills by eliminating at least 100 million tonnes of concrete waste,
• …while transforming CO₂ into a valuable commodity.”

Using a proprietary cement that’s not Portland they cure concrete blocks in 100% CO₂ chambers. The CO₂ comes from sources that would otherwise be vented to the atmosphere. So this reduces emissions. Such precast concrete can be 15-50% of the local market.

CarbonCure Technologies

URL: https://www.carboncure.com/

Like Solida CarboCure aims to cure concrete blocks in 100% CO₂ chambers but with regular Portland cement. The CO₂ comes from sources that would otherwise be vented to the atmosphere thus reducing emissions.

Calix Cement and Lime

URL: https://www.calix.global/industries/industry-cement-lime/

Their kilns separate the limestone from the source of heat (fired natural gas instead of commonly used coal) and separately captures the CO₂ for other uses, e.g. for CarbonCure concrete.

Carbicrete

URL: http://carbicrete.com/

Uses slag a byproduct of steel-making instead of limestone to make ‘cement-free’ concrete.