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A New Foundation: Replacing Cement

Writer's picture: Sophie O'BrienSophie O'Brien

Cement is the glue of our society: we need it to construct buildings and critical infrastructure in cities and towns. Cement is mixed with water to form concrete, and is the second most consumed material after water. However, beyond newly paved roads and construction sites, the production of cement is responsible for about eight percent of total carbon emissions, which means that it is imperative to find alternatives to meet sustainability targets. In this blog post, we’ll share some background information about cement and discuss bioinspired initiatives to lighten its carbon footprint.


Cement production process

Cement is produced from the profuse burning of fossil fuels such as coal and petroleum coke in cement kilns to heat raw materials to very high temperatures (~1,500 ºC). The process relies on the extraction of raw materials like limestone, clay, and sand, which further propels mining industries. The heat from the kiln induces a chemical reaction that transforms the limestone into clinker (a combination of fused and sintered substances), which is then ground together with gypsum to form cement. A byproduct of this reaction is carbon dioxide, which occurs from fuel burning and during calcination in which limestone is heated to release CO2 from calcium carbonate within the limestone.


Properties of cement

As you now understand, cement production is highly energy intensive, so you may be asking yourself “Why do we go to such lengths to use this material anyways?” The answer lies in cement's special properties that make it an essential material for construction and the lack of a readily available alternative that can be scaled to the same level as the cement industry. Cement possesses unique binding properties such that, in the presence of water, it undergoes a reaction known as hydration that forms an extremely strong, adhesive paste. During hydration, calcium silicate compounds in cement react with the molecules in water to produce calcium silicate hydrate gel. As hydration progresses, the gel forms a network of microscopic-level structures composed of covalently-bonded silicon and oxygen atoms, constructing a dense and compacted matrix. Over time this gel then hardens and binds together with a variety of added aggregates (e.g. sand and ground rock) to form an infusible solid for construction-concrete. The longevity of cement is rooted in its chemical composition as well as its resistance to the environment, such as extreme temperature, moisture, and biological degradation, making cement a very low-maintenance material post-construction.


Designing cement from the bottom up

In order to relieve cement’s intense carbon footprint, researchers are currently diving into multiple ways of re-designing cement using a bioinspired approach.


One approach is harnessing the highly organized nano-composition of sea urchin spines to produce elastic concrete materials (1). Although concrete must be solid and strong for the construction of buildings and skyscrapers, it is important to keep in mind the necessity of flexibility that allows for safe infrastructure that can withstand environmental factors without any damage to the structural integrity of the building (e.g. how skyscrapers can shift several feet with the wind). By utilizing the highly ordered calcium silicate hydrate nanoplatelets interspaced with a polymeric binder inspired by sea urchins, the current random bonds found in cement could be vastly improved with these organic hybrids. This process would refashion cement to have a bending strength comparable to a seashell, which would overall increase the longevity of concrete to reduce the production of cement along with reducing the production of carbon dioxide.


A second bioinspired approach to cement might include introducing bio-based additives in the formation of new hydraulic cement or methods to increase the longevity of existing cement and concrete structures so that less cement needs to be manufactured globally. One interesting approach is to use microbes for long-lasting, rapid, and active crack repair.(2) Microbial “self-healing” can work because of the ability of microorganisms, in particular certain bacteria (such as Bacillus sphaericus) to produce calcium carbonate (CaCO3) through autotrophic pathways that consume CO2. There are also heterotrophic pathways too that can result in “biomineralization”, referring to the ability of microorganisms to feed on and then mineralize components around them. Can we let the bacteria do the job of extending the life of cement while taking CO2 out of the atmosphere?


For more information on both of these exciting technologies, see the links to their published journal articles:

  1. Andreas Picker et al., Mesocrystalline calcium silicate hydrate: A bioinspired route toward elastic concrete materials. Sci. Adv., 3 ,e1701216(2017).DOI:10.1126/sciadv.1701216

  2. S. Udhaya, et al., “Experimental study on bio-concrete for sustainable construction”, Materials Today: 2023, https://doi.org/10.1016/j.matpr.2023.03.676.


Spotlight: Take a look at this company, a start-up that is designing biocement: https://biomason.com/. Biotech and Cement - the intersection of two major industries. Let’s see if they can come up with something!


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