Sulfur Concrete in Plain English

We’ve introduced Dr. Marwa Al-Ansary to you as a civil and environmental engineer, working for Shell on (amongst others) sulfur utilization in materials such as Thiocrete (a type of sulfur concrete).

But what is sulfur concrete really, and why do we care about this? As with many questions we might have, Wikipedia has an answer to that:

"Sulfur concrete is a composite construction material, composed of sulfur, aggregate (generally a coarse aggregate made of gravel or crushed rocks and a fine aggregate such as sand). Cement (commonly Portland cement) and water important compounds in normal concrete are not part of sulfur concrete. The concrete is heated above the melting point of sulfur ca. 140°C. After cooling the concrete reaches a high strength, not needing a prolonged curing like normal concrete. Sulfur concrete is resistant to some compounds like acids which attack normal concrete. Sulfur concrete was developed and promoted as building material to get rid of large amounts of stored sulfur produced by hydrodesulfurization of gas and oil. Sulfur concrete is also a possible building material for a lunar base. Up to 2011 Sulfur concrete is only used in small quantities when fast curing or acid resistance is necessary."

Sadly enough, Wikipedia is using a lot of jargon in this explanation. The explanation focuses on the following topics:

What ingredients do we need for sulfur concrete?
Regular concrete is a combination of sand, stones, cement and water. For those of you that like to DIY around in the backyard, you might be familiar with the 1-2-3 and 1-2-4 recipes of throwing it all together and making fresh concrete. Sulfur concrete on the other hand is made without water, and without cement: it’s simply sulfur, sand and stones.

How do we make sulfur concrete?
Unlike regular concrete, in which you mix everything together, get a liquid product and then wait, sulfur concrete is made by heating the sulfur product with the stones and sand such that they get glued together. This process is similar to making asphalt. Upon cooling, the product has its final strength, and you don’t need to wait like with regular concrete, which reaches its strength over time.

What are the benefits of sulfur concrete as compared to normal concrete?
Sulfur concrete is made without water and cement. As a result, the costs and energy for water supply becomes obsolete. Moreover, the carbon footprint of the product is reduced. Regular concrete leaves a large carbon footprint because the production of cement requires very high (1450^oC) temperatures and the process itself is responsible for 5% of all CO₂ emission worldwide.

In regular concrete, the cement forms “tubes” inside the material which can take in water. Upon freezing, this water expands and the inner pressure can become so high that the concrete cracks. Sulfur concrete does not have these tubes, and therefore performs better in freeze-thaw cycles.
As sulfur concrete is made by heating the components, it can also be recycled by crushing, reheating and remolding, reducing the waste associated with regular concrete construction.
If you’ve made regular concrete before, you’ve seen that at first it is almost liquid, and then it starts building up its strength over time (we typically test it after 28 days to see how strong it is). Sulfur concrete gains it strength right when it is made – upon cooling down the product has its final strength.

Why is Shell making concrete?
Sulfur is a byproduct from the process of refining gas and oil. To look for ways to implement this product, Shell stimulated research into sulfur concrete, using a sulfur-product to replace part of the bitumen in asphalt and innovative fertilizers for agriculture.

Is it a new invention?
Sulfur concrete has been around since the 1970s. However, because the cost of the modification of sulfur for use in concrete used to be very high, the range of applications was rather small. Now, with the development of the competitively-priced sulfur-concrete binder, the product can finally compete with regular concrete in price, and a wide range of possibilities opens up.

What’s the caveat?
As you can recycle sulfur concrete by heating it up to 135^oC, it is not suitable for applications which require temperatures of above 100^oC. Therefore, building with this product will require the right provisions such that in the case of a fire, the structure is safe (and doesn’t “melt down”).



This post originally appeared on the TEDx Delft website.

Why Blend In if you can Stand Out?

I initially wanted to blog about Dr. Marwa Al-Ansary because she is a female civil engineer and researcher, working on concrete (sulfur concrete) who enjoys writing a poetry – enough to entice my curiosity! Little did I know about the bold decisions she made in her life to pursue her interests, and her performance has left me in full admiration.

From Egypt to the United Kingdom to Qatar to the Netherlands – this researcher, engineer, woman has come a  long way to pursue her dreams.


Marwa grew up in a family with mostly boys, and from an early ago on, she’d tell everybody: “I want to become an engineer”. Growing up with so many boys around her, her family was worried, and wondered how they could raise her to become a lady. They grew even more worried when it turned out that her childhood hobby became collecting waste materials and taking that into her bedroom. No one understood her treasure hunts and only saw a kid carrying rubbish into her house. She proudly announced on the TEDxDelft stage today that, 15 years later, she got a degree certifying her to work on other people’s rubbish!

As a young child, she showcased her researcher’s spirit, by always asking questions. Her science teachers were not too happy having her in the classroom – she’d ask question that were either too difficult or too stupid, as they said.

When she graduated with the highest honors from secondary school, she ran home to bring the good news to her family, and tell them that she now finally can go and pursue her dream of becoming an engineer. But her family didn’t approve of her choice, so with a heavy heart she started med school, and 2 weeks later announced she made a switch to mass communications to become a journalist. But secretly, she had enrolled in engineering – and this remained a secret for the next two years. When her mother discovered that secret, she decided to stand up for herself and stay in engineering. However, she made a promise to her family, that one day she’d become a Doctor in Engineering and fulfill her mother’s dream that her daughter would become a Doctor – a promise she kept.

When she decided to stand up for her dream and become an engineer, it was the first time that she went her way and took a bold decision. Many years later, when she was finalizing her PhD in Cambridge, she renounced a promising offer for an academic career and instead decided to join the oil and gas industry. Her adviser thought it was a terrible idea, but she just smiled and took the challenge. Five patents and two international awards later, she again has proven that as the odd duck she can truly make a change.

Sometimes we worry so much about how to blend in, how to conform to others, that we forget ourselves, Marwa explains. We hold ourselves back, while our diversity and different views can truly make a difference. She sums it all up by saying: ” Why do you want to blend in, when you have the opportunity to stand out?”

This post originally appeared on the TEDx Delft website as a live blog during the event.