By Braden Boyd
This article is part of our student collaboration series.
What really happens when you add water to cement? In Dr. Tyler Ley’s educational production of “Hydration Theater”, he answers just that. Broken into five acts, this excursion into the molecular level of cement paste demonstrates what really occurs as cement is hydrated with water! It covers how this aqueous solution of cement and water react with one another in an exothermic way to give us what we know as concrete! The production also offers a fun way to teach those who view it about a critical step in theproduction of concrete. Inthe opening scene, the viewer's attention is captured and held by the enthusiasm of Dr. Tyler Ley and his students, as they convey the process of hydrating a cement grain on stage.
Prologue - First Seconds
The play opens with acement grain, C3S,that has not been hydrated. Aswater is added,and its molecules begin to tear at the cement grain. This attack frees Calcium Ions and Silicon Ions from the cement grain and releases them into the solution. TheOH-and the H+ in the water first reacts with the C3Sof the cement grain and then theC3Aand Gypsum and forms Ettringitein the solution. When thisoccurs, ions still collect and build larger and larger in the background.
Early age C-S-H emerges onto the stage to join the cement grain, forming around it as a kind of protective layer. This occurs due to the reactions of the ions that are still floating in the solution.The water molecules on stage then try and attack the cement grain again, but this time the C-S-H is there to defend it! The dense microstructure of the C-S-H makes it harder for water to reach the cement grain. Still, whilemost of the water molecules are kept out, some were still able to reach the cement grain. (#SAYNOTOH2O) Water molecules continue to try and attack the cement grain, reducing the heat of the molecules and releasing more and more ions.
Image 1: First physical change of the cement grain as it is hydrated by water. The image on the left represents the grain before hydration, and the right after hydration.
Act 2 - Induction Period
This act focuses onthecalcium ions in the solution and how they grow and buildhigher and higher in the solution. Then suddenly Calcium Hydroxide emerges on to the stage and breaks down the C-S-H molecules! This leavingthe cement grain open to a surge of attack from the water molecules. It is during this induction period that the cement is able to be place and worked before it begins to harden.
Image 2: Second physical change of the cement grain as it hydrated by water. The image on the left represents the hydrated cement grain, and the image on the right represents the grain after the ettringite has attached and extended out.
No longer having a layer of C-S-H to protect it, the cement grain begins to bebombarded by water molecules on stage. This leads to the heat of the particle increasing andcauses more C-S-H to form. Then the Ettringite, which had been floating in the solution,attachesto the surface of the C-S-H! TheEttringite then beginsto absorb water and extend out. This again changesthe physical layout of the cement grain, which along with the C3S of the cement grain, providestheinitial strength gain for the cement grain.
The cement grain has now grown dense from all the layers of CSH and ettringite that have formed due to the attacks from the water moleculesthrough the hydration process.The high density of these layers preventing the OH-and H+ of the water from reaching the cement grain. When the water molecules do reach the cement grain, the layersbecome even more densefrom the resulting reaction. This making it even harder forthe water molecules to reach thecement grain again.The reaction between the cement grain and the water is an exothermic reaction, so the cement grain begins to cool as it becomes harder and harder for the water molecules to reach it.
The reaction rate between the cement grain and the water moleculeshas come to an almoststandstill, as the water molecules are unable to reach the C3S inside the grain. Still,the water molecules continue to bombard the cement grain with attackson each side, trying to find a weak point in the structure. The hydrated cement grain withstood the attacks and repelled the water molecules. This is because the process of hydrating cement grains is a fusion controlled reaction. Still,a few of the sneakier watermolecules were able to find ways through the cement grain’s structure and reach the C3S inside. This process continues, and the cement grain again changes its shape, gaining the ability to have friction with other grains and provide true strength. Overall, I found the production of Hydration Theater to be both insightful and educational in how cement grains are hydrated. Theformat itself, aneducational theater production, was something I had not yet been introduced to, and I found it to be a very intriguing and fun way to learn. Dr. Tyler Ley and his enthusiastic cast truly capture the viewers’attention on stage through their enthusiasm as they transition from scene to scene. Through the cast and other means ways of representing cement grains, Dr.Tyler Ley has truly found aninventive and fun way to educate us all on what really happens when water is added to cement grains. I’m not alone in this opinion either!
“Lovely.. expecting more learning videos.. we’re hungry bro”-Arasan K
“This is a great way to learn about hydration of concrete. Highly recommended for anyone who wants a clear and basic understanding of the concept!”-ConcretePavements
These comments are not alone in how many who have seen Hydration Theater feel! Fortunately, theplay has already made its way to video and has been made available to all through YouTube! Wouldn’t you like to be able to explain how hydrating cement really works? To learn what each molecule and charge does as a single cement grain is introduced to water in a fun and new way! Just as many others who have already caught this production, I recommend that everyone find a chance to view this educational production of “Hydration Theater”! Soon you too will be “hungry” for more productions just like it! #Hydration #Theater #HungryForKnowledge
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Dr. Tyler Ley, Ph.D, P.E., is a professor of structural engineering at Oklahoma State University. He was named a Most Influential People in the Concrete Industry by Concrete Construction Magazine in 2019, and was named the outstanding professor at a research university by the Oklahoma Foundation of Excellence in 2018. He has a passion for researching and educating people about what he considers to be the greatest material in the world.