Hamlin M. Jennings, adjunct professor in the Department of Civil and Environmental Engineering and principal investigator in the Concrete Sustainability Hub, died on July 8 at his home in Cambridge, Massachusetts, after a battle with cancer. He was 68.

A prominent scientist and engineer, Jennings was widely recognized as a preeminent researcher and leader in the field of cement chemistry. He developed fundamentals of cement sciences that were transformational in concrete engineering applications, including the first fully quantitative model of the nanostructure of calcium silicate hydrate (C-S-H), the major component of hydrated cement.

Jennings joined the MIT Concrete Sustainability Hub in 2010 as the inaugural executive director, leading a multi-disciplinary team of physicists, materials scientists, engineers and architects, and pushing them to new frontiers of science-based engineering.

When Jennings started his career in cement science in the late 1970s, the field was classically divided in two branches: cement chemistry and mechanics. Only a small number of researchers were exploring the intersection of chemistry, materials science, and mechanics. Trained as a physicist and materials scientist, Jennings recognized that a true materials science approach for cementitious materials remained to be developed. For the next 35 years, he led advances in the field, ultimately defining what is now known as the materials science of cement-based materials.

Jennings was born on August 4, 1946, in Massachusetts. His father was a professional accountant. His mother was a professor of chemistry at Wheaton College. He graduated with a BS in physics from Tufts University in 1969, and a PhD in materials science from Brown University in 1975. Following a research fellow position at the University of Cape Town in South Africa, he began studying cementitious materials at Imperial College in London, where he was strongly influenced by Hal F.W. Taylor, considered the father of modern cement chemistry.

Jennings joined the National Institute of Standards and Technology (NIST) of the U.S. Department of Commerce as a physical scientist from 1982 to 1987, where he built a group in computational materials science of concrete aimed, for the first time, at blending physical chemistry of cement with prediction of mechanical behavior. During this time, he developed the first computer model of cement hydration. This groundbreaking work was quickly recognized by his contemporaries and it launched a whole new field of computational cement science, leading ultimately to the development of NIST’s Virtual Cement and Concrete Testing Laboratory.

Jennings joined Northwestern University as an associate professor in 1987, becoming a full professor in 1994 and serving as chair of the Department of Civil and Environmental Engineering from 2002 to 2006. Jennings’ growing scientific reputation was instrumental in the establishment at Northwestern of the Advanced Cement-Based Materials Research Center, a National Science Foundation-sponsored multi-institutional and multi-disciplinary research center aimed at expanding and improving the application of cement and concrete to meet society’s pressing future needs for housing, shelter, hospitals, and infrastructure.

Jennings broke new ground in cement science in the mid-1980s with his proposition that the performance of concrete materials can be captured in terms of quasi-equilibrium phase diagrams of the hydration products. A decade later, this fundamental contribution enabled the development of ultra-high-performance concrete, which attains properties like mild steel, and which revolutionized the concrete world. In research, these phase diagrams became the foundation for the implementation of molecular science approaches of cement hydrates, the binding phase of concrete.

In 2000, Jennings published his most widely cited and influential paper, entitled simply “A model for the microstructure of calcium-silicate-hydrate in cement paste.” This was known for years as the “colloid model” of C-S-H, and more recently and appropriately, as the “Jennings model” of C-S-H. Hamlin continued to refine and extend the model and its associated insights into the nanostructure and behavior of C-S-H, particularly with regard to the role of water in the smallest pores and spaces. He published a major update to his model in 2008 called “CM-II” that described the internal structure of the fundamental C-S-H particles. He led a large group of researchers to publish, just one week before his death, an important paper on the hysteresis behavior of water in C-S-H during drying and rewetting.

The Jennings Colloid Model closed the loop between molecular understanding and manufacturing of cement-based materials so that it is now possible to design cement-based materials with specific strength, fracture and durability properties. These quantitative breakthroughs on the science front resulted in many industrial concrete materials innovations, including seeded cement-based materials, innovative cement-based materials for oil- and gas well applications, and silicate-based protective coatings for metals. 

Jennings’ most recent research efforts at MIT were aimed at developing sustainable cement-based materials to meet India’s need for housing and infrastructure. In this research, he returned to the very foundation of his unique thermodynamic framework for cementitious materials, at the intersection of materials science and mechanics as a basis for predicting and fine-tuning long-term durability properties.

Jennings, an entrepreneurial inventor who carried his research findings all the way from the lab to full commercial production, was also a highly sought consultant for the concrete and cement industry, the glass and fiberglass industry, and real-estate development. With his unique blend of science-inspired engineering, he proposed a new vision for cement-based materials in the 21st century — one that capitalizes on the availability of the raw materials and recognizes the social impact of the concrete on our living conditions while minimizing the environmental footprint.

Throughout his distinguished career, Jennings was dedicated educator, an inspiring instructor, and a generous and encouraging mentor. He left a lasting impact on his many students and colleagues; in the classroom, on the drawing tables and whiteboards in his offices at Northwestern University and MIT, and through the more than 200 scholarly papers he authored and co-authored.

Hamlin Jennings is survived by his wife, Glenys Jennings; his mother, Bojan Jennings; and his daughter, Ashley Jennings.

Hamlin's contributions to the cement and concrete community are astounding, but all of us here at MIT know that his greatest contributions were to the people that he invested his time in: students, postdocs, and colleagues. We'll treasure the memories we had with him and do our best to live up to the standards he set.

Why I am going to miss Hamlin.

When Hamlin came to MIT to get the Hub up and running, I finally had a chance to get to know him, even though we had met years before when he gave a seminar at MIT. I found Hamlin to be a wonderful colleague, conscientious, dignified, and unpretentious. We had similar ideals about the academic career and how important are personal relations in setting examples for the younger generations. We were comfortable exchanging ideas and opinions, and enjoyed each other's company. Hamlin did not have an easy time with the many demands associated with the Hub's growth through Phase I, but he persevered and it was only after the transition to Phase II that he was able to start a collaboration with his young colleagues in the Hub, principally Matthew Pinson, then a graduate student in Physics, and Enrico Masoero, a postdoc who later became a faculty in the U.K. Hamlin led the project with his broad knowledge and deep physical insight on the problem of water sorption-desorption isotherm, while his collaborators provided superb technical expertise in modeling and data analysis. A paper in Physical Review Applied, selected as an "Editors' Suggestion, appeared just this month. I know I am not alone in appreciating Hamlin as a caring individual dedicated to share his considerable knowledge of cement science and technology. We have no one else like him in the Hub. He will be missed a lot in the years ahead. Sid Yip, Emeritus - Nuclear Science & Engineering and Materials Science & Engineering, MIT

I appreciated Hamlin's contribution to my career

Hamlin Jennings will live on in my fondest memories as an highly intellectual, highly focused and extremely good spirited, warm and trusting man. Over the years we worked together on many technical / business projects and Hamlin was always consistent and determined to properly define the opportunity, remain solution oriented and work relentlessly to achieve the goal. He was very committed to his family, friends and helped many folks along the way. Hamlin represents the best in people that I have had the privilege to know.My warmest thoughts are with his family. I will miss you Hamlin.A friend & business partner,Vince TruantCEO/FounderMatrix Ventures

I was a postdoctoral associate at the CSHub when Hamlin wasthe hub’s director. I was also one of the researchers that Hamlin used to meetevery Monday morning at the Dome Café at MIT, to discuss about the action ofwater in cement.

We know how transformational and inspirational Hamlin hasbeen for the community of cement science. Further than that, Hamlin was also aterrific mentor and instructor, with his ability to act as a portal between theingenuous and creative ideas of young researchers and the big body ofstate-of-the-art knowledge in cement science. When presented with a new idea,he always listened carefully and sometimes responded immediately, other times instead he would ask for some days to think about it, which he would punctually dobefore coming back with a precise counter-test. This had a magnetic effect onyoung researchers like me, especially because such a deep level of considerationcame from a world-leading scientist like him. I also imagine that this modusoperandi reflected Hamlin’s organization of his knowledge into two domains: onecontaining the mole of experimental facts that he knew encyclopedically andthat needed to be understood, and the other domain containing the models, manyof which he inspired and developed, and that he considered valid only as far asthey were able to be consistent with all (not only some) of the experimentaldata that he knew. Hamlin’s passion for new ideas was the manifestation of hisconstant process of reformulating, refining, and sometimes entirely revisingthe domain of models that he considered to be sound. In this daily effort, Hamlinhad the special combination of creativity, mental agility, humbleness, andstrength that are needed to sit comfortably at the interface between confidencein one’s own ideas and prompt willingness to change them.

I had the privilege of spending many hours talking withHamlin during the past two years. Hamlin initiated and led a new line ofresearch in cement science, which now involves hundreds of committedresearchers around the world. He told memany times how he believed that this growing wave of research will soon lead toa “revolution” in cement science, and that such revolution will be driven mainlyby our ability to “connect the dots” that are already out there in theliterature. His colleagues at MIT and many more elsewhere now share this visionand continue the research that he inspired and nurtured.

I met hamlin to about seven years ago, beginning to work for him at his home in small projects, which turned out to be in a large renovation project of his whole house, and during those years he with his dedication and goodness transformed our business into a great friendship that few had the opportunity to see and know, we had the great projects together and some already underway, but the weather was not in our favor, and not allow this to happen. but what really matters and the fact that he has been part of my life and showing me how a man can be good, and makes the difference in people's lives, I'm still young, and during this walk of life, there were few people which I found with the same charisma, warmth and kindness as my friend Hamlin, that God can comfort his family and ease the pain of the loss of one so dear and special person as Hamlin. I thank God for giving me an opportunity to be with you during these few years. But that will be eternal, I would give anything to have u here on our side, but God chose him to be with him, Surely somewhere special, like a special person. Thank you for all you did. I will always remember u forever.

With affection and love of his friend Rafael.

The quality that struck me the most about Hamlin was his humility. He didn't gather a group around him because he wanted to be at the center of concrete science research (although he has been). He gathered people because he knew that he could help us. He wanted to bring together people from different disciplines, and introduce us to the various problems in the interesting world of concrete.

And when we gathered, he didn't want to tell us all his thoughts and ideas, but to listen. He always believed that he could learn from what each of us had to say. I'm sure we came up with many incorrect ideas at those meetings, but with his encouragement to put our ideas forward, and really get to the heart of where they came from and their implications, and see whether they matched with other knowledge, we came to a very useful model, outlined in the paper we all wrote together and published in Physical Review Applied last month.

Hamlin was very encouraging of young researchers. He really cared about us, and how we were progressing in our lives and academic careers. He was very happy to see me move on from MIT to a postdoctoral position at the University of Chicago, and I am grateful for the influence he has had on me.

Hamlin Jennings is a great loss for the construction materials industry! I had the great honor and privilege to have worked with Hamlin during my undergraduate years, and he became my PhD adviser during my graduate studies.I consider him the person who attracted my to the world of cement and construction materials. He always transmitted great passion for cement chemistry, and rendered it a fascinating world! I recall numerous stimulating conversations about cement chemistry, and how I always walked away fascinated and excited. He taught me to think in "another box," and if I wanted to change things I needed to become part of the system first!I owe Hamlin a lot of my passion for cement chemistry and science! Materials by Design

Posted on behalf of Lydia Pratt:

We have had the pleasure and honour of being able to claim Hamlin Jennings and his family as a good friend to Professor Peter Pratt’s family for over 35 years. We first knew him when he became a highly valued Research Assistant to Peter Pratt at Imperial College, London. A great rapport built up with everyone there. So much so he was appointed a warden at one of the Halls of Residence and became even more popular when he provided a traditional Thanksgiving dinner for the students – this is still in the annals of Imperial College.

We had the joy of meeting his family in Massachusetts and came to love them deeply, with many welcoming visits since.

Hamlin, when professor at North Western University, arranged for Peter Pratt to be a distinguished visitor there for the fall semester of 1989. Hamlin and Glen’s hospitality knew no bounds. Knowing him has enhanced our lives and happy times will live on in our memories forever.

Lydia Pratt

Hamlin was a thoughtful and caring influence at every academic institution he touched. Since his mother Bojan taught for decades at Wheaton and daughter Ashley earned her B.A. there, he also participated in the planning and creation of the Jennings Family Endowed Scholarship Fund to add to the Student Prize that Bojan first established. A positive guiding force for academia, who knew and demanded the highest intellectual rigor from everyone around him. All this with an easy smile and a happy laugh at every turn. Sad loss for family, friends and colleagues.

I first knew professor Hamlin M Jennings from a Chinese textbook when I was a college student, I learn his theory on cement hydration twenty three years ago, that time I dreamed of being a graduate student of him at Northwestern, later,I became a visiting scholar worked with him during 2005~2006 at Northwestern, and I invited him to China trice. He is a very prominent scientist on cement materials, my colleagues and students truly adored him. Both times, my students and I got a lot of inspiration from him.

Last years, we meet at 10th HSHP, I am so glad he was so interested in my work on low carbon concrete, after his speech in my university, he went my laboratory to see how the scattering-filling coarse aggregate worked and the long time specimens of low carbon cement we made, my students get inspired by his questions and suggestions. He listened carefully to my students' presentation and give some instruments. Late, I knew he was diagnosed with cancer, but that time he looked great and worked hard, a lot of person told my I got a handsome instructor.

He is deeply devoted scientist, he gave the cement material science a great milestone and also a lighthouse.

I knew this shock news yesterday, and I make a cup of Kongfu tea at my hotel room, I wished him enjoy it.

He will be missed a lot in the years ahead by us, a group of scholars on cement materials science and engineering from Wuhan University of Technology.

A studens and a friendPaul Shen

I was one of Hamlin's first disciples in the field of cement hydration thirty nine years ago, when he was a visiting research fellow at the University of Cape Town. He was an intellectually challenging, stimulating, and rigorous scientist and an excellent teacher. But most of all, he was a decent, kind person and a loyal friend. I was honored to be associated with him and his work. My thoughts go to his family, his friends, and his colleagues. David Pitman

Reprinted with permission of MIT News