About Us

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John Gajda, PE (licensed in 27 US states and 4 Canadian provinces) has over 30 years of consulting experience, and is a Fellow of the American Concrete Institute (FACI).  He is long-time voting member of ACI 207 Mass and Thermally Controlled Concrete, and is also the former chair of this committee.  John is also a long-time voting member of ACI 301 Specifications for Concrete Construction, and is the chair of the subcommittee responsible for the mass concrete requirements of ACI 301.  He is also member of the ACI Board of Direction.  

John has worked on the mass concrete of over 2000 projects around the world, including many high-profile projects, and projects with high performance and/or high strength concrete. John routinely gives presentations on mass concrete and has published many papers on the topic.  Some of these papers can be accessed through the mass concrete tab of this website.  

John received his M.S. and B.S. degrees in materials engineering from Iowa State University.  Aside from mass concrete, he has a wide range of experience including: thermal properties of concrete, energy use buildings, use of alternate raw materials in cement manufacturing, NDT, carbon dioxide (CO2) absorption of concrete, delayed ettringite formation, alkali silica reactivity, and concrete in radiation environments.

Dr. Jonathan Poole received a B.S., M.S., and Ph.D. in Civil Engineering from the University of Texas at Austin.  He has over 15 years of experience in civil engineering, construction, and concrete materials.  He served as president of SEAoT Austin Chapter, and was co-recipient of the Wason Medal for Materials Research in 2011, and is the current chair of ACI 207 Mass and Thermally Controlled Concrete.  

Dr. Poole is a long-time voting member of ACI 207, a long-time voting member of ACI 305 Hot Weather Concrete, a voting member of ACI 301 Specifications for Concrete Construction, and a voting member of the ACI 301 Specifications for Mass Concrete subcommittee. Dr. Poole’s graduate research was on mass concrete, with numerous papers authored and co-authored on the subject. In addition, he helped develop the Texas ConcreteWorks modeling software for mass concrete. 

Matthew D’Ambrosia, PhD, PE, FACI is Principal and Co-Founder of MJ2 Consulting where he specializes in solving difficult problems for the construction industry. Dr. D’Ambrosia has over 25 years of experience in concrete materials behavior and research. His interests include materials optimization for specialized applications, durability-related mechanisms such as volume change and cracking, as well as new approaches for prediction and verification of service life and sustainability. He has expertise with large infrastructure projects throughout the world, such as tall buildings, bridges,  highways, dams, and power plants. He is a Licensed Professional Engineer in thirteen states.

Dr. D’Ambrosia teaches instructional courses for the industry and is Adjunct Professor in the Department of Civil and Environmental Engineering at Northwestern University.   He is a Fellow of the American Concrete Institute (FACI), where he currently serves as Chair of ACI 209C on Creep and Shrinkage, voting member of ACI 318A and numerous other committees.  He is a member of and former Chair of the ACerS Cements Division. He received his B.S. in Civil Engineering from the University of Iowa, and M.S. and Ph.D. in Civil Engineering from University of Illinois at Urbana-Champaign. 

Mr. Feld specializes in mass concrete consulting and thermal properties of concrete. He has worked on over 500 mass concrete projects throughout the United States and Canada, producing thousands of thermal control plans to help contractors, owners, and engineers manage temperatures and temperature differences in mass concrete placements. Additionally, Mr. Feld regularly helps his clients work toward understanding and meeting project mass concrete specifications and advocates for specification modifications as appropriate to provide performance-oriented alternatives.

Mr. Feld is a member of ACI 207 – Mass and Thermally Controlled Concrete. Through this committee work, Mr. Feld has authored a special publication intended to clarify and improve the industry definition for mass concrete. He has also authored other mass concrete articles, and has been invited to present on the topic of mass concrete at many highly regarded industry venues.

Ms. Jennings is a Senior Petrographer specializing in the evaluation of cementitious and other building materials through the use of optical microscopy. With over 20 years of experience, she has developed expertise in identifying the causes of concrete distress, troubleshooting concrete performance issues, evaluating stucco systems and materials, and documenting floor system failures. She has performed examinations of mortar and concrete from numerous historical structures, and coordinated laboratory testing programs for several large-scale projects. Her experience also includes the evaluation of aggregates for use in concrete and determination of the air-void system parameters of hardened concrete.

With an educational background in civil/structural engineering, and early work experience in structural evaluation and rehabilitation, Vicki brings a unique perspective to her projects, bridging the macroscopical and microscopical evaluation of structures and materials. 

Jose Pacheco, PhD, PE received a B.S. in Civil Engineering from Universidad Autonoma de Nuevo Leon, Mexico, and a M.S. and Ph.D. in Civil Engineering from the Delft University of Technology, The Netherlands.  Dr. Pacheco’s expertise is focused on concrete service life predictions, corrosion protection, and concrete durability, repair and troubleshooting. He is an active voting member of various ACI, AMPP, RILEM and fib Committees with emphasis on concrete durability, service life predictions, and concrete repair.

Jan Vosahlik, PhD, PE, boasts over a decade of experience in concrete and cement-based materials. His expertise covers a wide array of topics, including concrete workability, pumpability, rheology, mixture development and optimization, construction troubleshooting, and mass concrete. Additionally, he is well-versed in new product and technology R&D, particularly in additive manufacturing with concrete. Before joining MJ2 Consulting, Dr. Vosahlik led the R&D efforts of a material science team at a construction automation technology startup, where he focused on new concrete technologies. 

Jan is an active member of the concrete community, serving as a voting member on numerous ACI committees. His involvement includes committees:

134 – Constructability, 238 – Workability, 329 – Performance Criteria for Ready Mixed Concrete, and 123 – Research and Current Developments. 

He is also currently a lecturer in the Maseeh Department of Civil, Architectural, and Environmental Engineering at the University of Texas in Austin. 

Jan earned his B.S. degree in Structural and Transportation Engineering from the Czech Technical University in Prague, followed by his M.S. and Ph.D. in Civil Engineering from Kansas State University. 

Dr. Lallas has a background at the intersection of structural engineering and advanced materials, with experience in experimental evaluation and computational tools to model precast concrete sections.  Her work has focused on novel materials such as sustainable low carbon concrete, high volume fly ash concrete, and ultra high performance concrete (UHPC).