CP Tech Center welcomes new associate director
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CP Tech Center Program Manager and Portland Cement Concrete (PCC) Lab Director, John Adam, PE (Iowa), has been selected as the CP Tech Center's newest associate director to manage multifaceted, multiyear research projects from inception through final deliverables. He will also provide technical assistance to paving professionals and presentations to stakeholders toward the goal of further advancing concrete pavement design, construction, and maintenance.
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Adam joined the CP Tech Center in 2018 after 33 years with the Iowa Department of Transportation (DOT), most recently as Highway Division Director and Chief Engineer and earlier as Statewide Operations Bureau Director, and after 6 years in industry as Senior Vice President for Knight Engineering.
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Mixture proportioning with less cement for improved performance + reduced CO₂ impact
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An integral part of the Performance-Engineered Mixtures (PEM) program has been providing tools to contractors for proportioning mixtures with a high probability of meeting specified performance measures while reducing environmental impacts.
A number of state agencies and contractors have adopted an approach to mixture proportioning developed by the CP Tech Center. This approach is based on the premise that given a fixed w/cm ratio and binder type, mixture performance will not improve above a certain paste content threshold. Though contrary to popular perception, research has demonstrated the validity of this premise.
The CP Tech Center approach to mixture proportioning therefore starts by seeking a combination of locally available aggregates to fit the "tarantula curve." The volume of space between solid particles in the resulting blend is then measured in the lab. Next, the paste's binder type, w/cm ratio, and air void system requirements are selected. Specifications often directly address these parameters to assure the needed durability and strength. The last step is adding sufficient paste (including air) to fill the voids between aggregates as well as a limited additional amount of paste to achieve required workability. While this amount of paste is best determined by preparing trial batches, experience has shown the total amount needed is typically about 1.5 times the volume of voids.
A spreadsheet developed to help practitioners apply this method of mixture proportioning has been used in a number of applications. For example, the Wisconsin DOT has permitted contractors to reduce their minimum cementitious content if they adopt this procedure, with positive results reported by both contractors and agency. Noteworthy has been the repeated finding that mixture performance using this method is not compromised—indeed in some cases it has improved, with projects' CO₂ footprint also reduced.
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Does this approach to mixture proportioning work?
Before (left) vs. after (right) mixture proportioning as described above
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Join upcoming CP Tech Center webinars
on Tuesdays at 12 pm (CST)
September 14:
Advancements in Performance-Engineered Mixtures (PEMs)
October 12:
Sustainability: Recycle & Bicycle
November 9:
Understanding Penetrating Sealers for Concrete Pavements
All webinars offer Professional Development Hours (PDHs)
and are available for signup here.
(Previous webinar recordings, slide handouts, and speakers' Q&A responses are available here.)
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MIT's Concrete Sustainability Hub (CSHub) seeks a new executive director, as former executive director Jeremy Gregory has assumed directorship of the newly formed MIT Climate and Sustainability Consortium
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On the road again to talk concrete pavements
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CP Tech Center service to the concrete paving community over the past month has included a hybrid of online and face-to-face interactions.
Performance-engineered mixtures (PEM) have been a key topic of discussion, beginning with CP Tech Center Director Peter Taylor, Associate Director Gordon Smith, and Technology Transfer Engineer Jerod Gross presenting an overview of PEM to members of the Arkansas DOT (ARDOT) on July 27th. Attendees included representatives from ARDOT'S materials, construction, and research divisions. Discussion focused on limitations of the slump test, advantages of mixture prequalification testing, review and improvements to state specifications, the applicability of PEM to bridge decks, and the importance of quality control.
From August 23rd to 24th, Gordon Smith, Bob Conway (FHWA), and Tom Van Dam (NCE) visited Nashville, Tennessee, to share about PEM again, this time with over 20 engineers from the Tennessee DOT (TDOT) headquarters and regional offices, including from TDOT's materials and tests, operations, and structures divisions. This two-day event included a PEM overview along with discussion of reasons for change, the AASHTO PP 84 specification, as well as science and testing. The second day in particular provided a great opportunity for open discussion on items specific to the department and for conversation on applying PEM in practice as it relates to quality, training, and implementation.
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Along the same lines, Gordon Smith joined concrete industry friends at the PCA Promotion Forum in Nashville held from August 25th to 27th to discuss various initiatives surrounding concrete as a sustainable and resilient solution for buildings and transportation infrastructure.
Addressing construction, Peter Taylor joined the Australian Society for Concrete Pavements' Annual Conference held online on August 18th to present about the effects of vibration on concrete mixtures.
Gordon Smith provided a CP Tech Center activity update at the July 20th virtual mid-year meeting of the Transportation Research Board (TRB) AKC50 Concrete Pavement Construction Committee.
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Similarly, CP Tech Center Associate Director Steve Tritsch shared CP Tech Center activity and project updates with around 160 participants at the Arkansas Concrete Pavement Conference.
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The Oklahoma/Arkansas ACPA chapter staff and volunteers organizing this event, held in person on August 25th in Little Rock, took to heart the safety of exhibitors and attendees by arranging for social distancing during presentations, meals, and breaks.
Though COVID remains with us, CP Tech Center staff are continuing to serve the concrete paving industry not only online but also again on the road.
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The CP Tech Center's Executive Board of Directors has recently welcomed a new member, John M. Becker, who has extensive concrete paving knowledge, experience, and contacts across both agency and industry.
For the past 21 years, Becker (PE, North Carolina and Pennsylvania) has represented the concrete pavement industry in Pennsylvania, where he currently is the president of the ACPA Pennsylvania Chapter (ACPA/PA).
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Becker previously served FHWA for 16 years, five as a member of the Pavement Division Concrete Team. Becker is a past president of the Harrisburg section of the American Society of Highway Engineers (ASHE). He earned his Bachelor and Master of Science degrees in Civil Engineering from the University of Illinois.
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As demonstrated every year by ACPA/PA's Annual Concrete Conference, John and the organization he leads are passionate about providing technical, educational, and promotional assistance to their local cement and concrete paving industries and about the longer life pavement that quality concrete paving provides. The CP Tech Center is therefore pleased John Becker has joined its executive board.
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Paving Association Execs
Please forward this newsletter to your members as appropriate.
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