The American Concrete Institute's Fall Convention was held earlier this month in Cincinnati; the following is a summary of committee activity involving NRMCA staff representation:
122 – Energy Efficiency of Concrete and Masonry Systems – The committee is progressing with development of two new standards. One standard will provide guidance on dealing with thermal bridges in concrete and masonry structures. This standard is designed to provide an alternative to ASHRAE 90.1 requirements, which are unfavorable to the industry and contain details that cannot be constructed. The committee reviewed a draft from the consultant and are awaiting the next version for further action. The other standard will provide the quantitative information required to model concrete and masonry building envelope components for use in building energy models. Scott Campbell maintains representation on ACI 122.
132 – Responsibility in Concrete Construction – The committee is finalizing a special publication and document to address responsibility associated with repair of concrete structures. The committee is addressing responsibilities of the designer in ACI 318 as they relate to establishing construction documents. It is finalizing a Tech Note on responsibilities care of test specimens for acceptance of concrete at the jobsite. It has begun work on revising its existing guide document on responsibility, ACI 132R. The committee also discussed a document that to discuss clarity in project drawings and consistency with specifications. Colin Lobo maintains representation on ACI 132.
201 – Durability – The committee has completed a Tech Note (TN) on joint deterioration in pavements due to deicers and balloted a TN on iron sulfide minerals in aggregate, specifically Pyrrhotite. The committee will include a chapter on Microbial Induced Corrosion (MIC) of Concrete in is guide, ACI 201.2R. A task group is considering performance alternatives to w/cm in ACI 318, specifically for Exposure Class C2 exposure class. The consensus of this task group is to suggest criteria based on bulk resistivity combined with strength. It could eventually result in establishing requirement for formation factor (based on resistivity measurements). Efforts will be made to include the determination of formation factor in ASTM C1876 and to include an option of accelerated curing to predict later age properties of concrete mixtures containing SCMs. Committee 201 will establish a subcommittee to develop code requirements for durability.
The committee is developing a review paper on physical salt attack and a report on alkali-aggregate reactivity, jointly with the ACI Aggregates Committee. The committee finalized two special issues of ACI Materials Journal on durability in 2019: one on Chlorides and Corrosion and a second on SCMs. Karthik Obla maintains representation in ACI 201 and chairs the task group for performance alternatives.
211 – Mixture Proportioning – The committee is completing numerical examples of mixture proportioning which will become part of the primary document on mixture proportioning ACI 211.1. A document on developing 3-point curves for trial batches had been approved by the committee and submitted for the ACI review process. Task groups are developing documents on assessing aggregate gradations and aggregate packing models. The committee is close to finalizing a document on proportioning concrete with ground limestone and mineral fillers. Karthik Obla maintains representation on ACI 211.
214 – Strength Tests – The committee is working on a revision to the 214R guide document. A TN “Using two instead of three 4x8 in. cylinders for acceptance testing” is being held in response to the ACI review process. The committee is also progressing on a TN on Cylinder vs Cube strengths. Karthik Obla maintains representation on ACI 214.
232 – Fly Ash – The committee is finalizing a TN on limits on the quantity of fly ash in specifications based on an NRMCA Specification in Practice topic. The committee is working on the new TN on Harvesting Fly Ash that will include guidance on sampling. The committee held a mini session of four presentations that discussed test methods for pozzolanic reactivity using methods based on quantifying bound water, calcium hydroxide consumption, and isothermal calorimetry. ASTM E50 will develop a new document on proper sampling practice for harvesting coal combustion products. Karthik Obla is the vice chairman of this committee.
240 – Pozzolans – A TN on glass pozzolans is being developed and will be expanded to a larger committee report. The committee endorsed a research proposal for funding by the Concrete Research Council that will look at making largescale blocks to investigate the ASR performance of natural pozzolans. The natural pozzolan association will organize a symposium in Colorado in 2020. Karthik Obla maintains representation on ACI 240.
301 – Specifications for Structural Concrete – The committee has completed its work on the next version of the specification. It spent all its meeting time resolving comments from the ACI review process. It is anticipated that this will result in a revised specification that will be available for public comment (part of the ACI process for standards) in December. After those comments are addressed, the next version of ACI 301 will be published around Summer 2020. The committee has made several revisions to the specification in this cycle and has ensured that relevant revisions to ACI 318 have been addressed in ACI 301. In anticipation of completing this cycle, the process of selecting the leadership and members for the next cycle of ACI Committee 301 has begun. Colin Lobo maintains representation on ACI 301.
318 – Building Code for Structural Concrete – ACI 318-19 has been published. A summary of revisions relevant to concrete materials and mixtures was published in Concrete inFocus. A new ACI Committee 318 has been established to develop the next version of ACI 318 scheduled for 2025. Several errata to ACI 318-19 have been compiled. The committee has established several code change items for new business resulting from the last cycle. New subcommittees on sustainability and performance-based wind design have been established. The subcommittee on sustainability will review aspects in the code that represent restrictions to sustainability and establish guidance in an appendix on concepts of sustainability and resilience. Initiatives will evaluate the use of recycled materials and impact of the durability requirements on concrete mixtures. Colin Lobo will maintain representation on ACI 318 and ACI 318 subcommittees A (concrete materials) and N (sustainability).
325 – Concrete Pavements – The committee currently has four documents under development or revision. The committee is rewriting ACI 325.12R-02 (Reapproved 2014): Guide for Design of Jointed Concrete Pavements for Streets and Local Roads and is being be led by Brian Killingsworth. Revisions to this document have been completed and will be balloted over the winter. The committee is developing ACI 325.YR Report on Precast Concrete Pavements - State of the Practice which is based upon work completed by Tayabji for SHRP2. The committee developed ACI 325.14R.17 Guide for Design and Proportioning for Concrete Pavements which was published by ACI in 2017.
A revision has been completed of ACI 325.11R Accelerated Techniques for Concrete Paving and was published earlier this year. Work is also underway to update ACI 325.ZR: Design and Construction of Continuously Reinforced Concrete Pavements and ACI 325.13R-06: Concrete Overlays for Pavement Rehabilitation. This work will continue over the next year. Killingsworth will ensure that considerations for streets and local roads will be included in all documents. Brian Killingsworth maintains representation on ACI 325 on concrete pavements.
329 – Performance Criteria for Ready Mixed Concrete – The committee is developing a guide performance specification using the AIA MasterSpec section 033000 on cast-in-place concrete to propose specification language and additional guidance information that will minimize prescriptive requirements and propose performance alternatives. The committee approved an introductory chapter on the guide performance specification. A partial chapter that briefly describes test methods that could be used for mixture evaluation/prequalification and acceptance was balloted and reviewed at this meeting. Additional tests will be added to this chapter and sections of the specifications with advisory information are being developed for letter ballot. Colin Lobo (secretary) and Karthik Obla maintain representation on committee 329.
330 – Parking Lots – The ACI 330 Committee continues to work on revising the ACI 330 Guide report. Each chapter has been balloted and comments were addressed during the fall meeting. The complete document will be sent to TAC by January with comments on the agenda for the March meeting. The 330.1-14 Specification will be reviewed and changes made. Amanda Hult maintains representation in ACI 330.
522 – Pervious Concrete –The committee is currently revising the ACI 522 specification. Comments from TAC were addressed during the fall meeting. All negatives were addressed and revised document will be sent out for balloting. The 522R document will be balloted by chapters. Amanda Hult maintains representation in ACI 522.
555 – Recycled Materials – The committee is revising its document: Removal and Reuse of Hardened Concrete to include a section on crushed concrete aggregates from returned concrete based on research work conducted at the NRMCA Research Laboratory. The committee featured a mini session which included several presentations for characterizing RCA. Karthik Obla maintains representation in ACI 555.
560 – ICF Design – The committee approved wording for a proposed code change to ACI 318 regarding ICF construction. It also agreed to collect information on the prevalence of ICF buildings over two stories. Scott Campbell maintains representation on ACI 560.
ACI Convention Notes: Colin Lobo delivered a presentation at a session on Innovations in Concrete Technology, titled Perspective of a Material Supplier: Performance Specifications for Concrete Materials and Mixtures.
For more information, contact Colin Lobo at clobo@nrmca.org or Karthik Obla at kobla@nrmca.org.
National Ready Mixed Concrete Association