NRMCA Engineering Staff attended the American Concrete Institute's Fall Convention held from October 22-26, in Dallas and filed the following committee summaries as they relate to the ready mixed concrete industry.
132 – Responsibilities in Concrete Construction – The committee published ACI PRC-132.1-22: Responsibility for the Care of Test Specimens for Acceptance of Concrete—TechNote that is available from ACI. The committee has completed a guide to responsibilities in concrete repair and rehabilitation that will be published soon. The committee has begun revising ACI PRC-132-14 Guide for Responsibility in Concrete Construction. The committee hosted a well-attended Hot Topic session discussing impact of sustainability initiatives on constructability with representatives from the designer, contractors and ready mixed producer. It is planning a session at a future convention to outline the completed document responsibilities for concrete repair and rehabilitation. Colin Lobo maintains representation on ACI 132.
201 – Durability – Several chapters of the guide to durable concrete (201.2R) that have been updated and revised are in the ACI review process. A document jointly developed by 201 and Committee 221 on Aggregates is making progress. A joint subcommittee of members of Committees 201 and 222 has been formed to develop a summary report on exposure classes related to chlorides and applicable requirements for concrete. Karthik Obla maintains representation in ACI 201.
211 – Mixture Proportioning – A presentation on mixture submittals is being developed for the Educational Committee. The committee is working on the review process to finalize a document on three-point curves for mixture evaluation. A subcommittee is completing a report on aggregate packing models for optimizing mixtures. The committee indicated interest in developing a document on mixture proportioning based on the combined aggregate void content. Karthik Obla maintains representation in ACI 211.
214 – Evaluation of Results of Tests – The committee decided to work on updating the Guide document PRC 214.4 to include guidance on dealing with outlier core test results. There is interest in developing a tech note on the cost of non-standard testing of concrete. Karthik Obla maintains representation in ACI 214.
216 – Fire Resistance and Fire Protection of Structures – The ACI 216 Committee balloted several updates for the revised edition of ACI 216.1, Code Requirements for Determining Fire Resistance of Concrete and Masonry Construction Assemblies. The updated edition of the standard will include a new chapter on loads in fire addressing strength reduction factors, load factors and load combinations. Additionally, the committee is finalizing the new rational design guide on determining fire resistance. The document will provide guidelines for determining fire resistance through analytical methods in addition to the existing prescriptive methods. Shamim Rashid-Sumar maintains representation on ACI 216.
232 – Fly Ash – The American Coal Ash Association will track the annual utilization of harvested ash, almost 2 million tons of which has been used this year. The committee is working on a new report on the use of crushed bottom ash as a supplementary cementitious material. The report on high volume fly ash concrete will be updated with new research to provide guidance on its use in high early-strength applications. There was an update on the various research projects addressing fly ash supply which should be completed by June 2023. Sessions planned for future ACI conventions include use of bottom ash and harvested ash, and the use of Performance/Prescriptive options for fly ash. Karthik Obla maintains representation on ACI 232.
301 – Specifications for Structural Concrete – The subcommittee responsible for Section 4 on concrete mixtures is working on a significant reorganization of that section to consolidate and categorize submittals and other revisions related to alkali silica reactions and approved changes to ACI 318. The subcommittee responsible for post tensioned systems in Section 9 is working on developing separate sections for bonded and unbonded PT construction. The committee discussed revisions being proposed by subcommittees to other sections of the specification, including broadening the section on expansive cements to applications other than slabs and defining types of concrete that would require thermal control plans based on section dimension or mixture composition.
This will be an attempt to redefine “mass concrete” in the specification. The committee discussed potential revisions to address curing of test specimens at the jobsite for acceptance tests. A new subcommittee on sustainability was formed to develop some specification language on submittals for concrete with reduced embodied carbon. The committee is working toward a revision to the ACI 301 specification to be published after 2025. Colin Lobo maintains representation on ACI 301.
318 – Building Code for Structural Concrete – ACI Subcommittee A on Concrete Materials is progressing on several code change proposals. Approved items by the main committee at this meeting include provisions that criteria for field cured specimens for post tensioning and formwork, including inspection requirements consistent with those in IBC, including provisions to inspect post-tensioning grout pockets and revising exposure class C2 for external chlorides to include air-borne chlorides for structures close to the ocean. Work in progress includes updating curing requirements with alternatives to terminate curing based on age or in-place strength, removing Exposure Class F3 and the limits on SCMs for concrete exposed to deicer scaling, the acceptance process for density of lightweight concrete, addressing sampling at the point of placement at the option of the designer and several other minor changes, including reducing the commentary in Chapter 26.
Subcommittee N on Sustainability balloted a new Appendix on Sustainability at the main committee; received several comments that were addressed at this meeting. The revised appendix will be re-balloted at the Main Committee. The appendix is not mandatory but can be used by the designer if there is a sustainability goal on a project. The appendix includes structural system sustainability, system resilience and documenting concrete materials for reduced environmental impact. ACI 318 is working toward publishing the revised code in 2025. Most of the new content to the code has to be approved within the next year. Colin Lobo maintains representation on Subcommittees A and N and on the 318 Main Committee.
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 led by Brian Killingsworth. Revisions to this document have been completed and TAC is currently reviewing. 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 the FHWA. Work is also underway to update ACI 325.ZR: Design and Construction of Continuously Reinforced Concrete Pavements. This work will continue over the next year. ACI 325.13R-06: Concrete Overlays for Pavement Rehabilitation has also been updated and is currently being balloted. 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 – ACI 329 is working on developing a guide to writing a performance specification. The committee completed a ballot adding to a chapter that briefly describes various test methods and requirements for concrete. It will complete the chapter on test method descriptions before the next meeting and will ballot portions of the guide specification with commentary. Karthik Obla and Colin Lobo maintain representation on ACI 329.
330 – Parking Lots – The ACI 330 Committee is completing the ACI review process to finalize the ACI 330.1 specification. Mini sessions on jointing and pre-construction meetings for joint performance were presented. The committee will explore the need for expansion joints in parking lots/site paving at the next meeting. Amanda Hult maintains representation in ACI 330.
332 – Residential Concrete – The ACI 332 Committee discussed its plans to update to ACI 332-20: Code Requirements for Residential Concrete and Commentary and include a new chapter on Above Grade Walls. The committee intends to incorporate references and provisions of PCA 100, Prescriptive Design of Exterior Concrete Walls for One- and Two-Family Dwellings, which is now under the responsibility of NRMCA, into the revised code. The committee discussed timelines to ensure the revised code could be referenced in the 2027 edition of the International Residential Code (IRC). Scott Campbell maintains membership on ACI 332.
522 – Pervious Concrete – The ACI 522 Committee is completing the review process to finalize the ACI PRC 522, Guide to Pervious Concrete, with an anticipated early 2023 release. Mini sessions on mixture proportioning were held during the meeting. Amanda Hult maintains representation in ACI 522.
560 – ICF Buildings – A technical mini-session including Detecting Voids in ICFs using GPR by Kevin MacDonald; Presentation of a Structural Design Example of an ICF Shear Wall by Craig McKee and a recording of Earthquake Performance Comparison of Multistory Apartment Building Constructed of Various Materials by Evan Reis were presented during the committee meeting. The committee’s guide document update of example problems, 3.1. ACI PRC-560-22, has been published. An update was provided on the status of PCA 100, which has been renamed NRMCA 100 and is currently being updated. The committee also discussed the impact of Publication IR 19-6 on Flat Wall Insulating Concrete Form (IFC) Construction, which was recently issued by the California Division of the State Architect (DSA). The committee will be considering future actions to counteract the limitations placed on ICF construction in DSA’s publication. Scott Campbell and Shamim Rashid-Sumar maintain representation on ACI 560.
Concrete Research Council (CRC) – The Research Council of the ACI Foundation is soliciting research proposals that support the activity of ACI committees. Funding was available to support 10 proposals that is typically split between research on materials and structural. Each proposal receives funding of $50,000 from CRC. The committee will select these projects at the Spring Convention. The committee is selecting award recipients for the Philleo and Boase awards to recognize lifetime achievement in the materials and structures research areas, respectively. Colin Lobo maintains representation on ACI CRC.
Presentations by NRMCA – Karthik Obla presented on Optimizing Concrete Mixtures based on Aggregate Packing, at a session organized by the ACI 211 Committee. Shamim Rashid-Sumar presented on The Top Ten Ways to Reduce Concrete’s Carbon Footprint as a panelist during the 123 Forum session titled Do Building Codes and Standards Support Sustainable Development?
For more information, contact Colin Lobo or Karthik Obla.
National Ready Mixed Concrete Association