The American Concrete Institute's Fall Convention was held virtually in late October. 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 will provide guidance on dealing with thermal bridges in concrete and masonry structures. This standard has been sent to the ACI Technical Activity Committee (TAC) for the first round of external reviews. The other standard will provide the quantitative information required to model concrete and masonry building envelope components for use in building energy models and has gone through the first round of balloting and comment response. Scott Campbell maintains representation on ACI 122.
201 - Durability - The committee is revising the guide to durable concrete (201.2R). Chapter 9 on corrosion will be updated with discussions on modified ACI 318 chloride exposure classes and concrete requirements. The new document will contain a chapter on iron sulfide minerals in aggregate. The committee will ballot a Tech Note (TN) on iron sulfide minerals in aggregate, specifically Pyrrhotite and the one on physical salt attack. The guide will also address Microbial Induced Corrosion (MIC) of Concrete. Several ASTM standards have been developed on MIC: ASTM C1894, ASTM C1898, and ASTM C1904. Karthik Obla maintains representation in ACI 201.
211 - Mixture Proportioning - A guide to proportioning concrete with ground limestone and mineral fillers has been published. In revising its primary document on mixture proportioning (ACI 211.1), the committee addressed the comments on the ballot for completing comprehensive numerical examples of mixture proportioning. A document on developing 3-point curves for trial batches will be reworked following the ACI review process. Task groups are developing reports on assessing aggregate gradations and aggregate packing models. Karthik Obla maintains representation on ACI 211.
214 - Strength Tests - The committee is working on a revision to the 214R guide document that will include statistical concepts for tests other than strength and other revisions. The committee’s revised guide for obtaining cores and interpreting test results (214.4R) will be published shortly. The committee is working on Tech Notes on using two instead of three 4x8 in. cylinders for acceptance testing and cylinder vs. cube strengths. Karthik Obla maintains representation on ACI 214.
216 – Fire Resistance and Fire Protection of Structures – The ACI 216 Committee continues to work on revising ACI 216.1, Code Requirements for Determining Fire Resistance of Concrete and Masonry Construction Assemblies. The next edition of the standard will include a new chapter on loads in fire addressing strength reduction factors, load factors and load combinations, and fire scenarios in addition to the ASTM E119 standard fire curve. The update will bring ACI 216.1 closer to other international standards in supporting performance approaches to concrete fire design and analyses.
In parallel, a task group of the committee is developing a new rational design guide on determining fire resistance. The document will establish engineering design criteria for exact calculation of fire resistance for existing concrete elements. In summary, the document will provide guidelines for determining fire resistance through analytical methods in addition to the existing prescriptive methods and will be referenced by the revised ACI 216 standard. NRMCA is reviewing Chapter 3 of the design guide on Fire Scenarios.
The technical committee is also involved in the development of a new chapter on fire in ACI 562, Code Requirements for Assessment, Repair, and Rehabilitation of Existing Concrete Structures. The chapter will focus on the impact of fire on repair, including post-fire event assessments of existing structures as well as consideration of external factors such as fiber-reinforced fibers and anchorage. Provisions for assessments will be prescriptive with an emphasis on level of damage and repair of concrete. Shamim Rashid-Sumar maintains representation on ACI 216.
232 - Fly Ash - A Tech Note on limits of fly ash in concrete has been finalized and will be published this year. A TN on potential use of harvested fly ash from impoundments is in process. The committee will add information on harvested fly ash in the main ACI 232.2R document. Karthik Obla maintains representation on ACI 232.
240 - Pozzolans - The committee voted on the proposals to recommend for funding to the ACI Foundation. A Tech Note on “What is a Pozzolan” is being finalized. A report on ground glass pozzolans is being developed. Karthik Obla maintains representation on ACI 240.
301 - Specifications for Structural Concrete - ACI 301-20 has been published. A summary of changes is published in the October 2020 edition of ACI Concrete International. The newly formed committee chaired by Daniel Toon with United Forming met to discuss addressing new business resulting from public comments and comments from the Technical Activities Committee that could not be addressed in the previous cycle. Additional new business will be generated by the 301 subcommittees. A revised ACI 301 specification is expected to be published in 2025. Colin Lobo maintains representation on ACI 301.
318 - Building Code for Structural Concrete - ACI Subcommittee A on concrete materials is working on several code change proposals to include clarification on chloride limits, alterative cementitious materials, including materials with an ASTM specification like ground glass pozzolans, clarification of several issues for concrete mixtures and acceptance testing in Chapter 26 on construction documents.
ACI Subcommittee D, on structural members, has advanced the NRMCA-sponsored code change proposal to the main committee regarding correcting the ICF building height limitation The Code Case (request for formal interpretation) clarifying that ICF walls are not limited to two stories has been published in Concrete International.
Subcommittee N on sustainability is working on developing an Appendix to ACI 318 that will address resilience, design systems impacting sustainability, concrete mixture metrics for environmental impact, use of recycled materials, alternative cements and supplementary cementitious materials, and sustainability performance metrics.
The 318 main committee worked through several design-related code change proposals that have been balloted and approved a few. It is unlikely that a supplement to the code will be published in 2022, thereby freeing up time to propose and approve additional proposals for publishing a revised ACI 318 by 2025.
321 - Concrete Durability Code - ACI 321 is a new committee formed to develop a code for durability. The committee had its first meeting at this convention. It will address durability requirements for buildings (covered by ACI 318) and other structures. Task groups were formed to develop exposure classes for all forms of concrete deterioration, including abrasion.
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 NRMCA's 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. 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 will be balloted over the winter. 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 balloted and approved additional summaries of test methods that will be included in Chapter 5 of the proposed guide performance specification that is intended as information to the specifier. There are additional test methods that are being developed for this chapter that will be balloted. A draft of Section 1 of a specification (in MasterSpec) format with advisory information and will be balloted shortly. Karthik Obla and Colin Lobo maintain representation on ACI 329.
330 - Parking Lots - The ACI 330 Committee revised the Category D design charts in the ACI 330.2R-17 Guide for the Design and Construction of Concrete Site Paving for Industrial and Trucking Facilities document to accommodate a 20-year design. This change is to provide consistency with other 330 documents. The changes have been approved. The ACI 330R-08 document has been revised and will be known as the Guide for the Design and Construction of Commercial Concrete Parking Lots and Site Paving. It is scheduled to be published in 2021. The committee is currently reviewing the specification and expects it to be ready for publication in 2022. Amanda Hult maintains representation in ACI 330.
522 - Pervious Concrete - The committee is working to address TAC comments on the 522R guide document. 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. Karthik Obla maintains representation in ACI 555.
560 - ICF Buildings - The committee met and endorsed an ACI Foundation proposal developed by the University of Washington on maximum reinforcement spacing and the use of fiber reinforcement in lightly loaded concrete walls. The UW proposal is for the second phase of a project that NRMCA provided with first phase funding.
For more information, contact Colin Lobo at clobo@nrmca.org or Karthik Obla at kobla@nrmca.org.
National Ready Mixed Concrete Association