The American Concrete Institute's Spring Convention scheduled for Chicago from March 28 - April 1 was cancelled, but several committees met online. 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 is currently being balloted in the committee and all comments that were already received were discussed during the virtual committee meeting. The standard is expected to be forwarded for the ACI review process in May. The other standard will provide the quantitative information required to model concrete and masonry building envelope components for use in building energy models and is still under development. Scott Campbell maintains representation on ACI 122.
201 – Durability: The committee is revising the guide to durable concrete (201.2R). This revision will include discussion on resistivity tests and formation factor as measures of potential durability of concrete and address concrete requirements for exposures classes in the revised ACI 318 Building Code. The guide will also address Microbial Induced Corrosion (MIC) of Concrete. A new ASTM standard guide, ASTM C1894, has been published on this topic. A smaller code writing committee is working on a separate document - Code Requirements for Durability – and targeting completion for the end of the ACI 318 code cycle in 2025. The committee is finalizing a TN on iron sulfide minerals in aggregate, specifically Pyrrhotite, and has drafted one on physical salt attack. ACI 201 is working with the aggregate committee to update the report on alkali-aggregate reactivity. Karthik Obla maintains representation in ACI 201.
211 – Mixture Proportioning: A guide to proportioning concrete with ground limestone and mineral fillers is finalized and will be published by summer. In revising its primary document on mixture proportioning (ACI 211.1), the committee is completing comprehensive numerical examples of mixture proportioning. A document on developing 3-point curves for trial batches is in 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, use of percent within limits in specifications and other revisions. The committee is completing a revision to the guide for obtaining cores and interpreting test results (214.4R). 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.
232 – Fly Ash: The committee is finalizing a TN on limits fly ash in concrete based on the NRMCA Specification in Practice topic. A TN on harvested fly ash from storage areas is in process. A new guide from ASTM Committee E50 on sampling for harvesting coal combustions products was noted. The committee has planned tech sessions on “Coal-combustion Byproducts Reimagined” which will get into harvested fly ash, bottom ash and beneficiated fly ash for a future convention. Karthik Obla is the vice chairman of this committee.
240 – Pozzolans: This committee did not meet. A TN on “What is a Pozzolan” is being finalized. A TN on ground glass pozzolans is being developed. The natural pozzolan association has organized a symposium in Colorado for September 23 - 24. More information can be found at the NPA website. Karthik Obla maintains representation on ACI 240.
301 – Specifications for Structural Concrete: The committee received about 200 comments from the public review of the specification. The committee addressed all comments that were not editorial in nature over three virtual meetings. Some revisions were made to Section 4 on concrete materials to the mixture proportioning section and requirements for alkali aggregate reactions. The committee is on track to finalize and publish ACI 301-20 by summer. A new Committee 301 will be formed for its first meeting at the ACI Fall convention. Colin Lobo maintains representation on ACI 301.
318 – Building Code for Structural Concrete: ACI Subcommittee A on Concrete Materials did not meet but has some ballot activity. Some of this is to resolve new business items identified in the past cycle and to address new code change proposals or improve clarity in existing provisions.
ACI Subcommittee D, on structural members, met online and was attended by Scott Campbell. The subcommittee discussed an error in the ICF provisions in ACI 318-19. The standard incorrectly implies that ICF buildings are limited to two stories in height. To correct this error NRMCA, along with ACI 560, has taken a two-pronged approach. First, a Code Case (request for formal interpretation) clarifying that ICF walls are not limited to two stories was submitted. This has been approved by the subcommittee. Additionally, a formal code change was developed to remove the two-story limit and clarify the requirements for ICFs. The subcommittee has approved this in general, with a task group appointed to determine if any minor wording changes are desired. The Code Case and the change proposal will be submitted for ballot of the ACI 318 main committee this summer.
Subcommittee N on sustainability is considering several initiatives. These include addressing resilience, sustainable design, concrete mixture metrics for environmental impact, use of recycled materials, alternative cements and supplementary cementitious materials and sustainability performance metrics. The subcommittee is working toward developing an appendix in ACI 318.
The 318 main committee met online and content was primarily informational as it was not conducive to discussion. One minor code change on a structural provision was approved. For a supplement to 318-19 to be published (in 2022), revisions will need to be approved by the committee by the end of 2020. The ballot schedule was discussed for the rest of the year. Colin Lobo maintains representation on ACI 318 and ACI 318 Subcommittees A (concrete materials) and N (sustainability).
329 – Performance Criteria for Ready Mixed Concrete: The committee did not meet. Resolution of a ballot on proposed section of a guide performance specification were resolved with the negative voters with no objections from other members. New sections of this document will be balloted shortly.
330 – Parking Lots: The ACI 330 Committee continues to work on revising the ACI 330 Guide report. Comments from the ACI review process are being addressed by the committee. The committee will meet before the fall meeting to complete the comments. Committee is pushing for ACI approval this year. Amanda Hult maintains representation in ACI 330.
522- Pervious Concrete: The committee is currently revising the ACI 522 specification. Comments from ACI review were addressed during the fall meeting. At this meeting public comments were addressed. The committee has requested a publish date for the specification. The committee addressed comments on the 522R guide document. Amanda Hult maintains representation in ACI 522.
555 – Recycled Materials: The committee did not meet; it 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.
Concrete Research Council (CRC) is a council under the ACI Foundation. CRC provides funding for research or initiatives that primarily benefit the work of ACI committees. Projects are solicited annually and awarded based on available funds. This year, CRC deliberated on several submissions and selected eight projects: four on materials and the remaining four on structural research. Funding is in the amount of $50,000 per project. Colin Lobo maintains representation on ACI CRC.
For more information, contact Colin Lobo at clobo@nrmca.org or Karthik Obla at kobla@nrmca.org.
National Ready Mixed Concrete Association