The American Concrete Institute's Spring Convention took place in Anaheim, CA, the week of October 15. The following a summary of technical committee activity involving NRMCA Staff representation:
201 – Durability Five tech notes are being developed: 1. Repair of structures affected by physical salt attack; 2. Recommendations for mitigating physical salt attack in new construction; 3. Joint deterioration due to deicers; 4. Iron sulfide (Pyrrhotite) in Concrete Aggregate; 5. Microbial Induced Corrosion of Concrete. The committee agreed to support a proposal for funding by the ACI Foundation to investigate the cause of ASR failure in exposure blocks (not field concrete) where the cementitious system was considered acceptable when tested by the ASTM C1293 concrete prism test criteria.
The committee has approval to develop two mandatory-language documents: 1. Standard Specification for Obtaining Durability in Design; 2. Standard Specification for Executing Durable Concrete in Construction. Karthik Obla delivered a presentation to the committee, based on NRMCA research, that proposed a performance alternative to w/cm for ACI 318 Exposure Class C2. A task force was formed to review and finalize a proposal to ACI Committee 318 for the 2019 Code. Karthik Obla maintains representation on ACI 201 and is part of the task groups.
211 – Mixture Proportioning The committee is working on resolving negatives on several chapters of the ACI 211.1 document. Task groups are developing documents on 3-point curves for trial batches, assessing aggregate gradations and aggregate packing models. The committee is planning a technical session on the topic “Specifications and ACI 211.” Karthik Obla maintains representation on ACI 211.
214 – Strength Tests The committee is working on a revision to the 214R document. The draft will include guidance on percent within limit (PWL) specifications and will address determining target average values for specified flexural strength, rapid chloride permeability and elastic modulus, with consideration of statistical principles. Two tech notes are being developed: 1. Cylinder vs Cube strengths; 2. Using two instead of three 4x8 in. cylinders for acceptance testing. Karthik Obla maintains representation on ACI 214.
232 – Fly Ash The committee is close to publishing the revised document ACI 232.2R, Use of Fly Ash in Concrete. The committee addressed all comments from the ballot of the Tech Note “Limits on the Quantity of Fly Ash in Concrete.” The Tech Note is based on a NRMCA Specification in Practice topic. This document will now move to TAC. Karthik Obla is the vice chairman of this committee.
240 – Pozzolans This committee is developing a Tech Note on Pozzolans derived from ground glass. A task group continues to investigate the relevant test methods to evaluate natural pozzolans for use in concrete. There were presentations RILEM committee development of pozzolanic activity testing and by Kirkland Mining on its plans to mine natural pozzolan deposits in Arizona. The next convention will feature a session on How to Evaluate ASR Mitigation Performance of High-Alkali Pozzolan. Karthik Obla maintains representation on ACI 240.
301 – Specifications for Structural Concrete The committee is working on revisions for the next version of ACI 301 scheduled to be published in 2020. Revisions currently in progress impact most sections of the specifications and the committee spent most of its time on resolution to balloted revisions. Several revisions have been proposed for Section 4 on concrete mixtures include alkali aggregate reactions, including options for lightweight sand for internal curing and the use of mineral fillers; considerations for self-consolidating concrete; addressing minimum cement content for floors and simplifying cold weather temperature limits for delivery of concrete. The committee is developing revisions to the specification for approved changes to ACI 318. Colin Lobo maintains representation on ACI 301.
318 – Building Code for Structural Concrete ACI 318 is scheduled to be published in 2019. Revisions have to be approved by the summer of 2018 for it to be in the new code. There are various code change proposals in progress on the design section of the code.
For concrete materials sections impacting Chapter 19 and 26, about 18 changes have been approved. They require the use of certified technicians; updating some terminology; improving clarity on the definitions and requirements for strength tests; advising the engineer that a higher strength may be specified to be consistent with the w/cm required for durability; including a provision to test for modulus of elasticity on the proposed mixture (pre-qualification); permitting the calculation of chlorides in lieu of testing; expressing chloride limits on the basis of cementitious materials as opposed to cement only; clarifying chloride limits with aluminum or galvanized embedments; core conditioning procedures consistent with ASTM C42; permitting the use of ASTM C595 blended cements containing limestone for concrete exposed to sulfate when qualified by test and permitting the use of mineral fillers.
The subcommittee is also working on code change proposals on simplifying the determination of lambda used in design for lightweight concrete, including a new option for sulfate resistance of concrete while adding provisions that will permit the use of shotcrete; addressing the use of recycled aggregate in concrete; addressing conditions where the designer would consider specification for alkali silica reactions and revising the inspection provisions for concrete to be consistent with the International Building Code.
Approved changes are being balloted for revision in ACI 301. Colin Lobo maintains representation on ACI 318 and ACI 318 Subcommittee A.
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 led by Brian Killingsworth. Revisions to this document will be completed this winter and balloted in the spring. 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 has developed ACI 325.14R-17 Proportioning, Quality Control and Evaluation of Concrete Pavement Strength Relationships and was published this year. A revision is underway of ACI 325.11R Accelerated Techniques for Concrete Paving. Work is nearly complete and will be balloted in the next few months. Work is also underway to update ACI 325.ZR: Design and Construction of Continuously Reinforced Concrete Pavements over the next few months. Lastly, ACI 325.13R-06: Concrete Overlays for Pavement Rehabilitation is being reviewed and updated. 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.
329 – Performance Criteria for Ready Mixed Concrete The committee has completed a Tech Note based on NRMCA Specification in Practice regarding the inclusion of minimum cementitious materials content in specifications; it will be published soon. The committee’s primary objective is to develop a Guide to Writing a Performance-Based Specification. Members are working on developing content based on an outline. The chapters will suggest specification clauses with rationale in the MasterSpec format so that it can be effectively used by practicing engineers. The committee discussed various test methods and their use, followed by an evaluation of different concrete member types and the potential performance properties that could be specified. The committee received a presentation on the FHWA Performance Engineered Mixtures for Pavements, AASHTO provisional standard PP84, that outlined the options in the guide specification and upcoming implementation efforts. The committee discussed sponsoring technical sessions at future conventions and identified a few potential topics. Colin Lobo (secretary) and Karthik Obla maintain representation on Committee 329.
330 – Parking Lots The ACI 330 Committee is currently revising 330R-08. The 330.2R-17: Guide for the Design and Construction of Concrete Site Paving for Industrial and Trucking Facilities was published this past summer. There will be an ACI Webinar to discuss the document in detail on the first Tuesday in April. Amanda Hult maintains representation in ACI 330.
522 – Pervious Concrete The ACI 522.1-13 Specification for Pervious Concrete Pavement revision is complete and will be out for balloting prior to the Spring 2018 meeting. All committee comments have been addressed for the revision of 522R document and will be sent to TAC for approval after ballot. The next pervious concrete competition will be held at the Fall 2018 convention in Las Vegas, NV. Amanda Hult maintains representation in ACI 522.
555 – Recycled Materials The document Removal and Reuse of Hardened Concrete is being revised to include a section on crushed concrete aggregates from returned concrete based on research work conducted at the NRMCA Research Laboratory. Several chapters have been balloted and the committee plans to complete the document soon. The committee continues to organize many technical sessions on the use of recycled materials in concrete at ACI conventions due to the continued interest on these topics. The committee meetings are well attended. Karthik Obla maintains representation in ACI 555.
Other Information
A CRC-funded (ACI Foundation) project is assimilating the variations on recommendations and requirements for durability in ACI committee documents and standards. The group will make recommendations to the impacted committees to harmonize guidance and requirements on durability in ACI documents. CRC is soliciting projects for funding in 2018. At least four projects will be funded. Colin Lobo maintains representation on ACI CRC.
A series of four technical sessions were held to honor Ward Malisch, who served most recently as the technical director of American Society for Concrete Contractors. Ward has worked at ACI and is a past editor of Concrete Construction magazine. A wide range of interesting topics that have been of interest to Ward were included in the sessions. Colin Lobo presented on Should You Reject the Load of Concrete After 90 Minutes, where he discussed balancing between lost revenue with rejecting acceptable concrete to that associated with extended haul time and delays on pours. The sessions were recorded and will be available at ACI University in the future. Some of the presenters have committed to write papers for an ACI Special Publication.
National Ready Mixed Concrete Association