NRMCA Attends ACI Fall 2018 Convention, Files Update on Key Committee Action
The American Concrete Institute's Fall Convention was held last week in Las Vegas. The following is a summary of committee activity involving NRMCA staff representation:
132 – Responsibility in Concrete Construction – The committee continues to work on a Tech Note on the responsibilities associated with complying with requirements for initial curing of strength test specimen at the jobsite. Colin Lobo maintains representation on ACI 132.
201 – Durability – Three Tech Notes are being developed: Joint deterioration due to deicers; Iron sulfide (Pyrrhotite) in Aggregates and Microbial Induced Corrosion (MIC) of Concrete. Karthik Obla chairs a task group considering performance requirements for ACI 318 durability exposure classes. The group will initially focus on chloride and freeze thaw exposures and is considering the use of a formation factor requirement using the basis of a NIST model for pore solution conductivity. The 201 Subcommittee on Obtaining Durability in Design will develop a standard on attaining 50 to 100-year service life for structures exposed to chlorides. The Subcommittee on Executing Durable Concrete in Construction developed a framework for the standard. Mini sessions were held on MIC, deterioration that occurs in waste water treatment structures due to the bacteria that causes sulfuric acid damage. ASTM Subcommittee C13.02 has some test methods on MIC and is developing additional tests and a guide on MIC. The committee is developing a review paper on physical salt attack. The committee is also planning sessions on AAR for a future convention. The committee is collecting papers for two special issues of ACI Materials Journal on Durability in 2019: one on Chlorides and Corrosion and another on SCMs. Karthik Obla is the joint editor for the chlorides special issue. Karthik Obla maintains representation in ACI 201.
211 – Mixture Proportioning – The committee continues to work on revising its primary document on mixture proportioning ACI 211.1. A guide for selecting proportions for pumpable concrete has been published. A document on 3-point curves had been approved by the committee and is in the ACI review phase. Task groups are developing documents on assessing aggregate gradations and aggregate packing models. A document on proportioning with ground limestone and mineral fillers has been approved. Karthik Obla maintains representation on ACI 211.
214 – Strength Tests – The committee is working on revising the 214R guide document. A Tech Note “Using two instead of three 4x8 in. cylinders for acceptance testing” is being held in response to the ACI review process. The Committee was asked to develop a standard to estimate the actual in-place strength from the core tests. This is needed for evaluation of structures in seismic regions. The committee has completed a Tech Note on Cylinder vs Cube strengths and is working through the ACI review process. Karthik Obla maintains representation on ACI 214.
232 – Fly Ash – The committee has developed a Tech Note on Limits on the Quantity of Fly Ash in Concrete based on an NRMCA Specification in Practice topic and is being revised following ACI review. A Tech Note on Recovered Fly Ash is being finalized. Karthik Obla is the vice chairman of this committee.
240 – Pozzolans – A Tech Note on pozzolans derived from ground glass is being developed. The next TRB meeting will feature a one-day workshop on natural pozzolans. The natural pozzolan association will hold a symposium on May 16-17 in Wickenburg, AZ. More information is available at http://pozzolan.org/. Karthik Obla maintains representation on ACI 240.
301 – Specifications for Structural Concrete – The committee has essentially completed its revisions for the next version of the specification scheduled for release in 2020. It will address final approved changes to ACI 318 that are relevant to the specification. This meeting was spent on resolving remaining negatives on revisions. On completion of the final revisions, the document will be sent for ACI review and public comment. There are several useful revisions for the ready mixed industry in Section 4 of ACI 301. Colin Lobo maintains representation on ACI 301.
318 – Building Code for Structural Concrete – ACI 318 is scheduled to be published by Spring 2019 for it to be referenced in the next edition of the International Building Code. More than 25 code change proposals were reviewed and approved over two-day marathon meetings. The Code has been submitted for ACI review and comments will be addressed at a special meeting in December. Following that, the document will be available for public review and comment – a requirement of the process – before it is finalized. For concrete materials sections in Chapters 19 and 26, about 20 change proposals have been approved. At this meeting, changes approved were: inclusion of shotcrete (dry-mix and wet-mix) in the Code; a caution on use of alternative cements to be permitted when approved by the designer; a caution on the use of recycled aggregate with approval by the designer; requiring the designer to consider specification requirements for alkali aggregate reactivity for members that will be moist in service and establishing the “lambda” factor for design of lightweight concrete members on the basis of equilibrium density. Colin Lobo maintains representation on ACI 318 and ACI 318 Subcommittee A.
329 – Performance Criteria for Ready Mixed Concrete – Tech Note ACI 329.1T-18, Minimum Cementitious Materials Content in Specifications, has been published. This can be useful to address this issue commonly seen in specifications. Initial drafts of a guide to writing a performance specification were reviewed by the committee. Members volunteered to develop these sections that include suggested specification clauses and information to the specifier. MasterSpec Section 033000 format will be used. The Committee will start balloting these sections as they are written. Colin Lobo (secretary) and Karthik Obla maintain representation on Committee 329.
330 – Parking Lots – The ACI 330 Committee continues to work on revising its Guide document ACI 330R. Each chapter has been balloted and comments addressed during this meeting. The complete document will be balloted before the next meeting. Amanda Hult maintains representation in ACI 330.
522 – Pervious Concrete – ACI review comments on the guide to pervious concrete, 522R, were addressed and revisions and a new format is being finalized. The ACI 522.1-13 specification comments were discussed and changes were made accordingly. The specification will be sent out shortly for ballot. 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 organizes technical sessions on the use of recycled materials in concrete as there is continued interest on these topics. Karthik Obla maintains representation in ACI 555.
• Karthik Obla delivered a presentation on Cement Contents and Mixture Proportioning in a session organized by the Mixture Proportioning committee.
• Colin Lobo delivered a presentation in a session on performance specifications – identifying several prescriptive requirements that can be eliminated. The session included presentations from several high-profile projects, from DOT, infrastructure, and high-rise buildings, where performance alternatives had to be negotiated to accomplish the work.
• A Hot Topic Session discussed the issue of the 90-minute delivery limitation for ready mixed concrete. The speakers discussed the different options available to the producer for extended delivery times. Research from the New Jersey Institute of Technology CIM program was presented. There is a proposed revision to remove the numerical 90-minute limit in ASTM C94 and for a specific time limit to be established when concrete is ordered.
• Several papers discussed the development of SCC with low cementitious contents of 370-500 lb/yd3. These had high w/cm (>0.60) but were reported to have adequate freeze thaw durability. Paste volume was about 30%. Aggregate packing using models such as Compressible Packing model and the Fink and Dinger model were discussed.
• ACI Concrete Research Council (CRC) has funded eight project proposals in 2017. It is currently soliciting projects for the next funding phase that will be decided in December. Funding is at the level of $50,000 each. Projects should demonstrate benefit of their work to documents of ACI Committees. The ACI CRC partners with the RMC Research & Education Foundation and foundations of allied industry groups. Colin Lobo maintains representation on ACI CRC.