A new Ready Mixed Concrete Research & Education Foundation report reflecting work at the National Ready Mixed Concrete Association’s College Park, Md. laboratory addresses the lack of a consistent and cost-effective concrete permeability test method. “Reliability of Resistivity Tests of Concrete” authors evaluate mix design and specimen preparation factors that impact resistivity measurement; their conclusions can be incorporated in standards driving agency and engineer specifications in public and private concrete construction.
The report cites the increasing acceptance of a non-destructive, easy-to-perform electrical test method that predicts concrete permeability and serves as an alternative to prescriptive water/cementitious material ratio specifications. Authors contrast the procedure with the benchmark ASTM C1202 – 19 Standard Test Method for Electrical Indication of Concrete’s Ability to Resist Chloride Ion Penetration, which they characterize as deficient, “more expensive and subject to error by less proficient testing agencies.”
“The current way of specifying for durability is to impose a maximum w/cm limit on concrete,” says 2020 RMC Foundation Chairman Ted Chandler (Chandler Concrete). “Unfortunately, this is not verifiable and does not recognize the significant benefit provided by supplementary cementitious materials. In order to optimize concrete mixtures, we need performance-based specifications to allow for innovation, and we need reliable test methods to be used for quality assurance by specifiers and owners. This research provides us the means to do both.”
“Allowing for optimization of modern concrete mixtures is essential to building sustainable, long-lasting and affordable infrastructure,” notes Executive Director Julie Garbini. The new Foundation report builds on a library of guides and studies behind the industry’s Prescriptive-to-Performance Initiative, aimed at optimizing concrete for strength and durability, sustainability, and improved competitiveness with other building systems, she adds.
RAPID CHLORIDE AND RESISTIVITY MEASUREMENT DATA POINTS
“Reliability of Resistivity Tests of Concrete” authors chart benchmark figures for two test methods’ gauge of permeability characteristics. Coulomb and electrical current levels reflect rapid chloride ion penetration and resistivity of thin section, 2-in. diameter cylindrical specimens. The full 64-page report is posted at www.rmc-foundation.org.
SALUTE TO CONCRETE DELIVERY PROFESSIONALS
National Mixer Driver Appreciation Week, October 5-9, will afford ready mixed concrete producers and their allies an opportunity to acknowledge the hard work, dedication and customer service of delivery professionals across the industry. The National Ready Mixed Concrete Association announced the event in conjunction with a rescheduling of this year’s National Mixer Truck Driver Championship to September 2021. The competition is a major draw of the ConcreteWorks Conference and Expo, originally set this year for September 25-27 in Colorado but moved to October 7-8 in virtual format.
A just-launched Mixer Driver Appreciation Week portal at www.nrmca.org includes an open thank you letter from NRMCA Chairman John Carew (Carew Concrete & Supply) and President Michael Philipps; driver thank you letter template for individual producers; and, polo or T-shirt, cap and tumbler store. Like the Driver Championship, Appreciation Week is sponsored by NRMCA Affiliate, the Truck Mixer Manufacturers Bureau.