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MINI SESSION: Advances in Early-Age Testing for Long-Term Performance of Concrete
Monday, October 18, 2021 3:30 PM - 4:30 PM
The early-age properties of concrete materials have a significant effect on the long-term performance of concrete structures. A fundamental understanding of the properties of concrete at early age is critical to ensure long-term structural integrity and safety of concrete structures. A number of methods of early-age testing have been introduced to allow predictions of the long-term durability of concrete. The objective of this session is to bring together researchers, material suppliers, and contractors to discuss the recent developments in early-age testing for long-term performance of concrete. Abstracts that provide fundamental or practical contributions are invited.
(1) Increase awareness about the importance of early-age properties for long-term durability;
(2) Provide a forum for exchange of ideas related to early-age testing for long-term performance;
(3) Foster future sessions on innovative methods for early-age testing for long-term performance;
(4) Enhance the multidisciplinary aspect of innovative cement and concrete research.
This session has been approved by AIA and ICC for 1 PDH (0.1 CEU). Please note: You must attend the live session for the entire duration to receive credit. Mini Sessions will not be available on-demand.
Effects of Zero-Stress Temperature on Cracking Risk of Concrete Structures
Presented By: Vinh Dao
Affiliation: The University of Queensland
Using Early-Age Resistivity Testing to Predict Long-Term Concrete Durability
Presented By: Andrew Fahim
Affiliation: Giatec Scientific Inc.
Description: Current standards and specifications, including ACI 318, rely on prescriptive specifications that define a concrete mixture in terms of its constituents and mixture proportions. In contrast, performance-based specifications define a mixture in terms of a set of measurable properties that show the mixture will satisfy in-service performance criteria. These properties could range from plastic properties such as slump or slump flow to long-term durability performance for concrete exposed to freeze-thaw, chloride exposure, sulfate exposure, among other factors. This work presents a method to utilize continuous resistivity testing for use in performance-based specifications and in projecting the long-term concrete durability. The method is based on using resistivity measurements, during early ages (1 to 28-days), as well as a knowledge of the concrete pore fluid conductivity, to deduce the volume and connectivity of the pore structure of concrete. The continuous measurements do not only allow for calculating the diffusion coefficient at a given point in time, but also in projecting the changes in diffusion coefficient with respect to concrete maturity. The capabilities of this approach and its limitations are discussed in this work and the recommended procedure is demonstrated with several examples.
Real-Time Monitoring of Concrete Strength Development at Early Age for Optimal Traffic Opening
Presented By: Luna Lu
Affiliation: Purdue University
Description: It is an urgent need to develop a reliable in-situ sensing method to determine the strength
of concrete at its very early ages due to fast paced construction. To address this need, my lab has developed a reliable and efficient in-situ nondestructive testing (NDT) method for monitoring of early-age strength gain of concrete using electromechanical impedance (EMI) method coupled with piezoelectric sensors. The EMI method involves bonding/embedded a sensor on/into concrete which is then electrically excited by an impendence analyzer. In principle, development of stiffness in concrete will be reflected in the measured impedance of sensors due to their piezoelectric effect.
We have systematically investigated the feasibility of using piezo sensor to test the compressive strength gain of cement paste, mortar, and concrete sample with different water-to-cement ratio and various proportions of supplementary cementitious materials incorporated at its very early age. The sensing results have achieved very high correlation with cylinder testing (R > 0.95). The field testing of our piezoelectric sensors has been done on interstate highway I-465, I-70 and I-74 patching and paving work. In this talk, I will discuss the principle of sensing technology, field implementation results and the potential opportunity for concrete industry.
Early-Age Tensile Creep Testing for Low Heat Performance Concrete (LHPC)
Presented By: Matthew D'Ambrosia
Affiliation: MJ2 Consulting, PLLC
Description: Mass concrete structures experience tensile stresses at early age that can result in detrimental cracking if not properly managed. The industry currently prescribes several methodologies for managing the developing stress, including precooling, post-cooling, and insulation of surfaces, all of which add cost and time to the project. Low heat performance concrete (LHPC), a relatively new technique made possible with supplementary cementing materials (SCMs), takes advantage of the unique early creep characteristics of relatively high SCM concrete. Higher early creep rates have been observed in laboratory studies, including uniaxial and ring-type restrained tests, which give greater potential for tensile stress relaxation, thus reducing the tendency for cracking in mass concrete structures. Field examples will be provided, as well as recommended protocol for specifications and quality testing in practice.