International Concrete Abstracts Portal

The movement of ultra-high-performance concrete (UHPC) toward wide scale acceptance within the concrete industry has generated interest in developing improved test methods to provide quality assurance for this material. Most test methods currently used to measure the tensile behavior of ultra-high-performance concrete require specialized testing equipment that is not typically owned by precast or ready-mix production facilities. These test methods provide reliable data for quality assurance of newly developed concrete mixes, but they are impractical as quality-control tests, which would need to be performed for every UHPC placement. This paper presents the development of a simple and inexpensive test to measure tensile strength and ductility for UHPC and serve as a quality-control test. This method was developed from the double-punch test, commonly referred to as the “Barcelona test,” but has been revised to incorporate substantial changes to the loading and data collection requirements to eliminate the need for expensive, specialized equipment. It was determined that the modified test method could produce reliable results using a load-controlled testing procedure with manually recorded data points taken every 0.635 mm (0.025 inches) of vertical displacement for ductile concrete specimens. It was also determined that specimen surface grinding, loading rate, and punch alignment did not significantly influence the test results. However, the fabrication of the specimens, specifically the rate and method at which the molds were filled, had a significant effect on the results. Accordingly, any recommended standardized test method based off of this procedure should have requirements on specimen fabrication.

This study explores technological advancements enabling the utilization of GFRP bars in concrete structures, particularly in coastal areas. However, GFRP bars often encounter reduced bend strength at specific bend locations, which may pose a challenge in their practical application. Various properties such as the strength of bent GFRP bars are crucial for quality assurance, yet existing testing methods stated in ASTM D7914M-21 and ACI 440.3R-15 have limitations when applied to different GFRP bent shapes. Furthermore, those methods require special precautions to ensure symmetry and avoid eccentricities in specimens. To address these challenges, CSA S807:19 introduced a simpler standardized testing procedure that involves embedding a single L-shaped GFRP stirrup in a concrete block. However, the specified large block size in CSA S807:19 Annex E may pose difficulties for both laboratory and on-site quality control tests. Therefore, CSA S807:19 Annex E (Clause 7.1.2b) permits the use of a customized block size, as long as it meets the bend strength of the FRP bars without causing concrete splitting. To date, very few prior research has explored the use of custom block sizes. Therefore, this study aims to thoroughly investigate the strength of bent FRP bars with custom block sizes and without block confinement. Such an investigation serves to highlight the user-friendliness and efficiency of the CSA S807:19 Annex E method. The study recommends two block sizes: 200x400x300 mm (7.87x15.75x11.81 in) for bars <16 mm (0.63 in) diameter and 200x200x300 mm (7.87x7.87x11.81 in) for bars <12 mm (0.39 in). Additionally, the study cautions against using confinement reinforcement, especially with smaller blocks, as it could interfere with the embedded bent FRP bar. Furthermore, the study suggests incorporating additional tail length to mitigate the debonding effects resulting from fixing the strain gauges to the bent portion of the embedded FRP bar. By exploring these modifications, the study seeks to enhance the effectiveness of the testing procedure and expand its practical application for both laboratory and on-site quality assurance. The findings hold implications for the reliable testing of GFRP bars' strength, advancing their use as reinforcement in concrete structures.

This is a second article in a series discussing a study to evaluate laser scanning for concrete quality assurance applications. It focuses on the use of laser scanning technology to evaluate floor flatness and levelness. F-numbers obtained using a Type II device and laser imaging devices were compared and evaluated for their repeatability and reproducibility.

A successful concrete repair project requires a close coordination of efforts between the three major parties involved: the owner, the licensed design professional (LDP), and the contractor. Lack of coordination and clear understanding of the professional and contractual responsibilities, as well as the expectations, of each party involved in a concrete repair project, could result in long legal disputes to attempt to sort out the responsibilities of each party. The greatest victim of the dispute is usually the structure itself. The American Concrete Institute (ACI) has led the effort to develop responsibility guidelines in concrete construction. ACI 132 identifies and suggests the allocation of responsibilities to various parties involved in concrete construction. ACI 132 document is applicable to general concrete construction, and it does not consider the particularities of evaluating and repairing existing concrete structures. ACI 562 provides minimum requirements for assessment, repair and rehabilitation of existing distressed concrete structures, including a discussion on the responsibilities of the licensed design professional for the evaluation and repair of concrete structures. This paper discusses the responsibilities of the licensed design professional, the contractor, and the owner through a repair case study. The paper demonstrates the need to expand ACI 132 and/or ACI 562 to include responsibility guidelines for concrete repair projects.

ACI is offering a new certification program—Concrete Quality Technical Manager (CQTM). The CQTM program is intended to identify and confirm individuals who possess the knowledge and experience necessary to supervise an effective concrete quality assurance/quality control program, manage those duties on behalf of a ready mixed concrete company, or represent the design professional in technical matters pertaining to the concrete used on a project.