International Concrete Abstracts Portal

Through uniaxial tensile tests, the mechanical behavior of bone shaped concrete reinforced with glass textile and carbon textile impregnated with epoxy resin was verified using a stress-strain response curve. It was observed that elements reinforced with glass fabric presented different mechanical responses depending on the textile reinforcement rate. In samples with two layers of glass fabric, three stages were formed, as predicted in the literature. In the specimens reinforced with only one layer, the structural incapacity of the element was observed. For samples reinforced with carbon textile, there were problems with slipping and spalling caused by the concentration of stress at the ends of the piece. Even so, it was possible to clearly determine the three stages in the curve response of the material. The stresses experimentally obtained in the elements reinforced with carbon textile obtained results approximately five times greater than those of the glass fabric.

Prompt-gamma activation analysis (PGAA) is an elemental analysis method based on radiative neutron capture that has a high sensitivity to chlorine (Cl). To evaluate the feasibility of replacing the conventional wet chemistry method, ASTM C1152, with PGAA, four mixtures of concrete were prepared with Cl added, ranging from a 0.004 to 0.067% mass fraction of Cl in concrete. The PGAA method detected levels of 100 μg/g Cl in concrete. While both the PGAA and C1152 methods gave results systematically below the nominal values of added Cl, the PGAA data showed excellent correlation (R2 of 0.999) with the C1152 results measured on the same samples. Given that PGAA can measure Cl in concrete as well as C1152 and is faster and less labor-intensive, it can be a candidate for development as a standard method for an alternative to the latter.

Ground-glass pozzolan has recently been considered a supplementary cementitious material by Canadian (CSA A3000) and American (ASTM C1866/C1866M) standards, but limited studies have been done on ground-glass use on-site. So, in this study, several sidewalk projects were performed by the SAQ Industrial Chair at the University of Sherbrooke from 2014 to 2017 on fields with different proportions of ground glass (that is, 10, 15, and 20%) in different conditions considered in such a cold climatic region. Sidewalks are a nonstructural plain concrete element that are among the most exposed to chloride and freezing and thawing in saturated conditions of municipal infrastructures. Coring campaigns were carried out on these concretes after several years of exposure (between 5 and 8 years). The results of core samples extracted from the sites were compared to the laboratory-cured samples taken during the casting. These laboratory concrete mixtures were tested for fresh, hardened (compressive strength), and durability (freezing and thawing, scaling resistance, chloride-ion penetrability, electrical resistivity, and drying shrinkage) properties (up to 1 year). The results show that ground-glass concrete performs very well at all cement replacements in all manners in terms of long-term performance. Besides that, using ground-glass pozzolan in field projects also decreases the carbon footprint and environmental and glass disposal problems.

In marine structures, concrete requires adequate resistance against chloride-ion penetration. As a result, numerous studies have been conducted to enhance the mechanical properties and durability of concrete by incorporating various pozzolans. This research investigated the curing conditions of samples including zeolite and metakaolin mixed with micro-/nanobubble water in artificial seawater and standard conditions. The results indicated that incorporating zeolite and metakaolin mixed with micro-/nanobubble water, cured in artificial seawater conditions, compared to similar samples that were cured in standard conditions, improved the mechanical properties and durability of concrete samples. The 28-day compressive strength of the concrete samples containing 10% metakaolin mixed with 100% micro-/nanobubble water and 10% zeolite blended with 100% micro-/nanobubble water cured in seawater increased by 25.06% and 20.9%, respectively, compared to the control sample cured in standard conditions. The most significant results were obtained with a compound of 10% metakaolin and 10% zeolite with 100% micro-/nanobubble water cured in seawater (MK10Z10NB100CS), which significantly increased the compressive, tensile, and flexural strengths by 11.13, 14, and 9.1%, respectively, compared with the MK10Z10NB100 sample cured in standard conditions. Furthermore, it considerably decreased the 24-hour water absorption and chloride penetration at 90 days— by 27.70 and 82.89%, respectively—compared with the control sample cured in standard conditions.

Statistical process control (SPC) procedures are proposed to improve the production efficiency of precast concrete tunnel segments. Quality control test results of more than 1000 ASTM C1609/C1609M beam specimens were analyzed. These specimens were collected over 18 months from the fiber-reinforced concrete (FRC) used for the production of precast tunnel segments of a major wastewater tunnel project in the Northeast United States. The Anderson-Darling (AD) test for the overall distribution indicated that the data are best described by a normal distribution. The initial residual strength parameter for the FRC mixture, f D 600, is the most representative parameter of the post-crack region. The lower 95% confidence interval (CI) values for 28-day flexural strength parameters of f1, f D 600, and f D 300 exceeded the design strengths and hence validated the strength acceptability criteria set at 3.7 MPa (540 psi). A combination of run chart, exponentially weighted moving average (EWMA), and cumulative sum (CUSUM) control charts successfully identified the out-of-control mean values of flexural strengths. These methods identify the periods corresponding to incapable manufacturing processes that should be investigated to move the processes back into control. This approach successfully identified the capable or incapable processes. The study also included the Bootstrap Method to analyze standard error in the test data and its reliability to determine the sample size.