Abstract Ground-glass pozzolan (GP) obtained by grinding the mixed-waste glass to a similar fineness as cement can act as a supplementary cementing material (SCM), given that it is an amorphous and a pozzolanic material. The GP showed promising performance in mortar and concrete mixtures in laboratory and in large-scale field applications, enabling it to be a useful new SCM. However, while there are results about the use of GP in mortar and concrete, there is no single study covering all the aspects of using GP in mortar and concrete that satisfies the requirements of the ASTM and CSA Standard Specifications. This review on the use of GP in mortar and concrete compiles and analyzes the available data concerning the characteristics, production rates, and performance of GP used in mortar and concrete to provide the necessary information for updating the ASTM and CSA Standard Specifications to consider the GP as a new SCM.

Abstract Pervious concrete (PC) is a sustainable concrete material that is being used as a strategy for reducing stormwater-related runoff and recharging ground water. As part of a smart cities initiative of the Government of India, pervious concrete pavement (PCP) mixtures were studied in the laboratory for different properties and implemented in the field to function as parking lots and walkways. A labor-based methodology was used in the construction of eighteen PC slabs encompassing six different mixtures. The construction practices followed were rational and demonstrated to the field engineers how to carry the technology further. The field-produced mixtures had higher porosity and lower density compared to laboratory mixtures. The infiltration capacities (IC) of field PC slabs were similar to those determined in the laboratory. The single-sized graded mixtures depicted lower IC compared to the mixtures with graded aggregates, which was attributed to thicker cement paste coating in single-sized aggregates, while the mixtures with lower cement-to-aggregate ratio depicted higher IC. The coring procedure resulted in a loss of aggregates that may have provided erroneous values of the in-situ properties, and hence, a methodology is deemed essential to investigate the in-situ characteristics using nondestructive techniques. In the future, the differences in the porosity between field and laboratory mixtures should be accounted for in order to avoid an overestimation of the PC properties and to achieve rational designs of PCP as most of the properties are dependent upon porosity.

Abstract Accelerators are used to accelerate cement hydration, thereby reducing setting time and increasing early age strength gain. Accelerators are typically developed for use at low temperatures; however, they may be used in other applications such as high early strength concrete mixtures for pavement patching, which requires short closure time. In this study, the effects of a commercial accelerator on the hydration of cement pastes made with Type I ordinary portland cement are investigated at four temperatures. At lower temperatures (10°C and 23°C), the accelerator decreases the time to reach the silicate peak and sulfate depletion peak time and increases the peak heights. At higher temperatures (37.5°C and 50°C), the silicate and sulfate depletion peak times or heights do not change appreciably. At high temperatures, the pastes are very likely undersulfated, as indicated from calorimetry data with added sulfate. The accelerator does not significantly increase the cumulative heat release at 72 hours in any of the pastes. The results from pastes in the laboratory are used to interpret flexural strength results obtained from field concrete. Flexural strength results indicate that accelerated concretes cured at high temperatures have lower strength as compared to concretes cured under standard curing temperatures. The addition of sulfate increases the flexural strength of accelerated concrete cured at higher temperatures. From these results, it is evident that the accelerator is not effective at higher temperatures and that the addition of accelerator may negatively impact hydration and strength gain at higher temperatures. The addition of sulfate alleviates some of the negative impact of accelerator at higher temperatures.

Abstract The uniaxial compression tests were carried out on the prism specimens of plastic fiber–reinforced rubber concrete with three water-binder ratios and six kinds of plastic fiber contents, and the stress-strain curves were monitored. According to the uniaxial compression test, the change rule of the rising and falling of the stress-strain curve and the change of the peak strain were analyzed. Based on the features of the stress-strain curves, the uniaxial compressive constitutive model for plastic fiber–reinforced rubber concrete is proposed containing constitutive parameters A and B. By using the regressive analysis with the least squares principle method for the experimental data, we propose the mathematical expression of the constitutive parameters “a” and “b” of the rubber concrete, which demonstrates the specific relationship between the constitutive parameters A and B. Thus, the constitutive equation for plastic fiber–reinforced rubber concrete was obtained.

Abstract This paper investigates the change in micromorphology of two binders and their respective warm mix asphalt binders before and after aging using atomic force microscopy (AFM) and optical microscopy. The control (PG 64-22) and crumb rubber modified (CRM) binders were blended with two different types of wax additives (L, a wax-based composition including crystal controller, and S, a long chain aliphatic hydrocarbon) and then artificially short-term and long-term aged using the rolling thin film oven and pressure aging vessel procedures. L is a wax based composition including crystal controller and S is a long chain aliphatic hydrocarbon. The AFM tapping-mode imaging technique was used to analyze the microstructure and the Superpave asphalt binder test was used to measure the rheology properties. In general, the results of this study indicated that (1) a correlation was observed between the changes in micromorphology (the distribution of dispersed domains and matrix) and rheology properties regardless of the aging, binder, and wax types; (2) the addition of crumb rubber into the base binder decreased the dimension of the catana phase (“bee-like”) structure, which increased the quantity of these structures; (3) the opposite trend was found between the aged control binder and the aged CRM binder regarding the size of the bee-like structure; (4) the long-term aging seemed to have a significant effect on the microstructures of the warm control and CRM binders; and (5) the inclusion of S and L was observed to have a similar trend for both binder types in terms of increased size of the bee-like structure and no bee-like structure, respectively.

ABSTRACT In this study, the properties of rubberized concrete were examined and finite-element (FE) models were developed to investigate the accuracy of a current concrete material model in predicting the compressive behavior of rubberized concrete. The rubber particles, with a size of 1.18 mm were used at 0 %, 6 %, 12 %, and 18 % volume replacement of fine aggregate, keeping the proportions of gravel, water, and cement the same in all mixtures. Cylindrical and beam specimens were prepared and tested to evaluate the effect of rubber content on the density, compressive strength, elastic modulus, and damping ratio of the concrete. The results indicated that the damping ratio of rubberized concrete increased by 5.5 %, 27.8 %, and 64.8 % with rubber replacement of 6 %, 12 %, and 18 %, respectively. In addition to the experimental study, non-linear finite-element analysis was carried out using LS-DYNA software (Livermore Software Technology Corporation). The FE model developed in this paper was able to closely simulate the compressive behavior of the rubberized concrete specimens. The stiffness, compressive strength, volumetric response, and the dilation behavior obtained using the FE analysis agreed well with the values measured in the experimental work. The results show that the current concrete material model can be considered for rubberized concrete, provided that the compressive strength is modified to account for the reduction in strength caused by the added rubber.

Abstract The direct tension pull-off test (ASTM D7522/D7522M-15, ASTM D4541-09e1, ASTM C1583/C1583M-13 and others) is the only practical, in situ test to assess bond strength of materials bonded to a concrete substrate relatively. Although the method is prescribed, there are a number of variations anecdotally seen in practice which may affect the uniform interpretation of the test method results. In particular, it was hypothesized that both shear and normal stresses introduced by the drilling process damage the sample affecting results disproportionately with the depth of cut. This study systematically investigated this hypothesis with the aim of providing improved guidance associated with depth, and indeed method, of core drilling. Preformed, hand-drilled, and core-drilled specimens were tested, and the results were compared. Additionally, a system for applying a controlled torsional moment to the specimens was used to quantitatively investigate the effect of such force being applied during the specimen preparation. This study also investigated the effect of using square cuts. Hand-drilled and core-drilled specimens were observed to have reduced pull-off capacity—exhibiting a reduction of 0.03 MPa/mm depth and 0.04 MPa/mm depth, respectively—with increased core depth, although this was not attributed to the torsion that may be present during the drilling process. Square specimens exhibited marginally lower capacity than comparable round specimens and a similar increased reduction in capacity of 0.05 MPa/mm depth of cut. Finally, a discussion of the implications and interpretation of pull-off test results is presented.

Abstract This experimental investigation employing leaching characteristics of concrete made with E-waste plastic [high-impact polystyrene (HIPS)] was carried out using the toxicity characteristic leaching procedure (TCLP). The heavy metals, such as Cd, Cu, Zn, and Pb, were analyzed from concrete with varying percentages of HIPS (0 %, 10 %, 20 %, 30 %, 40 %, and 50 %) at various ages, such as 28, 60, and 90 days. The concentrations of Cd in the TCLP extracts of all the samples were found to be lower than the regulatory level of 1 mg/l at 28, 60, and 90 days. The Cu, Zn leachate content decreased with curing, and all samples were found well below the prescribed level of 100 mg/L and 500 mg/L, respectively. The concentrations of Pb in the TCLP extracts of all the samples were found to be lower than the regulatory level of 5 mg/L at 28, 60, and 90 days. The results are also compared with Resource Conservation and Recovery Act (RCRA) prescribed limits for Cd, Cu, Zn, and Pb, which are 0.5 mg/L, 130 mg/L, 500 mg/L, and 1.5 mg/L, respectively, and which are within limits.

Abstract The number of people wanting to use electrical tests to determine the transport properties of concrete has increased with advancements in the portability of hand-held testing devices. Electrical measurements are an attractive test method to quantify transport properties of cement-based materials since they can be performed rapidly. There is a high potential for using these tests in quality control or mixture qualification. However, electrical measurements can be significantly influenced by curing and storage conditions, which can impact the degree of saturation, degree of hydration, sample temperature, and pore solution chemistry. This study proposed a general equation that described the electrical resistivity measurements in cementitious systems and possible methods to account for some of these conditioning-induced changes. It is proposed that these tests are useful in the determination of the formation factor, a numerical quantification that describes the microstructure. A comparison of the formation factor obtained from rapid electrical measurements using the Nernst-Einstein relationship was compared to a migration test with the goal of proposing a curing methodology for rapid electrical tests that allows for the determination of a true transport property.