The inadequate disposal of household appliances by consumers and industries have annually been generating enormous amounts of polymeric waste (PW). So, the interest in reuse of PW in civil construction has increased. The production of new cementitious materials, such as concrete with PW, proves to be a promising solution to inappropriate disposal of this waste. In this study, self-compacting concrete (SCC) was developed with partial replacement of the coarse aggregates by polymeric waste (PW) from the recycling of refrigerators. In the SCC reference mixture, Portland cement, silica fume, sand, gravel and superplasticizer were used. The study also grouped the gravel as replaced by 5%, 10%, 15% and 20% of PW. In order to analyze the samples, the following tests were used: spreading, viscosity, passing ability, compressive strength, tensile strength, microstructure, modulus of elasticity, specific gravity, absorption, voids index and electrical resistivity. The SCC found showed adequate homogeneity and viscosity, staying within the normative parameters. The mechanical resistance was above 20 MPa; specific mass between 1870 to 2260 kg/m3; modulus of elasticity ranged from 34 to 14 GPa; and electrical resistivity between 319 to 420 ohm.m. Due to the mechanical resistance, the SCC with PW can be used for structural purposes and densely reinforced structures such as pillars, beams and foundation elements.
Plane problems of linear fracture mechanics were solved with the dual boundary element method (DBEM) using the tangential differential operator (TDO) in traction boundary integral equation (BIE). The numerical implementation employed same shape functions for conformal and non-conformal interpolations with nodal parameters fixed at the ends of elements. Different collocation point positions were used in crack surfaces according to continuity requirements related to each BIE type employed. The aim of this paper is presenting a simple implementation for fracture analysis. Results obtained in the literature for stress intensity factors were included to show the accuracy of the formulation.
Superabsorbent polymers (SAP) have gained the attention of the engineering field for applications in cementitious composites. Recently, many studies have addressed using these materials as an alternative to controlling recurrent pathologies, especially retraction in the hardening stage. This study conducted a literature review in the Scopus and Web of Science databases to identify relevant studies for future research in this area. Analyses were performed using the RStudio software program, where data on the number of publications, the main authors and journals, the most used keywords, and most common countries of publication were analyzed. Furthermore, bibliographic coupling and co-citation analyses were carried out. The results indicate that the most published authors were De Belie, Snoeck and Liu J., and the most cited authors were Jensen, Schrofl and Snoeck. Although Brazil is among the fifteen most published countries, it was not among the most cited, showing lacks in studies. In total, 343 articles were found in the Scopus database and 369 in the Web of Science.
A formulation is presented to perform crack propagation analyses in cohesive materials with the dual boundary element method (DBEM) using the tangential differential operator in the traction boundaryintegral equations. The cohesive law is introduced in the system of equations to directly compute the cohesive forces at each loading step. A single edge crack is analyzed with the linear function to describe the material softening law in the cohesive zone, and the results are compared with those from the literature. Keywords: cohesive model, crack analysis, dual boundary element model, plane problems, tangential differential operator. INTRODUCTIONThe surfaces of cracks behind the (fictitious) crack tip are not completely separated in some materials, such as concrete, brittle polymers, fiber-reinforced composites, tough ceramics and some alloys. The tractions can be transferred across the crack line along a relatively long extension of the crack, which is commonly called the wake zone, the bridging zone, or the cohesive zone. The main assumption is the occurrence of material softening beyond the peak load in a narrow layer with a negligible volume behind the fictitious crack tip, in which the action can be replaced by cohesive forces (Fig. 1). Two types of constitutive laws for the material in the cohesive zone have been used in the literature. This study employs a traction-displacement relationship in the cohesive zone instead of using a material constitutive law that is defined in terms of stresses and strains accompanied by a layer thickening law. Barenblatt [1] introduced a cohesive model that employed a fictitious crack. Hillerborg et al.[2] proposed a function for a softening model related to an opening (mode I) crack (Fig. 2), which allowed finite element analyses of the problem to be performed, such as those by Petersson [3], Carpinteri [4], and Rots [5].The boundary element method (BEM) is superior to the finite element method (FEM) in crack propagation analysis because remeshing of the domain is not necessary when the crack grows, and new elements can be introduced without affecting the existing elements. The coincidence of two crack surfaces requires two different boundary integral equations (BIEs) for the solution. The dual boundary element method (DBEM) is a technique that is employed for crack propagation analysis. The position of the collocation point to solve the traction BIE and the strategy to treat improper integrals are the essential features of the formulation. The tangential differential operator (TDO) in conjunction with integration by parts is an interesting procedure for reducing the order of singularity in fundamental solution kernels of traction BIEs when Kelvin-type fundamental solutions are employed. Kupradze [7] first presented an application using the TDO, and Sladek [8] employed the TDO in a curved crack solution. Bonnet [9] presented regularized formulations for the BEM employing the TDO for gradients in potential problems and in stress BIEs for elasticity problems, includin...
Crack propagation in a single-edge notched beam is analyzed with the three-point bending test. Two constitutive laws that describe the material softening in the cohesive zone were tested, and their results were compared. The dual boundary element method (DBEM) is employed with the traction boundary integral equation using the tangential differential operator. A constitutive law was introduced in the system of equations, and the cohesive forces were directly computed at each loading step. The results are compared with the experimental and numerical results available in the literature.
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