Recovery of Excavated Materials as an Alternative Solution to Earth Building Materials

The tunnel excavation works generate huge quantities of earth. These excavated materials are primarily stored in landfills. This paper proposes an alternative solution for valorizing excavated earth in earthen constructions. Firstly, the excavated earth was characterized using differential and gravimetric thermal analysis (DTA / TGA), infrared spectra (FTIR), and X-ray diffraction. Hence, sand, fine particles, and water extracted from excavated earth are used to elaborate mortars’ stabilized with cement, lime, and slag. Short hemp fibers were also used to diminish shrinkage cracks. The quantity of stabilizers was fixed to 5% by weight of the excavated earth while the water/solid ratio was maintained constant and equal to 0.45. Five different mortar formulations were performed using excavated earth and were cured for 28 days in a controlled environment before testing. Compressive and three-point flexural tests were carried out to determine specimens’ mechanical properties. The characterization results show that the excavated earth are mainly composed of dolomite, calcite, quartz, and clay. While, the mechanical results show that the stabilized excavated earth with cement additive presents higher mechanical properties relative to the other additives.

STUDYING THE MECHANICAL PROPERTIES OF HYBRID COMPOSITES USING NATURAL ADDITIVES WITH EPOXY

The fundamental goal of the present study is to study the effects of the natural additives with vegetable and animal sources in form (i.e. the short fibers and particle) on mechanical characteristics epoxy. (The wood dust WD, cow bones CB, date palm fiber DP, and sheep wool SW) have been chosen as natural additives with a variety of the weight ratio reinforcements for epoxy matrix, which is based upon the hybrid composites that have been produced by hand lay-up approach. Tensile, compression and flexural tests have been performed based on the American society for the testing and materials (ASTM) for the characterization of hybrid composites it has been discovered that mechanical characteristics may be increased or decreased according to the material additive type, its origins, and the utilized percentage of weight.

Strength and Toughness of Waste Fishing Net Fiber-Reinforced Concrete

In this study, we estimate the potential efficiency of waste fishing net (WFN) fibers as concrete reinforcements. Three WFN fiber concentrations (1, 2, and 3% by volume) were mixed with concrete. Compressive strength, toughness, splitting tensile strength, and biaxial flexural tests were conducted. Compressive strength decreased but other properties increased as a function of fiber proportions. According to the mechanical strength observations and the ductility number, WFN fibers yielded benefits in crack arresting that improved the postcracking behavior and transformed concrete from a brittle into a quasi-brittle material. It is inferred that WFN fiber is a recycled and eco-friendly material that can be utilized as potential concrete reinforcement.

Static and Dynamic Four-Point Flexural Tests of Concrete Beams with Variation in Concrete Quality, Reinforcement Properties and Impact Velocity

This paper discusses the results from three experimental test series previously conducted. The tests consist of quasi-static monotonic and dynamic four-point flexural tests on reinforced concrete beams. The effect of varying material and load parameters on the plastic strain distribution and energy absorbed by the reinforcement is discussed. The main findings are the significant effect of the post-elastic region of the steel reinforcement and the impact velocity during dynamic loading. The results will be used to validate and construct numerical models in future work, where the findings presented can be investigated further.

Mechanical characterization of jute fiber based biocomposite to manufacture automotive components

In this research work, samples of the biocomposite were manufactured using the vacuum assisted resin transfer molding (VARTM) technique, whose matrix is a polyester resin and the reinforcement is a biaxial fabric (90°) made with jute fiber. Then, tensile and flexural tests were carried out on standardized specimens under ASTM standards, in order to mechanically characterize the jute-polyester biocomposite. In both destructive tests, the results showed a linear-elastic behavior with brittle fracture and greater strength of the jute-polyester biocomposite, with respect to the thermosetting matrix’s properties. Subsequently, a finite element based static analysis was performed, with the help of the ANSYS software, to determine the mechanical behavior of interior opening handle for a car door. In it, a model sensitivity study was run to determine the influence of the mesh type and identify the convergence of mesh. Later, the static analysis results were obtained: critical zone, maximum operating stress and safety factors. The results obtained computationally validate the use of jute-polyester biocomposite, as a substitute for the manufacture of an interior opening handle for a car door. Finally, a scale model of the piece made with jute-polyester biocomposite was manufactured.

Axial variation in flexural stiffness of plant stem segments: measurement methods and the influence of measurement uncertainty

Background Flexural three-point bending tests are useful for characterizing the mechanical properties of plant stems. These tests can be performed with minimal sample preparation, thus allowing tests to be performed relatively quickly. The best-practice for such tests involves long spans with supports and load placed at nodes. This approach typically provides only one flexural stiffness measurement per specimen. However, by combining flexural tests with analytic equations, it is possible to solve for the mechanical characteristics of individual stem segments. Results A method is presented for using flexural tests to obtain estimates of flexural stiffness of individual segments. This method pairs physical test data with analytic models to obtain a system of equations. The solution of this system of equations provides values of flexural stiffness for individual stalk segments. Uncertainty in the solved values for flexural stiffness were found to be strongly dependent upon measurement errors. Row-wise scaling of the system of equations reduced the influence of measurement error. Of many possible test combinations, the most advantageous set of tests for performing these measurements were identified. Relationships between measurement uncertainty and solution uncertainty were provided for two different testing methods. Conclusions The methods presented in this paper can be used to measure the axial variation in flexural stiffness of plant stem segments. However, care must be taken to account for the influence of measurement error as the individual segment method amplifies measurement error. An alternative method involving aggregate flexural stiffness values does not amplify measurement error, but provides lower spatial resolution.

Experimental and Numerical Investigation on the Size Effect of Ultrahigh-Performance Fibre-Reinforced Concrete (UHFRC)

In the last few years, there has been increasing interest in the use of Ultrahigh-Performance Fibre-Reinforced Concrete (UHPFRC) layers or jackets, which have been proved to be quite effective in strengthening applications. However, to facilitate the extensive use of UHPFRC in strengthening applications, reliable numerical models need to be developed. In the case of UHPFRC, it is common practice to perform either direct tensile or flexural tests to determine the UHPFRC tensile stress–strain models. However, the geometry of the specimens used for the material characterization is, in most cases, significantly different to the geometry of the layers used in strengthening applications which are normally of quite small thickness. Therefore, and since the material properties of UHPFRC are highly dependent on the dimensions of the examined specimens, the so called “size effect” needs to be considered for the development of an improved modelling approach. In this study, direct tensile tests have been used and a constitutive model for the tensile behaviour of UHPFRC is proposed, taking into consideration the size of the finite elements. The efficiency and reliability of the proposed approach has been validated using experimental data on prisms with different geometries, tested in flexure and in direct tension.

Strength Characteristics of Concrete with Waste Polypropylene as Modifier for Pavement Construction

The demand for a better performing pavement and the need to convert the ever-growing polymer waste into beneficial use necessitated the need to develop and characterize a polypropylene modified concrete for use in pavement construction. This research focuses on characterizing the strength of concrete produced with waste polypropylene waste as modifiers for pavement construction. The materials used in this research are fine and coarse aggregates, cement and polypropylene waste chairs (PWC). Tests were performed on the aggregate and fresh concrete to determine their suitability and characteristics for use in concrete for pavement. Two concrete grades 1:2:4 and 1:3:6 was produced into 200 mm, 400 mm and 500 mm long paving stones on which compressive and flexural tests were performed. Results obtained showed that 400 mm 1:2:4 grade concrete has the highest compressive strength of 27.36 N/mm2 at 10% polypropylene composition. The 200 mm 1:2:4 concrete grade paving stone with 10% polyprpopylene composition has the highest flexural strength of 12.90 N/mm2. The 200 mm at 10% polypropylene composition correlation coefficient has that the highest value of 0.98 which better explains the compression-flexural strength relationship and validates the 200 mm length at 10% polypropylene composition paving stone as the most adequate length of paving stone for pavement construction. It was concluded that the 200 mm long 1:2:4 concrete grade paving stone at 10% polypropylene composition is the best length of paving stone that can give an adequate flexural strength which is the most important requirent in concrete pavement requirement.