Analysis of Measured Parameters in Relation to the Amount of Fibre in Lightweight Red Ceramic Waste Aggregate Concrete

The present study provides a correlation and regression analysis of lightweight waste aggregate concretes with varying degrees of fibre reinforcement. The concrete mix contains pre-soaked red ceramic waste aggregate, expanded clay coarse aggregate and Portland cement. Copper-coated crimped steel fibre was used as the reinforcement. The experimental results included properties measured by destructive test methods—compressive strength, splitting tensile strength, static modulus of elasticity, the limit of proportionality, shear strength; and by non-destructive test methods—dynamic modulus of elasticity and surface electrical resistivity. These properties were analysed to study the relevancy and significance between non-destructive and destructive methods of measurement in the case of different amounts of fibre. The results show differences in the degree of fit to the linear and quadratic regression curves for pairs of destructive and non-destructive test results. As expected, the linear relationship can be applied in a few cases, but the quadratic curve must be used for a few pairs. Another observation is that it is not possible to neglect the amount of fibre in the correlation analyses of the measured properties.

Experimental and Numerical Verification of the Railway Track Substructure with Innovative Thermal Insulation Materials

The article aims to present the modified structural composition of the sub-ballast layers of the railway substructure, in which a part of the natural materials for the establishment of sub-ballast or protective layers of crushed aggregate is replaced by thermal insulation and reinforcing material (layer of composite foamed concrete and extruded polystyrene board). In this purpose, the experimental field test was constructed and the bearing capacity of the modified sub-ballast layers’ structure and temperature parameters were analyzed. A significant increase in the original static modulus of deformation on the surface of composite foamed concrete was obtained (3.5 times and 18 times for weaker and strengthen subsoil, respectively). Based on real temperature measurement, it was determined the high consistency of the results of numerical analyses and experimental test (0.002 m for the maximum freezing depth of the railway line layers and maximum ±0.5 °C for temperature in the railway track substructure–subsoil system). Based on results of numerical analyses, modified railway substructure with built-in thermal insulating extruded materials (foamed concrete and extruded polystyrene) were considered. A nomogram for the implementation of the design of thicknesses of individual structural layers of a modified railway sub-ballast layers dependent on climate load, and a mathematical model suitable for the design of thicknesses of structural sub-ballast layers of railway line were created.

Influence of Concrete Strength Class on the Long-Term Static and Dynamic Elastic Moduli of Concrete

Construction materials, among which concrete is by far the most used, have followed a trend of continuously increasing demand in real estate. A relatively small number of research works have been published on the long-term material properties of concrete in comparison to studies reporting their findings at standard curing ages of 28 days. This is due, in part, to the length of time one must wait until the intended age of concrete is reached. The present paper contributes to filling this gap of information in terms of the strength and dynamic elastic properties of concrete. The dynamic modulus of elasticity may be used to assess the static modulus of elasticity (Young’s modulus), a key property used during the design stage of a structure, in a non-destructive manner. This paper presents the results obtained from laboratory tests on the long-term (6 years) characterization of concrete from the point of view of dynamic shear and longitudinal moduli of elasticity, dynamic Poisson’s ratio, static modulus of elasticity, compressive and tensile splitting strengths, and their change depending on the concrete strength class.

Concrete Compressive Strength by Means of Ultrasonic Pulse Velocity and Moduli of Elasticity

Developing non-destructive methods (NDT) that can deliver faster and more accurate results is an objective pursued by many researchers. The purpose of this paper is to present a new approach in predicting the concrete compressive strength through means of ultrasonic testing for non-destructive determination of the dynamic and static modulus of elasticity. For this study, the dynamic Poisson’s coefficient was assigned values provided by technical literature. Using ultra-sonic pulse velocity (UPV) the apparent density and the dynamic modulus of elasticity were determined. The viability of the theoretical approach proposed by Salman, used for the air-dry density determination (predicted density), was experimentally confirmed (measured density). The calculated accuracy of the Salman method ranged between 98 and 99% for all the four groups of specimens used in the study. Furthermore, the static modulus of elasticity was deducted through a linear relationship between the two moduli of elasticity. Finally, the concrete compressive strength was mathematically determined by using the previously mentioned parameters. The accuracy of the proposed method for concrete compressive strength assessment ranged between 92 and 94%. The precision was established with respect to the destructive testing of concrete cores. For this research, the experimental part was performed on concrete cores extracted from different elements of different structures and divided into four distinct groups. The high rate of accuracy in predicting the concrete compressive strength, provided by this study, exceeds 90% with respect to the reference, and makes this method suitable for further investigations related to both the optimization of the procedure and = the domain of applicability (in terms of structural aspects and concrete mix design, environmental conditions, etc.).

Dynamic to Static Modeling

Dynamic-to-static modulus conversion has long been recognized as a complicated and challenging task in reservoir characterization and seismic geomechanics, and many single- and two-variable regression equations have been proposed. In practice however, the form and constants of the regression equation are variable from case to case. I introduce a methodology for estimating the static moduli called dynamic-to-static modeling (DTS). The methodology was validated by laboratory tests (ultrasonic and triaxial compression tests) to obtain dynamic and quasi-static bulk and Young’s (elasticity) moduli. Next, rock deformation phenomena were simulated considering different parameters affecting the process. The dynamic behavior was further modeled using rock physics methods. Unlike the conventional dynamic-to-static conversion procedures, the method considers a wide range of factors affecting the relationship between the dynamic and static moduli, including strain amplitude, dispersion, rock failure mechanism, pore shape, crack parameters, poromechanics, and upscaling. A comparison between the data from laboratory and in-situ tests and the estimation results indicated promising findings. The accuracy of the results was assessed by the analysis of variance (ANOVA). In addition to modeling the static moduli, DTS can be used to verify the static and dynamic moduli values with appropriate accuracy when core data is not available.

Temperature dependence of dynamic and static modulus of elasticity of lightweight expanded clay aggregate concrete

The paper presents experimental research the static and dynamic modulus of elasticity of lightweight expanded clay aggregate concrete with averaged density of 1000 kg/m3. The static and dynamic modulus are obtained depending on the influence of temperature in the range from 5 to 50 °C with a step of 15 °C. The dynamic modulus was determined without pre-compression with a testing machine Asphalt Mixture Performance Tester. Besides the modulus of elasticity of lightweight concrete, the temperature dependence of unconfined compressive strength was also determined. Analysis of experimental data showed that with an increase in temperature, strength and modulus of elasticity slightly decrease, which is typical for concretes. For all cases, the temperature dependence can be characterized according to the linear law. Comparison of the static and dynamic modulus of elasticity showed that the dynamic modulus is 60-74% greater than the static modulus over the entire range of the studied temperatures.

Mechanical and microstructural behavior of concrete containing marble and nano silica

Purpose The purpose of this study is to perform comprehensive investigation to assess the mechanical properties of nano-modified ternary cement concrete blend. Nano silica (NS) (1%, 2% and 3%) and waste marble dust powder (MD) (5%, 10% and 15%) was incorporated as a fractional substitution of cement in the concrete matrix. Design/methodology/approach In this experimental study, 10 cementitious blends were prepared and tested for compressive strength, flexural strength, splitting tensile strength and static modulus of elasticity. The microstructural characteristics of these blends were also explored using a scanning electron microscope along with energy dispersive spectroscopy and X-ray reflection. Findings The results indicate an enhancement in mechanical properties and refinement in pore structure due to improved pozzolanic activities of NS and the filling effect of MD. Originality/value To the best of the authors’ knowledge, no study has reported the mechanical and microstructural behavior of concrete containing marble and NS.

Prediction of Mechanical Properties of Hardwood Species Using the Longitudinal Vibration Acoustic Method

Acoustic test methods such as longitudinal vibration have been developed to predict the elastic properties of wood. However, attention has not been shifted to using this method to predict other mechanical properties, especially on Nigeria's preferred, and lesser-used wood species. Thus, we further investigate relationships among mechanical and acoustic properties of selected hardwood species with a view of predicting the mechanical properties of wood from acoustic parameters. Clear wood samples (324) of 20 by 20 by 20 mm3 were collected axially from Albizia adianthifolia, Gmelina arborea, Delonix regia, and Boscia anguistifolia trees, and conditioned before testing. The longitudinal vibration method was adopted to test for the dynamic (acoustic) parameters and properties (fundamental frequency, damping factor, dynamic modulus of elasticity, sound velocity, specific elastic modulus, radiation coefficient, acoustic conversion efficiency, acoustic impedance) while the universal testing machine was used to test for the mechanical properties (static modulus of elasticity, modulus of rupture, maximum compression strength parallel to grain). The damping factor, dynamic modulus of elasticity, and acoustic impedance were the best acoustic parameters that significantly correlated with the static modulus of elasticity (−0.57, 0.81, 0.76), modulus of rupture −0.64, 0.82, 0.85) and maximum compression strength parallel to grain (−0.52, 0.78, 0.84), respectively. There was a significant difference in the mechanical properties with respect to species, thus A. adianthifolia and G. arborea were mechanically better than D. regia and B. anguistifolia for construction or structural purposes. This study revealed that additional new acoustic measures are suitable for inferring mechanical wood properties.