Search results

This study aims at designing consistent and durable concrete by making use of waste materials. An investigation has been carried out to evaluate the performance of conventional and optimal concrete (including 5% GP) at high temperatures for different exposure times.

An experimental work is carried out to compare the conventional and optimal concrete with respect to weight loss, mechanical strength characteristics (compressive, tensile and flexural) after exposed to 100, 200 and 300 °C with 1, 2 and 3 h duration of exposure followed by cooling in furnace for 24 h and then air cooling.

The workability of granite powder modified concrete decreases as percentage of replacement increases. Compressive, tensile and flexural strengths all increased at 100 °C when compared to strength characteristics at normal temperature, regardless of the exposure conditions, and there was no weight loss noticed. For 200 and 300 °C, the strengths were decreased compared to normal temperature and an elevated temperature of 100 °C, as weight loss of concrete specimens are observed to be decreased at these temperatures. So, the optimum elevated temperature can be concluded as 100 °C.

Incorporating pozzolanic binder (granite powder) as cement replacement subjecting to elevated temperatures in an electric furnace is the research gap in this area. Many of the works were carried out replacing GP for fine aggregate at normal temperatures and not at elevated temperatures.

Aluminum alloy AA5083 is applicable in ship building, military, railway and industry because of its excellent properties like resistance to chemical and sea water attack. However, its performance is affected by weak wear resistance. Hence, this should be solved to improve the performance of AA5083 alloy in the aforementioned fields. The purpose of this research is to enhance the wear properties of AA5083 alloy.

In this research, AA5083 alloy was reinforced with industrial wastes such as red mud and granite particles using stir casting method. Totally, four types of composites were fabricated, namely, AA5083/3 Wt.% red mud (C1), AA5083/3 Wt.% granite (C2), AA5083/1 Wt.% red mud-2Wt.% granite (C3) and AA5083/2 Wt.% red mud-1Wt.% granite (C4). Wear properties such as mass loss and coefficient of friction (COF) were analyzed for different wear parameters. Further, the mechanical properties like hardness and tensile strength were investigated.

Results showed that the inclusion of reinforcement particles improved the wear and mechanical properties of AA5083 alloy (C0). The C2 sample displayed the maximum hardness of 87 HV and tensile strength of 317 MPa owing to the inclusion of 3 Wt.% granite particles. Furthermore, the wear study results showed that the C2 sample displayed the minimum mass loss and COF. It was concluded from this research that C2 sample could be a good candidate to be applicable in marine, military, railway and industrial applications with improved performance.

This work is original as the industrial waste is used as reinforcements in the performance improvement of AA5083 aluminum alloy.

The purpose of this paper is to investigate the mechanical behavior and propagation of cracks of numerical granite samples through the Brazilian split test and to provide a reference for predicting the behavior of real granite samples.

The numerical models of granite containing two fissures are established using the parallel bond model (PBM) and the smooth joint model (SJM) in PFC2D. The peak stresses, number of cracks and anisotropic ratios are obtained to study the influence of the mineral composition and the angle of inclination of rock bridge on the strength, failure mode and deformation characteristics.

The numerical results obtained show that the mineral composition has a marginal influence on the peak stress. When the angle of inclination of rock bridge β increases, the peak stress drops to its minimum value at β = 90° and then gradually increases to a relatively low level. The behavior of cracks falls into three categories based on the distribution of cracks. By analyzing the stress–strain curve and the process of crack propagation for sample No. 4 with β = 60°, it is found that the process of failure can be divided into four stages and tensile cracks dominate. The anisotropic ratios of peak stress and a number of cracks obtained show that the peak stress is low anisotropic and the number of cracks is medium anisotropic.

This paper presents a numerical simulation method to analyze mechanical behavior and propagation of cracks under different conditions. The proposed method and the results obtained are useful for predicting the behavior of real granite samples in laboratory and engineering projects.

Accurate presentation of the rock microstructure is critical to the grain-scale analysis of rock deformation and failure in numerical modelling. 3D granite microstructure modelling has only been used in limited studies with the mineral pattern often remaining poorly constructed. In this study, the authors developed a new approach for generating 2D and 3D granite microstructure models from a 2D image by combining a heterogeneous material reconstruction method (simulated annealing method) with Voronoi tessellation.

More specifically, the stochastic information in the 2D image is first extracted using the two-point correlation function (TPCF). Then an initial 2D or 3D Voronoi diagram with a random distribution of the minerals is generated and optimised using a simulated annealing method until the corresponding TPCF is consistent with that in the 2D image. The generated microstructure model accurately inherits the stochastic information (e.g. volume fraction and mineral pattern) from the 2D image. Lastly, the authors compared the topological characteristics and mechanical properties of the 2D and 3D reconstructed microstructure models with the model obtained by direct mapping from the 2D image of a real rock sample.

The good agreements between the mapped and reconstructed models indicate the accuracy of the reconstructed microstructure models on topological characteristics and mechanical properties.

The newly developed reconstruction method successfully transfers the mineral pattern from a granite sample into the 2D and 3D Voronoi-based microstructure models ready for use in grain-scale modelling.

This paper aims to investigate the 28-day compressive strength of concrete produced with aggregates from different sources.

Coarse aggregates were crushed granite and natural local stones mined from Umunneochi, Lokpa and Uturu, Isuakwato, respectively, in Abia State, Nigeria. Fine aggregate (river sand) and another coarse aggregate (river stone) were dredged from Otammiri River in Owerri, Imo State, Nigeria. The nominal mix ratios were 1:1:2, 1:2:4 and 1:3:6, whereas the respective water–cement ratios were 0.45, 0.5, 0.55 and 0.6.

The compressive strength of granite concrete, river stone concrete and local stone concrete ranged 17.79-38.13, 15.37-34.57 and 14.17-31.96 N/mm², respectively. Compressive strength was found to increase with decreasing water–cement ratio and increasing cement content.

Granite concrete should be used in reinforced-concrete construction, especially when a cube compressive strength of 30 N/mm² or higher is required.

Granite concrete exceeded the target compressive strength for all the concrete specimens, whereas river stone concrete and local stone concrete failed to achieve the target strength for some mix proportions and water–cement ratios.

This paper studies the integration of production and maintenance planning for an unreliable production system subject to gradual deterioration. The goal of this planning is to optimize production and maintenance while reducing workers' exposure to silica dust. The objective will therefore be to offer manufacturers a production strategy that minimizes the total cost of production while considering the health of employees.

Adequate prevention methods are determined and integrated into the granite transformation production system, which evolves in a stochastic environment. With the failure rate of the dust reduction unit being a function of its degradation state, the authors solve the optimization problem using stochastic dynamic programming in the context of nonhomogeneous Markov chain.

The resulting planning strategy shows that one can manage stock optimally while ensuring a healthy environment for workers. It ensures that crystalline silica prevention equipment is available and effective and defines the production rate according to a critical threshold, which is a function of the age of the dust reduction unit.

This article illustrates that it is possible to integrate silica dust reduction measures into production planning while remaining optimal and ensuring the health of operators. In the present study, the machined granite was assumed to be a natural granite, and production takes place in a closed environment.

The originality of this work lies in its development of an optimal joint production and maintenance strategy, which considers limits of exposure to crystalline silica. An optimal production and maintenance control policy considering employees' health is therefore proposed.

Solid wastes are today one of the worst problems in the word, mainly because of the increase in volume and the high capacity of environmental contamination. The aim of this work is to analyze the possibility of use sawing granite wastes as alternative ceramic raw materials for the production of bricks and roof tiles. Samples were collected from wastes of several granites companies from the northeast region of Brazil. They were submitted to particle size and mineralogical characterization. Some ceramic compositions were prepared with granite waste and submitted to technological tests. The results indicated that the wastes have particle size distribution and mineralogical composition similar to conventional non‐plastic ceramic raw materials. These wastes can be used in substitution of conventional raw materials in ceramic formulations in proportions up to 50 per cent. This can be important to save traditional raw materials from the region and decreasing the aggression to the environment.

The rigid spherical particle models proposed in the literature for modeling fracture in rock have some difficulties in reproducing both the observed macroscopic hard rock triaxial failure enveloped and compressive to tensile strength ratio. The purpose of this paper is to obtain a better agreement with the experimental behavior by presenting a 3D generalized rigid particle contact model based on a multiple contact point formulation, which allows moment transmission and includes in a straightforward manner the effect of friction at the contact level.

The explicit formulation of a generalized contact model is initially presented, then the proposed model is validated against known triaxial and Brazilian tests of Lac du Bonnet granite rock. The influence of moment transmission at the contact level, the number of contacts per particle and the contact friction coefficient are assessed.

The proposed contact model model, GCM‐3D, gives an excellent agreement with the Lac du Bonet granite rock, strength envelope and compressive to tensile strength ratio. It is shown that it is important to have a contact model that: defines inter‐particle interactions using a Delaunay edge criteria; includes in its formulation a contact friction coefficient; and incorporates moment transmission at the contact level.

The explicit formulation of a new generalized 3D contact model, GCM‐3D, is proposed. The most important features of the model, moment transmission through multiple point contacts, contact friction term contribution for the shear strength and contact activation criteria that lead to a best agreement with hard rock experimental values are introduced and discussed in an integrated manner for the first time. An important contribution for rock fracture modeling, the formulation here presented can be readily incorporated into commercial and open source software rigid particle models.

The purpose of this paper is to present a method for evaluating the structural dynamic characteristics of a flying probe tester.

The dynamic characteristics of a flying probe tester framework were analyzed based on a finite element analysis method. First, modal analysis was carried out to characterize the modal parameters of the structure. Second, the harmonic response was analyzed according to the modal analysis and the response curve of the structural system was studied. Finally, transient analysis was conducted to obtain the transient response of the structures at the beginning of the vibration.

The natural frequency and the response frequency of a natural granite structure was the highest and the transient vibration displacement amplitude was the smallest compared with cast iron and artificial stone structures.

A comprehensive understanding of the dynamic characteristics of the framework of a flying probe tester with three different materials has been achieved. The results of the analyses provide a reference for the framework design of a flying probe tester.

The purpose of this paper is to describe a practice that has implications for increasing product innovation in a variety of industries.

The case describes a market orientation and product innovation program to increase a company's competitiveness. At the organization's request, its name has been changed. The author is indebted to an executive with contacts in the company for insight into the company's operations.

The case provides information and a solid action approach to increasing company competitiveness by strengthening a firm's market orientation and new product innovation. The subject company remedied a lack of product development and management skills by training and hiring new specialists to operate a new department. In addition, it put a reward and communication program in place that increased its intelligence generation, dissemination and corporate responsiveness.

As in all case studies, the specific conditions found in one organization may not be found more generally in others. Readers are cautioned that the conclusions drawn in the case may have limited applicability.

The case depicts a professional implementation of a market orientation improvement program as well as development of product management and innovation functions. Other organizations may find the techniques of value in their own efforts.

The case is a unique implementation of a new product innovation and market orientation that has a comprehensive foundation. It offers lessons that may be applied to other companies faced with similarly competitive, consumer and technological environments.