Effects of Aggregate Size on the Concrete Strength

With the advancement in the technology, there is an immense growth in the field of construction as well, of which concrete forms the basic unit. Concrete is the structural material consisting of a hard, chemically inert particulate substance, known as aggregate (usually sand and gravel), that is bonded together by cement and water. Aggregate can be fine or coarse, depending on its size. Fine and coarse aggregates make upto 65-80% of the bulk of concrete volume and reduces the cost of concrete formation (1/4 to 1/8 of the cost of cement). Keeping this thing in view, this study is done to find the size of aggregate having more strength so that a particular size of aggregate can be used to meet our demands. The aggregates used are of the size 10mm, 20mm 40mm and mixture of 10mm, 20mm and 40mm. The concrete cubes (150mm x 150mm x 150mm) prepared are tested after 7 days, 14 days and 28 days of curing. The grade of concrete used in this research is M30. Keywords: Concrete, Compressive strength, aggregates, Concrete cubes, cement, water-cement ratio, mix design, M30 grade, Compressive Testing Machine (CTM), curing

Physiognomies and Strength Investigation of Concrete Part Blended by Wood Ash

Introduction: Cement during its manufacture emits enormous CO2, and heat to the atmosphere and deteriorate the environment affecting its sustainability. Wood ashes (WA) are the by-products wood based power plants, timber mills as wood dust, barks from forestry, paper industry, and forest fire are simple wastes and are noxious to atmosphere. Present study is investigating the strength and durability of concrete when blended with 0%, 10%, 30%, and 40% wood ash replacing cement to have these wastes effective waste management. Methodology: The process of investigation is to find the chemical constituents of fly ash, and its suitability to part substitute cement by using X-ray fluorescent spectrometer (XRF), and digital compressive testing machine (CTM) and Universal Testing Machine (UTM) to verify the physical, chemical, and mechanical properties to assess appropriate strength of wood ash blended concrete (WABC). Results: Strength characteristic at various proportion of mix of (WABC) on testing exhibited decreasing trend on increasing WA percent. The blended concrete exhibited the required compressive strength at 10% addition of WA and after curing for 28days. By utilizing wood ash as cement substitute the environment can be saved from black carbon and further deterioration.

Structure and Strength of Isothermally Heat-Treated Medium Carbon Ti-V Microalloyed Steel

Isothermal transformation characteristics of a medium carbon Ti-V microalloyed steel were investigated using light microscopy, scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), and by uniaxial compressive testing. Samples austenitized on 1100 °C were isothermally treated in the range from 350 to 600 °C and subsequently water quenched. The final microstructure of the samples held at 350 °C consisted of bainitic sheaves and had compressive yield strength, approximately from 1000 MPa, which is attributed to high dislocation density of low bainite. At 400 and 450 °C, acicular ferrite became prevalent in the microstructure. It was also formed by a displacive mechanism, but the dislocation density was lower, leading to a decrease of compressive yield strength to approximately 700 MPa. The microstructure after the heat treatment at 500 °C consisted of coarse non-polygonal ferrite grains separated by pearlite colonies, principally dislocation free grains, so that the compressive YS reached a minimum value of about 700 MPa. The microstructure of the samples heat-treated at 550 and 600 °C consisted of pearlite and both grain boundary and intragranular ferrite, alongside with some martensite. After 600 s, austenite became stable and transformed to martensite after water quenching. Therefore, the presence of martensite increased the compressive YS to approx. 800 MPa.

Experimental studies on bolted glubam connections

This paper reports tensile and compressive test results of bolted glubam (glued laminated bamboo) connections. The tensile tests were carried out with two types of specimens designed for tensile loadings in the longitudinal and transverse directions in relevance to the orientations of the bidirectional bamboo strips (fibers). In each direction, the specimens were further divided into nine groups according to different combination conditions of end and edge spacings. Compressive tests were executed for three groups of bolted glubam connections, with varying thickness of the main board and bolting conditions. The tensile experiments show that the failure of the specimens is strongly influenced by the loading directions. Recommended end distance and side distance are provided, whereas the load carrying capacity is analyzed. Based on the compressive testing results, failure modes and load displacement relationships are analyzed, in which the yield bearing capacity is shown to be close to that given by the equations in existing design specifications for timber structure.

Two-step synthesis of polyurethane/multi-walled carbon nanotubes polymer composite to achieve high percentage particle reinforcement for mechanical applications

The present work has been aimed to synthesize Polyurethane (PU)/Multi-Walled Carbon Nanotubes (MWCNTs) composite using a two-step method to enhance mechanical properties. In the first step, films (0.2 mm thickness) have been synthesized using a solution mixing method to disperse MWCNTs in the PU matrix. In the second step, thin films of uniformly dispersed MWCNTs in the PU matrix have been compression molded to synthesize PU/MWCNTs composite required for real mechanical applications. The two-step method has the advantages of solution mixing as well as compression molding method. The results of quasi-static nanoindentation tests indicated that in comparison to pure PU, elastic modulus and hardness have been enhanced by 124% and 53% respectively for 10 wt% PU/MWCNTs composite. Fracture resistance of PU/MWCNTs composites, with 7 wt% of MWCNTs, has been enhanced by 52% as compared to pure PU. To understand bulk behavior, nanoindentation results have been cross-verified with compression testing. Results of compressive testing shown that the modulus of composite material has been significantly improved under the influence of the increasing composition of MWCNTs. A noticeable improvement of 52% has been observed in compressive modulus of 10 wt% composite in equivalence to pure PU. The overall improvement in mechanical behavior has been attributed to the uniform dispersion of MWCNTs in the PU matrix by the two-step synthesis method.

Development of compressive testing device for glass fiber based single face corrugated structure sheet, and estimation of buckling strength of straight panel of that structure sheet

<abstract> <p>This work aims to reveal the in-plane-compressive characteristics of Glass Fibre based single face corrugated Structure Sheet (GFSS) by developing a loading holder of the both ends of the panel of GFSS in the direction of the cross machine direction. A grooved end-support device was developed and exmined. In order to set stably and quickly a straight panel of GFSS on the compressive-testing apparatus, the width and the depth of the holder's groove were varied against the geometrical size of the panel, and the stability and reproducibility of compressive deformation of the panel was experimentally investigated. When changing the height of the panel and reinforcing the both ends of the panel by dipping instant adhesives, the deformation behavior and the buckling strength was characterized in three modes: a short height crushing without lateral deflection, a small lateral deflection mode as the intermediate state, and a triangle-like folding as a long height crushing.</p> </abstract>

Development of Unidirectional Cellular Structure with Multiple Pipe Layers and Characterisation of Its Mechanical Properties

This study is concerned with the development of a new unidirectional cellular (UniPore) copper structure with multiple concentric pipe layers. The investigated UniPore structures were grouped into three main types, each having a different number of pipes (3, 4, and 5 pipes per transversal cross-section) and different pore arrangements. The specimens were fabricated by explosive compaction to achieve tightly compacted structures with a quasi-constant cross-section along the length of the specimens. The bonding between copper pipes was observed by a metallographic investigation, which showed that the pipes and bars were compressed tightly without voids. However, they were not welded together. The mechanical properties were determined by quasi-static compressive testing, where the typical behaviour for cellular materials was noted. The study showed that porosity significantly influences the mechanical properties, even more so than the arrangement of the pipes.