An Experimental Investigation On CBR Improvement Of Sand-Flyash Mix Using Geogrid Layers

Vol. 4  Issue 3
Year: 2014
Issue: Jun-Aug
Title:An Experimental Investigation On CBR Improvement Of Sand-Flyash Mix Using Geogrid Layers
Author Name:Rajiv Chauhan and R.Sharma
Synopsis:
Development of an adequate network of roads, especially in remote rural areas is of vital importance for the socioeconomic development of a country. Search is being made to find alternative materials, for use in pavement construction. Fly ash, lime and cement are the commonly used materials for soil stabilization. Geosynthetics, Geotextiles and Geo-grids are also used nowadays in roads for subgrade improvement in road construction. This paper presents the laboratory CBR test results conducted on sandy soil mix with fly ash for unreinforced and reinforced cases. The reinforcement was done using geogrids in layers at different depths in CBR mould. The fly ash was varied from 15% to 35% in sand sample. All the tests were conducted at Optimum moisture content (OMC) and maximum dry density (MDD) of mixes. The results of California Bearing Ratio (CBR) tests have shown considerable improvement with the use of reinforcement. The maximum increase in CBR value with Geo- grid was observed with the 2 layers of Geo-grid use. The increase in value of CBR was from 6% for virgin soil to 13% with use of geogrids.

Reducing The Life Cycle Cost of Reinforced Concrete Structures by using Fiber in Concrete

Vol. 4  Issue 3
Year: 2014
Issue: Jun-Aug
Title:Reducing The Life Cycle Cost of Reinforced Concrete Structures by using Fiber in Concrete
Author Name:Badrinarayan Rath, Shirish Deo and Gangadhar Ramtekkar
Synopsis:
A major challenge for concrete in today’s engineering is to build structures with lowest possible life cycle cost for sustainability. One of the major problems with reinforced concrete structures is the corrosion of steel reinforcement. It is one of the primary causes of premature deterioration of RCC (Reinforced Cement concrete) structures. The damage caused by corrosion seriously limits the service life of many concrete structures. The cost to rehabilitate these deteriorated concrete structures is expensive. As a result, over the past two decades, extensive research has been conducted to improve the durability of existing and new concrete reinforced structures. Plain concrete is a brittle material, with low tensile strength and strain capacities. To help overcome these problems, there has been a steady increase over the past years in the use of fibre reinforced cements and concretes (FRC). In general, the most important advantage of adopting Steel Fiber Reinforced Concrete (SFRC) is the increase of tensile strength, enhancement of toughness and increased resistance to crack propagation with the help of stress transfer from the matrix to the fibres. Addition of fibres has also shown modest increase in compressive strength. FRC thus exhibits strain hardening behaviour after first cracking as well as improvement in energy absorption capacity. Reduction of cracks shall increase initiation period of corrosion of reinforcement in RCC by many years, thereby increasing durability and reducing service life cost of the structure

Hydraulics of Fluid Flow in a Single Cohesive Crack: A Review of Some Basic Concepts

Vol. 4  Issue 2
Year: 2014
Issue: Mar-May
Title:Hydraulics of Fluid Flow in a Single Cohesive Crack: A Review of Some Basic Concepts
Author Name:K. K. Pandey and V. Kumar
Synopsis:
Present review discusses the scope and limitations of basic equations of continuity and momentum used in the study of flow behavior in single crack. The continuity equation for liquid flow used in the literature does not account for source and sink which occurs during crack wall leakages. In two-phase continuity equation, inter-phase transfer terms have been identified to be used as source or sink terms. Navier-Stokes momentum equation and its simplifications under various assumptions, leading to derivations of Stokes and Reynolds equations, and their limitations along with computational difficulty in crack flow problems is discussed. Emergence of Local Cubic Law (LCL) equation and its limitations has been indicated. Validity of LCL equation has been tested in the literatures under the influence of various factors. The relative importance of inertial and viscous forces show that LCL equation is valid for Reynolds number of 10 and a non-linear relation between pressure gradient and volumetric flow rate need to be used when Reynolds number is between 10 and 100. The use of scaling law used in the fracture mechanics shows that in smooth walled fracture, the volumetric flow rate vary with fifth power of crack aperture and so this law is termed as 'quintic' law. There are few published works in literature to study the effect of slip boundary condition in deriving the correction factor in hydraulic conductivity of fracture using Beaver-Joseph slip boundary conditions in case of smooth permeable fracture walls. Some works have shown that formulation of momentum equation for different flow regimes of two phase flow in cracks is a difficult task.

Relationship Between The Optimum Usage Of Copper Slag As Fine Aggregate And Compressive Strength In Copper Slag Admixed Concrete

Vol. 4  Issue 2
Year: 2014
Issue: Mar-May
Title:Relationship Between The Optimum Usage Of Copper Slag As Fine Aggregate And Compressive Strength In Copper Slag Admixed Concrete
Author Name:Binaya Patnaik, Seshadri Sekhar. T and Srinivasa Rao
Synopsis:
The rapid urbanization and natural resources scarcity had created a huge demand for non-conventional resources in the construction industry. Copper slag, which is a by-product obtained during the refining and metal smelting process of Copper Ore having Silica (SiO ) as a major composition, could potentially be used as a partial replacement of Sand in 2 the manufacturing of Concrete. In the present Experimental Investigation, for M30 grade of Concrete, fine aggregate (River Sand) was partially replaced with Copper Slag from 0% to 50% and compressive strength at the ages of 28 & 90 days were investigated. Finally, mathematical equations were derived for compressive strength at 28 & 90 days with percentage of Copper Slag used as partial replacement of Fine aggregate in copper slag admixed concrete.

Plastic Optic Fiber (POF) Based Phase Difference Measurement Method For Estimation Of Crack Mouth Opening Displacement (CMOD) In Concrete

Vol. 4  Issue 2
Year: 2014
Issue: Mar-May
Title:Plastic Optic Fiber (POF) Based Phase Difference Measurement Method For Estimation Of Crack Mouth Opening Displacement (CMOD) In Concrete
Author Name:K. Samrajyam, B. Sobha, T. D. Gunneswara Rao and R.L.N. Sai Prasad
Synopsis:
Crack detection and measurement of crack width in concrete are important for structural health monitoring of structures. In this paper, we report on a technique for estimation of crack mouth opening displacement ((CMOD) in concrete specimens of M20 composition. It is based on the principle of using Plastic Optical Fiber(POF) based strain displacement sensor employing phase difference measurement technique. The motivation for the method has been to improve on the sensitivity of detection of crack width measurement and propagation by looking at the phase changes rather than amplitude changes as attempted earlier by the authors.

Investigation on Characteristics of Fly Ash and Crusher Waste Stabilized Black Cotton Soil Bricks

Vol. 4  Issue 2
Year: 2014
Issue: Mar-May
Title:Investigation on Characteristics of Fly Ash and Crusher Waste Stabilized Black Cotton Soil Bricks
Author Name:T.Sekar
Synopsis:
An experimental investigation has been carried out to study the feasibility of manufacturing bricks from locally available black cotton soil using industrial waste materials such as fly ash and crusher waste. In order to study the characteristics of brick, a total of 504 numbers of brick specimens of 230 x 110 x 70 mm size were cast in three series by combining black cotton soil, fly ash and crusher waste in different proportions. The brick specimens were then air dried, baked in kiln and tested for compressive strength, water absorption, efflorescence and density as per IS:3495 code. Also, for comparison purpose, 18 numbers of conventional burnt clay bricks and 18 numbers of pressed type water cured cement fly ash bricks were tested for the aforesaid brick properties. Test results obtained in the present investigation indicate that it is possible to manufacture good quality bricks from locally available black cotton soil by suitably adding either fly ash or crusher waste or both, and such bricks can be used in lieu of conventional burnt clay bricks or pressed type water cured cement fly ash bricks presently in use for various construction activities.

Plastics and FRP Materials used in Railways

Vol. 4  Issue 2
Year: 2014
Issue: Mar-May
Title:Plastics and FRP Materials used in Railways
Author Name:Pawan Malik
Synopsis:
The emergence of Plastic industries has become a boon for various engineering applications. Plastics are durable, light weight materials, which are easy to transport. The major advantage of plastic is it is recyclable in nature, which helps to conserve landfill space, natural resources and reduce pollution. Earlier in railways, wooden, concrete or steel sleepers are used. Due to their high cost and limited life span, nowadays plastics sleepers are used all over the world at large scale. An attempt has been made to study various engineering plastics used in railways and the advantages of plastics over other construction materials. Moreover, special attention is given to Fiber reinforced plastics (FRP) i.e. plastics composites. The study concluded that plastics composites are more reliable, more economically viable and have longer life span.