Copper or ferrous slag as substitutes for fine aggregates in concrete

Thomas, Job,Thaickavil, Nassif N.,Abraham, Mathews P. Techno-Press 2018 Advances in concrete construction Vol.6 No.5

The ever-increasing cost of natural sand and the environmental impacts of extracting manufactured sand (quarry sand) calls for exploring the potential to use alternative materials as fine aggregates in concrete. Copper slag and ferrous slag are industrial by products obtained from the smelting process of copper and iron respectively. A large quantity of copper slag and ferrous slag end up being disposed as waste in landfills and this poses a serious threat to the environment. Copper slag and ferrous slag have similar physical and chemical properties as natural sand and also exhibit pozzolanic activity. This paper studies the technical feasibility of industrial by-products such as copper slag and ferrous slag to replace the fine aggregate in concrete by evaluating the workability, strength and durability characteristics of concrete. The test results indicate that the strength properties are not affected by 40% or 100% replacement of quarry sand with iron slag or copper slag. However, 40% replacement of quarry sand with iron slag or copper slag in concrete is recommended considering the durability aspects of concrete.

Experimental study on circular CFST short columns with intermittently welded stiffeners

Job Thomas,T.N. Sandeep 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.29 No.5

This paper deals with the experimental study on strength the strength and deformation characteristics of short circular Concrete Filled Steel Tube (CFST) columns. Effect of vertical stiffeners on the behavior of the column is studied under axial compressive loading. Intermittently welded vertical stiffeners are used to strengthen the tubes. Stiffeners are attached to the inner surface of tube by welding through pre drilled holes on the tube. The variable of the study is the spacing of the weld between stiffeners and circular tube. A total of 5 specimens with different weld spacing (60 mm, 75 mm, 100 mm, 150 mm and 350 mm) were prepared and tested. Short CFST columns of height 350 mm, outer tube diameter of 165 mm and thickness of 4.5 mm were used in the study. Concrete of cube compressive strength 41 N/mm² and steel tubes with yield strength 310 N/mm² are adopted. The test results indicate that the strength and deformation of the circular CFST column is found to be significantly influenced by the weld spacing. The ultimate axial load carrying capacity was found to increase by 11% when the spacing of weld is reduced from 350 mm to 60 mm. The vertical stiffeners are found to effective in enhancing the initial stiffness and ductility of CFST columns. The prediction models were developed for strength and deformation of CFST columns. The prediction is found to be in good agreement with the corresponding test data.

Fresh and hardened properties of concrete containing cold bonded aggregates

Thomas, Job,B., Harilal Techno-Press 2014 Advances in concrete construction Vol.2 No.2

The properties of fresh and hardened concrete made using three types of artificial cold bonded aggregates are determined. The properties, namely, slump, water absorption, compressive strength and splitting tensile strength of concrete containing artificial aggregate are reported. The variables considered are aggregate type and water-to-cement ratio. Three types of cold bonded aggregates are prepared using fly ash and quarry dust. The water-to-cement ratio of 0.35, 0.45, 0.55 and 0.65 is used. The test result indicates that artificial aggregates can be recommended for making the concrete up to a strength grade of 38 MPa. The use of quarry dust in the production of artificial aggregate mitigates environmental concerns on disposal problems of the dust. Hence, the alternate material proposed in this study is a green technology in concrete production.

Design for shear strength of concrete beams longitudinally reinforced with GFRP bars

Thomas, Job,Ramadassa, S. Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.1

In this paper, a model for the evaluation of shear strength of fibre reinforced polymer (FRP)-reinforced concrete beams is given. The survey of literature indicates that the FRP reinforced beams tested with shear span to depth ratio less than or equal to 1.0 is limited. In this study, eight concrete beams reinforced with GFRP rebars without stirrups are cast and tested over shear span to depth ratio of 0.5 and 1.75. The concrete compressive strength is varied from 40.6 to 65.3 MPa. The longitudinal reinforcement ratio is varied from 1.16 to 1.75. The experimental shear strength and load-deflection response of the beams are determined and reported in this paper. A model is proposed for the prediction of shear strength of beams reinforced with FRP bars. The proposed model accounts for compressive strength of concrete, modulus of FRP rebar, longitudinal reinforcement ratio, shear span to depth ratio and size effect of beams. The shear strength of FRP reinforced concrete beams predicted using the proposed model is found to be in better agreement with the corresponding test data when compared with the shear strength predicted using the eleven models published in the literature. Design example of FRP reinforced concrete beam is also given in the appendix.

Design for shear strength of concrete beams longitudinally reinforced with GFRP bars

Job Thomas,S. Ramadass 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.1

In this paper, a model for the evaluation of shear strength of fibre reinforced polymer (FRP)-reinforced concrete beams is given. The survey of literature indicates that the FRP reinforced beams testedwith shear span to depth ratio less than or equal to 1.0 is limited. In this study, eight concrete beamsreinforced with GFRP rebars without stirrups are cast and tested over shear span to depth ratio of 0.5 and1.75. The concrete compressive strength is varied from 40.6 to 65.3 MPa. The longitudinal reinforcementratio is varied from 1.16 to 1.75. The experimental shear strength and load-deflection response of the beamsare determined and reported in this paper. A model is proposed for the prediction of shear strength of beamsreinforced with FRP bars. The proposed model accounts for compressive strength of concrete, modulus ofFRP rebar, longitudinal reinforcement ratio, shear span to depth ratio and size effect of beams. The shearstrength of FRP reinforced concrete beams predicted using the proposed model is found to be in betteragreement with the corresponding test data when compared with the shear strength predicted using theeleven models published in the literature. Design example of FRP reinforced concrete beam is also given inthe appendix.

Finite element analysis of shear critical prestressed SFRC beams

Ananth Ramaswamy,Job Thomas 한국계산역학회 2006 Computers and Concrete, An International Journal Vol.3 No.1

This study reports the details of the finite element analysis of eleven shear critical partially prestressed concrete T-beams having steel fibers over partial or full depth. Prestressed concrete T-beams having a shear span to depth ratio of 2.65 and 1.59 and failing in the shear have been analyzed using 'ANSYS', The 'ANSYS' model accounts for the nonlinear phenomenon, such as, bond-slip of longitudinal reinforcements, post-cracking tensile stiffness of the concrete, stress transfer across the cracked blocks of the concrete and load sustenance through the bridging of steel fibers at crack interface. The concrete is modeled using 'SOLID65?eight-node brick element, which is capable of simulating the cracking and crushing behavior of brittle materials. The reinforcements such as deformed bars, prestressing wires and steel fibers have been modeled discretely using 'LINK8'-3D spar element. The slip between the reinforcement (rebar, fibers) and the concrete has been modeled using a 'COMBIN39" non-linear spring element connecting the nodes of the "LINK8' element representing the reinforcement and nodes of the 'SOLID65' elements representing the concrete. The "ANSYS' model correctly predicted the diagonal tension failure and shear compression failure of prestressed concrete beams observed in the experiment. The capability of the model to capture the critical crack regions, loads and deflections for various types of shear failures in prestressed concrete beam has been illustrated.