Techno Press
Tp_Editing System.E (TES.E)
Login Search


You have a Free online access.
acc
 
CONTENTS
Volume 2, Number 2, June 2014
 

Abstract
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.

Key Words
concrete; artificial aggregate; fly ash; properties; cold bonded

Address
Job Thomas and Harilal B.: Cochin University of Science and Technology, Kochi, PIN 682022 Kerala, India

Abstract
This paper presents a nonlinear finite element analysis(FEA) in order to investigate the flexural performance of one-way slabs strengthened by epoxy-bonded steel plates. Four point loading scheme is selectively chosen. A model is developed to implement the material constitutive relationships and non-linearity. Five Slabs were modeled in FEM software using ABAQUS. One slab was un-strengthened control slab and the others were strengthened with steel plates with varying the plate thickness and configuration. In order to verify the accuracy of the numerical model, a comparison was done between the experimental results available in the literature and the proposed equations by ACI 318-11 for the calculation of ultimate load capacities of strengthened slabs, the agreement has proven to be good and FEA attained accurate results compared with ACI code. A parametric study was also carried out to investigate the influence of thickness of steel plate, strength of epoxy layer and type of strengthening plate on the performance of plated slabs. Also, the practical and technical feasibility of splitting the steel plate in strengthening process has been taken into account. For practical use, the author recommended to use bonded steel plate as one unit rather than splitting it to parts, because this saves more effort and reduces the risk of execution errors as in the case of multiple bonded parts. Both techniques have nearly the same effect upon the performance of strengthened slabs.

Key Words
finite element analysis; concrete slabs; steel plates; ABAQUS

Address
Ibrahim M. Metwally: Reinforced Concrete Department, Housing & Building Research Centre, P.O. Box 1770 Cairo, Egypt

Abstract
This paper presents chloride induced corrosion durability of reinforcing steel in geopolymer concretes containing different contents of sodium silicate (Na2SiO3) and molarities of NaOH solutions. Seven series of mixes are considered in this study. The first series is ordinary Portland cement (OPC) concrete and is considered as the control mix. The rest six series are geopolymer concretes containing 14 and 16 molar NaOH and Na2SiO3 to NaOH ratios of 2.5, 3.0 and 3.5. In each series three lollypop specimens of 100mm in diameter and 200mm in length, each having one 12mm diameter steel bar are considered for chloride induced corrosion study. The specimens are subjected to cyclic wetting and drying regime for two months. In wet cycle the specimens are immersed in water containing 3.5% (by wt.) NaCl salt for 4 days, while in dry cycle the specimens are placed in open air for three days. The corrosion activity is monitored by measuring the copper/copper sulphate (Cu/CuSO4) half-cell potential according to ASTM C-876. The chloride penetration depth and sorptivity of all seven concretes are also measured. Results show that the geopolymer concretes exhibited better corrosion resistance than OPC concrete. The higher the amount of Na2SiO3 and higher the concentration of NaOH solutions the better the corrosion resistance of geopolymer concrete is. Similar behaviour is also observed in sorptivity and chloride penetration depth measurements. Generally, the geopolymer concretes exhibited lower sorptivity and chloride penetration depth than that of OPC concrete. Correlation between the sorptivity and the chloride penetration of geopolymer concretes is established. Correlations are also established between 28 days compressive strength and sorptivity and between 28 days compressive strength and chloride penetration of geopolymer concretes.

Key Words
geopolymer; concrete; durability; sorptivity; corrosion; chloride permeability

Address
Faiz U.A. Shaikh: Department of Civil Engineering, Curtin University, Perth, Australia

Abstract
The development in roller compacted concrete (RCC) is replacing the conventionally vibrated concrete (CVC) for faster construction of dam during last three-four decades. Notwithstanding, there have been relatively less works reported on the utilization of RCC in dam constructions, especially the dams having considerable height. Further, the Ghatgar dam was the only dam in the tropical country like India constructed using the technology of RCC until two years back. However, with the completion of 102.4 m high Middle Vaitarana Dam (MVD), owned by Muncipal Corporation of Greater Mumbai (MCGM), India, has become the first largest roller compacted concrete dam. The paper traces step by step aspects of the mix design of RCC in respect of the afore-mentioned project besides the construction aspects; and also, demonstrates as to how 12.15 lacs cubic meter of roller compacted concrete was placed within the record duration of 15.2 months, thus, rendering the MVD as the ninth fastest RCC dam in the world. The paper also discusses the various mix proportioning, quality control, constructional features and instrumentation with respect to the high RCC dam such as Middle Vaitarana.

Key Words
Conventionally vibrated concrete (CVC), Roller compacted concrete (RCC), Compaction, Layers, Placement, Zero slump

Address
V.B. Ashtankara:Middle Vaitarna Dam Project Municipal Corporation of Greater Mumbai (MCGM) Fort, Mumbai-400001, India

H.S.Chore: Department of Civil Engineering, Datta Meghe College of Engineering, Airoli, Navi Mumbai -400708, India

Abstract
In this study, the fracture toughness KIC of high performance concrete (HPC) was determined by conducting three-point bending tests on eighty notched HPC beams of 500 mm x 100 mm x 100 mm at high temperatures up to 450oC (hot) and in cooled-down states (cold). When the concrete beams exposed to high temperatures for 16 hours, both thermal and hygric equilibriums were generally achieved. KIC for the hot concrete sustained a monotonic decrease tendency with the increasing temperature, with a sudden drop at 105oC. For the cold concrete, KIC sustained a two-stage decrease trend, dropping slowly with the heating temperature up to 150oC and rapidly thereafter. The fracture energy-based fracture toughness KIC\' was found to follow similar decrease trends with the heating temperature. The weight loss, the fracture energy and the modulus of rapture were also evaluated.

Key Words
high performance concrete; high temperature; fracture toughness; test conditions

Address
Binsheng Zhang, Martin Cullena and Tony Kilpatrickb: School of Engineering and Built Environment, Glasgow Caledonian University, Glasgow G4 0BA, Scotland, United Kingdom


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com