Abstract
The performance of steel fiber reinforced geopolymer concrete beam column joints under cyclic loading was
investigated. The volume fraction of fibers considered were 0.25% (19.62 kg/m3), 0.5% (39.24 kg/m3), 0.75% (58.86 kg/m3) and 1% (78.48 kg/m3). A total of fifteen specimens were prepared and tested under reverse cyclic loading. Test results were analyzed with respect to first crack load, ultimate load, energy absorption capacity, energy dissipation capacity, stiffness degradation and load deflection behavior. Test results revealed that the addition of steel fibers enhanced the performance of geopolymer concrete beam column joints significantly. The joints were analyzed using finite element software ANSYS. The analytical results were found to compare satisfactorily with the experimental values.
Key Words
geopolymer concrete; steel fiber; beam column joint; ductility; stiffness degradation; energy dissipation
Address
S. Deepa Raj: Department of Civil Engineering, College of Engineering Trivandrum, Kerala, India
N. Ganesan: Department of Civil Engineering, National Institute of Technology Calicut, Kozhikode, Kerala, India
Ruby Abraham: Marian Engineering College, Kerala, India
Abstract
As confining materials for concrete, steel and fibre-reinforced polymer (FRP) composites have important applications in both the seismic retrofit of existing reinforced concrete columns and in the new construction of composite structures. We present a comprehensive review of the axial stress-strain behaviour of the FRP-confined concrete column. Next, the mechanical performance of the hybrid FRP-confined concrete-steel composite columns are comprehensively reviewed. Furthermore, the results of FRP-confined concrete column experiments and FRP-confined circular concrete-filled steel tube experiments are presented to study the interaction relationship between various material sections. Finally, the combinations of material sections are discussed. Based on these observations, recommendations regarding future research directions for composite columns are also outlined.
Key Words
FRP-confined concrete; the hybrid FRP-confined concrete-steel composite columns; the mechanical performance; the interaction relationship
Address
Chong Rong: State Key Laboratory of Green Building in Western China of Xian University of Architecture & Technology, Xi\'an 710055, China; College of Civil Engineering, Xi\'an University of Architecture & Technology, Xi\'an 710055, China
Qingxuan Shi: State Key Laboratory of Green Building in Western China of Xian University of Architecture & Technology, Xi\'an 710055, China; College of Civil Engineering, Xi\'an University of Architecture & Technology, Xi\'an 710055, China; Key Laboratory of Structural Engineering and Seismic Resistance Education, Xi\'an University of Architectural & Technology, Xi\'an 710055, China
Hongchao Zhao: College of Civil Engineering, Xinjiang University, Xinjiang 830000, China
Abstract
This paper reports the effect of Rice Husk Ash (RHA) in geopolymer concrete on strength, durability and microstructural properties under ambient curing at a room temperature of 25oC and 65+-5% relative humidity. Rice husk was incinerated at 800oC in a hot air oven. and ground in a ball mill to achieve the required fineness. RHA was partially added in 10, 15, 20, 25, 30 and 35 percentages to fly ash with 10% of GGBS to produce geopolymer concrete. Test results exhibit that the substitution of RHA in geopolymer concrete resulted in reduced strength properties during initial curing. In the initial stage, workability of GPC mixes was affected by RHA particles due to the presence of dormant particles in it. It is evident from the
microstructural study that the presence of RHA particles densifies the matrix reducing porosity in concrete. This is due to the presence of RHA in geopolymer concrete, which affects the ratio of silica and alumina, resulting in polycondensation reactions products. This study suggests that incorporation of rice husk ash in geopolymer concrete is the solution for effective utilization of waste materials and prevention of environmental pollution due to the dumping of industrial waste and to produce eco-friendly concrete.
Key Words
rice husk ash; microstructure; bond strength; strength; curing; carbonation
Address
Shalini Annadurai: Department of Civil Engineering, Sona College of Technology, Salem-636005, Tamil Nadu, India
Kumutha Rathinam: Department of Civil Engineering, Sri Venkateswara College of Engineering, Sriperumbudur-602117, Tamil Nadu, India
Vijai Kanagarajan: Department of Civil Engineering, St. Joseph\'s College of Engineering, OMR, Chennai-600119, Tamil Nadu, India
Abstract
The present work proposes new engineering models for determining corrosion initiation time in concrete reinforcing steels in marine environment. The models are based on Fick\'s second law that is commonly used for chloride diffusion. The latter is based on deterministic analyses involving the most influencing parameters such as distance of the concrete structure from the seaside, depth of steel concrete cover, ambient temperature, relative humidity and the water-cement ratio. However, a realistic corrosion initiation time cannot be estimated because of the uncertainties associated to the different parameters of the models. Therefore a reliability approach using FORM/SORM method has been applied to develop the proposed engineering models integrating a limit state function and a reliability index B. As a result, the corrosion initiation time is expressed by new exponential engineering models where the uncertainties are associated to the model parameters. The main emerging result is a realistic decision tool for corrosion planning inspection.
Abstract
In this paper, an experimental study was conducted on the compressive behavior of steel tube confined concrete (STCC) and concrete-filled steel tube (CFST) columns with active and passive confinement. To create active confinement in the STCC and CFST specimens, an innovative method was used in this study, in which by applying pressure on the fresh concrete, the steel tube was laterally pretensioned and the concrete core was compressed simultaneously. Of the benefits of this technique are improving the composite column behavior, without the use of additives and without the need for vibration, and achieving high prestressing levels. To achieve lower and higher prestressing levels, short and long term pressures were applied to the specimens, respectively. Nineteen STCC and CFST specimens in three groups of passive, short-term active, and longterm active confinement were subjected to axial compression, and their mechanical properties including the compressive strength, modulus of elasticity and axial strain were evaluated. The results showed that the proposed method of prestressing the STCC columns led to a significant increase in the compressive strength (about 60%), initial modulus of elasticity (about 130%) as well as a significant reduction in the axial strain (about 45%). In the CFST columns, the prestressing led to a considerable increase in the compressive strength, a small effect on the initial and secant modulus of elasticity and an increase in the axial strain (about 55%). Moreover, increased prestressing levels negligibly affected the compressive strength of STCCs and CFSTs but slightly increased the elastic modulus of STCCs and significantly decreased that of CFSTs.
Key Words
active confinement; prestressing; mechanical properties; confining pressure; STCC; CFST
Address
Mahdi Nematzadeh and Saeed Fazli: Department of Civil Engineering, University of Mazandaran, Babolsar, Iran
Abstract
Fracture properties of concrete depend on the mix proportions of the ingredients, specimen shape and size, type of testing method used for the evaluation of fracture properties. Aggregates play a key role for changes in the fracture behaviour of concrete as they constitute about 60-75 % of the total volume of the concrete. The present study deals with the effect of size and quantity of coarse aggregate on the fracture behaviour of steel fibre reinforced self compacting concrete (SFRSCC). Lower
coarse aggregate and higher fine aggregate content in SCC results in the stronger interfacial transition zone and a weaker stiffness of concrete compared to vibrated concrete. As the fracture properties depend on the aggregates quantity and size particularly in SCC, three nominal sizes (20 mm, 16 mm and 12.5 mm) and three coarse to fine aggregate proportions (50-50, 45-55, 40-60) were chosen as parameters. Wedge Split Test (WST), a stable test method was adopted to arrive the requisite properties. Specimens without and with guide notch were investigated. The results are indicative of increase in fracture energy with increase in coarse aggregate size and quantity. The splitting force was maximum for specimens with 12.5 mm size which is associated with a brittle failure in the pre-ultimate stage followed by a ductile failure due to the presence of steel fibres in the post-peak stage.
Abstract
The present investigation is to identify an optimum mix combination amongst 28 different types of artificial lightweight aggregates by pelletization method with aggregate properties. Artificial aggregates with different combinations were manufactured from fly ash, cement, hydrated lime, ground granulated blast furnace slag (GGBFS), silica fume, metakaolin, sodium bentonite and calcium bentonite, at a standard 17 minutes pelletization time, with 28% of water content on a weight basis. Further, the artificial aggregates were air-dried for 24 hours, followed by hardening through the cold-bonding (water curing) process for 28 days and then testing with different physical and mechanical properties. The results found the lowest impact strength value of 16.5% with a cement-hydrated lime (FCH) mix combination. Moreover, the lowest water absorption of 16.5% and highest individual pellet crushing strength of 36.7 MPa for 12 mm aggregate with a hydrated lime-GGBFS (FHG) mix combination. The results, attained from different binder materials, could be helpful for manufacturing high strength artificial aggregates.
Key Words
metakaolin and ferrochrome ash; aggregates/recycled aggregates; cement; construction materials; fly ash/slag; furnace slag; lightweight aggregate (LWA); silica fume
Address
Kolimi Shaiksha Valia and S. Bala Murugan: Department of Structural and Geotechnical Engineering, School of Civil Engineering, Vellore Institute of Technology, Vellore 632014, Tamil Nadu, India
Abstract
In this study, effect of recycled aggregates and polypropylene fibers on the response of conventionally reinforced concrete element subjected to tensile loading in terms of tension stiffening and strain development was experimentally investigated. For this purpose, concrete prisms of 100x100 mm cross section and 500 mm length having one central deformed steel re-bar were cast using fibrous and non-fibrous Recycled Aggregate Concrete (RAC) with varying percentages of recycled aggregates (0%, 25%, 50%, 75% and 100%) and tested under uniaxial tensile load. For all fibrous RAC mixes, polypropylene fibers were used at constant dosage of 3.15 kg/m3. Effect of recycled aggregates and fibers on the compressive strength of concrete was also explored in this study. Through studying tensile load versus global axial deformation of composite and strain development in concrete and steel, it was found that replacement of natural aggregates with recycled aggregates in concrete negatively affected the cracking load, tension stiffening and strain development, and this negative effect was observed to be increased with increasing contents of recycled aggregates in concrete. The results of this study showed that it was possible to minimize the negative effect of recycled aggregates in concrete by the addition of polypropylene fibers. Reinforced concrete element constructed using concrete containing 50% recycled aggregates and polypropylene fibers exhibited cracking behavior, tension stiffening and strain development response almost similar to that of concrete element constructed using natural aggregate concrete without fiber.
Address
R. Hameed, K. Hasnain, M. Rizwan Riaz, Qasim S. Khan: Civil Engineering Department, University of Engineering and Technology Lahore, Pakistan
Zahid A. Siddiqi: Civil Engineering Department, University of Lahore, Pakistan
Abstract
This paper describes the experimental studies carried out to determine the properties of fresh and hardened concrete with Recycled Plastic Waste (RPW) as a partial replacement material for fine aggregates. In the experimental study, RPW was used for replacing river sand and manufactured sand (M sand) aggregates in concrete. The replacement level of fine aggregates was ranging from 5% to 20% by volume with an increment of 5%. M40 grade of concrete with water cement ratio of 0.40 was used in this study. Two different types of RPW were used, and they are (i) un-activated RPW and (ii) activated RPW. The activated RPW was obtained by alkali activation of un-activated RPW using NaOH solution. The hardened properties of the concrete determined were dry density, compressive strength, split tensile strength, flexural strength and ultrasonic pulse velocity (UPV). The properties of the concrete with river sand, M sand, activated RPW and un-activated RPW were compared and inferences were drawn. The effect of activation using NaOH solution was investigated using FT-IR study. The micro structural examination of hardened concrete was carried out using Scanning Electron Microscopy (SEM). The test results show that the strength of concrete with activated RPW was more than that of un-activated RPW. From the results, it is evident that it is feasible to use 5% un-activated RPW and 15% activated RPW as fine aggregates for making concrete without affecting the strength properties.
Key Words
concrete; recycled plastic waste; river sand; manufactured sand; strength
Address
M. Ashok: Department of Civil Engineering, National Institute of Technology (NIT), Tiruchirappalli-620015, Tamil Nadu, India; Corrosion and Materials Protection Division, CSIR-Central Electrochemical Research Institute, Karaikudi- 630003, Tamil Nadu, India
P. Jayabalan: Department of Civil Engineering, National Institute of Technology (NIT), Tiruchirappalli-620015, Tamil Nadu, India
V. Saraswathy, S. Muralidharan: Corrosion and Materials Protection Division, CSIR-Central Electrochemical Research Institute, Karaikudi- 630003, Tamil Nadu, India
Abstract
The recovery of waste proves a solution with two impacts: the environmental impact by the reduction of pollution
and the gain of the occupied space by this waste, and the economic impact by the use of these lasts in the building and in the area of public works. The present research consists in recovering a waste marble (thrown powder exposed to the different meteorological phenomena) generated by the quarry marble of Fil-fila, located at the east side of Skikda in the north-east of Algeria, and add it, as sand in the composition of sand concrete. To carry out this research, we analyzed the evolution brought by
the substitution of ordinary sand by marble waste sand, with 25%, 50%, 75% and 100% on the properties in the fresh state (density, workability and air content) and in the cured state (compressive strength, tensile strength, surface hardness and sound velocity). For durability we tested water absorption by immersion and chloride penetration. The results obtained are compared with control samples of 0% of substitution rate. In order to have a good filling of the voids in the granular skeleton; we added a
quantity of limestone recycled fines from the quarries and for a good workability a super-plasticizing additive. The results showed that the partial substitution modified both the fresh and the hardened characteristics of the tested concretes, the durability parameters also improved.
Address
Boughamsa Ouassila, Hebhoube Houria, Kherref Leila, Belachia Mouloud, Abdelouahed Assia and Rihia Chaher: Department of Civil Engineering, LMGHU Laboratory, University of Skikda, Algeria
