N. M. Al-Akhras, University of Dammam, Dammam, Saudi Arabia M. Y. Abdulwahid, Koya University, Kurdistan Regional, Iraq
Huge amounts of olive waste residues are accumulated every year in olive-oil-producing countries, making an environmental impact. This study investigates the utilisation of olive waste ash in mortar mixes to reduce the environmental pollution arising from olive waste residue. Three olive waste ash levels were considered in the study: 5, 10 and 15%. The other experimental parameters investigated in the study were: replacement type (cement or sand), curing type (moist and autoclaving) and aggregate type (silica and limestone sand). The properties investigated in the study include: fresh properties (workability and setting time), mechanical properties (compressive and flexural strength) and microstructure of mortar. The mortar mixture proportions were 1: 3: 0.7 by weight for cement, sand and water, respectively. The results showed that the setting time and workability of mortar decreased with increasing the olive waste ash content. The mechanical properties of mortar increased with increasing the olive waste ash content as a partial replacement for the sand. On the other hand, the compressive and flexural strength of mortar decreased when more cement was replaced with olive waste ash. The mechanical properties of olive waste ash mortar using silica sand showed higher values compared to those using limestone sand. Scanning electron microscopy images show that the hardened matrix of mortar containing 15% olive waste ash as a partial replacement for silica sand was denser and had a more homogeneous microstructure in comparison with the reference and mortar mixes with olive waste ash as cement replacement.
Strength properties of HPC using binary, ternary and quaternary cementitious blends
K. Chinnaraju, Anna University, Chennai, Tamilnadu, India K. Subramanian, Coimbatore Institute of Technology, Coimbatore, Tamilnadu, India S. R. R. Senthil Kumar, P.P.G. Institute of Technology, Saravanampatti, Coimbatore, Tamilnadu, India
Use of high-performance concrete for structural applications has grown substantially in recent years. This paper focuses on studying the effect of different supplementary cementitious materials (silica fume, fly ash, ground granulated blast furnace slag, and their combinations) on strength characteristics of high-performance concrete. An experimental test programme was conducted to study the effect of such admixtures on compressive strength at 7 days and 28 days, splitting tensile and flexural tensile strengths at 28 days for high-performance concrete. A set of 60 different concrete mixtures were cast and tested with different cement replacement levels (0, 10, 20 and 30% by weight of cement) by various combinations of fly ash and ground granulated blast furnace slag with silica fume as addition (0, 2.5, 5, 7.5, 10 and 12.5% by weight of cement) for each combination. Super plasticiser was added at different dosages to achieve a constant range of slump for desired workability with a constant water-binder (w/b) ratio. Based on the test results the influence of such admixtures on strength aspects were critically analysed and discussed. A regression analysis has been carried out to relate compressive strength to flexural and splitting tensile strengths.
E. T. Dawood, School of Housing, Building and Planning, Universiti Sains Malaysia, Penang, Malaysia M. Ramli, School of Housing, Building and Planning, Universiti Sains Malaysia, Penang, Malaysia
The use of steel fibres in concrete or mortar is known for its potential to enhance the flexural toughness, the energy dissipation and the impact resistance for many structural applications, especially in building repairs and other civil engineering works. The use of steel fibres in flowable mortar provides a great advantage in arresting cracks and enhancing the flexural rigidity of the composite material. Hence, this experimental investigation was performed to provide a clear indication and understanding of the behaviour and structural performance in engineering construction. The experimental tests conducted were: density, compressive strength, splitting tensile strength, flexural strength and toughness indices tests. These tests are required to show that the best performance of high-strength flowable mortar or high-strength flowing concrete could be fulfilled by using steel fibres and the optimal percentages of silica fume as partial replacement of cement. The conductivity of the repair material was evaluated by adoption of some combined systems of repair materials with concrete to determine the bond action of this repair material (flowable high-strength system). The results indicate that the high-strength flowing concrete has an excellent performance in terms of compressive strength for the repaired system. On the other hand, the high-strength flowable mortar improves significantly the tensile strength of the repaired system.
M. Farzam, University of Tabriz, Iran N. A. Fouad, Institut für Bauphysik, Leibniz University,Germany J. Grünberg, Institut für Bauphysik, Leibniz University,Germany M. Y. Fard, University of Tabriz, Iran
The main objective of this paper is to study the effect of eccentricity of loads on the ultimate punching resistance and rotational capacity of slabs. A mechanical model recently proposed by Muttoni, which has been developed to predict the punching capacity of slab-column connections under concentric loads, is developed in the same manner as that of Broms to be applicable for the investigation of rotational capacity of slabs under eccentric loads. Furthermore, the effect of eccentricity of load on the ultimate punching resistance and the rotational capacity of slabs with respect to column is numerically studied performing a non-linear finite-element analysis using Atena. The numerical analyses consist of calculations of selected punching tests. The factors affecting the behaviour of the connections, such as the ratio of tension reinforcement, the type of reinforcement steel and the concrete compression strength are studied parametrically. The results of the analyses are compared with Eurocode 2 and ACI code predictions and with the mechanical model previously proposed by Broms and the model developed by Muttoni.
Placement of concrete underwater is necessary in the implementation of most in-shore, and off-shore structures. The pouring of underwater concrete is considered to be a challenge for engineers, even during the design stage or during implementation and supervision. This is because many precautions must be taken to ensure the success of the casting process. The most important of these is to protect the fresh concrete from the water during the casting process to avoid the risk of wash-out of the cement past and segregation of aggregates. Concrete can be placed underwater successfully through good design of the concrete mix and choosing the most suitable method for placing of the concrete. There are new techniques for underwater concreting such as grouted aggregate; this is known as the two-stage concrete method. The main objective of this paper is to present the capability of pouring concrete underwater using this method. A laboratory model was prepared, visually investigated and tested by extracting core samples, then performing compressive, tensile and ultrasonic pulse velocity tests. From the results obtained it has been observed that concrete can be poured successfully underwater using the two-stage method, and it is recommended that this research may be developed by using different water-cement ratios and cement-sand ratios to obtain the optimum mix design; also, different types of aggregates, which are available in local quarries, may be used.
Torsion strengthening of RC beams with carbon fibre composites
J. J. Holtz Silva Filho, PUC-Rio, Brazil E. de Souza Sánchez Filho, Fluminense Federal University, Brazil M. de Souza Lima Velasco, PUC-Rio, Brazil
This paper presents the results of an experimental and theoretical study designed to evaluate the behaviour of reinforced concrete beams subjected to torsion and strengthened with carbon fibre composites. A total of seven beams, each with the dimensions 200x400x4200 mm, were tested. Test results reveal marked increases in the torsion capacity of 38% and 40% for each series of beams. The effective axial stress of a theoretical model for bonding the carbon fibre composites is incorporated in the space truss with softening model. The predictions of this proposed model are then compared with tests results. A high degree of agreement is verified between the experimental and theoretical values.
