Life cycle assessments of concrete structures - a step towards environmental savings
Petr Hajek, Czech Technical University in Prague, Czech Republic Ctislav Fiala, Czech Technical University in Prague, Czech Republic Magdalena Kynclova, Czech Technical University in Prague, Czech Republic
Considering the volume of concrete produced and the number of concrete structures built, the problem of the associated environmental impact forms a significant part of the entire global problem of sustainable development. Utilization of environmentally optimized concrete structures thus creates a potential for increasing the quality of construction and consequently a reduction of the environmental impact. A life cycle assessment (LCA) is a complex, multi-parametric assessment of the environmental impact of the structure over its whole life cycle. It covers, in one assessment process, all the essential environmental issues, including CO2 emissions, energy consumption, water consumption, waste generation, etc. In the case of concrete, selected criteria should support the design and construction of high-quality and at the same time environmentally friendly concrete structures. The principal problem is to collect relevant environmental input data for specific concrete types plus transport and production processes which can be used in the LCA procedure.
Structural systems for protection against extreme events
Klaas van Breugel, Delft University of Technology, The Netherlands
Typical for extreme events is their multidisciplinary nature, and, consequently, solutions for protection against extreme events should mirror their inherent characteristics. This article discusses different types of hazards and extreme events in order to illustrate the complexity and scale of the problem. Concepts for judging hazards and associated risks are dealt with. Some features of the traditional risk concept are discussed, followed by a proposal for an extended risk concept, to be applied when dealing with extreme hazards. The emphasis will be on aspects that are typical of "low-probability/high-consequence risks", particularly industrial risks. The potential role of structural (concrete) protective systems for mitigating the consequences of industrial accidents is emphasized. Throughout this article, the role of structural designers and their possible contribution to the debate on adequate protection against extreme events is addressed.
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.
