Indubhushan Patnaikuni

Properties of high-strength steel fiber-reinforced concrete beams in bending

Abstract This paper presents research results of ten high-strength reinforced concrete beams and steel fiber-reinforced high strength concrete beams, with steel fiber content of 1% by volume. The enlarged ends of mild carbon steel fibers with three different dimensions were selected. This research shows that the flexural rigidity before yield stage and the displacement at 80% ultimate load in the descending curve are improved, and crack number and length at comparable loads is reduced after the addition of steel fibers. The descending part of the load-displacement curve of the concrete beams without steel fibers is much steeper than that with steel fibers, which shows that the addition of steel fibers makes the high strength concrete beams more ductile.

Transition zone in high performance concrete during hydration

Abstract A number of transition zone studies are available in the literature for normal strength concrete. High performance concrete behaves differently from normal strength concrete and very few transition zone studies are available for high performance concrete. The weakest unique transition zone between cement paste and coarse aggregate particle controls many important properties of concrete such as compressive strength. In this paper the relationship between transition zone microstructure and compressive strength property of high performance concrete using Australian industrial silica fume and Australian aggregates is investigated. Based on the scanning electron microscopic studies of transition zone, it has been found that high performance concrete transition zone thickness increases while compressive strength increases. Further, high performance concrete transition zone thickness is much less than the thickness of transition zone of normal strength concrete. This thin transition zone also enhances compressive strength. It has been observed that silica fume presence in the transition zone significantly enhances compressive strength. Silica fume particles consume calcium hydroxide, which is present in transition zone, and make the zone dense and uniform.

Correlation of strength of 75 mm diameter and 100 mm diameter cylinders for high strength concrete

Abstract Results of statistical analysis of test data are presented to establish if there is a correlation between the strength of 75- and 100-mm-diameter cylinders for concrete with strength between 110 and 160 MPa. A linear regression analysis showed that strength measured on 75-mm cylinders is within 5% of the corresponding strength measured on 100-mm cylinders. A more detailed analysis of the difference between the mean strengths of the two sizes of cylinder of each group of the tests indicated that 75- and 100-mm cylinders measure the concrete strength within 4%. It is concluded that 75-mm cylinders are suitable for compressive strength testing of high strength concrete (>100 MPa). For strength of concrete greater than 150 MPa, 75-mm cylinders are likely to measure smaller concrete strength than the corresponding 100-mm cylinders.

How to Develop a Practical Asset Management Tool

Asset management is a process of optimising the asset lifecycle. Due to the advancement of information technology, organisations have started using sophisticated software without understanding its calibrations and the detailed processes involved. Usage of software should be limited and the software should be simple to use. Asset Management cannot be performed in isolation from the field staff. No software can give us a perfect solution; in fact the field data is the most important information which must be incorporated in our asset management model/plan. The asset management team and field staff should work together in refining the asset management model and they should understand the implications of each input variable. Hence there is a great need to define a simple process in order to get an effective asset management model which can be used by an ordinary asset management practitioner. The objective of this paper is to develop a strategy which can assist to simplify the asset management process.

Prediction of Life-Cycle Expenditure for Different Categories of Council Buildings

The prediction of the performance or service life of a building system and their components is a very complex task. Although many papers related to material and component durability have been published over the past two decades, they had a negligible impact on the development of an effective approach for durability design. ISO presents a valuable methodology based on the factor method in the area of service life estimation but it requires considerable local knowledge about degradation of components and materials. The factor method on the other hand is fairly simple but identifies the main parameters influencing service life. The result, however, is only a single figure for service life and does not take into account the variability of the processes involved. A lot of work is being done in the area of service life prediction, but there is very little that can be readily used by building asset managers. Hence, there is a great need to develop a simple model which can be easily calibrated and used. The model proposed here can be easily implemented by practitioners and would be of benefit to infrastructure managers of city councils.

Mechanical Properties of High Volume Fly Ash Concrete Reinforced with Hybrid Fibers

Fly ash substitution to cement is a well-recognized approach to reduce CO2 emissions. Although fly ash concrete is prone to brittle behavior, researchers have shown that addition of fibers could reduce brittle behavior. Previous research efforts seem to have utlised a single type of fiber or two types of fibers. In this research, three types of fibers, steel, polypropylene, and basalt as 0%, 0.50%, 0.75%, and 1% by volume of concrete, were mixed in varying proportions with concrete specimens substituted with 50% fly ash (class F). All specimens were tested for compressive strength, indirect tensile strength, and flexural strength over a period of 3 to 56 days of curing. Test results showed that significant improvement in mechanical properties could be obtained by a particular hybrid fiber reinforcement combination (1% steel fiber, 0.75% polypropylene fiber, and 0.75% basalt fiber). The strength values were observed to exceed previous research results. Workability of concrete was affected when the fiber combination exceeded 3%. Thus a limiting value for adding fibers and the combination to achieve maximum strengths have been identified in this research.

Performance of high-volume fly ash concrete incorporating lime water

The use of concrete containing high-volume fly ash (HVFA) has recently gained popularity as a resource-efficient, durable, and sustainable option for a variety of concrete applications. The long-term creep and drying shrinkage of HVFA concrete containing 65% fly ash (HPFA-65) incorporating lime water has been investigated up to 1 year. Moreover, tensile strength and elastic modulus of HVFA-65 concrete have been examined in conjunction with microstructural development. The HVFA-65 concrete achieved similar to 200 microstrain of creep at the first 50 days; however, it only obtained approximately 100 microstrain between 50 and 365 days. This is equivalent to one-third of total creep strain displayed by portland-cement (PC) concrete, and also half of the predicted creep strain in accordance with AS 3600. Amalgamation of calcium-alumina-silicate-hydrate (C-A-S-H) gel with calcium-silicate-hydrate (C-S-H) gel was seen to positively affect the compactness and packing density of the gel matrix, which in turn influences the strength and elastic modulus development in HVFA-65 concrete. Early-age curing is also identified as significant in controlling drying shrinkage of the concrete.

Passive Solar Energy in Buildings

Energy usage in society is a common factor in residential homes and in the commercial and industrial sectors. In order to obtain adequate energy to maintain our current lifestyle, we have been extracting minerals and fossil fuels from the earth thus damaging the natural environment.

Performance Analysis of Hybrid Fiber Reinforced High Volume Fly Ash Cement Composite

Fly ash is a well-known pozzolanic material that can be used in high volume as a partial replacement of cement. This paper attempts to characterize the mechanical properties of hybrid fiber reinforced high volume fly ash (HVFA) cement mortar. An experimental program was designed to show how the addition of steel (ST), polypropylene (PP) and basalt fibers (BF) in various volume fractions affected under an applied compressive and flexural load. High volume flyash cement composites were reinforced with fibers at 1.0, 1.5 and 2.0% by volume and these mixtures were tested for the compressive stress-strain curves. Different sizes of fibers are combined to modify the crack propagation mechanism, thus producing an increase in the peak strain and the post-peak ductility. From this study, the most effective hybrid fiber was found to be the composition of 1.0% ST + 0.5% PP + 0.5% BF (H7). Scanning electron microscope (SEM) analysis of the microstructure was also carried out to determine the durability characteristics of basalt fibers in HVFA cement mortar.

Sustainable Housing Construction to Reduce Greenhouse Gas Emissions

Global warming is a reality due to the curent level of greenhouse gas emissions globally. Housing construction should take into account factors which contribute to global warming while making the construction affordable in view of the greenhouse gas emissions and the continually increasing energy costs. It is important that housing construction overcomes the irrationality of the current conventional construction method which is not only expensive but has poor thermal performance and ignores the significant environmental impact of high embodied energy of the building process which contributes to the greenhouse gas emissions. Because of this there is a need for developing improved low cost sustainable building techniques. This paper presents an innovative rammed earth core concrete jacket walling system that can provide significant improvements in environmental impact, comfort and cost of both building the house and the cost of operational energy. The construction uses mainly local natural materials with very little high energy processing there by reducing the embodied energy of the construction. Not only using local materials in this construction but also only basic building skills are required for construction workers and therefore the system is ideally suited to rural areas and has potential application to developing countries. This method of construction has better performance in case of earth quakes which saves many lives. The paper presents a discussion of the efficiency of such high thermal mass solutions and describes the construction process.