B. C. Udayashankar

Environmental sustainability is the need of the hour. The dependency on natural river sand has to be decreased, and an environment friendly disposal of waste rubber tires needs to be promoted. The application-specific properties of concrete such as damping or vibration absorbing capacity can be enhanced, by the use of scrap rubber tires as aggregates in concrete. This paper evaluates the feasibility of using shredded waste rubber as a partial replacement to fine aggregate, with respect to mass, by conducting investigations on its mechanical properties. In addition, the effect of polymeric fibers which is incorporated in rubberized concrete is probed. The reuse of waste rubber and fiber resulted in improved ductility and damping ratio; however, it reduced the strength values. At a maximum of 7.5% replacement in both plain rubberized and fiber reinforced rubberized concrete, the loss in strength percentage is within acceptable limits making it suitable for use as vibration attenuators in applications such as road curbs and barriers, paving blocks, trench filling, and machine foundations.

Rapid urbanization, industrialization, and change of life style of people has increased the rate of solid waste generation by leaps and bounds in the developing countries. Municipal solid waste generation varies with place to place and the standard of living of the people residing in cities. Solid waste consists of organic matter, which undergoes degradation and produces foul smell, if not properly managed. Therefore management of the garbage had reached a very critical stage and now emphasis has been given to its collection, treatment, and final disposal. Generally in Indian cities, waste is collected and simply dumped outside the cities which are called as landfill sites. Any method of disposal other than composting will be uneconomical, required skilled person, and also pollute air, water, and soil. Large quantity of plant nutrients gets wasted in other methods of disposal. Composting is not a method of waste disposal but it is a method of recycling the waste. Municipal solid waste is one of the potential organic nutrient residues, which upon recycling leads to a valuable compost, which is vital for growth and development of plants. Sewage sludge is rich in micro-organisms, organic content, as well as nutrient elements. So in this study co-composting of municipal waste with sewage sludge has been taken up to conserve nutrients. In the present work studies were conducted on municipal solid waste, mixed with sewage sludge in different proportion, to check the technical viability of the integrated system of composting. Addition of sewage sludge to waste for composting not only increases decomposition rate and fertility value, it also solve the problem of sludge disposal from treatment plant. It will save the cost of sludge treatment. Municipal waste compost can be regarded as being valuable in soil management practices because of their organic matter content.

Controlled low strength material (CLSM), as defined by the American Concrete Institute (ACI) Committee, is a self-flowing cementitious material consisting typically of portland cement, fine aggregates, supplementary cementing materials, and water. In this present experimental study, industrial by-product, namely, ground-granulated blast-furnace slag, is used as a constituent material in CLSM. Mixture proportions were developed for CLSM containing the industrial by-product (GGBS) and were tested in the laboratory for flow and unconfined compressive strength properties. The cardinal aim is to analyze the experimental data generated to formulate a phenomenological model to arrive at the combinations of the ingredients to produce CLSM to meet the desired flow and strength. An independent set of data is generated to examine the validity of the phenomenological approach.

Fly ash based geopolymer composite cubes were cast using class F fly ash, ground granulated blast furnace slag (GGBFS) as binders. The fluid-to-binder ratio was varied keeping all other parameters constant. The geopolymer composites were cured in different conditions. The composites were tested for compression at different ages. It is interesting to note that the variation of the strength with various fluid-to-binder ratios is unique irrespective of combination of materials, curing conditions, fluid content, and molarity of the fluid. The strength data generated was generalized to arrive at a phenomenological model. The model represents an unique pattern of strength development for the series of composite materials. The validity of the model was examined with an independent set of experimental data generated by the authors and Rangan. It was found that the predicted strengths were in line with the experimental strengths having a percentage error less than 6.0. The model is effective in re-proportioning of geopolymer composites in the field.