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Recycling, sustainability and environmental stewardship are some of the concepts that are in the front line now-a-days. Some strategies that can be adopted in order to bring these concepts in to the construction processes are the efficient use of materials, use of recycled materials, reduction in the waste materials produced etc. Use of recycled concrete aggregates as a substitute for natural (virgin) aggregates is a way to bring in these concepts into the manufacture of concrete. An experimental investigation was conducted to assess the effect of replacement of normal coarse aggregate with recycled coarse aggregate (prepared from old concrete specimens) on M25 grade concrete. Different levels of replacements studied include 0%, 20%, 50%, 80% and 100% were considered. The properties studied are fresh properties as well as mechanical properties which include compressive strength, split tensile strength and flexural strength. It is concluded from the study that as the RCA content increases, it is necessary to increase the cement content and or to decrease the water cement ratio in order to attain target compressive strength.

Journal of Architectural Engineering Technology AbstractInnovations in construction 'time waste' management are scarce. Construction delays are usually caused by time wastes at activity levels, and scholarly studies primarily don't deal in explaining waste at singular activity levels. Experience based heuristics play the most important role in fixing the duration of activities by managers. But, construction activities are prone to highly improbable and complex process flows, making heuristics unreliable. This happens due because the probabilities of construction uncertainties in one project being similar in forthcoming projects are meagerly low. Thus, the experience gained by the project management personnel over the years, may not be handy at predicting actual durations and costs of the forthcoming project with sufficient accuracy.The only practical solution would be a fixation of cost and time standards for singular construction activities based on the complete history of projects completed and those personnel involved in it. In a nutshell, it would mean globalizing or at least nationalizing heuristic data of delays and wastes in order to facilitate meaningful future predictions. This can be achieved by devising a mechanism of centralization of construction process related data into a single entity at the national/international level -Data Collection System (DCS). As part of this system, synchronization of personnel and construction site data should take place at every instance a new construction process is activated anywhere within the boundary of existing DCS. A collection of inventory data, material data, labor data, stakeholder data, activity delay data, time waste data, etc. should form the core data in this data center. Data obtained from heuristics should then be converted to mathematical distributions that could then be used for predictions in future construction scenarios. This would result in giving better and better results as the process of data entry proceeds. The scope of this study is limited to construction activities from Indian construction sites involving core and shell in buildings. "Cost overrun" in:(1) Beam and slab construction, (2) Column construction and, (3) Block work is mathematically modeled as probability distributions.US naval code NAVFAC P-405 is employed for site independent duration calculation. As part of this study, steps on using NAVFAC -405 in calculating delays are explored in detail. Beta, Normal, and extreme value distributions were seen to fit cost overruns in these activities. This could then be entered into the DCS.