STUDY ON RECYCLED AGGREGATE CONCRETE WITH BLENDED GGBS

Abstract With the rapid growth in construction activities, it is important to assess the amount of construction and demolition waste being generated and analyse the practices needed to handle this waste from the point of waste management and disposal and also with regard to waste utilization in concrete from the sustainability aspects. Construction and Demolition (C&D) waste constitutes a major portion of total solid waste production in the world, and most of it is used in landfills. Research by concrete engineers has clearly suggested the possibility of appropriately treating and reusing such waste as aggregate once again in concrete, especially in applications such as bed concrete and in road beds for pavement i.e. where works are of less importance as regards to the strength. The use of such waste as recycled aggregate in concrete can be useful for both environmental and economic aspects in the construction industry. In present study, five concrete mixes were used; first mix had only natural coarse aggregate and in remaining mixes natural coarse aggregate was partial replaced by 10%, 20%, 30% and 40% recycled coarse aggregate. In all the mix cement was replaced by 10% GGBS. Here an attempt is made to assess the strength and durability characteristics of concrete made using construction and demolition waste recycled coarse aggregate

Relative contribution of monsoon precipitation and pumping to changes in groundwater storage in India

The depletion of groundwater resources threatens food and water security in India. However, the relative influence of groundwater pumping and climate variability on groundwater availability and storage remains unclear. Here we show from analyses of satellite and local well data spanning the past decade that long-term changes in monsoon precipitation are driving groundwater storage variability in most parts of India either directly by changing recharge or indirectly by changing abstraction. We find that groundwater storage has declined in northern India at the rate of 2 cm yr−1 and increased by 1 to 2 cm yr−1 in southern India between 2002 and 2013. We find that a large fraction of the total variability in groundwater storage in north-central and southern India can be explained by changes in precipitation. Groundwater storage variability in northwestern India can be explained predominantly by variability in abstraction for irrigation, which is in turn influenced by changes in precipitation. Declining precipitation in northern India is linked to Indian Ocean warming, suggesting a previously unrecognized teleconnection between ocean temperatures and groundwater storage.by Akarsh Asoka, Tom Gleeson, Yoshihide Wada and Vimal Mishr