Abstract
Recycled aggregates (RA) possess the ability to be recycled, if undesirable properties are counteracted viz, porous mortar attached to it, with high water absorption and low density, this technique, accelerated carbonation can be one such to technique to counteract undesirable properties of RA, replacement of 20% of cement by glass powder assists in reducing w/c ratio<sup>[1][6]</sup> when used in concrete<sup>[2] </sup>suppress ASR reaction<sup>[1]</sup>, this paper explains a new possibility of recycling concrete, work done and findings for improvising Recycled aggregate concrete (RAC) and exploring the feasibility for use of RA in the near future.
Highlights
Aggregates obtained from C&D waste can be utilized as partial substitute for natural aggregate in new concrete, but due to their previous usage these aggregates surrounded by inter-transition zone mortar, develop undesirable properties such as high water absorption, prone to cracks under loading and weaker transition zone, limits the usage of these aggregates at higher content incorporation of glass powder will counteract the problem of water absorption[5][6] and further carbonation of recycled aggregate in which CO2 reacts with hydrated and un-hydrated byproducts of mortar attached to Recycled aggregates (RA) to form CaCo3[7], which is formulated by the following reactions[7]
Accelerated carbonation chamber: accelerated carbonation chamber is an air tight sealed container where compressed CO2 is maintained at pressure around 0.2 to 0.4 MPa, with 50-60% relative humidity (RH) with concentrated brine solution to prevent formation of carbonic acid on reacting with water (Fig.4 + 5) aggregates are processed for period of 48 hours
1. water absorption was reduced from 2.38% to 2.17% and specific gravity of RA was increased from 3 to 3.17
Summary
Due to rapid growth in the population and industry the demand for natural sources has increased which are reducing availability of resources and creating stress on natural resources, in order to fulfill the demand there is necessity to find alternate source and recycle materials back to industry, and closed loop recycling is the most appropriate sustainable methodology to reuse waste streams back into new production as it will create energy saving , reduce the demand on primary resources and deviate waste from reaching landfills in some circumstances , waste streams cannot be reused in the production of new material of their restriction applied on quality, Several studies have been carried out to study feasibility of industrial waste and rejects, as pozzolanic and aggregates wastes like slag, rice husk ash, plastic, glass etc. in concrete, milled glass powder is a potential substitute for cement, Use of glass in construction application as a replacement for cement provided to be advantageous. Glass powder fine and possess pozzolanic property, when it is partially replaced assists in formation of CSH gel suppress ASR reaction and reduces w/c when in concrete [1]. Aggregates obtained from C&D waste can be utilized as partial substitute for natural aggregate in new concrete, but due to their previous usage these aggregates surrounded by inter-transition zone mortar, develop undesirable properties such as high water absorption, prone to cracks under loading and weaker transition zone, limits the usage of these aggregates at higher content incorporation of glass powder will counteract the problem of water absorption[5][6] and further carbonation of recycled aggregate in which CO2 reacts with hydrated and un-hydrated byproducts of mortar attached to RA to form CaCo3[7], which is formulated by the following reactions[7]. Ca (OH)2 + CO2! CaCO3 + H2O C"S"H + CO2! CaCO3 + SiO2 # nH2O 3CaO.Al2O3.CaSO4.32H2O!Al2O3.nH2O+3CaCO3+3(CaSO4.2H2O)+ (26-n)H2O 2CaO.SiO2+2CO2+nH2O ! 2CaCO3+SiO2+nH2O 3CaO.SiO2+3CO2+nH2O !3CaCO3+SiO2+nH2O The hydrated bi-products present in attached cement mortar C-S-H ,Ca(OH), ettringite (calcium trisulpho aluminate) and calcium mono-aluminate and un-hydrated cement particles containing C3S and C2S are carbonated to form calcium carbonate, this calcium carbonate formed, fills the micro pores present in attached cement mortar which decreases porosity and water absorption and increases the density of recycled aggregate[7]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: International Journal of Recent Contributions from Engineering, Science & IT (iJES)
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
