Development Of Geopolymer Concretes Wıth Constructıon Demolıtıon Waste
Özet
All around the world, sustainability of degrading infrastructures is a growing concern. Conventional concrete which is the main building block of these infrastructures consists of Portland cement as the main binding phase. Globally, there is an increasing trend in the cement consumption and as the emerging countries continue developing, the trend is expected to continue increasing. However, production of Portland cement is significantly energy-inefficient, carbon-intensive and accounts for 5 to 8% of total human-driven CO2 emissions. Prolonged sustainability therefore necessitates the design and production of construction materials that are eco-friendly in nature. For true infrastructural sustainability, hence, a paradigm shift is necessary in terms of both greenness of conventional concrete material and improved infrastructural durability for the sake of less frequent repairs.
Construction and demolition applications have become one of the leading sectors in the world with the increased number of repetitive repair/renovation/maintenance of buildings, roads, bridges and other structures. However, each year, significant amounts of solid waste are generated as a result of the abovementioned applications requiring to be tackled properly. There are multiple adverse effects of construction and demolition waste (CDW) which include (i) waste landfilling of very large clean lands, (ii) causing hazardous pollution which jeopardize the surroundings and (iii) wasting of natural resources. Although “zero CDW” seems unpractical since the waste generation is unavoidable, effective solutions to minimize the amount of CDW generated must be sought for the sake of environmental, social and economic benefits.
To counteract the negative effects of Portland cement production and favour increased materials’ greenness, “geopolymers” are being researched widely nowadays. Geopolymer is a cement-free binding material obtained by the alkali-activation of certain aluminosilicate source materials. The source materials are generally obtained from industrial by-products including fly ash, slag, etc. Moreover, along with the significantly superior materials’ greenness, geopolymers are being repeatedly reported to have high strength and enhanced durability performance (especially in terms of acid, corrosion, fire and frost resistance), although large-scale production and applications of geopolymer concretes are very restricted since the performance properties of ultimate geopolymeric materials are largely dependent on the selected aluminosilicate source material, availability of which is highly dependent on the geography.
The current research aims at developing “green” geopolymeric concrete whose constituents are entirely obtained from CDW for truly sustainable infrastructural development. For the purposes of the research, firstly, geopolymeric binding phases were developed using the inert portion of CDW which is largely composed of waste concrete, wall/roof members including different types of bricks/tiles and waste glass. Secondly, CDW-based aggregates with different sizes were incorporated into the geopolymeric binders to obtain “green” mortar and concrete mixtures. After evaluating the mechanical and micro-mechanical properties of geopolymer concretes, the focus was placed on the assessment of a set of durability properties. Successful outcomes and wide knowledge transfer of the current research are believed to make benefits in the lives of individuals by not only lowering the cost-inefficient and environment-unfriendly repairs of infrastructures but also completely recycling the CDW which is troubling all countries around the world with easy-to-implement, low-cost and energy-efficient techniques.
