چکیده:
Concrete is the major material used in construction all over the world which is increasing annually. However, concrete is related to harmful emissions of carbon dioxide (CO2) mostly caused by cement production that leads to environmental destruction (1, 2). In 2018, 55.6 gigatons of CO2 were emitted, while around 5-7% of total global emissions of CO2 are laid on cement production and it is predicted to rise at 30% in 2050 (3). Current strategies have been introduced into the civil engineering industry such as new generation concrete and cement production processes to minimize environmental impact (2, 4). The main actions for decreasing emissions are described in this paper as a review by using sites namely Google Scholar, PubMed, and Science Direct. A recent system has been introduced to recycle construction and demolition waste (CDW) for new building construction (5). Also, decreasing clinker factor and increasing the role of supplementary cementitious materials (SCMs) in the cementitious materials like replacing portland cement using SCMs that are principally derived from industrial by-products, such as blast-furnace slags and coal combustion fly ashes can be another solution; low-carbon blended cement with the high volume of SCMs, or the utilization of concrete mixtures in which the fly ash replaces 50% or more of the portland cement have increased significantly in recent years (6, 7, 8, 9). Compared to portland cement, the impact of blast-furnace slag and fly ash is about an order of a magnitude lower (10). Moreover, portland cement clinker reduction in the concrete by using superplasticizers and highly reactive cement as well as optimization of the particle-size distribution and water content reduction would be effective (1). Another way is to add the mineral fillers like limestone powder. Portland limestone cement (PLC) concretes which have up to 10% limestone, provide competitive properties with portland cement concretes (11, 1). Binder use efficiency is another crucial strategy for decreasing environmental impacts. The use of industrial waste such as Ground Calcium Carbide Residue (CCR) and ground Bagasse Ash (BA) to produce eco-friendly concrete is useful (4, 12). Using different dosages of sawdust as a replacement for sand, or using alternative fuels are other proper ways (13, 3). Moreover, one of the most promising alternative cementing systems for general concrete applications currently appears to be those based at least in part on calcium sulfates and other similar systems that make good use of the potential synergies among calcium sulfate, calcium silicate, and calcium aluminate hydrates (8). Finally, changing the focus from the cement production optimization tooptimization of the concrete production industry, responsible for most of the cement consumption based on literature data analysis using two new environmental indicators Binder Intensity and CO2 Intensity would be another solution. There is a potential to reduce significantly the cement content on concrete, being possible to increase concrete production without increasing cement production and CO2 generation (3).
However, these studies could be limited by the availability of these resources and the supplies of such by-products of suitable quality. Using these potentially more CO2-efficient technologies on a large enough scale to have a significant global impact, many changes to the formulation and processing of concrete are also required and we will have to develop the performance data needed to justify changes to construction codes and standards. A great deal more research is required to solve significant unresolved processing and reactivity questions and to establish the durability of concretes made from such cement (8, 12, 11).
خلاصه ماشینی:
Current strategies have been introduced into the civil engineering industry such as new generation concrete and cement production processes to minimize environmental impact (2, 4).
Also, decreasing clinker factor and increasing the role of supplementary cementitious materials (SCMs) in the cementitious materials like replacing portland cement using SCMs that are principally derived from industrial by-products, such as blast-furnace slags and coal combustion fly ashes can be another solution; low-carbon blended cement with the high volume of SCMs, or the utilization of concrete mixtures in which the fly ash replaces 50% or more of the portland cement have increased significantly in recent years (6, 7, 8, 9).
Keywords: CO2, Concrete, Cement, Clinker, Supplementary cementitious materials, Fly ash, limestone powder, Binder, calcium sulfate References: 1-Proske, T.
In IOP Conference Series: Materials Science and Engineering (Vol. 603, No. 3, p.