The climate change is a major problem that the world facing today. Since the cement responsible for 10% of the world total CO2 emission, searching for green building material is imperative to limit the emission of CO2 accompanied with cement manufacture. In addition, green concrete could be more sustainable and durable which increases its application in the future (Müller et al. 2014).
1.1 Statement of purpose
Due to the high global production and utilization of cement, the purpose of this report is to show methods to assess and lowering the environmental impact of the concrete and finding ways to develop its performance.
Therefore, the report will explain the advantages of using green concrete and focusing specifically on using waste material as a replacement of aggregate. It is also shows some principle of green chemistry to develop new and sustainable cement.
2.0 Green concrete and sustainability
The aim of using green concrete to reduce the environmental impact by using waste material as one or more of its components. It is also required life cycle sustainability and high performance. The main objective behind the idea of green concrete is to lower the green house emission and to reduce the consumption of natural resources such as limestone, clay, etc. in cement manufacture. It is also concept less energy because the material of Portland cement required huge amount of coal and fossil to heat it up for the suitable temperature. Moreover, using green concrete in building is reducing energy consumption owing to its ability to resist temperature changes (Marinkovic et al. 2017, p. 636)., as result the architect can design building with more cooling and heating efficiency. This will result sustainable development without destruction to the environment.
3.0 Common waste materials used in green concrete
The usage of some waste materials as substance of cement in a way to prove concrete properties and reduce its environmental impact.
3.1 Fly ash as SMC in green concrete
It is clear that Fly ash (FA) not consider as waste material anymore but it can be useful as by-product. Moreover, it is probable that using large portions of FA as substitute for cement to reduce the CO2 emission (Suhendro 2014, P. 3143) Furthermore, According to Liew, Sojobi & Zhang (2017, P. 1067) “The benefits derived from the use of fly ash were increase in compressive strength bulk density and linear shrinkage, porosity reduction, improvement in bending toughness and ductility”, which make it a prefect replacement of natural aggregate. Nerveless, it is necessary to select the correct type of FA to avoid any negative affect such as increased in setting time, strength development become slower and difficult to use in cold weather. In brief the environmental effect of High FA concrete is lower than standard concrete and it is more economy and more sustainable.
3.2 Silica fume as SMC in green concrete
The utilization of silica fume (SM) has a lot of benefits on concrete including; enhancement flexural and compressive strengths, developed pozzolanic activity, developed durability and increase “multi-range macroporosity properties” which used in the lightweight concrete (Liew, Sojobi & Zhang 2017). However, the disadvantages of SF are lowering the workability, decrease in long-term compressive strength and increase corrosion in reinforcement in marine environment.
3.3 Glass waste as SCM in green concrete
Recycling glass (GS) can be recycled up to 100% without lost in quality or purity, when concrete contains GS as raw material shows a better “resistance to freezing and thawing, chloride penetration, surface scaling and good resistance to Na2CO3 and H2SO4” (Liew, Sojobi & Zhang (2017, P. 1069), while the negative effect of it is decrease in compressive strength and slump reduction at high containing of glass waste. Thus it is clear that the utilization of FA, SF and GS to produce green concrete is result high quality of concrete and less Carbone footprint.
4.0 Green chemistry and industrial ecology
There are a huge opportunities lie in the use of cement based on different composition, green chemistry and binding-phases. It is allowed the cement to be synthesized from diversity of materials including recycled resources and mineral wastes that decrease the energy required during manufacturing. Utilizing geopolymers in sustainable concrete has less CO2 emission than ordinary cement, the material that has been used is an activated alkali aluminosilicates which result concrete with sufficient strength and high chemical resistance. Nonetheless, the chemistry of geopolymerisation still understanding and needed to be support (Suhendro 2014, p. 312). Furthermore, there are three promising cement alternatives (alkali-activated cements, magnesia cements and sulfoaluminate cements) which were reviewed then compared with Portland cement. Alternative cements show that they are considerable potential in terms of environmental, engineering and economic properties. Hance the geopolymer concrete has high performance which made it comparable with other high strength concrete.
5.0 Conclusion and recommendation
In conclude, the need to initiate to reduce CO2 emission on large scale is crucial. As cement manufacture cause huge pollution to the environment, efforts have been done to limit its impact. Using waste materials as substance to cement is not only decrease the CO2 emission, it I also enhance concrete properties. Further studies required in the long term to improve green concrete properties that increase its conception.