The change in our world is unavoidable. We outface with this current situation because of the fast change that have become undisciplined. Belonging to the present time of our economic and industrial evolution appear to be unsustainable. Population increase, urbanization, technological advancements, and their effect on the environment are undoubtedly in the company of the key factors that are setting today’s world.  At the beginning of the twentieth century, the world’s population was 1.5 billion people, 6 billion at the end of the twentieth century, the exponential increase from 1.5 to 6 billion people during the short span of time is eruptive (population matters , 2018). The increase of urbanization of our planet is proportionate to the population growth in the last years. Both have contributed to the huge increase in size of energy, transportation, and manufacturing of the world economy through twentieth century. The biggest mistake in our technology world was that the choices was limited because they did not anticipate the effects of their use overall but in the short term, so the consequences were unpredictable.
For example, according to Hawken  only 6% of the total worldwide flow of materials, approximately about 500 billion tons a year, ends up in consumer products, while the rest (94%) ends up to the environment in the form of damaging solid, liquid, and gaseous wastes resulting into pollution. And unfortunately, this phenomenon is going on for a couple of centuries now (Malhotra, 1986). However, because of the increase in pollutants, the environmental challenge that we are facing is for the whole of the world and not for a regional. The past 100 years the earth’s atmosphere have a rapid increase concentration of greenhouse gases and pollutants which are caused from human activities which is driving the climate change due to global warming. Based on scientific research, this is the most important challenge in our days. Therefore, the Worldwatch Institute has recorded that, since 1990s, a lot of environmental and weather associated disasters are getting worse and worse with the passage of time all over the worls..  As a result, without exhausting natural resources, we risk the environment in which we live and from which we derive the whole economy.
Environmental impact of concrete
Portland cement is the main hydraulic binder that is used in concrete production (PCA, 2018), is an industry product that has very high embodies energy and thus consumes large amounts of energy and also emit large emissions of carbon dioxide (CO2), greenhouse gas to manufacture (Milne, 2018) . Specifically, concrete consists of 12% Portland cement, 8% water (any natural source), and rest aggregate (PCA, 2018). With all the construction going around the whole world, we are consuming more than 10 billion tons of aggregate (sand and rock), and 1 billion tons of mixing water annually in addition to the 1.6 billion tons of cement. 
Thus, in total the concrete industry uses 12.6 billion tons of natural resources per year, which is more than any another industry in the world. Another reason that affect the ecology of the planet apart from manufacturing cement are mining for raw materials, manufacturing/processing and transportation, which consume significant energy additionally to the 3 billion tons of the raw materials that are used for cement production every year.
How can we cut down the environmental impact of the concrete industry?
To reduce the environmental impact due to excessive use materials in the long term, their consumption should be reduced. For the next 50 years, the concrete rate consumption is hard to be reduced, so we must embark on using industrial ecology for short-term sustainable development. Which can be achieved by using the waste from one industry can be used as the source of raw materials for another industry. Also, reportedly, every year over 1 billion of tons of construction/demolition wastes are generated. Many cost effective methods as segregation of waste or others are available to recycle most of the materials including the requirement of aggregate for the fresh concrete mixtures. 
As a result, if we start making improvements to our resource efficiency, sustainable development will come soon.
The aim is to emphasis the use of concept of embodies energy of the materials and thus figuring out the best combination of materials/waste that can be utilized to prepare concrete for better sustainable environment.
The main issues discussed in the dissertation are:
1. To review the materials available to replace the use of concrete.
2. To review the need of recycled materials.
3. To review the ways that we can achieve sustainability in concrete.
2. Energy consumption in buildings
The ever-increasing use of energy worldwide has prompt major issues about impediments in supply, depletion of energy sources and the huge environmental burden involving global warming, ozone layer depletion and climate change. Energy consumption associated with buildings, both residential and commercial, has, in developed countries, significant contribution (between 20% and 40%) to the global energy consumption, outreaching other main sectors, such as industrial and transportation. The continuously growing population, the increased need for building services, along with occupants spending more time in the buildings, further strains the energy supply and demand crisis. Because of this, efficiency of energy utilization in buildings has become a major priority of energy policy regionally, nationally, and internationally. HVAC systems in the buildings are the main nodes where most of the energy use is concentrated. The present study examined the information available involving energy consumption in buildings, and especially information associated with HVAC systems. Several questions emerged: for example, was the essential information accessible for analysis? Which were the major types of buildings? In the breakdown, what end uses should be considered? Information from different countries was compared, particularly for commercial type buildings, and offices were analyzed separately in greater detail.
2.1. Energy usage worldwide
As mentioned above, energy use has become a major problem worldwide. Data on consumption of energy from the International Energy Agency (IEA) (IEA, 2018) indicate that, in the period from year 1984 to year 2004, primary energy usage has increased by 49% and carbon dioxide emissions by 43%, with a mean annual increase of 2% and 1.8%, correspondingly (Fig.1). Interestingly, data from prediction studies show that this rapid increase in energy use will continue in the future. Particularly, emerging nations, such as Middle East, Southeast Asia, South America, and Africa, are expected to increase their energy use at a mean annual rate of 3.2%, and to even outgrow the mean annual rate in the developed countries, like North America, Western Europe, Japan, Australia, and New Zealand, by 2020 (Fig.2). Noteworthy is the example of China that according to the study, the energy consumption will increase two folds by the year 2020 with a mean rate of 3.7% annually.
Figure 1: Primary energy consumption, carbon dioxide emission and world-population
Reference year 1984. Source: International Energy Agency (IEA) (IEA, 2018).
Figure 2: Global energy use by region (IEA, 2018).
Source: Energy Information Administration (EIA) (IEA, 2018).
Interesting results can be obtained from the analyzing of the trend of world energy indicators  between 1973 and 2004 (Table 1):
(1) Population growth is well below the GDP, thus with time the per capita income for the households is set to increase.
(2) Energy demand is growing at a higher rate than population stressing the already strained primary energy supply and demand, leading to the increase of its per capita value on 15.7% over the last 30 years,
(3) Carbon dioxide emissions growth rate is lower than energy consumption, but still showing a significant 5% increase during this period,
(4) electrical energy consumption has seen an explosive demand increase (over two and a half times) leading to a 18 % percentage increase in final energy consumption by the end users in 2004,
(5) Advancement in technology has decreased the energy consumption rate for obtaining the raw materials/primary energy, has resulted in the decline of 7% points.
(6) Higher GDP growth has a positive impact on the energy extraction, generation, transmission and utilization, resulting in an overall improvement of the global energy efficiency.
Figure 3:Global energy indexes from 1973 and 2004 (Brunel University, 2018)
Source: International Energy Agency (IEA) (IEA, 2018) (Brunel University, 2018).
Taken together, the above data support the link between energy use, economic progress and population increase, and challenge global policy efforts to reverse this course by implementing renewable and green technologies to increase energy efficiency. The truth is that globalization, the increased need for comforts and facilities, especially in emerging nations and the expansion of networks of communication, all lead to increased energy demand and, subsequently, to fossil fuel exhaustion and profound environmental consequences.
2.2. Energy usage in the buildings
For the most part, the energy consumption as a whole can be broken down into three wide categories: industry, transport and ‘other’, with the last category including service sector, agriculture and residential (Seed, 2018). Therefore, gathering data on building energy consumption becomes extremely challenging since it only accounts for a fraction of the services incorporated in the category ‘other’. However, taken its huge impact in total energy consumption in developed nations (taking up 20–40% of the total of the final energy consumption) (Seed, 2018), it becomes apparent that it should be regarded as a separate category and the third main sector, along with industry and transport, and be divided, at least, in two sub-sectors: dwellings and commercial buildings.
The continuously growing human population, the increased need for building services and amenities, along with the increase in time spent indoors, have resulted the energy consumption levels in the buildings comparable to the that of transportation and industrial activities (Table 2). In fact, industrial energy consumption has experienced a significant reduction in energy consumption ratio of nine points from 1973 to 2004, whereas the ‘other’ sector shows an increase in ratio for the same time period that is believed to be due to buildings.
Figure 4:World final energy consumption by sector (Seed, 2018)
Source: IEA (IEA, 2018) (Seed, 2018).
Despite the difficulty in gathering data on building energy consumption, by analyzing findings on the evolution (Fig. 3) and importance (Table 1) of building energy consumption (Seed, 2018), we were able to make some comparisons between countries or continents and to draw some conclusions:
(1) Fig.3 demonstrates building energy consumption use from 1994 to 2004 among UK, EU, Spain and USA. There was observed an annual 0.5% increase in UK building energy consumption, which falls below the EU annual rate of 1.5%. Interestingly, in Spain, energy consumption in the buildings was found to increase at an annual rate of 4.2%, much higher than both of the EU and Northern America’s (1.9%) rates combined. Potential causes may well be the economic expansion, the development of the building infrastructure and the advancements in building-services and particularly environmental control systems.
(2) Table 1 demonstrates final building energy consumption (%) both commercial and residential among UK, EU, Spain and USA for the year 2004. Notably, in 2004, EU total (residential and commercial) building consumption was found 37%, higher than industry (28%) and transport (32%). Even higher in total building energy use was found to be the UK with 39%, which is slightly above the EU figure. Partly, this was due to a deviation from the industry towards the service sector. Spain had the lowest rate of 23% consumption, but this number is predicted to increase rapidly the following years, due to the growing economic development, and to meet the EU average.
Figure 5 Energy consumption of buildings. Reference year 1994 (Luis Pe´rez-Lombard, 2007)
Source: Eurostat and EIA.
Table 1 Weight of buildings energy consumption (Seed, 2018).
Final energy consumption (%) Commercial Residential Total
USA 18 22 40
UK 11 28 39
EU 11 26 37
Spain 8 15 23
World 7 16 24
Year 2004. Sources: EIA, Eurostat, and BRE (Seed, 2018) (IEA, 2018).
Commercial and public-sector buildings, for e.g. hospitals, schools, museums, restaurants, hotels etc make up the service sector and require a number of energy services like HVAC, lighting and refrigeration. The continuously increasing population and the growing economy generate increasing needs in health, education and comfort services. In turn, increased demands in services lead to increased energy consumption. For instance, in USA, service energy consumption increased by 7% from 1950s to 2004. In addition, in the UK energy use in the service sector in 2004 reached 11% of the total energy use, same as the average European service energy consumption. In Spain, however, service energy consumption was relatively low, only 8%, but it is expected to increase massively, considering that it has multiplied by 2.5 between the years 1980 and 2000.
With regards to the residential sector, the factors determining energy consumptions are mainly the size and location. For example, small apartments consume less energy since there is less conditioned and transfer area, and less occupation (Seed, 2018). Other factors determining consumption as well as type of energy in residencies are the architectural design, the weather, energy systems and the economic level of the residents (Luis Pe´rez-Lombard, 2007). It is estimated, that dwellings in developed nations consume more energy (primary and final) compared to dwellings in emerging nations and will keep increasing with the establishment of new appliances, such as air conditioners and computers (Seed, 2018). Residencies in the USA use 22% of the final energy consumption, while in the EU it is 26%. In UK it accounts for 28% of the total use, compared with 15% in Spain. That is largely due to the climate difference, UK has a more severe weather, as well as on building architecture, prevalence of independent houses over blocks.
A prediction study performed by the EIA (Energy Information Administration) International Energy Outlook , examined future possible trends in building energy consumption(Fig.4). It was found that in the following 20 years, energy consumption in buildings will increase by 34%, at a mean rate of 1.5%. It was further estimated that in 2030, non-domestic sectors and dwellings will account for approximately 33% and 67% of total consumption, respectively. Southeast Asian spreading and subsequent construction rising will lead to an increased demand of energy in the residential sector. Interestingly, it is expected by 2020, that developed and non-developed nations will have analogous energy consumption in buildings. Rapidly growing emerging nations with galloping economies, trading and population, are followed by pressing demands for education, health and other services and, therefore, higher energy consumption. Particularly, it is believed that in the next 25 years, non-developed countries will double their energy use in the public services sector, with mean increase rate approximately about 2.8% per annum.
Figure 6 Buildings energy consumption outlook (Luis Pe´rez-Lombard, 2007).
Source: EIA (Luis Pe´rez-Lombard, 2007).
2.3. Heating, ventilation, and air conditioning (HVAC)
Due to the continuously increased energy consumption and release of CO2 in the build environment, energy efficiency in buildings and savings methods have become a main concern of energy policy globally (Luis Pe´rez-Lombard, 2007). An obvious example is the European Energy Performance of Buildings Directive (EPBD) (Luis Pe´rez-Lombard, 2007) . Particularly significant is the heating, ventilation, and air conditioning (HVAC) system that comprises the largest energy end use in both the commercial and non-commercial sectors and has become a necessity along with the need for thermal comfort (Seed, 2018).
Its prevalence becomes apparent when it is examined in contrast with another end uses. Table 4 represents energy-consumption percentage by various end use in the domestic sector among four different regions, Spain, Europe, USA and UK. It can be seen, that, at large, in dwellings HVAC takes up about three times the energy use than that of Domestic hot water (DHW). In the non-residential sector, HVAC energy consumption is estimated by the IDEA , as well as by other sources , to take up about 48%, still lower than the 57% observed in the USA. The burden of the HVAC at the European level remains unknown. Nevertheless, several sources have identified an important increase in air conditioning, particularly in southern regions, such as Spain and Italy.
Table 2 Energy consumption by end uses in the residential sector.
Figure 7: Energy usage (Luis Pe´rez-Lombard, 2007)
European administration data at national, regional or local levels are inadequate to provide the necessary information for effectively planning future energy policies and for directing action upon each of the end uses (Luis Pe´rez-Lombard, 2007). Governmental funded research by sector should be initiated for residential  and commercial buildings  in order to produce a complete database of the building stock (such as location, type, area, and age) and of energy parameters (such as, consumption, expenditures, and end uses) that will enable efficient planning for the future (Seed, 2018).
In developed regions, HVAC use takes up about half of the energy use in buildings which is almost 1/5th of the total national energy consumption. In addition, predictive studies estimate a huge increase of approximately 50% in energy use and conditioned area in the European Union  in the following 15 years.
2.4. Commercial buildings
In commercial buildings, the amount and form of energy needed depends hugely on the type of use and activities. This makes the data analysis very complicated since very few sources present findings typologically. Nevertheless, following reviewing of numerous data sources, some generic conclusions may be drawn:
(1) In the last few years in the UK, due to the expansion of floor area and the enhanced servicing levels outweighing increased efficiency, energy use in the non-commercial sector has been stabilized to some extent. This sector expands at a higher rate in other European countries mainly because of the enhanced application of HVAC systems in new buildings . Furthermore, new building construction rates in the UK are normally approximately 2%, whereas in Spain, for example, the mean annual new build rate is 6.1% increasing since 2000 and estimated to keep increasing. In 2003, service sector accounted for 11% of total energy use in the UK and was lower than the USA rate (18%) and equal to the EU (11%) (Seed, 2018). From the above, it becomes apparent that the service sector should not be overlooked when planning energy policies, since it has the highest growing rate compared to other sectors like residential and industrial.
(2) From the non-residential building, office and retail are the most energy consuming categories taking up more than 50% of the total energy use. Hotels and restaurants, hospitals and schools follow in that order (Figure 8).
Figure 8: Energy use in the commercial sector by building type (Seed, 2018)
Year 2003. Sources: EIA, IDAE and BRE.
(1) As it is being illustrated in Fig. 5, HVAC is the major end use in all building types with a load reaching almost 50% for office buildings. Lighting is next in the rank with 15% weight and appliances follows with 10%. How energy end use is allocated depends on the building type (Fig.5) as well as in the energy intensity of the buildings (Table 6). Thus, it is apparent that independent studies would develop according to building types.
Figure 9 Consumption by end use for different building types.
Figure 10: Average energy usage by buildings type in USA
Year 2003. Source: EIA.
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