Keywords

Highlights

  • Introducing ecology of construction is important step to achieve sustainability in infrastructures.

  • Ecosystems as a source of lessons and models for transitioning built environment onto sustainable path.

  • Earth construction and plant-based building materials bring sustainability in construction.

  • It is important to develop carbon-negative cement to use in modern infrastructures.

1 Introduction

It is becoming an increasingly heated topic of discussion among concerned scholars from different fields to look for the way to make cities healthy. The researches carried out to build healthy cities are no longer restricted to urban planners, architectures, or engineers, but ecologists and even microbiologists are also entering into this area.

Urban resilience is now being recognized as the approach to healthier and more sustainable cities facing various challenges (Shao et al. 2016). The infrastructure of any city depends on building materials that could pose potential threat to the environment or ecosystem. However, to accommodate the growing population, rapid construction of infrastructure is obvious. Among the materials of construction, concrete is the world’s most consumed man-made material. It is in fact most widely used material on this earth after water. However, the production of Portland cement, an essential constituent of concrete, leads to the release of significant amounts of CO2, a greenhouse gas (GHG); production of one ton of Portland cement produces about one ton of CO2 and other GHGs (Naik 2008). A review of the recent trends in the global production of cement in 2015 shows that the estimated amount of cement produced over the world was 4.6 billion tones (Fig. 1), where China alone consumed 51.3% of it (CEMBUREAU 2015).

Fig. 1
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World Portland cement production in 2015

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In the current global setting, building construction and operation result in 50% of all emissions worldwide. In order to city become sustainable, the construction industry must manage its environmental impact in an optimal fashion. Table 1 summarizes quantities of energy and CO2 produced by common building materials. Due to its negative impact on the environment, cement is not considered at all a sustainable material. Thus, urban sustainability problems due to cement usage can be categorized as the wicked one (Rittel and Webber 1973).

Table 1 Embodied energy and emission of building materials
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2 Ecological Wisdom for Sustainable Construction

The concept of ecological wisdom as explained in Xiang (2014) prevails in the nature and provides sustainable solutions to combat environmental issues associated with cement. In case of building materials, ecological wisdom is manifested in the results of millions of years of experiments on sustainable habitats by nature (Achal et al. 2016). In ecologically meaningful engineering projects are developed in harmony with the existing ecosystems for overall environmental benefit. Ecological wisdom reminds responsibilities that all citizens on earth should bear in mind and carry out in fighting against the ecological crisis and provides a blueprint for human beings to develop a low carbon economy of sustainable development (Xu et al. 2012). Ecosystems are the source of important lessons and models for transitioning built environment onto sustainable path. Green (or ecological) infrastructure is one strategy to enhance and expand ecosystem services (Steiner 2016), and sustainable building materials are highly required for it.

Buildings are the most significant components of the built environment that are perhaps also the most significant embodiment of human culture (Kibert et al. 2002).

In the modern era of building design, ideas of several eminent architects and planners like Neutra, Mumford, McHarg, and Wells have coalesced into today’s ecologically sustainable construction (Kibert et al. 2002). Neutra pointed out how badly flawed human products are compared with nature and also provided concept on how building structures mimic nature’s system. For example, a reinforced concrete structure bears more than glancing similarity to the skeletal structure of a vertebrate. Neutra advocated connections between living spaces and the green world of organic (Neutra 1971). Lewis Mumford, on the other hand, advocated ecotechnics that rely on local sources of energy and indigenous materials in which variety, craftsmanship, and vernacular are important and add value to ecological consciousness (Luccarelli 1995). McHarg put emphasis on integrating environmental sciences, ecology, and biological sciences in planning for sustainable built environment (McHarg 1969). Malcolm Wells supported approach to ecological design and gave importance on knowledge of biological foundations by architects (Wells 1991).

Since the beginning of the 1990s, construction industries, architectures, and engineers have been articulating a concept, commonly known as ‘sustainable construction’ that seeks to change the nature of how the built environment is designed, built, operated, and disposed of it (Kibert et al. 2002). This was long time back advocated by Neutra, Mumford, McHarg, and Wells, a nature-based design. Sustainable construction is the creation of built environment that follows ecologically sound principles, and thus, type of building materials used in it plays a great role to reduce environmental and resource impacts.

Ecological wisdom provides us necessity to use new concept building materials mostly inspired from nature (or nature-based design) in the construction industry to achieve sustainability . It is very important to integrate ecology in construction engineering and to make construction behaving in a natural manner (Kibert et al. 2002). Thus, construction ecology supports building materials, which are integrated with eco-industrial and natural systems and preserves natural system functions.

Nature always develops the design solutions with fine-tuned mechanical properties especially of biological origin that inspire engineers in designing structures by mimicking them (Ehrlich 2010). Anthills or coral reefs are natural building habitats made in a sustainable manner for millions of years. Such biological systems of nature serve as prominent inspirational source due to their remarkable variety of simple to complex structures and functions, which confer a huge impact on sustainable materials since several decades (Jain et al. 2013). These habitats work with nature to combat any difficulty and construct sustainable building structures (Fig. 2). Anthills are extremely tall structures made on this earth compared to their construction engineers, of high mechanical strength with cementing material coming from saliva of termites in the form of lignin. On the other hand, corals use carbon dioxide as raw material to form reefs that act as the most prolific mineralizer on the planet. Corals build reefs by natural interaction between CO2 and water that precipitates as CaCO3 after reaching equilibrium (Kleypas et al. 1999). The reef formation process is totally opposite to cement production, where carbon dioxides are released into the environment. Biomimicking such process could lead to the production of low energy cement, and amount of cement can be reduced during construction significantly. Answers to many environmental problems remain practically unanswered; however, there is always solution through understanding the principle of ecological wisdom to achieve sustainability . Many such building materials (anthills, coral reefs, silk, teeth, bone, skin, shells, and many more) based on such concept have been summarized in detail (Achal et al. 2016).

Fig. 2
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A representative diagram of anthill: sustainable building practice by ants

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In order to ensure sustainable cement production in the current era, the construction industry needs to change. The two most important challenges facing the industry are a pressing need to reduce CO2 emissions and improve energy efficiency (Imbabi et al. 2012). Thus, it is very important to find green, environmentally, and economically sustainable alternative building materials of lower embodied energy that emit less CO2. Even in Europe itself, buildings are responsible for more than 40% of the energy consumption and greenhouse gas emissions (Lechtenbohmer and Schuring 2011); thus, the use of building materials with lower embodied energy becomes a priority area under the sustainable development concerns of Horizon 2020 (Pacheco-Torgal 2014).

The easiest way for architects to begin incorporating sustainable design principles in buildings can be achieved by careful selection of environmental sustainable building materials. Natural materials are generally lower in embodied energy and toxicity than man-made materials. They require less processing and are less damaging to the environment. When low embodied energy natural materials are incorporated into building products, the products become sustainable (John et al. 2005). Some of the building materials that can bring sustainability in modern infrastructure constructions are described below.

3 Clay-Based Building Materials

The use of clay as a sole binder to make building materials has been used in construction date back to thousands of years ago (Staniec and Nowak 2011). It is also often known as earth construction. Clay-based construction technologies (such as rammed earth, adobe, and wattle and daub) have been widespread because of simplicity of manufacturing procedure and availability of raw materials (earth). Around 30% of the world’s population lives in earth-made constructions (Houben and Guillard 1994), with approximately 50% of them located in developing countries. Among it, adobe constructions are very common basically in Latin America, Africa, the Indian subcontinent, and other parts of Asia, Middle East, and Southern Europe.

Adobe literally means sun-dried brick is one of the oldest and most widely used natural building materials, which presents some attractive characteristics, such as low cost, local availability, the possibility to be self-/owner-made with unskilled labor, good thermal insulation, and acoustic properties (Varum et al. 2014).

Some ancient structures built centuries back are still performing satisfactorily. One example is Hakka rammed earth buildings (also known as Fujian Tulou), in Fujian Province of China with a history of 3000 years. Figure 3a shows a typical Tulou building, while Fig. 3b presents a whole view of Hakka village. These rammed earth buildings have thick (~1 m) outer walls, and inner wooden structures make up floors and rooms. They are 3–5 stories in height and round or square in shape. Each building has hundreds of rooms and could accommodate 800 people. The buildings have great engineering values in terms of low energy consumption for comfortable living, sustainability , and durability (Liang et al. 2013), which inspired modern construction to learn lessons from traditional earth buildings.

Fig. 3
figure 3

Source http://www.china.com.cn/aboutchina/zhuanti/fjtl/node_7047538.htm

a A typical Tulou building and b a whole view of Hakka village.

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The clay-based material suitable for buildings is generally exploited from soil in site with a proper composition essentially of clay and other elements, such as aggregate (stone, gravel, sand), natural fibers (straw, bamboo, wood). Clay consists of particles <2 μm, works as a binding agent, and akin to cement in concrete. In earthen architecture load-bearing walls, infilling of walls, roof structures can be constructed from earth.

Clay-based materials show important advantages over conventional ones (concrete, masonry), in particular concerning with significantly low embodied energy, manufactured in site, using simple technological manipulations, readily reused, and recycles at the building end of life (Akbari et al. 2012; Darling et al. 2012). Thus, the energy consumed and carbon emission of clay-based materials create a striking contrast with concrete; clay-based materials create nearly one-fifth compared to that of concrete blocks during production (Fetra et al. 2011). Moreover, clay has affinity for water, can absorb water vapor in excess, or release it when it is scarce. Furthermore, clay-based construction has better performance in terms of thermal comfort. A case study carried out by Jaturapitakkul et al. (2007) showed that indoor temperature reduced by 3 °C compared to that of cement block walls with clay-based building structure, indicating lower energy demand to maintain thermally comfortable buildings with clay-based construction.

However, the main concern in the use of clay-based materials is regarding its durability. As clay is the only binder in mortars to ensure the strength and stabilization (Montana et al. 2014), clay-based materials tend to generate cracks after shrinkage through which water can penetrate into wall, which reduce the mechanical strength (Hamard et al. 2013). Moreover, the negligible tensile strength and limited capacity to dissipate energy also affect the durability (Ernest et al. 2016). Also, over-exploitation of natural resources has placed a greater threat to the environment. Therefore, developing alternative materials has been considered a priority in sustainable design and construction (Kariyawasam and Jayasinghe 2016). Overall, earth construction or clay-based building material is associated with low embodied energy, low carbon dioxide emissions, and very low pollution impacts.

4 Modern Clay-Based Building Materials

The properties of rammed earth can be improved by stabilizing it by chemical means, especially by mixing with cement. Cement stabilization has gained popularity due to higher and faster strength gain, durability, and ability to obtain acceptable properties with low percentage of cement. Stabilizing earth with cement forms cement-stabilized rammed earth (CSRE), a building material with sufficient strength and durability but low in embodied energy (Kariyawasam and Jayasinghe 2016).

The case study by Reddy et al. (2014) demonstrated the scope for reducing the carbon emissions in the construction sector through the use of cement-stabilized rammed earth construction. They constructed CSRE school complex area of 1691.3 m2 that consisted of 15 classrooms, an open-air theater, and a service block (Fig. 4). The construction involved a very simple procedure where soil, sand, and cement were mixed in a rotary drum mixer and used to construct school building. The reconstituted soil contained 13% clay fraction, while 8% ordinary Portland cement was used as a stabilizer. The data showed low embodied energy of 1.15 GJ/m2 for the CSRE building as against 3–4 GJ/m2 for conventional burnt clay brick load-bearing masonry buildings. Considerable amount of embodied energy was saved by the use of CSRE and other alternative building concepts. This case study clearly demonstrated the scope for reducing embodied energy of buildings in the construction sector by adopting modern rammed earth construction.

Fig. 4
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Reprinted with permission from Reddy et al. (2014)

View of the CSRE school complex.

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In some types of ancient earthen techniques (such as adobes and cobs), natural fibers are added in the earth mortars to distribute shrinkage cracks throughout the wall mass and enhance cohesion and shear resistance (Keefe 2005). Moreover, strengthening system consists of high-performance fibers (such as glass fiber, carbon fiber) which are embedded into the earth matrices so that externally strengthen structures was developed (Liu et al. 2014). The reinforcing system could help to increase the dissipate energy in flexion, which could increase the ability of earthquake resistant (Ernest et al. 2016). Besides, mixing a chemical-based agent other than clay, such as cement and lime, could gain higher mechanical compression strength and resistance to erosion with low percentage of cement (Minke 2012). Although the chemical modification makes up the defect of clay-based material, the modified earth material with inorganic binders is hard to reuse and recycle at the end of life of the building, resulting in the waste of farmland resources. Modern clay-based materials provide a sustainable and healthy alternative to conventional masonry materials (Pacheco-Torgal and Jalali 2012).

5 Plant-Based Building Materials

Global warming, energy savings, and life cycle analysis issues contributed to the rapid expansion of plant-based materials for buildings, which can be qualified as environmental friendly, sustainable, and efficient multifunctional materials (Amziane and Sonebi 2016), and it brought the concept of ‘agro-concrete.’ Agro-concrete is a mix between granulates from lignocellular plant matter coming directly or indirectly from plants, which form the bulk of the volume, and a mineral binder (Amziane and Arnaud 2007).

The use of crushed hemp (shiv), flax, and other plants associated with mineral binder represents the most popular solution adopted in the beginning of this revolution in building materials. Bio-based aggregates come from the stem of plants cultivated either for their fibers (hemp, flax, etc.) or for their seeds (oleaginous flax, sunflower, etc.). In addition, wild plants such as bamboo, dis stem, lechuguilla fibers, kenaf bast fibers, wood shaves, sulfite pulp fibers, and eucalyptus kraft pulp are often used to make lightweight concretes (Amziane and Sonebi 2016; and references therein).

Hempcrete is one special type of well-researched bio-based building material obtained by mixing hemp wood with 70% slaked lime, 15% hydraulic lime, and 15% pozzolana (Amziane and Arnaud 2007). It is estimated that approximately 1.8 tons of CO2 are sequestered for every ton of hemp shiv used, and thus, taking into account the CO2 emitted for binder production and depending on the recarbonation of the lime, 117–18 kg of CO2 are sequestered into a one cubic meter of hempcrete (references in Amziane and Sonebi 2016).

Kenaf (Hibiscus cannabinus) fibers are emerging as promising alternative building materials that will provide a much-needed boost to the construction industry. Kenaf plants have property to absorb and decompose carbon dioxide in the atmosphere very rapidly to fix carbon as an integral component of fibers, and thus, it is assumed that building materials constructed with this plant will sequester carbon dioxide. Further, the use of plant-based fiber reinforcements as building materials is regarded as a significant step to achieve the construction with sustainability .

The unique selling point of bio-based building materials made with plant aggregate is its ability to effectively insulate a building, using a natural material. However, bio-based building materials typically exhibit a comparatively low mechanical strength (Amziane and Sonebi 2016).

6 Supplementary Cementitious Materials (SCMs)

The addition of supplementary cementitious materials makes cement more attractive for sustainable building purposes. It is used to replace clinker in cement or cement in concrete because they possess pozzolanic and cementitious properties and, under certain conditions, are capable of enhancing concrete properties (Mehta 1985). Supplementary cementitious materials are often incorporated in the concrete mix to reduce cement contents that ultimately reduces CO2 emission. Further, it improves workability, increases strength, and enhances durability of concrete structures. More importantly, SCMs are often industrial by-products; thus, the use of such materials lowers the environmental impact. The use of supplementary materials for clinker replacement can reduce CO2 emissions up to 12% compared to the maximum 5% achieved by other strategies when a 10% of SCM is increased in the mix (García-Gusano et al. 2015). Development of construction materials capable of reusing a high waste content is an important research line in order to fulfill the resource efficient Europe 2020 milestone related to the management of waste as a resource (Pacheco-Torgal 2014).

Fly ash, granulated blast furnace slag, silica fume, rice husk ash, and sugarcane bagasse ash are industrial by-products, very commonly used as SCMs in the partial replacement for cement (Bapat 2012). As it reduces the amount of cement needed for concrete, it lowers the energy and CO2 impacts of concrete.

The use of fly ash in cement to avoid carbon emissions from the production of clinker should be considered from an integral and holistic perspective for sustainable building practices (Vargas and Halog 2015). The substitution of 25% of Portland cement with fly ash has been shown to reduce the greenhouse gas emissions of 25 and 32 MPa concrete blends by 13 and 15%, respectively (Flower and Sanjayan 2007).

Concrete has been successfully constituted fly ash as up to 50% of the cementitious material. However, it is often used to replace typically 30% of the mass of Portland cement in a concrete mix, for example, to lower permeability and reduce initial heat evolution (Imbabi et al. 2012).

Granulated blast furnace slag (or slag) is a by-product of the iron and steel industry. Greenhouse gas emission reductions up to 39% have been reported with granulated blast furnace slag (Blankendaal et al. 2014). The possibility to use slag aggregates, as a partial replacement in concrete, should make the recycling procedure more attractive for steel manufacturers.

Silica fume is a by-product of the production of silicon and silicon alloys in electric arc furnaces. It is added to cement to produce high-performance concretes that are much stronger and more durable than other concretes made using blended cements, in addition to reducing the permeability of concrete and therefore able to better protect steel reinforcement (Imbabi et al. 2012). According to the US Environmental Protection Agency , 1 lb of CO2 is avoided for every 2.2 lbs of SCM substituted in a cement, or 0.432 kg of CO2 per kg of SCM (Norchem 2011).

7 Agro-Cement

Plant by products such as rice husks, sugarcane, and corncobs can produce biosilica. When residues containing biosilica are burned and then blended with Portland cement, the final product is called biocement (Hosseini et al. 2011). This biocement is other than of microbial origin; thus, we are using the term agro-cement (as most of the plants used in it are of agricultural values) for such cement in this article. The use of agro-cement has shown environmental, economic, and technical benefits. It reduces clinker consumption and its related energy use and CO2 emissions.

A literature review on recent development of biocement (agro-cement) research is presented in Hosseini et al. (2011). Agro-cement coming from plant by-products of sawdust, rice husk, corncob, sugarcane, wheat straw, bamboo leaf is known to improve the compressive strength of mortar ranging from 18 to 103 MPa when added to replace 6–20% of the Portland cement in a mixture (Hosseini et al. 2011; and references therein). Thereby, agro-cement is treated as an environmentally friendly product that reduces CO2 emission by partially replacing Portland cement, thus reducing the volume of this material produced by cement manufacturers.

Rice husk ash as high as 30% improved the resistance to water permeability of the resulting concrete with compressive strength similar to that prepared with Portland cement alone was reported (Saraswathy and Song 2007), while agro-cement with high content of rice husk ash had also good sulfate and chloride resistance than ordinary Portland cement (Chindaprasirt et al. 2007, 2008).

Agro-cement made with vetiver grass ash considerably improved mortar resistance against acid or chemical attack, probably because calcium hydroxide reacts with the biosilica to form C-S-H gel. Moreover, such mortar had better resistance to water permeability than cement from Portland cement alone (Nimityongskul et al. 2003). Mortars blended with corncob ash cement were also investigated with respect to improved impermeability and acid resistance (Adesanya and Raheem 2010).

Agro-cements such as sugarcane bagasse ash, wheat straw ash, oil palm ash also improved the sulfate resistance of concrete when partially replaced with ordinary Portland cement, and resistance was higher than concrete made up of Portland cement alone (Singh et al. 2000; Jaturapitakkul et al. 2007; Binici et al. 2008). The various researches indicate that plant by-products that produce silicon-rich residues could be good candidates to consider for efficient partial replacement for ordinary Portland cement.

8 Carbon-Negative Cements

It is very important to find alternate building materials or cement that could replace conventional Portland cement to achieve carbon reduction, and it is subject of interest by researchers worldwide to develop the next generation of cements.

Calcium sulfoaluminate cement is one of such novel cement that uses limestone as one of the raw materials in their production and provides similar performance to Portland cements. It offers a 20% reduction in CO2 emissions by requiring a lower kiln firing temperature and therefore burning less fossil and fossil-derived fuels (Imbabi et al. 2012).

Calcium aluminate and calcium alumina silicate cements are special type of cements used for its ability to reach high strength at a very early stage. Their production reduces the amount of CO2 emission; however, these are more expensive and less readily available than Portland cement.

Another type of novel cement is based on water-activated magnesium oxide that requires 30% less energy for its production; however, it was commonly used well before Portland cement ever came into existence. Based on its advantages over Portland cement that include its permeable nature to make it in terms of heat regulation and control in the design of dwellings, a working formulation of ‘carbon-negative cement’ derived from magnesium silicates is undergoing (Imbabi et al. 2012). Magnesium-based cement is known to absorb more CO2 than it produces during the manufacturing process. Carbon-negative cement has yet to become marketable product capable of competing with the common Portland cement.

The four companies who have used multiple techniques to develop a successful carbon-negative cement product are Novacem of Britain, Carbon Sense Solutions of Nova Scotia, Canada, and Calera and Blue Planet both from California. Each company has been developing its own unique technology to create carbon-negative cement. Unfortunately, most have been unsuccessful and are out of business.

The cement of Novacem is based on magnesium oxide (MgO) and hydrated magnesium carbonates. The company claimed that the production process to make 1 ton of Novacem cement absorbs up to 100 kg more CO2 than it emits, making it a carbon-negative product (Novacem 2011). On the other hand, Carbon Sense Solutions uses carbon curing technology to retrofit concrete plants to recycle waste products into creating a ‘greener’ concrete.

The Calera Corporation has a process that mimics marine cement, similar to what is found in the coral reef, taking the calcium and magnesium in seawater and captured carbon dioxide from effluent gases to form carbonates. This technology absorbs CO2 during the production of cement rather than emitting it.

Blue Planet also mimics nature’s process for hardening tissues in living organisms based on carbon capture and mineralization technology. As per their principle, wherever there is saltwater near fresh water, there is an untapped, universal, and abundant power source that forms osmotic pressure between salt and fresh water and generates alkalinity. Blue Planet’s alkaline solution is combined with CO2 from flue gas to form carbonates (Blue Planet 2016).

9 Biocement

Biocement is microbial-based building material. It is the product of biomineralization where cementing material comes from microbially induced carbonate precipitation in the form of CaCO3. It has three constituents, namely alkalophilic microbes, substrate solution (urea), and calcium ion solution (Achal et al. 2013; Rong and Qian 2012).

Biocement is treated as novel material that is able to improve compressive strength of cement-based materials, reduce porosity, and thus diminish diffusion of moisture and other deleterious materials. By reducing intrusions, biocement improves the durability of structures that is another step toward sustainability . The importance of biocement as a sustainable building material has been explained in detail in Achal et al. (2015).

10 Conclusion

The concept of ecological wisdom leads us to understand natural systems and let us attempt to emulate some of nature’s sustainable ways in infrastructural construction by means of sustainable building materials. There is enormous global demand for cement or replacement of this non-sustainable building material in construction industry. The industry is looking for ways to reduce CO2 emissions from the construction of modern infrastructures. The prevalence of ecological wisdom brings sustainable materials in the form of clay-based or plant-based building materials, new carbon-negative cements, new supplementary cementitious materials, agro-cement, or biocement that can be blended with ordinary Portland cement to reduce environmental impacts without compromising strength and durability of infrastructures, thus creating sustainable construction.