Advanced high-performance concrete structures – challenge for sustainable and resilient future

Development and recent changes in natural and socio-economic environment requires new technical solutions for construction of new and reconstruction and modernization of existing structures. Structures and all built environment should be better prepared for new conditions – they should be sustainable and resilient. Concrete is building material with high potential for new technical solutions resulting in needed environmental impact reduction and consequent social and economic improvements. The paper presents potential contribution of concrete industry, advanced highperformance concrete and concrete structures to Sustainability Development Goals specified in UN 2030 Agenda for Sustainable Development and presents basic principles of implementation of sustainability approach into design of concrete structures and particularly to fib Model Code 2020.


World is changing
Considering scale line -one year for entire life of the Earth -the human civilization exists only last 90 seconds and RC structures are used in last one second.Earth existed long before humans developed on the Earth and will exist long after the conditions on the Earth will not be suitable for human life.Sustainability is about preservation of environmental, social and economic conditions on our planet in the form which will enable survival of humans on the Earth as long as possible [1].The question raised in this paper is how concrete, as the second most used material after water and the most used construction material, can help in this process.
Changing of the climate on the Earth is innate and everlasting process; environmental conditions are continuously changing due to continental drift followed by volcanic, seismic effects and due to man-made impacts.Human life conditions for life are modified -and as a consequence biodiversity is irrecoverably changed.This process was in previous periods very slow, enabling consecutive adaptation of life forms (incl.humans) to changing environmental conditions.However, nowadays environmental conditions are changing faster, particularly caused by human activities.
The world faces increasing number of natural disasters and increasing economic and social problems and challenges.New research results have shown how global climate changes are happening faster than anticipated.Floods, tropical storms, hurricanes, tornados, wildfires, heat and cold waves, longer periods of drought etc. are more and more frequent and with higher intensity.Due to rising and aging human population, these effects threaten more people.Climate change-related effects like floods, storms, hurricanes, tornados, heat and cold waves, extreme dry weather and fires are more and more frequent.The probability of a natural disaster is now nearly five times higher as it was in the 1970s, because of the increasing risks due to climate change.In the same period of 40 years 1970 -2010 the world population increased 1.8 times from 3.7 to 6.8 billion.As the population and number of natural disasters grow, so does the impact of natural disasters on humans is increasingsee intersection in the Figure 1.Continuously growing intersection leads to costlier and deadlier disasters around the world [2].
Recent examples: In the last year 2015 a massive earthquake with magnitude 7.8 devastated Nepal, killing more than 8,800 people, damaged or destroyed nearly 900,000 buildings, created avalanches in the Himalayas, and left almost one million children out of school [3].
Mount Merapi in Java, Indonesia has regular eruptions with an interval of between 1-18 years.Recent eruptions in the 1994 killed 64 lives and the latest 2010 eruption killed 386 people and displaced permanently or temporarily more than 303,233 people [4] (Figure 2a).economy impacts and causes extensive humanitarian crises, influencing a quality of human life on the Earth.
Considering above mentioned situation and development trends, it is necessary to evaluate and modify existing principles and methods of structural design, corresponding techniques of construction and operation of structures.The principle goal is to enhance structures and entire built environment to be more resilient in the situation of changing natural and socio-economic conditions in the world.

Regional specifics
In different regions there are different major risks of natural disasters.The world's greatest earthquake zones are the circum-Pacific seismic belt and central Asia.Hurricanes are most common in the Pacific, however, hurricane Katrina in 2005 occurred in the South Atlantic (Figure 3b).The world's deadliest floods were several times in Asia.
Due to global warming effects Arctic sea ice and glaciers are rapidly melting, sea-level rise may be accelerating, and forests (important carbon capture) are being transformed.The impacts of climate change cover warming temperatures, changes in precipitation, rising sea levels and increases in the frequency or intensity of some extreme weather events [1,5].In many areas of the world are active volcanoes.They are the most intensive agents of geologic change.Volcano during eruption can eject extremely high amounts of ash and gases (mostly CO2 and SO 2 ) into the atmosphere and cover the ground with vast amount of lava and ash.As a result, the most extreme impact of volcanic eruptions is their effect on climate change -Fig.2. Also, in other parts of the World there occur some natural disasters.Very damaging floods attacked Europe several times in last decades, see Figure 3a.
So called, the Little Ice Age was a period of cooling that occurred after the Medieval Warm Period, between roughly AD 1300 and 1850 [6].In central Europe, the Little Ice Age was characterized by increased droughts and by increased flood frequency.Concerning weather-related extremes and catastrophic consequences, 1342 was an extraordinary year in most parts of Central Europe [7].The precipitation event caused in July 1342 millennium flood called St. Mary Magdalene's Flood, most probably exceeded in damage any other reported event in historic and recent times in Central Europe [8].
These impacts threaten our health by affecting the quality of food, water, air, and the entire quality of environment we live.These impacts initiate human migration -climatic refugees.
With respect to some prognosis of climate changes in Europe, there could be expected increasing number of heavy rains (followed by floods) and more frequent heat waves in the future.

Sustainability and resilience
The World Summit on Social Development identified sustainable development goals, such as economic development, social development and environmental protection [9].With respect to the general principles of sustainability, the three essential pillars should be considered in the whole life cycle of buildings:  environmental integrity,  economic efficiency, viability and feasibility  social equity and well-being.
Due to increasing number of natural and man-made disasters it is urgent to modify principles of structural design and construction technology for development and maintenance of buildings and all built environment in order to be more resilient.Resilience is the capacity to adapt the system to changing conditions and to maintain or regain the functionality.It means to transform the existing structure or design/construction of new structure to be better prepared for reduction of risks caused by natural or man-made impacts.Of course, the reduction of environmental impacts (especially global warming) is urgently needed to slow down the process of climate change [5].
Figure 4 presents scenarios with disruption of function caused by disaster.As a consequence of disaster and associated direct impacts to a structure, the level of stop the operation and demolish the structure; • modernisation / renovation of structure to the performance level before disaster; • modernization to the higher level of quality following developments of standards.Only structures with reduced environmental impacts and in the same time with high level of resilience can be sustainable in the changing environmental as well as social situation of the forthcoming era.Resilience after disturbance of structure by disaster and shock [5].a.The level of performance is recovered to the level before disaster.b.The level of performance is recovered to the higher-level following developments in standard requirements.

Role of concrete and concrete structures from the view point of sustainability and resilience 2.1 Concrete use -advantages and disadvantages
Concrete is after water the most used material in the world.The production of concrete in the industrialized world annually amounts to 1.5-3 tone per capita [10].World cement production has been 12 times increased in the second half of the last century [11].
Why we are using such high amount of concrete?Concrete used for load bearing structure enables long service life of buildings.Concrete structures are usually more resistant to various climatic conditions, they have a good capability of withstanding wear, and they do not easily subject to degradation processes.This consequently results in lower operating and maintenance cost.The main advantages of concrete for new structures and reconstructions are: (i) thermal mass (stabilizing indoor environment), (ii) acoustic properties (improving air-born sound insulation), (iii) fire resistance, (iv) long term durability, (v) structural safety, including high resistance to natural hazards, (vi) maintainability and (vii) flexibility.With respect to specifics of concrete presented as a strong and durable material it is possible to design and construct robust structures with high level of resiliency when faced to the exceptional natural or man-made disaster shocks.High structural safety and reliability, and higher fire resistance of concrete (compared to other materials) results in a high resistance to extreme conditions during natural disasters (floods, storms, winds, hurricanes, tornados, fires, earthquakes, etc.) and terrorist attacks.
Considering continuing increase of cement production, it is estimated that nowadays about 7-8% of global CO2 emissions is connected with cement industry.The Figure 5 shows a development of cement production in world regions presented by The European Cement Association -Cembureau [12].It is evident that the production of cement significantly grew in developing countries in Asia, Africa and CIS (Commonwealth of Independent States -some former Soviet Republics).https://doi.org/10.1051/matecconf/201819501001ICRMCE 2018 Fig. 5. World cement production by region -evolution 2001-2014 (prepared using the source Cembureau [12]).

Contribution of concrete and concrete structures to UN sustainable development goals
The construction industry as a whole is responsible for 30% of the total global resources, 40% of global energy consumption and up to 30% of the total global greenhouse gases.Furthermore, the construction industry is considered to be the industry that could potentially reduce its energy consumption with the lowest cost.
In October 2015, UN adopted a Resolution 70/1: Transforming our world: the 2030 Agenda for Sustainable Development [9].This Agenda is a plan of action for people, planet and prosperity and should stimulate action up to 2030 in areas of critical importance for humanity and the planet.The principal goal is to end poverty, protect the planet and ensure prosperity for all.There were specified 17 Sustainable Development Goals (SDGs) with 169 associated targets which are integrated and indivisible and balance three dimensions of sustainable development: economic, social and environmental.These new goals and targets came into effect on 1 January 2016 and guide the actions up to 2030.It is expected, that all stakeholders, all of us, will work to implement the SDGs Agenda within own countries and at the regional and global levels, taking into account national specifics and priorities.
One of the priorities is sustainable urban development as a crucial aspect influencing the quality of life of people.Construction industry as a main stakeholder responsible for the use of material and energy resources has a key role in the implementation of SDG actions in the process of design, development and operation of buildings, roads, bridges and other infrastructure creating urban built environment.Concrete and concrete structures play in this process significant role [13].
In the following subchapters of this paper there are presented selected targets, where concrete industry and concrete structures can contribute to solution of SDG goals.Nevertheless, this selection is not enclosed and can serve as an inspiration and motivation for other stakeholders involved in concrete industry and in development of built environment.For further rethinking you can use whole SDG system presented at UN web pages (www.un.org).

Contribution to SDG 1: end poverty in all its forms everywhere
One of the targets is resilience of the poor and those in vulnerable situations and reduction of their exposure and vulnerability to climate-related extreme events and other economic, social and environmental shocks and disasters.In case of extreme events and disasters concrete structures can provide: • high level of resistance; • high level of resilience; • concrete structures can serve as shelters for people in case of extreme events.

Contribution to SDG 3: ensure healthy lives and promote well-being for all at all ages
Concrete structures can contribute to targets of SDG 3 by following aspects: • standard concrete is non-toxic, there are not used any hazardous chemicals; • concrete can positively contribute to acoustic quality in buildings; • high performance quality of buildings and infrastructure can improve people's health and wellbeing.

Contribution to SDG 7: ensure access to affordable, reliable, sustainable and modern energy for all
One of the principal targets of SDG 7 is to double the global rate of improvement in energy efficiency by 2030.Concrete structures can contribute to this target by: • optimization of concrete mix, shape optimization and effective structural and technological concepts of concrete structure can result in a reduction of embodied energy in the concrete structure; • high thermal mass of concrete structures can reduce heating/cooling energy demands in buildings -especially reduce cooling energy demand in hot areas.

Contribution to SDG 8: promote sustained, inclusive and sustainable economic growth, full and productive employment and decent work for all
Advanced high-performance concrete structures can contribute to global resource efficiency in consumption and production.
• Recent development of concrete and new types of silicate composites including use of recycled components represents a great potential for resource efficiency in consumption and production.

Contribution to SDG 9: build resilient infrastructure, promote sustainable industrialization and foster innovation
Contribution to SDG 9 targets by concrete industry could be supported by Implementation of advanced concrete technologies with reduced environmental impacts and increased performance quality could significantly contribute to solution of global problems.This requires international cooperation, access to science, technology and innovation, dissemination of knowledge, support in education and cooperation in science.
It is evident from the above overview that optimized concrete structures using new types of concrete in advanced technologies can significantly contribute to fulfilment of some specific targets of Sustainable Development Goals, and especially can contribute to reduction of global environmental impacts and can support increase of sustainability and resilience of built environment and entire society.As stated in SDG17 the leading principle is to promote and support the development, transfer, dissemination and diffusion of environmentally favourable and efficient technologies to developing countries.The role of concrete industry in the process of sustainable development is important and essential.

Concept of sustainability approach in fib model code 2020
Sustainability should become a basic concept of any design, construction process, operation, maintenance and repair of concrete structure.The main scope of Commission 7 -Sustainability in International Federation for Structural Concrete (fib) is to develop a strategy as to how to incorporate sustainability issues into the design, construction, operation and demolition of concrete structures.Design concepts of concrete structures should be based on a sustainability framework considering environmental, economic and social aspects.The main focus should be on: the reduction of CO 2 emissions from concrete production, the reduction of energy use for construction and the operation of buildings (incl.thermal mass effect), an improvement in the performance quality of the internal environment (acoustics, thermal well-being, etc.), the reduction of waste to landfill, the development of sustainability metrics and data requirements needed for EPDs and other quality assessment, recycling and use of recycled materials (incl.recycled concrete), resiliency of structures, etc.The goal is to prepare a framework and data for the sustainable design of concrete structures to be implemented in a new model code.
Fib Commission 10 is currently developing new model code for design of concrete structures MC2020.Sustainability should be presented in MC2020 as a conceptual approach -as an "umbrella" for efficient/high quality design and operation of concrete structures through entire life cycle -considering all three pillars -social, environmental and economic.
Sustainability approach should be implemented into MC2020 in accordance with international standardization -ISO 15392 General principles.Environmental assessment should be solved using existing standard methodologies of LCA and economic pillar using standard methodologies of LCC.There are already standardized methodologies in ISO, CEN or other standard systems.The MC2020 should to specify the need for these assessments (LCA, LCC) and provide references to existing standards.

Fig. 1 .
Fig. 1.Increasing impact on growing population with increasing number of natural disasters.Intersection = impact on humans is growing in faster manner.At the same time, human population faces accelerating number of extreme social phenomena, like social unrest, instability of states, wars and increasing number of manmade disasters like terrorist attacks.As a consequence of natural and man-made disasters and socio-economic situation, human migration increases.This all results in enormous

Fig. 4 .
Fig. 4.Resilience after disturbance of structure by disaster and shock[5].a.The level of performance is recovered to the level before disaster.b.The level of performance is recovered to the higher-level following developments in standard requirements.
MATEC Web of Conferences 195, 01001 (2018) https://doi.org/10.1051/matecconf/201819501001ICRMCE 2018 performance dropped down below required performance level.After shock, caused by disaster, different scenarios of the future use and operation are possible: • • the use of concrete structures for development of high quality, reliable, resource efficient and resilient built environment -housings and infrastructure; • development and adoption of clean and environmentally sound technologies and industrial processes in production of concrete, concrete elements and structures and operation of concrete structures; • continuing scientific research of concrete structures and associated technologies for design, construction and operation; https://doi.org/10.1051/matecconf/201819501001ICRMCE 2018 • support of dissemination of advanced technologies, research and innovation into developing countries.