Concrete infrastructure’s durability is its key factor in sustainability

Sustainability. This concept of environmental responsibility and recycling is at the forefront of many minds today.

When it comes to construction, numerous parts play a role, primarily the materials used and the overall durability of the structure. In the case of reinforced concrete, admixtures offer various tools to ready-mixers. admixtures, concrete durability, and sustainability fit together to ensure concrete structures last longer, and the longer they last reduces the need to make replacement concrete, which is an energy intensive resource. Cement is the main component of concrete and blamed for as much as 8% of global Co2 emissions. Consequently, any reduction has significant implications for sustainability. today one more commonly hears of structures being built with a service design life of 100 years or more.

Cortec states that one of the biggest threats to concrete longevity is corrosion. under static conditions, reinforced concrete is at low risk for corrosion. however, when adding cracking, chloride exposure from seawater or deicing salts, and long-term carbonation to the equation, the vicious cycle begins. Corrosion causes reinforcing metal to expand, pushing on the concrete cover and causing it to spall off, subjecting the reinforcement to additional corrosives and deterioration. For this reason, corrosion inhibiting admixtures are often used in the construction of concrete buildings in harsh environments like seacoasts or regions that use heavy deicing salts. Cortec has a number of admixtures which meet the corrosion inhibitor requirements to promote greater concrete longevity.

Th E Q uAL i T i Es O f CO n CRETE

For centuries concrete has been a the primary material for sustainable infrastructure. today, advancements in concrete technology are improving its performance while limiting its environmental impact.

bryan perrie, CEo of Cement & Concrete Sa (CCSa), lists the vital qualities that make the world’s most popular and perennial building material sustainable: strength and durability: Concrete is a strong and durable material that can withstand high compressive forces and resist weathering, erosion, and many other adverse environmental factors. this makes it ideal for use in infrastructure that needs to last for many decades.

Versatility: Concrete can be designed and cast into different shapes and sizes, making it ideal for various applications in infrastructure. It can be used to construct buildings, bridges, tunnels, roads, and dams, and a wide variety of other structures.

Cost-efficiency: Concrete is a cost-effective material when compared to other construction materials and can also be produced using locally available materials to reduce transportation costs.

fire resistance: Concrete is highly resistant to fire, making it ideal for use in structures where fire safety is a concern.

Energy efficiency: Concrete structures have excellent thermal mass properties which means they can retain and release heat slowly, leading to substantial energy savings in buildings.

Concrete is a sustainable material that can be produced with lower carbon emissions than other construction materials. additionally, concrete structures can be designed to reduce energy consumption to further their carbon footprint.

perrie says to fully adhere to their ecological responsibilities, CCSa members are committed to stringent policies to champion sustainability and environmental preservation for the South african cement industry. “the industry believes the social and natural resources of South africa should not be compromised for the sake of economic development and have implemented best practices to reduce industry environmental impacts and greenhouse gas emissions long before being legally compelled to do so,” he states.

Muni C i PAL ADV i CE a thorough knowledge of concrete and its full potential is essential for municipal engineers to design, construct, and maintain safe and reliable infrastructure that meets the needs of South africa’s communities and ensure sustainability, says perrie. he says municipal engineers are responsible for designing and maintaining public infrastructure, such as roads, bridges, sidewalks, water systems, waste water plants, and buildings. “as concrete is one of the most commonly used materials in municipal construction projects, it is essential that municipal engineers have a strong understanding of the properties and benefits of concrete,” he feels. he says among the reasons why civic engineers should know more about concrete are:

• Material selection: Municipal engineers should know how to choose the right materials for the job, and be aware that concrete is the best choice for its sustainability, versatility, and low maintenance requirements. “Concrete can be manufactured to an enormous range of specifications to suit a wide variety of applications by using different mix designs or adding different materials. by fully understanding the properties of concrete, engineers can make informed decisions about how to use it in their designs.”

• Design considerations: Concrete has a unique design capacity with important factors that can impact and enhance the aesthetics and performance of infrastructure. Concrete can be cast into different shapes and sizes to suit various applications in infrastructure such as for the construction of new buildings, bridges, tunnels, roads, and dams, and a wide variety of structures. “by understanding these factors, municipal engineers can design concrete structures that are safe, reliable, and sustainable.”

• Construction management: Municipal engineers are responsible for managing construction projects from the beginning to completion, including overseeing the concrete processes. by having a thorough understanding of concrete, they can ensure that the concrete is designed properly and being applied correctly and that any issues are addressed promptly. “Concrete also provides faster construction which means reduced carrying costs and faster revenue generation. this facilitates more timely payback of financing charges and faster revenue generation for any developer or owner, including municipalities,” perrie adds;

• Maintenance and repair: Municipal engineers are also responsible for the maintenance and repair of public infrastructure and, as concrete structures also require periodic maintenance and repairs, the engineers should have a solid understanding of concrete properties and repair techniques to help extend the lifespan of these structures and ensure public safety. “Eventually, when it comes to re-use, concrete is an inert material that is easily recyclable. old concrete, that has reached the end of its service life, can be reused as aggregate for new concrete mixtures. the addition of industrial by-products such as fly ash, silica fume and blast furnace slag enhance the various performance properties of concrete, whilst incorporating waste materials that would otherwise be deposited in landfills.”

D ECARBO

nisAT i O n

the science of substituting clinker in cement with a portion of alternative cementitious materials has paved the way for substantial gains in decarbonisation.

adding to the information in the afriSam article on page 16, afriSam process engineer, Marieta buckle, says the company has reduced its carbon dioxide emissions per ton of cement by 33% since 1990. an important factor in this sustainability journey has been the use of extenders – mainly fly ash and granulated blast furnace slag.

“We have been on this journey for many years before buzzwords like ‘net zero’ were in common use,” says buckle. “our project green Cement began in 2000, involving significant research and development being invested; among the outcomes, we were able to launch our Eco building Cement in 2010 as the lowest carbon footprint product.” afriSam became arguably the world’s first construction materials supplier to ‘carbon footprint’ all its production operations, including cement, aggregate and readymix concrete, she notes. Its carbon dioxide rating system indicates each product’s carbon footprint relative to ordinary portland Cement (opC). buckle explains that producing clinker is the most energy intensive aspect of cement manufacturing – and is therefore a prime driver of carbon dioxide emissions. a central strategy at afriSam has therefore been to promote decarbonisation by reducing the portion of clinker in cement while maintaining its strength and other properties. as an added advantage the utilisation of extenders also enables formulation of cement products that have improved characteristics specific to the application.

“afriSam’s extensive research and development effort has been able to develop a cement mix that comprises up to 70% of alternative materials,” says buckle. “Such a mix would contain only 30% of clinker while still providing the required cementitious properties for the application. Importantly, it consumes less energy – and generates fewer carbon emissions – in the production process.”

“by using what are essentially waste materials like fly ash and slag, we can leverage the energy that has already been consumed in generating them as by-products,” she says. “apart from the value of recycling a waste product, we can make our cement production gradually more sustainable by reducing the energy that is required.”

600mm wide, for instance. they can be taken to site on a bakkie and placed in the structure by two workers. With ordinary concrete panels, it would require a crane to move them.”

Mudaliar adds: “Cement is one of the biggest contributors to carbon emissions on the planet, and this application reduces the concrete volume by 80%.”

gREE n RE n OVAT i O n MAKE A D iffERE n CE

renovations can be exciting, but they can also generate a lot of waste and have a negative impact on the environment. green renovations are becoming increasingly important due to growing concerns about climate change and environmental sustainability.

Calvin venkates, CEo of the construction company posch group says that a green renovation is a sustainable approach to renovating a building that aims to reduce waste, minimise environmental impact, and improve energy efficiency.

he says that incorporating refurbishing and recycling ideas into a renovation project makes it possible to create an ecofriendlier workplace while preserving the building’s history and character that are both sustainable and stylish. according to venkates, this approach can save materials from ending up in landfills and reduce the renovation project’s carbon footprint. additionally, it can add value to the building, as sustainable features and designs are increasingly becoming a selling point for modern workplaces.

nEW insuLATiOn PRODuCT sOOn TO BE On MARKET

Entrepreneurs Satish Mudaliar and Carl Supra have developed a new form of precast concrete panel which they claim provides a high degree of insulation, because of the 80mm void inside the 100mm concrete panel.

It provides insulation not only from heat but sound, says Supra. their r&d development of the panel commenced with polystyrene and polyurethane, they explain, but they found their current technology beats those options on price.

“our product sets new standards because of the 80% void – and a void costs nothing. to manufacture it requires a steel frame and the concrete is poured around the plastic void. It’s suited to mass manufacture which keeps costs down. It is as solid as concrete and easier to transport,” says Mudaliar.

It is suited to applications such as internal walls, affordable housing, schools and also has applicability in supermarkets. the product is in the developmental stage with the final test still to be completed.

Supra says polystyrene concrete has been around for some time and is an excellent medium for construction, but extremely cumbersome to work with on site. “With our mass manufacturing, we can send a structure in a box on the back of a truck – it is that light, but still strong. on site, there is a steel structure that the panels fit into wherever you are in the world, where it can be cemented in.

“We’ve created a panel which has voids in it which displaces 80% of the concrete but with the same strength. Each side of the panel is 10mm thick, and it is poured in such a way that the concrete flows across and joins up with the other side to make a composite structure. We place a woven polypropylene cloth designed in such a way that it’s feathered in order to adhere to the concrete and embeds into the two sides, with additives to make it flexible. this can then be moulded 2.4m high and venkates notes that there are many ways to incorporate refurbishing and recycling ideas into a renovation project: preserving historical features during a renovation can add character and charm to a building while reducing waste. For example, refurbishing the façade, windows, and flooring can help maintain the building’s original architecture while giving it a modern look. during a renovation, materials such as concrete, wood, metal, and fittings can be recycled rather than thrown away. these materials can be used in the refurbishment or donated to local organisations for reuse. Not only does this reduce waste, but it can also save money on buying new materials.

“green renovation presents a sustainable and chic approach to renovating buildings while retaining their historical significance and distinctive features. by adopting green renovation techniques, we can contribute to a sustainable future and create workplaces that are both visually appealing and environmentally responsible,” venkates says. n