Redefining Sustainable Construction with Admixtures

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Redefining Sustainable Construction with Admixtures | FutureBusiness

The goals of sustainable construction are to reduce the industry’s impact on the environment. Methods involved in sustainable construction included using renewable and recyclable materials, reducing the energy consumption of the finished building, protecting habitats during and after the construction phase, reducing on-site waste and the embodied energy in building materials. 

In Europe, the construction industry is responsible for 34.7 percent of the continent’s total waste. Green buildings minimise waste with their lower environmental impact and use of renewable sources and materials. There is a perception that sustainable construction is expensive, which can make it seem the less attractive option. However, The World Green Building Council’s 2018 report shows that although cost remains a concern, owners of green buildings report that money is saved through reduced operating costs thanks to the sustainable materials used

The most sustainable materials include recycled metals such as steel, as well as straw bales, reclaimed or recycled wood, mud bricks and wood bricks. This article will focus on sustainable concrete. 

Concrete is a widely used synthetic material, but also one of the most environmentally unfriendly. Its manufacture alone is responsible for about 5% of global carbon dioxide (CO2) emissions. Fortunately, many companies are now exploring ways to reduce emissions by creating alternatives with plastic and other recyclables, which can reduce the carbon dioxide production by almost 50%.

Admixtures

Sustainable concrete is made with a variety of admixtures. Admixtures are an essential component of modern concrete, facilitating environmentally optimised mix design, innovative building design, improved job site placing and enhanced long term durability of the concrete.

Admixtures are chemicals added in very small amounts to the concrete to modify the properties while the concrete is still fluid and also after it has hardened and is in service. Despite the relatively small dosage, the modifications to concrete properties achievable by admixtures can reduce the ECO2 of concrete, mainly through the more effective use of the cementitious component, while maintaining and enhancing the properties of the concrete.

The Effect of Admixtures on Concrete

Aside from a better finish and reduced service life repair, there are many effects that admixtures have on concrete. Admixtures reduce the embodied carbon of concrete. The increased workability and decreased water/cement ratio means that the strength of concrete is increased without increasing cement content. 

Admixtures mean that the cement component is more effective, reducing carbon dioxide and energy. The durable life of the concrete is increased, due to reduced permeability. Lastly, admixtures can reduce the damage from harsh environments, including sub zero and marine locations. 

Types of Admixtures

Water reducing admixtures – These are designed to free trapped water that is present in concrete mixtures and are used in a variety of applications to ensure or improve workability. Can allow a reduction in water content by about 5 to 10 percent.

Superplasticisers -These reduce water content by 12 to 30 percent and can be added to concrete with a low-to-normal slump and water-cement ratio to make high-slump flowing concrete.

Accelerating admixtures – These increase the rate of early strength development, reduce the time required for proper curing and protection, and speed up the start of finishing operations. Accelerating admixtures are especially useful for modifying the properties of concrete in cold weather. 

Retarding admixtures – These slow the setting rate of concrete, are used to counteract the accelerating effect of hot weather on concrete setting. They can also entrain some air in concrete, as well as acting as water reducers. 

Set retarding admixtures. These slow the setting rate of concrete, are used to counteract the accelerating effect of hot weather on concrete setting. High temperatures often cause an increased rate of hardening which makes placing and finishing difficult. Retarders keep concrete workable during placement and delay the initial set of concrete.

Corrosion-inhibiting admixtures – These are a specialty admixture that is used to slow corrosion of reinforcing steel in concrete. Corrosion inhibitors can be used as a defensive strategy for concrete structures, such as marine facilities, highway bridges, and parking garages, that will be exposed to high concentrations of chloride. 

Advantages to Sustainable Construction

Cost reduction – A green building costs less than a normal building because fewer resources (e.g. water and energy) are required for the completion of the project. Furthermore, sustainable buildings have great Return on Investment. The value of the property is significantly increased with sustainable building.

Increased productivity – As reported by The Guardian, environmentally friendly workspaces help employees perform better while reducing absenteeism. The better the environment, the easier it is to concentrate and work effectively toward the completion of tasks.

Environmental protection – Recycled materials used during the construction process are contributing significantly to the protection of the environment and to the reduction of waste

Better quality of life – Sustainable construction offers improved health due to safer materials, increased productivity thanks to better surroundings and more effective noise protection are only a few of the advantages. Green buildings can improve life quality.

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Difficulties

Admixtures are an intricate solution to a large problem. In an interview with the BBC, Prof Scrivener says that there’s no point looking for intricate solutions that can just be used in some very sophisticated factories in the US. 

Around 90% of future cement production will take place outside the wealthy OECD countries. A concrete path to cutting concrete’s carbon emissions needs alternatives that will work well and cheaply for the coming building booms in India and Africa. For example, China made more concrete between 2011 and 2013 than the US did in the whole 20th Century.

SEE BELOW: Interview with John Ortiz & Shirin Fataei, MBCC Group

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