10 minute read
The Briefing
Concrete
Concrete Control
MIDDLE EAST Jose Vera-Agullo, ACCIONA R&D Concrete Manager, shares his insights on how to keep concrete cool while working in hightemperature areas
Building with concrete in very hot places, such as the Middle East, poses specific challenges. At high temperatures, the water in the concrete mix evaporates quickly, and this can affect the workability and strength once it sets. A second risk in high temperatures concerns the chemical reaction that takes place once cement is mixed with sand, gravel, and water to form concrete. This chemical reaction produces heat, and if the temperature of the mix rises above 70ºC and/or if the temperature difference between the concrete structure core and the surface goes above 20ºC, cracks could arise as the concrete sets, which weakens the resulting structure.
As a result, the temperature of the concrete mix must be carefully controlled throughout the building process and while it sets and cures to ensure the resulting structure is sound.
At ACCIONA, our global project teams work closely with the company’s concrete specialists at the Technical Services Department in Madrid to optimise the temperature and hydration of the concrete mix and ensure that it meets the project’s technical requirements, including strength and
40˚C
When ambient temperatures soar above 40ºC, experts recommend halting work
durability. Every project is different, which means that ACCIONA’s concrete specialists are much in demand, sometimes flying to the site of big projects to make their calculations.
They examine the quality of the local cement, the gravel and sand that will go into the input, the variation in temperature and humidity during the duration of the construction phase, as large, complex projects can take several years to complete.
In the UAE, where we were responsible for building the extension of the Dubai Metro Route 2020, concrete specialists were on hand to advise on the exact heat of hydration and temperature of the concrete mix at each phase of the project. During very hot days, we added ice flakes to the concrete mix to keep it cool during transport to the construction site and to control the chemical reaction as the cement set.
The technicians use specialist software based on finite element method to conduct simulations and predict how the concrete will behave as it cures. These calculations are then used on site to control the temperature and hydration of the mix.
Another tool used by our concrete specialists are temperature smart and wireless sensors. These are deployed at every stage of the process: they measure and transmit data on the temperature of the materials before mixing, during transport, and while it is poured and set.
At high temperatures, concrete sets too quickly, making it difficult to pour, handle and give shape to a structure. If it sets too quickly, cold joints can emerge between successive layers of concrete, and this may also weaken the structure. Getting the hydration and temperature right is therefore critical to the success of the building process.
The Dubai metro extension used 270,706 cubic metres of concrete during construction. For other big projects such as the Shuqaiq 3 reverse osmosis desalination plant in Saudi Arabia, already in operation, the total amount of concrete used during its construction was 80,000 cubic meters. Shuqaiq 3 has a capacity of 450M litres of potable water per day, enough to meet the needs of two million people.
To control the temperature of materials in very hot climates, options include storing them under cover to shield them from the sun; using cold air cannons to lower the ambient temperature; and spraying some of the materials with a mist of cold water. Insulating the storage silos, using heat-reflecting roofs, cooling silos with water, and building silos with double walls in which cold water can circulate are other methods that can keep materials cool before mixing.
One of the techniques deployed to adapt to the high temperatures of the
In demand
ACCIONA’s concrete specialists often fly to the site of major projects to make their calculations and assist with the concrete mix.
Major pour
The Shuqaiq 3 project in Saudi Arabia used 80,000 cu m of concrete during its construction. Gulf is the timing of concrete pouring and the frequency. Very often we time the concrete pours to start after the sun sets, to avoid direct sunlight and day-time high temperatures. We also couple this, under the guidance of our specialists, with specific quantities of concrete, depending on the shape and size of the pour, to ensure the curing time falls within the appropriate hours.
In extreme temperatures – an increasingly frequent occurrence due to global warming – concrete mixing trucks can be sprayed with liquid nitrogen to keep temperatures low during transport from the concrete plant to the project site. Concrete mixers are sometimes painted white to reflect heat or are covered with insulating materials to avoid excessive heating during transport.
In the Middle East, our project teams prefer to work in the cool hours of the day or at night to better control the temperature of the concrete mix. When ambient temperatures soar above 40ºC, or during windy days that accelerate evaporation, the technical experts recommend halting work as casting could be compromised.
On site, our teams have covered casting structures with tarpaulins to shield them from the sun, used cold air cannons to slow down the curing process, and when needed, spraying structures with water or curing agents to avoid concrete drying out too fast.
In fact, it is great to see that our people design solutions to optimise construction processes, as well as new technologies and materials that are more efficient at the work site, to reduce the potential impact on nature.
The Race to Net Zero C ountries globally are implementing long term strategies to reduce their greenhouse gas emissions, promote circular economy practices and ensure that their future-focused planning enables measures to minimise their carbon footprint. A key MIDDLE EAST question is whether planning has been Campbell Gray, CEO, Middle done holistically and whether there is sufficient urgency in those plans to meet East & Africa of Atkins, a member of the SNC-Lavalin the communicated net zero targets. Within the GCC, Saudi Arabia, the UAE and Bahrain have committed Group, reflects on the impact to becoming Net Zero and have announced their respective targets. of the Group’s recently released It was also announced during report, Engineering Net Zero for COP26 that the upcoming two meetings will be held in the Middle the GCC, and what the region East – Egypt in 2022 and the UAE in 2023, which aligns with the respective needs to do to achieve their governments’ commitment towards carbon neutrality ambitions accelerating their journey towards achieving a Net Zero Carbon future.
Meeting net zero targets takes time, effective policies, engineering advancements and of course government will-power. Time is not a luxury on offer but having target dates for Net Zero will motivate GCC countries to focus on planning schedules and accelerate build times, especially for energy systems. To meet their Net Zero targets, Saudi Arabia and the UAE have each released strategies that provide key milestones at either a country or, for the UAE, emirate level.
To help the region achieve its Net Zero targets, The SNC-Lavalin Group, including Atkins and Faithful+Gould, has launched the “Engineering Net Zero in the GCC” report that outlines challenges, opportunities, and key recommendations to decarbonise the energy, built environment, and transport sectors. Globally, the company has developed the ‘Engineering Net Zero’ (ENZ) programme, which focuses on leading the engineering industry to
achieve Net Zero Carbon as rapidly as possible, by helping clients manage climate risks and build climate resilience.
ENERGY TRANSITION The ongoing energy transition within the GCC is the foundation of governments Net Zero strategies. Decisions around heavy industry, the built environment or transport, directly influence opportunities within the energy sector. GCC countries are developing a mix of utility-scale solar, wind, waste-to-energy, and nuclear power as part of their planned lowcarbon energy mix. It is possible that build rates of both generation and grid integration projects, which must be considered in conjunction, may need to accelerate to meet government timelines.
The size and pace of clean energy targets in Saudi Arabia and the UAE, particularly when put into context of each country’s net zero targets, leaves no room for slow decision-making. Given the complexity of government plans, combined with the changing grid-connected energy mix that will include firm and intermittent power along with storage, countries will need an energy system architect (ESA) to enable decision making. An Energy System Architect (ESA) will ensure well-engineered plans can meet the net zero energy challenge which involves optimising the use of natural resources while overseeing decarbonisation strategies at the same time.
SUSTAINABLE CITIES Sustainable urban master planning is a key aspect of future net zero strategies. Sustainable cities need to consider liveability, work and access to essential services by a range of non-car and roadbased modes. Conscious design and planning that achieve Net Zero goals need to appreciate life-centric approaches to the built environment. Delivering high performance-built environment solutions for new and existing urban environments is a critical activity and will be at the forefront of decarbonising cities in the GCC. To help reduce carbon emissions for existing buildings, the company has developed DecarbonomicsTM, a datadriven solution to decarbonise the built environment in a cost-effective way to
Picking up pace
The construction sector is picking up the pace for digitalisation as clients demand more digital clarity and the financial benefits become obvious, says Campbell Gray.
Meeting the challenge
Countries will need energy system architects to enable decision making and ensuring plans meet the net zero challenge.
2023
The UAE will host COP28 in Abu Dhabi, with a focus on the economic case for inclusive climate action
enable asset owners to contribute to demand reduction and net zero goals.
Digital technologies will introduce new approaches to the construction process and provide data that can be analysed, understood and acted upon. The construction sector has been slow to digitalise, but the pace is accelerating, especially as more case studies reach the market on the benefits and as clients demand more digital clarity. Modular construction and green high performance building materials, including 3D printing, green cements, green steel using carbon capture, will clearly play a key role in decarbonising the built environment for new developments, but we need to move quicker
TRANSPORT AND MOBILITY GCC countries, in particular Saudi Arabia, the UAE and Qatar, have invested heavily in their transport networks in the past decade, but there can be no denying that for internal travel all countries are still heavily reliant on petrol-based car ownership and use, as well as road-based freight. Among other reasons, this is due to the rapid growth of cities and communities that have been designed around the car. Land-based public transport networks will play a major role in achieving GCC countries’ Net Zero strategies. Existing metro and tram networks are not yet extensive, however, and new lines are
needed that go to more locations if mass transit is to contribute significantly to a decarbonised transport network.
In addition, over the coming decades other technology options such as Hyperloop and maglev can induce much less friction than conventional rail systems and require less power to cover the same distance. The electric power for these systems, if they ever come to fruition, will need to come from clean sources for them to contribute to being a low carbon transport system. Aviation can actively electrify airport ground vehicles and install more solar power for use in terminals while longer-term research focuses on alternative or cleaner fuels for aircraft, including hydrogen.
In conclusion, achieving Net Zero targets in the GCC is a complex mission that will require ongoing government drive, clear strategies and measurable plans, collaboration between key stakeholders, a willingness to invest in new technologies and an understanding of the various interdependencies across industries within each country.
The energy, transport and built environment sectors are interconnected, and Net Zero decisions and policies on one, will have a direct and indirect impact on another. A holistic and joined up perspective is fundamental to transitioning to Net Zero in the most effective way and shaping a more sustainable and global future first approach across the region.
