Impacts of building elements on overall embodied CO2
Industry, architects and engineers alike are now tasked with incorporating low carbon products and sustainable solutions into their projects, and much can be done to that effect;
To limit the global temperature increase to 1.5 degrees Celsius above pre-industrial levels as agreed under the Paris Agreement, the Glasgow Climate Pact (COP26) aims for a 45% reduction in global carbon dioxide emissions by 2030 relative to the 2010 level, and to net zero by mid–century. Even so, the world will likely witness an increase of 2.4°C by 2100.
With a contribution of 8%, the global cement industry is the second-largest producer of CO2 and thus one of the main focus points of the COP26 climate targets. Recognizing this, Canada, Germany, India, the UAE and the UK have already pledged to attain net zero in the “major public construction” use of concrete and steel by 2050. In line with these goals, 40 global concrete and cement manufacturers under the GCCA are now committed to cutting CO2 emissions in half by 2030 on the path to achieving net zero by 2050.
Since the concrete structure provides the lion’s share (ca. 66%) of a building’s embodied carbon, concrete is the most pressing issue to address. As the carbon footprint of water and aggregates is negligible, the carbon footprint of concrete is determined almost entirely by cement (0.93kg CO2/kg), making it the largest contributor to embodied carbon in the built environment. In addition, cement production also generates high nitrogen oxide (NOx) and sulphur oxide (SOx) emissions, which contribute to acid rain, a further deterioration of public health and global climate change.
A multi-disciplinary challenge to achieve net zero embodied carbon by 2050. Mission alignment with:
PENETRON ADMIX is a sustainable, crystalline admixture that reduces concrete permeability. By providing comprehensive protection against concrete deterioration caused by chemical attack, corrosion, and freeze-thaw cycles, PENETRON ADMIX extends the service life of concrete structures. Easily mixed in during batching and unaffected by climatic conditions, it helps reduce the overall carbon footprint of concrete mixes and construction projects.
Concrete is porous and consists of microcracks, pores, and capillaries, which typically have a width between 0.1-0.5mm.
Water and water-borne chemicals enter the concrete through the capillary matrix.
When PENETRON ADMIX is added to the concrete, the active ingredients react to generate an insoluble crystal network.
This network seals voids and microcracks against water penetration, even under high hydrostatic pressure.
Water is unable to pass through the crystal formations and the concrete is now impermeable.
PENETRON ADMIX provides a self-healing capability as new hairline cracks that form throughout the life of the concrete are sealed as soon as water enters.
PENETRON ADMIX provides up to 100% permeability reduction. This maintains the proper alkaline environment necessary to keep the embedded steel passivated and prevent corrosion.
With water being the main cause for concrete deterioration, PENETRON’s permanent waterproofing protection largely eliminates the need for maintenance of concrete structures throughout their service life and the carbon footprint that comes with that.
Equally, by enabling self-healing of cracks up to 0.5mm throughout the service life of concrete, preventing water ingress and corrosion, the need for maintenance of concrete structures is largely avoided.
Before
After
The table above shows how PENETRON ADMIX-treated concrete designed for 50 or 100 years of service life, requires little or no maintenance – and allows a reduction in concrete cover – despite exposure to corrosion by chlorides or carbonation.
As a result, fewer maintenance cycles compared to conventional concrete reduce the building’s maintenance CFP by a minimum of 40% (3 in 5 cycles) and up to 300% (0 in 3 cycles).
A sustainable circular economy optimizes the use of natural resources and energy to minimize CO2 emissions. Conventional concrete, the second most consumed product in the world, consists of durable natural materials but fails when exposed to aggressive environments, resulting in frequent and costly repairs or replacement. This increases the use and processing of raw materials and energy, which increases CO2 emissions.
The embodied carbon footprint (CFP) of a building is the sum of:
By using a durable concrete mix with self-healing properties, the service life of a structure - defined as the number of years corrosion probability remains at ≤10% - can be extended by 60 years and more. At the end of its intended service life, a building may either stay in service as is, or receive a new façade, M&E upgrades and be re-purposed to serve a similar design life. As a result, (A), (B), (C), and (D) are either dramatically reduced or done away with entirely, effectively providing two structures with the CFP of a single structure.
With the global cement and concrete industry committed to Net Zero Carbon by 2050, and cement being the main carbon culprit, the obvious path forward is to reduce cement consumption by using supplementary cementitious materials (SCMs) such as fly ash, blast furnace slag, silica fume, volcanic ash, etc. As these SCMs are by-products of the coal and steel industry, they do not add to the CFP of building projects and add value beyond their binding ability. SCMs are increasingly embraced by the industry and also increasingly in short supply.
PENETRON ADMIX is fully compatible with the use of SCMs. It works equally well with OPC and SCM/OPC mixes, enabling a great reduction in the embodied carbon of the structure.
PENETRON ADMIX enables the use of a lower grade concrete while achieving the same or better durability. This allows for the use of a lighter, more flexible and yes, cheaper concrete to satisfy the same performance specifications.
Durability tests of concrete under attack from chloride penetration and carbonation were performed, with a maximum CFP value for PENETRON ADMIX of 4.9kgeqCO2/m³.¹
The CFP of concrete mixes was adopted from research carried out by the Building Services Research and Information Association (BSRIA) and the University of Bath¹, both in the UK. The research provides a large CFP database for the most common construction materials, including concrete (with and without supplementary cementitious materials) with a range of 28-day compressive strength² test results.
¹ Technical report RAA0036A-01 | ² https://ghgprotocol.org/Third-Party-Databases/Bath-ICE
Concrete durability can be determined as a function of the chloride migration coefficient and the concrete cover (Fick’s 2 nd Law of Diffusion).
The research cited here shows that PENETRON ADMIX mixed with a low-grade concrete provides better protection against chloride migration than a BS 8500-1 compliant mix with 40kg more cementitious materials, designed for a service life of 50 years.
Further, concrete cover may be reduced significantly with no reduction in the structure’s service life due to corrosion induced by chlorides for a low-grade concrete mix containing PENETRON ADMIX.
The results of the simulations comparing the prescribed mix of BS 8500-1 (control mix, prescribed mix) and the mix containing PENETRON ADMIX are reported in the following graphs, with cover thickness varying from the target cover thickness for 100 years (65 mm) to the target cover thickness for 50 years (50 mm) according to BS 8500 for exposure to seawater. The initial chloride content corresponds to a typical harbor structure subjected to saline fog.
For each assigned value of the concrete cover, the service life limit due to corrosion induced by chloride penetration of a low-grade concrete mix containing PENETRON ADMIX is greater than the corresponding higher-grade concrete prescribed by BS 8500-1.¹
These test results point to a potential 10% reduction in cementitious content, resulting in a lighter, more flexible, and cheaper concrete.²
¹ Technical report RAA0036A-01 | ² Technical report RAA0036A-01 | ³ MIX A - CFP = 369 kg eq-CO2/m³ | MIX B - CFP = 325 + (3.80 ÷ 4.00)*4.9 = 330 kg eq-CO2/m³
The role of PENETRON ADMIX in extending the service life of reinforced concrete exposed to carbonation was measured by comparing a low-grade concrete mix containing PENETRON ADMIX with a designated concrete mix (class XC3/XC4) as required by BS 8500-1. The latter is a durable concrete mix with a nominal concrete cover of 30 mm for a service life of 50 years, and contains 35 kg more cementitious materials.
Climatic chamber with prisms for accelerated carbonation (Swiss SIA 262/1-X standard)
The carbonation coefficient (K) values obtained for the two mixes after 90 days confirms that the lower grade concrete with PENETRON ADMIX provides superior protection against carbonation;
The research results¹ concluded that for each given value of mean concrete cover, the time to reach the service life limit due to corrosion induced by carbonation is many times greater for a low-grade concrete mix containing PENETRON ADMIX than the corresponding higher grade concrete mix prescribed by BS 8500-1. Moreover, this result allows a notable reduction in concrete cover.²
¹ Technical report RAA0036A-01 | ² Disclaimer : This research was done under laboratory conditions. Project engineers should calculate mixes and concrete cover based on a project’s concrete performance requirements. | ³ Calculating CFP of mix A, which is a nominal C40/50 and of mix B which is a nominal C32/40; MIX A - HIGHER GRADE - CFP = 369 kg eq-CO2/m³ | MIX B - LOWER GRADE - CFP = 329 + (3.15 ÷ 4.00)*4.9 = 330 kg eq-CO2/m³
Conventional waterproofing solutions for below-grade concrete structures often include one of the surface treatment options noted below, with their corresponding carbon footprints (CFPs).¹
The CFP of PENETRON ADMIX is assumed here as the CFP of clinker² and CFP of proprietary materials³. Considering the maximum dosage anticipated for the product in high performance concrete (4.0 kg/m³),⁴ the maximum value of CFP for PENETRON ADMIX is 4.9 kgeqCO2/m³.
The tables on the right compare the CFPs of different concrete mixes with PENETRON ADMIX on a m² basis for an average wall thickness between 0.25 and 0.35 m to the same mixes with the conventional surface treatments mentioned above.⁵
In summary, the removal of polymer-based, non-sustainable, waterproofing solutions for below-grade structures and replacement with crystalline technology (in combination with pozzolan cements used with Portland cement) reduces the carbon footprint per square meter of conventionally waterproofed concrete vs. self-healing concrete by an average of 20%, and up to 27%⁵.
¹ CFP values are adopted from comparative environmental life cycle impact of waterproofing solutions for flat roofs. Application of the studied solutions in the rehabilitation of military infrastructure (Miriana Gonçalves – MSc’s Thesis – Tecnico Lisboa, 2015) | ² 0.93 kgeqCO2/kg | ³1.514 kgeqCO2/kg | ⁴1% of 400 kg/m3 of binder | ⁵ Technical report RAA0036A-01
Multiple benefits are derived by avoiding the use of topical waterproofing treatments, especially for basements. A smaller excavation footprint, eliminating the need for waterproofing contractors to apply membranes, and no wait for ideal climatic conditions to install, etc. These factors contribute to optimized construction scheduling and reducing the structure’s CFP.
By combining the pouring and waterproofing stages, we can significantly accelerate the construction schedule, save resources and reduce the carbon footprint of the project.
Depending on the level of commitment towards achieving net zero carbon concrete by 2050, the following carbon footprint reductions can be achieved with PENETRON ADMIX:
¹ 20% reduction on substructure accounts for 5% on whole structure if basement concrete volume remains equal or greater than 25% of whole structure concrete volume
Penetron products, including PENETRON ADMIX, play a role in helping projects with their credit realization while achieving a range of internationally recognized standards such as Singapore Green Label, EPD, CDPH and GreenGuard Gold.
Less excavation is necessary when using PENETRON ADMIX as the need for space to apply a surface material (e.g. membrane) is eliminated. PENETRON ADMIX is added directly into the concrete.
A PENETRON or PENETRON ADMIX-treated concrete roof slab acts as the base of a roof garden system preventing water penetration through the slab.
PENETRON products assist in the rehabilitation, waterproofing and protection of existing structures increasing both concrete durability and service life.
PENETRON products eliminate waste, as they can be recycled together with the concrete after demolition whereas environmentally unfriendly petroleum-based products like membranes go into the landfill or have to be disposed of otherwise. Penetron packaging is fully recyclable.
Category: Interior paints and coatings applied on site;
Penetron products are certified green products that contain zero VOC.
PENETRON products contain zero VOC and thus will not expose construction workers to any odorous, irritating and/or harmful contaminants.
Penetron Admix is proven to slow down chloride diffusion and therefore prolongs corrosion of the reinforcement as measured and calculated by the 2nd Fick Law of Diffusion. This results in an extension of the service life of the concrete by up to 60 years in critical environments.
Option 2: Reduction of Total Waste Material;
Penetron products are recycled together with the concrete after demolition whereas environmentally unfriendly petroleum-based products like membranes go into the landfill or have to be disposed of otherwise.
Category: Interior paints and coatings applied on site;
Penetron products are certified green products that contain zero VOC. Applying Penetron will therefore not negatively affect the air quality on the project in regard to odorous, irritating and/or harmful contaminants.
Penetron Admix is proven to slow down chloride diffusion and therefore prolongs corrosion of the reinforcement as measured and calculated by the 2nd Fick Law of Diffusion. This results in an extension of the service life of the concrete by up to 60 years in critical environments.
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