Following discussions with Mota-Engil regarding the Parklane development in Kigali, Penetron Africa was requested to provide a technical perspective on concrete durability and its role in reducing the whole life carbon footprint of infrastructure.

The global construction industry is under increasing pressure to reduce greenhouse gas emissions while continuing to meet the growing demand for resilient infrastructure. Considerable effort has therefore been directed towards reducing the embodied carbon of concrete through supplementary cementitious materials, alternative binders, clinker reduction, improved manufacturing processes and emerging carbon capture technologies.

However, embodied carbon represents only the initial environmental cost of a concrete structure. Once placed, the structure begins a service life that may extend over many decades, during which maintenance, repair, rehabilitation and, ultimately, replacement can contribute substantially to its overall carbon footprint. A concrete structure that requires repeated intervention throughout its life may ultimately embody significantly more carbon than a structure with a marginally higher initial embodied carbon but a substantially longer service life.

This paper proposes that one of the greatest opportunities for reducing the environmental impact of concrete lies not only in reducing the carbon associated with its manufacture, but in maximising the durability and service life of the structure itself. By reducing permeability, slowing deterioration and minimising future repair interventions, durability becomes a primary mechanism through which lifecycle carbon emissions can be reduced.

In this context, concrete durability should be regarded not merely as a structural performance requirement, but as a fundamental component of sustainable infrastructure design.

Overview

Concrete continues to form the backbone of modern infrastructure. No other material currently offers the same combination of structural performance, durability, fire resistance, affordability, availability and scalability required to support the demands of rapidly developing economies.

While alternative construction materials and innovative structural systems continue to evolve, reinforced concrete will remain the primary material for buildings, transportation infrastructure, water-retaining structures and energy projects for the foreseeable future. The challenge facing the engineering profession is therefore not simply to replace concrete, but to use it more intelligently. If society is prepared to invest in both the financial and environmental cost associated with producing concrete, then every cubic metre placed should be expected to deliver the maximum possible value through an extended and reliable service life.

A structure that performs as intended for one hundred years represents a significantly better environmental investment than one requiring major repair or rehabilitation after only a few decades. By extending service life, the environmental impact of concrete can be substantially reduced without compromising structural performance, constructability or material availability. In doing so, durability shifts from being viewed solely as a performance requirement to becoming one of the most powerful tools available for delivering carbon infrastructure.

Durability is Sustainability (the carbon challenge)

The current sustainability debate is focused on reducing embodied carbon. However, these strategies largely address only the carbon associated with producing and placing concrete. They often overlook a far more significant contributor to the total environmental impact of a structure: premature deterioration and the repeated cycle of maintenance, repair, rehabilitation and eventual replacement throughout its service life.

Every cubic metre of concrete carries two fundamental investments. The first is the financial investment associated with extracting raw materials, manufacturing cement, transporting constituents, batching, placing and curing the concrete. The second is the environmental investment embodied in that same cubic metre through the energy consumed and carbon emitted during its production. Once the concrete has been placed, both investments have already been made. Any deterioration that shortens the intended service life of the structure effectively reduces the return on both.

Premature deterioration is therefore far more than a maintenance or quality issue. It is fundamentally a sustainability issue. Every repair requires new cement, new aggregates, new reinforcement, transport, equipment, labour and energy. Existing materials must often be demolished, removed and disposed of before replacement can occur, creating additional environmental impacts that are seldom considered during the initial design process.

Viewed from this perspective, the most sustainable concrete is not necessarily the concrete with the lowest embodied carbon on the day it is placed, but the concrete that continues to perform for the longest period with the fewest interventions. Extending service life delays or eliminates future repairs, preserves the original environmental investment and significantly reduces the whole life carbon footprint of the structure.

The Carbon Cost of Repair (concrete and sustainability)

Concrete itself should not be regarded as an environmental problem. A structure requiring major rehabilitation after only twenty years will inevitably carry a substantially larger whole life carbon footprint than an equivalent structure that continues to perform for one hundred years with minimal intervention. Sustainability therefore becomes, to a large extent, a durability problem.

Concrete deterioration is rarely a single event. It is typically the beginning of an accelerating cycle of maintenance and repair. The first intervention generally occurs once deterioration mechanisms such as carbonation, chloride ingress, sulphate attack or reinforcement corrosion have progressed to the point where structural performance or serviceability can no longer be maintained. Although repairs restore functionality, they seldom restore the structure to its original condition.

Repair interfaces introduce new material transitions, differential movement, construction joints and potential pathways for moisture ingress, each of which may influence the long-term performance of the repaired element.

As a result, maintenance intervals frequently become progressively shorter.

A structure originally designed to provide forty to fifty years of service may require its first major repair after only twenty years. Subsequent interventions often follow at ten-year intervals, then five years, before eventually becoming part of a continuous maintenance programme. Each repair introduces additional concrete, cement, reinforcement, transport, construction equipment, labour and energy, while also generating demolition waste, operational disruption and further embodied carbon. Over the design life of a structure, the cumulative environmental impact of repeated rehabilitation can ultimately exceed that associated with the original construction.

From a sustainability perspective, the objective should therefore not be limited to reducing the embodied carbon of the initial concrete mix. It should be to preserve the original environmental investment by delaying or eliminating the need for repair.

Durability Through Integral Crystalline Technology

Reducing the whole life carbon footprint of concrete ultimately depends on extending the period during which a structure performs as intended without requiring major intervention. This shifts the sustainability discussion from simply reducing the embodied carbon of construction materials towards improving the long-term durability of the structure itself. By reducing the frequency of maintenance, repair, rehabilitation and eventual replacement, durability preserves both the financial and environmental investment made during construction while significantly lowering lifecycle carbon emissions.

Penetron crystalline technology approaches this challenge by modifying the concrete matrix itself rather than relying on external protective systems. The crystalline admixture reacts with moisture and naturally occurring cement hydration products to form insoluble crystalline structures throughout the capillary network of the concrete.

As these crystals develop, they progressively densify the pore structure, permanently reducing permeability and limiting the movement of water and dissolved aggressive agents through the concrete.

This reduction in permeability directly addresses the principal deterioration mechanisms responsible for shortening the service life of reinforced concrete. Carbonation, chloride ingress, sulphate attack and the subsequent corrosion of reinforcing steel all depend on the transport of moisture, gases or dissolved ions through the concrete matrix. By restricting these transport mechanisms, crystalline technology slows the rate of deterioration, delays the onset of reinforcement corrosion and extends the functional life of the structure.

The crystalline system becomes an integral part of the concrete itself. It cannot be punctured, delaminated or become detached during construction or throughout the operational life of the structure. In the continued presence of moisture, the crystalline reaction remains active, allowing newly formed microcracks and capillary voids to become progressively sealed as they develop. The result is a more resilient concrete matrix capable of maintaining its durability over substantially longer service life while reducing the need for future maintenance and repair.

By extending service life through mechanism-based durability rather than relying solely on periodic maintenance or replacement of surface protection systems, integral crystalline technology provides a practical and immediately implementable contribution towards genuinely low-carbon infrastructure. It complements existing embodied carbon reduction initiatives while addressing one of the largest and most frequently overlooked sources of carbon emissions within the built environment: premature deterioration and repeated repair.

Durability as a Carbon Reduction Strategy

The greatest sustainability benefit of Penetron’s integral crystalline technology lies not in reducing the embodied carbon of concrete on the day it is placed… Parklane concrete deterioration is cumulative.

Once the first major repair has been undertaken, the repaired structure rarely behaves as a completely new structure. Repair interfaces, construction joints and transitions between old and new materials frequently become future points of weakness, allowing deterioration mechanisms to re-establish themselves.

Eliminating or substantially delaying that initial intervention represents the single greatest opportunity to reduce the lifetime environmental impact of a concrete structure. A structure that remains serviceable for one hundred years without major rehabilitation will almost invariably have a substantially lower whole life carbon footprint than one requiring repeated intervention, even if both structures began with similar embodied carbon values.

From this perspective, durability should no longer be viewed solely as a structural performance requirement or maintenance objective. It becomes a measurable carbon reduction strategy. Every year of service life preserved without repair protects the original environmental investment made during construction and reduces the cumulative carbon burden imposed over the life of the asset.

Compatibility with Low Carbon Concrete

The drive towards lower embodied carbon has accelerated the development of alternative cementitious systems incorporating supplementary cementitious materials. Improvements in embodied carbon should not be considered independently of long-term performance. A concrete mix with an exceptionally low embodied carbon provides little environmental benefit if poor constructability, reduced robustness or premature deterioration results in a shortened service life.

True sustainability therefore requires a balance between reducing the initial carbon footprint of concrete and ensuring that the finished structure achieves its intended design life under real construction and operating conditions.

This consideration is particularly relevant within many African markets, where long transport distances, elevated ambient temperatures, variable aggregate quality and evolving supply chains present additional challenges to concrete production. Under these conditions, maintaining predictable fresh concrete properties, including workability, open time and placing characteristics, becomes critical to achieving a dense, well-compacted and durable concrete structure.

Penetron’s integral crystalline technology has been specifically developed to enhance durability without fundamentally altering conventional concrete production and placement practices. The admixture is fully compatible with standard Portland cement systems as well as modern low carbon concrete incorporating supplementary cementitious materials such as fly ash, ground granulated blast furnace slag, calcined clays and other approved cement extenders. Rather than competing with these technologies, crystalline admixtures complement them by providing an additional mechanism through which service life can be extended and lifecycle carbon emissions reduced.

International Experience and Emerging Practice

The relationship between durability and sustainability is increasingly recognised within international engineering practice. While early sustainability initiatives focused primarily on reducing the embodied carbon of construction materials, there is growing recognition that the long-term environmental performance of infrastructure is equally dependent on durability, resilience and service life.

Designers are moving beyond the question of how to reduce the carbon associated with constructing a structure and are instead considering how to minimise the total environmental impact of that structure throughout its operational life.

This shift is reflected in the growing emphasis on whole life carbon assessment adopted by many international design standards, infrastructure owners and green building certification systems. Rating systems such as LEED, BREEAM, EDGE and Envision increasingly recognise lifecycle performance, resilience, reduced maintenance and asset longevity as important contributors to sustainable development. In this context, durability should no longer be regarded as a secondary engineering consideration, but rather as a fundamental sustainability objective.

Penetron’s integral crystalline technology has formed part of this evolution and has been incorporated into numerous commercial buildings, transportation projects, water-retaining structures and critical infrastructure developments throughout North America, Europe, the Middle East, Asia, Africa and Australia. The technology has been specified on projects certified under internationally recognised sustainability frameworks where long-term durability, reduced maintenance and resilience formed part of the overall environmental strategy. Projects such as Jewel Changi Airport in Singapore illustrate how durable concrete construction can contribute to long-term sustainability by reducing maintenance requirements, extending service life and preserving the environmental investment associated with the original construction.

Suitability for Rwanda

Rwanda presents a unique opportunity to integrate durability and sustainability from the outset. The country’s continued investment in transport infrastructure, water and wastewater systems, energy generation, commercial developments and sustainable urban planning demonstrates a clear commitment to long-term infrastructure performance.

Projects such as Parklane, Green City Kigali and the ongoing expansion of strategic public infrastructure provide an ideal platform for adopting lifecycle-based durability strategies.

Given the continued reliance on reinforced concrete as the primary structural material, improving durability represents one of the most practical and immediately implementable methods of reducing the environmental impact of future construction without introducing unnecessary construction complexity or supply-chain risk.

Conclusion

The global drive towards lower carbon construction is both necessary and inevitable. Considerable progress has already been made in reducing the embodied carbon of concrete through alternative binders, supplementary cementitious materials and improvements in cement manufacturing. These initiatives represent an important step towards more sustainable infrastructure and should continue to form part of the industry’s response to climate change.

However, embodied carbon represents only the beginning of a structure’s environmental journey. The true sustainability of concrete cannot be measured solely at the point of construction, but must be evaluated over the complete service life of the asset. A structure requiring major rehabilitation after only twenty years cannot reasonably be considered sustainable, regardless of the carbon savings achieved during its initial construction. Every repair introduces additional materials, transport, labour, equipment, demolition, waste and operational disruption, all of which contribute to the cumulative carbon footprint of the structure.

The most sustainable concrete is therefore not necessarily the concrete with the lowest embodied carbon, but the concrete that delivers the greatest service life with the fewest maintenance interventions. Penetron’s integral crystalline technology contributes directly to this objective by reducing permeability, limiting the ingress of aggressive agents and protecting the concrete matrix from the mechanisms responsible for premature deterioration.

By extending service life and reducing the need for future intervention, the Penetron technology complements existing low carbon concrete strategies while providing a practical and immediately implementable mechanism for reducing whole life carbon emissions.

In the pursuit of genuinely sustainable infrastructure, the greatest environmental benefit may not come from producing less concrete, but from ensuring that the concrete we do produce performs as intended for as long as possible.

Recommendation

It is recommended that sustainability strategies for major infrastructure projects incorporate durability as a primary design objective alongside embodied carbon reduction. This should include explicit consideration of permeability reduction, service-life design, lifecycle costing and resilience against deterioration mechanisms relevant to the intended exposure environment.

Penetron’s integral crystalline technology provides a practical mechanism-based approach to achieving these objectives. By reducing permeability, extending service life and minimising future maintenance requirements, the system complements existing low-carbon initiatives while addressing one of the largest and most overlooked contributors to infrastructure-related carbon emissions: premature deterioration and repair.

For projects such as Park Lane and future developments throughout Rwanda, a durability-based approach provides a technically robust, economically sound and environmentally responsible pathway towards genuinely sustainable concrete infrastructure.

About the Author

Wiljee Blom holds a National Diploma in Civil Engineering, is a Stage 3 Concrete Technologist, and has a postgraduate qualification in Business Management. He serves as Technical Manager at Penetron Africa, where his expertise is crystalline waterproofing technology and concrete durability solutions.

Related Articles