By Wiljee Blom, N-Dip (Civ. Eng.), Stage 3 Concrete Technologist, Technical Manager, Penetron Africa
In recent months, I’ve noticed increased industry chatter about laboratory metrics like Loss on Ignition (LOI). While LOI isn’t new to cement chemistry, it’s suddenly being promoted as if it were a measure of performance in reactive crystalline waterproofing admixtures. As engineers and specifiers, our responsibility is to cut through this noise and focus on what truly matters: proven, practical performance in concrete.
The reality is straightforward. LOI is a composition-based test. It measures the percentage of mass lost when a material is heated up to 1,000°C. This mass loss may result from free or absorbed moisture, carbonates breaking down, or organics burning off or it may simply indicate that the tested product has a higher resistance to heat. In the cement industry, LOI is mainly used as a quality control check to highlight impurities that may flag issues such as probability to absorb moisture etc. LOI however, is not an indication of reactivity. For products like cement, which are highly reactive and hydrate with water, not heat, LOI tells us nothing about reactivity. LOI certainly doesn’t tell us how cement or cementitious admixtures will perform in service. It says nothing about hydration, reactivity with cementitious by-products, formation of dense crystalline structures, permeability reduction, crack self-healing, chemical resistance, or resistance to hydrostatic pressure.
Performance of concrete and concrete additives is not tested in a furnace. It’s tested in reservoirs, bridges, tunnels, parking decks, marine piers, warehouses, pools, planters, and basements. Performance is proven in critical concrete structures across industry, energy, and mining and is exposed to water, chemicals, pressure, and time. That’s why I argue that only real-world performance testing, not raw composition metrics, or laboratory results over short term referencing performance at a point in time (e.g. 28 days) should guide our confidence in concrete solutions. What matters is long-term solutions and proven long-term performance.
Why LOI (or similar) unrelated testing fall short
When a material shows a higher or lower LOI value, it simply means more or less mass was burned away during the test. This can be influenced by many factors and generally indicates impurities such as free water or unburnt carbon that should not be present in dry products, but it may also simply indicate that the product is more stable at high temperatures. The point is this: none of these are performance indicators of how a crystalline admixture will behave in practice. They are far more relevant to issues of storage and transport than to actual performance in concrete.
In fact, a high LOI can signal the opposite of durability. It’s commonly used to indicate impurities that make a product susceptible to early hydration or degradation during storage. A cementitious product with a high LOI is more vulnerable to moisture uptake, which compromises stability. That doesn’t make it a stronger or more reliable waterproofing material. On the contrary, it points to reduced performance and reduced reliability.
I’ve seen this confusion play out in specification meetings, where procurement teams focus on LOI numbers as if they were performance guarantees or proof of reactivity for products that rely on hydration, not heat. It’s understandable – numbers seem objective and easy to compare – but not all metrics are valid for comparison. When specifying materials for 50- or 100-year infrastructure projects, we need relevant data that actually predicts how concrete will perform over decades of service and under varied exposure conditions.
For this reason, engineers and specifiers should treat LOI for what it is: a useful composition metric in cement chemistry, but certainly not a measure of performance.
What Matters: Performance-Based Testing
If we want to understand how concrete performs against water ingress, chemical attack, and long-term deterioration, the answer lies in performance testing. Internationally recognised standards replicate real-world conditions and measure how concrete behaves under pressure.
For example, ASTM C1202 is a widely used method for evaluating the electrical indication of a concrete’s ability to resist chloride ion penetration. It measures how permeable the concrete is to chloride ions, giving engineers a reliable indication of how concrete will resist reinforcement corrosion over its service life. When we review test reports, this is the kind of data that inspires confidence in a specification.
Similarly, DIN 1048 evaluates water penetration under pressure. In one recent documented case, untreated concrete showed significant water ingress, while concrete treated with crystalline admixtures showed negligible penetration under the same conditions. These results give specifiers confidence because they reflect what happens in real structures. However, it’s important to note that both ASTM C1202 and DIN 1048 are usually conducted on laboratory-prepared, uncracked concrete. In practice, concrete will crack, making those test conditions imperfect indicators. Crystalline admixtures like PENETRON address this by improving crack self-healing. This means that although cracks occur in practice, they will self-seal, restoring mechanical and permeability characteristics, and allowing accurate performance assessment under real-world conditions.
At Penetron Africa, our technologies are validated by such standards. These confirm permeability reduction, chloride resistance, service-life prediction models, carbonation resistance, hydrostatic pressure performance, and even crack self-healing under scanning electron microscope analysis. The difference between laboratory composition tests and performance testing is the difference between analysing the ingredients in a recipe and tasting the finished meal.
The Self-Healing Advantage
One of the most remarkable (and undervalued) advantages of crystalline waterproofing is the ability of the admixture to support self-healing of hairline cracks. When cracks form, moisture activates dormant crystalline compounds in the concrete. These react to form insoluble crystals that grow and seal the crack permanently.
What continues to fascinate me about this process is that it isn’t theoretical – it’s measurable and observable. The International Union of Laboratories and Experts in Construction Materials (RILEM) has done extensive work on self-healing efficiency. Their research confirms that self-healing is measurable, observable, and that it improves watertightness and durability over time. In fact, Penetron’s role in the European resHEALience campaign, conducted under the auspices of RILEM, further underscores the global research backing crystalline self-healing technology, demonstrating its impact on ultra-high durability concrete in some of the world’s most demanding environments
This validation matters enormously. It shows that self-healing is not just a marketing phrase but an established scientific phenomenon with recognised evaluation criteria. For engineers and specifiers, this means crystalline admixtures can be specified with confidence, knowing that micro-cracks will not compromise the long-term waterproofing integrity of the structure.
I have personally examined core samples from structures in service for over a decade. Under microscopic analysis, new crystal formations are clearly visible where moisture was present. This is evidence of ongoing crystalline activity that strengthens the structure over time.
Linking Durability and Sustainability
Durability is not only about technical performance. It’s also about sustainability. Cement production accounts for approximately 8% of global CO₂ emissions, which is relatively small when we consider that concrete is the second most used material in the world after water. The real issue however lies in failing to achieve design service life or durability goals. Every time a structure is repaired or rebuilt prematurely, we add to that footprint.
By using admixtures like Penetron, that are proven to extend service life, we can build structures that last significantly longer with minimal maintenance.
Longer service life means fewer repairs, fewer rebuilds, and fewer emissions associated not only with cement production but also with repair compounds, labour, transport, and site access for remedial work. In this way, concrete durability is directly linked to environmental responsibility, particularly as the repurposing and reuse of structures become more critical.
This connection is particularly important when we consider the scale of infrastructure development across Africa. We are building water treatment plants, ports, commercial centres, data storage facilities, all for a growing population, residential complexes, and industrial plants that must serve rapidly developing communities for generations.
The difference between a structure that lasts 50 years versus 150 years is not only about maintenance costs. It’s about the responsibility we carry for the entire carbon footprint of that infrastructure over its lifecycle.
For African markets, this is especially critical. Infrastructure investment must be both cost-effective and future-proof. A water reservoir, financial centre, or industrial facility that lasts 150 years instead of 50 has a measurable impact on community benefit, lifecycle costs, and carbon savings. When governments, municipalities, and private investors make decisions about infrastructure, long-term performance data, reflecting total cost of ownership and the bigger picture, becomes crucial to justifying the initial investment.
Case Studies in Africa
Across Sub-Saharan Africa, we see many examples of how performance-based testing translates into results on the ground.
The Kigali Finance Centre in Rwanda is one such example. PENETRON ADMIX safeguarded below-grade basements and luxury hotel pools, saving significant costs and time by eliminating membranes and improving concrete durability. The project team was initially sceptical about relying on integral waterproofing rather than membranes, but performance test data and a holistic look at the saved costs of construction time provided the confidence needed for specification.
At Rozendal Reservoir in South Africa, a municipal upgrade extended service life and avoided demolition, lowering the project’s carbon footprint while ensuring watertight performance. This project is especially notable because it demonstrates how crystalline technology can rehabilitate existing structures, not just protect new construction.
The Illovo Water Tower in South Africa is another compelling case. Repairs using PENETRON and PENECRETE MORTAR restored watertightness and extended service life under coastal conditions. The aggressive marine environment provided an excellent real-world test of material performance, far more demanding than any laboratory furnace.
These projects were not validated by LOI numbers or unrelated laboratory metrics. They were validated by how the structures performed in real conditions, resisting pressure, sealing cracks, and remaining durable for decades. When I visit these sites now, and in the years to come, their continued performance validates our focus on real-world testing rather than composition metrics.
The Path Forward
As technical professionals, we must keep our focus on what truly defines concrete durability. Composition metrics like LOI may serve a purpose in cement and supplementary cementitious material quality control, but they are not indicators of performance or service life.
What really matters are robust systems and performance under real-world conditions. RILEM‘s evaluation of self-healing concrete provides credible, independent validation of what engineers care about most: crack self-healing, chemical resistance, hydrostatic pressure resistance, efficiency against soft water and ASR, and long-term durability.
At Penetron Africa, our mission is to deliver total concrete protection by focusing on proven, performance-based outcomes. I remain convinced that the most sustainable, cost-efficient, and technically robust approach is to specify solutions tested under real-world conditions, not in a furnace.
The concrete we build today must stand for generations. Let’s make sure it stands strong, durable, and sustainable, backed by performance, not by metrics that fail to reflect reality.
Explore Penetron’s global case studies in crystalline technology to see how our solutions deliver measurable performance across Africa and beyond. You can also discover the specifications and test results of PENETRON ADMIX to understand how we meet the highest standards of durability and sustainability.
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 he specialises in crystalline waterproofing technology and concrete durability solutions.
