The insatiable hunger for concrete
Urbanization. Expansion. Citification. While urbanization refers to the population shift from rural to urban areas, citification describes the process by which a neighborhood or a region takes on city-like characteristics such as increased population density and formal infrastructure. Concrete acts as the foundational material for this expansion, enabling the construction of the massive infrastructure required to support growing populations. The evolution from rural land to a concrete jungle typically involves several distinct stages and conceptual shifts. Rapid urbanization directly drives the demand for high-grade materials. Industries must strategically place industrial plants near construction hot spots to meet the growing needs of large-scale residential and commercial projects. This massive use of concrete in citification has profound environmental and social consequences. Covering the ground with concrete (and asphalt) prevents water from recharging underground water sources, leading to a rapid decline in groundwater levels and increased polluted runoff into streams and other bodies of water. The urban critical zone is characterized by high population density and extensive impermeable surfaces, which alter energy and water cycles compared to natural environments.
The continued widespread use of concrete presents several critical environmental challenges, primarily driven by the production of its key binder—cement. While concrete is essential for global infrastructure, its environmental footprint is vast, accounting for approximately 7 to 8 percent of global carbon dioxide emissions. Concrete is the second most consumed material on Earth after water. It accounts for nearly 10 percent of global industrial water use, often in regions already facing significant water shortages and stress. The mining of sand and gravel for concrete leads to riverbed erosion, habitat destruction, and loss of biodiversity. Concrete surfaces absorb and retain heat, raising city temperatures compared to surrounding rural areas. Paving over natural land prevents water from soaking into the ground, which increases the risk of flooding and runoff, lowers local water tables, and disrupts natural ecosystems. Cement plants emit toxic substances, including particulate matter, which are linked to respiratory and cardiovascular diseases in nearby communities. The cement production process can release heavy metals (like lead, mercury, and chromium), which can contaminate local soil and water supplies.
Concrete and asphalt absorb solar energy during the day and slowly release it at night. They act like thermal sponges that keep cities warmer than natural landscapes. This effect is intensified by urbanization, where natural vegetation is replaced by impervious surfaces that lack the cooling benefits of shading and evapotranspiration. Concrete absorbs, rather than reflects, most of the sunlight that hits its surface. Unlike natural soil, concrete releases its stored heat slowly after sunset, preventing the urban environment from cooling down overnight.
Mountains are physically leveled to create flat land for cities, and their internal rocks are harvested to produce the concrete used to build those cities. Mountains, particularly those made of limestone, are quarried at a massive scale to extract the primary ingredient for cement. Rock is blasted and crushed into smaller chunks, mixed with other materials, and heated in kilns to create clinker, which is then pulverized into the fine powder we know as cement. As the global population grows, the hunger for concrete is literally eating away at mountain ranges across the world to provide materials for roads, bridges, housing, and flood control systems.
Scientists and local communities have raised alarms about the long-term impact of the flattening of mountains. Altering natural mountain landscapes can trigger landslides, flash floods, and soil erosion because it disrupts natural water drainage and weakens the land. The scale of earthmoving often leads to severe air pollution from dust particles and water contamination. Building on filled land (i.e., valleys filled with flattened mountain debris) carries a high risk of unpredictable subsidence or structural collapse.
Satiating the hunger for concrete in infrastructure requires a two-pronged approach: mitigating concrete’s high environmental impact and addressing its inherent physical vulnerabilities. Traditional cement in concrete may be replaced by other cement-like materials such as fly ash, slag, rice husk ash, volcanic ash, and pulverized crustacean shells (e.g., blue swimmer crabs and scallops abundant in the Philippines). Research shows that self-healing concrete may be fabricated with the correct mix of the aforementioned natural waste products. Instead of focusing our attention on the mountains, our attention should be drawn toward the utilization of the massive waste we have generated in our environment. Let our hunger be for environmental sustainability.
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Dr. Joel Tiu Maquiling may be reached at jmaquiling@ateneo.edu
