Jakarta, INTI – As the backbone of modern cities, cement plays a crucial role in urban temperature and sustainability. Conventional cement is often criticized for raising surrounding temperatures. This happens because conventional cement tends to absorb heat and transfer it into buildings, making interiors hotter and harder to cool.
If this pattern continues, the energy demand for cooling could trigger carbon emissions up to three times higher than current levels. An innovation in building materials is needed to create cooler and more environmentally friendly cities.
To address this issue, Chinese scientist Fengyin Du and his team at Southeast University discovered a way for cement to stop being a “city heater” and instead help cool urban areas.
Eco-Friendly Solution from the Construction Industry
This innovative cement is known for its ability to reflect sunlight, thereby reducing the temperature of buildings and surrounding environments. The natural cooling effect is believed to decrease dependence on air conditioning (AC), which has long been one of the largest energy consumers in urban areas.
The production process of this cement is also environmentally friendly. It is manufactured at lower temperatures, reducing emissions by approximately 25% compared to Portland cement. This is a significant breakthrough, considering the cement industry is one of the largest contributors to global emissions.
Moreover, the cement is strong. Compression tests show strength exceeding 100 MPa, surpassing many conventional mixes. It is scratch-resistant, unaffected by freeze-thaw cycles, and durable in corrosive liquids. After one year of exposure to outdoor weather and UV light, its reflective capability is almost unchanged.
Designed with Special Colors and Formulations
Du and his team designed the cement with a special formula, utilizing natural crystals on the cement surface, particularly ettringite minerals.
The formation of ettringite crystals and gel is made from relatively common raw materials: limestone, gypsum, alumina, and silica. After forming into granules, heating, and grinding, the mixture is then reacted with water.
To enhance light reflection, molds and air bubbles are used to create microcavitation on the cement surface. From this, crystals grow and form patterns that help scatter light.
Additionally, Du introduced attractive variations. By adding phosphor pigments, they created yellow, green, and red cement without reducing reflectivity. Even with color, the cement can still reflect 90% of sunlight.
This means architects and city planners have more design options to create bright and aesthetic urban spaces.
Proven Effective in Reducing Urban Heat
This innovative cement was tested on the roof of Purdue University. The results were remarkable:
- 5.4°C cooler than surrounding air temperature
- 26°C cooler than ordinary Portland cement
This means the cement no longer acts as a “heat trap.” Even at night, the material continues to release heat into the sky. Cooling occurs both day and night.
“This cement works like a mirror and a radiator. It reflects sunlight and releases heat into the sky, keeping buildings cool without electricity,” explained Du.
Additionally, the cement has micro-pores and aluminum-rich gel. This combination allows the surface to function doubly as a reflector and a radiator.
Life cycle studies show that one ton of this cement can reduce up to 2,867 kg of CO2 over 70 years of use. Even hot cities like Niamey and Mumbai could reach carbon-neutral targets faster with the use of this material.
Conclusion
The arrival of eco-friendly cement technology is a breath of fresh air for the construction sector. Besides helping reduce urban heat and carbon emissions, this innovation also assists architects and city planners in creating bright and aesthetic cities. It is only a matter of time before this innovation can be implemented in Indonesia.
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