In the year 2018, many interesting construction projects will be built in every part of the world. A 50km transit lane consisting of a series of bridges and undersea tunnels will connect Hong-Kong, Zhuhai and Macao, the three major cities on the Pearl River Delta. On the opposite side of the globe, the project of Hudson Yards in Manhattan is turning 28 acres onto a mixed-use development, numbering the total of 16 skyscrapers. With more than 18 million square feet of commercial and residential space, it will be the largest private real estate development in the country’s history. The structural demands of such mega-projects often involves the use of innovative building materials like ‘smart’ concrete and new cement blends.
As the second most essential substance of modern humanity, concrete is still in focus of construction materials and developments. However, despite its vast century-long application, concrete still holds many mysteries. It was only recently discovered that the cement in concrete carbonizes CO2 over time. Studies like this one show that we need more understanding of the materials molecular structure. At Rice University’s Multiscale Materials Laboratory, researchers have discovered an unknown principle of calcium-silicate-hydrate (C-S-H) behaviour. By controlling kinetics of these particles, they are working towards what they call ‘programmable cement’. By shaping its microstructure, they can compel these particles to self-assemble for much greater packing density than conventional cement structures.
The need for increased strength drives concrete designs and technologies today, with grades up to M80 now being used for many high-rise projects. However, due to the escalation in repair and replacement costs, manufactures are paying more attention to durability than strength. There are even indications that durability aside from strength will drive the concrete construction practice in the next decades. In the case of India, where a large number of overpasses and elevated roads that are extending up to 20km in length, the durability of the concrete is under question. Many of structures built within the last few decades have seen premature deterioration. The problem is that extensive repairs and renovations often cost more than the original projects. What we need is a holistic approach to concrete durability that can be achieved with quality raw materials.
Initially developed in Japan as a Quality Assurance measure, now SCC is being used for concrete structures all over the world. It leaves the manufacturing plant in a semi-fluid state and it’s placed in to the formwork without the use of compacting vibrators. Its fluidity makes it easier to settle between the formwork and the reinforcements, while it self-compacts. This property makes it exceptionally useful for structures which are heavily reinforced. The new generation polymer-based admixtures allow for increased fluidity without increasing the water content. Apart from these chemical admixtures, SCC benefits from more fine aggregates and mineral admixtures such as fly ash, ground granulated blast furnace slag (GGBFS), silica fume, rice husk and kaolin. Calcined kaolin manufactured by Alex International for Mining and Refractories (AIMR) is an anhydrous aluminium silicate derived from ultrafine natural kaolin. The calcination process increases the hardness of kaolin particles.
The modern construction industry is showing increased interest in wood as a rapidly renewable, carbon-sequestering material that leaves behind both concrete and steel in the environmental race. Collaboration of London’s DRMM Architects, American Hardwood Export Council and global engineering firm ARUP gave birth to CLT - hardwood cross-laminated timber panel made of North American tulipwood. Premiered in the DRMM’s ‘Endless Stair’ installation on the 2013 London Design Festival, its production is not licensed to Stuttgart-based manufacturer Züblinunder under the name Leno CLT. Unlike conventional CLT which typically consists of softwood spruce, the tulipwood version is stronger, even stronger than concrete by weight.
In a constant battle with gravity and the forces of nature, it seems that builders have depleted conventional physics and its laws. What remains is to tackle the building materials on the particulate level, as many innovative manufacturers are striving to use micro components and raw materials that provide superb strength and durability.