What would the characteristics of an ideal new age material for modular building be?
For starters, it would be sustainable in terms of production, in use and when recycled. It would also be lightweight, fireproof or fire resistant, would not produce toxic fumes when heated or in a fire and would be resistant to vermin attack, termites, and fungal or bacterial issues.
Such a material would be high performance in terms of in use characteristics, high strength and flexible enough not to be damaged by dynamic or imposed loads. It would be easy to transport, or able to be flat packed to site and then assembled. It would be able to use CAD CAM capabilities for automation and integration of BIM.
Its properties would be well understood and stable. The material would be easily integrated and assembled with aluminium, steel, glass and concrete or organic products such as timber.
It would not be toxic if it broken up or ground at any time, and it could be applied in areas where water is at a premium, and where low technology is the order of the day.
One such material was cement sheet and products reinforced with asbestos.
As we now know, the fibres – which do not easily break down – are a serious health hazard when released into the air. Asbestos is a silicon-based material, and occurs naturally when quartz or similar products are heated to extreme temperatures.
Glass fibres are not known to pose the same health hazards. Glass fibre reinforced resins have been widely used since the 1960s.
An alkali-resistant fibre was invented by Pilkington Glass which could be used to reinforce lightweight concrete or thin shell concrete products. This fibre-reinforced concrete has many of the benefits of fibreglass reinforced resins, with excellent fireproof qualities and longevity. GFRC, as it is known, has been in use in the construction industry in Australia since before 1980, and has performed very well.
The Grosvenor Place tower above the podium, in Sydney, is clad in a permanent form thin shell GFRC. Many types of stainless steel fixing and pins were used to fix natural granite to this façade. This allowed for a pre-fabricated and modular construction technology for the fast pace of the construction of this tower. The permanent formwork has performed well, using the natural stone as a “rain screen” and the GFRC as the watertight skin, with pressure equalization in vertical joints. Pressure equalisation through neoprene chambers is used in many varieties of aluminium, glass and pre-cast cladding to ensure that there is no major differential pressure in high winds.
Another innovation came through the polished stone integral faced GFRC used on the Parklane and Tattersal’s buildings in Sydney and Piccadilly plaza tower. In this case, the polished stone face was integrated with the thin shell GFRC pre cast elements. These cladding pre-cast elements have been in use for over 25 years. GFRC was polished and finished with Bon Flon third generation paint materials, which provide a finish similar to that applied to aluminium. GFRC must be stabilised to ensure moisture does not get into or through the GFRC composite material.
In the United States, companies such as Stromberg Architectural have a long history of creating traditional architecture and crafted facades by making a plug, or casting a feature such as column detail from an existing historic building. Sandstone columns, facades and window details have been recreated and the finished product can not be differentiated from the original. This has scope for preserving existing buildings or recreating facades which have been damaged. GFRC cladding can be designed to have steel fixings which are earthquake resistant and allow some flexibility in natural disasters such as hurricanes, cyclones and earthquakes.
Another US GFRC manufacturer of building panels is Clark Pacific.
The Broad Contemporary Art Museum, designed by Diller Scofidio + Renfro and currently under construction in Los Angeles, is being enclosed with an innovative GFRC panel skin. A total of 2500 panels, in more than 400 trapezoidal variations, are supported by a network of structural steel framing.
Middle Eastern countries have, for more than 20 years, also created a large number of architecturally individual buildings using GFRC panels and decorative details.
Figure 6 in this GFRC report is a fine example of this. Completed in the early 1984, the Corniche Towers was, at the time, the tallest building in Abu Dhabi.
GFRC has 30 years of use as a cladding material for high rise towers and has performed admirably, and now a new generation of materials may take fibre reinforced products to another level.
Glass Fibre Reinforced Magnesium board is being produced in the US, China and Europe. Whilst this material’s history in widespread use spans only a decade or so, it is notching up some impressive applications. Magnesium board is lightweight, is fireproof and can be used in areas traditionally where gypsum board has been used in the past: for linings for stud walls, linings of lift shafts and ceilings. The quality of current manufacture varies depending on the magnesium formula and the quality of the chemistry which is used to prove this new group of materials. Material properties depend on the amount and type of reinforcement in the board, the exact material formulations and conditions of curing of the board.
In terms of the versatility of a cast material, it is possible to scan a building element such as a window sill, frame, a column or architrave or any traditional stone building element and then to use CAD CAM equipment to cut a facsimile in foam, to be used as a plug for a mould. The mould can then be used to replicate an existing feature. This is extraordinary when considering the repair of buildings and monuments damaged in fire, natural disasters, cyclones storms earthquakes or by terrorist action. It is now much quicker and cheaper to recreate stone details in GFRC composite materials. It is possible to recreate older buildings which may have been lost in wars, fires and tempest.
The possibilities for fibre reinforced products are not confined to the first world. Experiments are being undertaken to use cheaply procured local concretes reinforced with natural organic fibres. Fibre reinforcing includes hemp strands which are stronger than many steels, are resitant to rot and are not affected by vermin such as termites. Animal hair such as horse hair, goat or camel hair when encaptulated is a sturdy building material, and has been in use for centuries as in horsehair and lath plaster in the UK to render timber frames fireproof. Fibre reinforced concretes can use local sands which are not necessarily washed of salt and other impurities. This may provide for inexpensive durable building materials for developing countries.
Thin shell, lightweight precast technology perfected with the use of GFRC makes for ideal materials for the modular construction and the integration of BIM technology, whether in the first word or in developing countries.