5 Emerging Material Trends in Precast Concrete Technology
The precast concrete industry is continuously innovating; driven by shifts in global markets, increasing customer expectations and pressures from increasing labour costs. Producers are constantly searching for ways to improve productivity, increase quality and maximize their bottom line. Further, heightened environmental awareness and an emphasis on project life-cycles has placed a higher demand on sustainable construction practices especially on reducing waste, greenhouse gas emissions and energy consumption. Given that concrete is the most common constituent construction material and also the most abundant manufactured material in the world, this has had a major propulsive effect on the development of better concrete technologies in general but particularly for the precast market. You might ask why that is, and the answer is simple:
The United States alone holds almost $1.5 trillion in civil infrastructure including transportation, utility and municipal works. These assets are in dire need of repair and rehabilitation, with precast concrete coming to the fore due to the advantages of offering both a high quality product and accelerated construction times.
There have been notable advances in concrete technology in the last 50 years, some of which have become the state-of-practice, but in general the norm has lagged behind the state-of-the art, partially due to the length of time that it takes to conduct research in the industry. However, the following 5 technologies have most recently emerged and are now gaining popularity:Blended Cements
This technology makes use of industry by-products like fly ash and blast furnace slag, which otherwise would have required land for its disposal. This also consumes less natural lime stone and emits less CO2. Common blends are around 50% Portland cement + 30% slag cement + 20% fly ash, to improve concrete performance. Some jurisdictions allow tax credits for the use of blended cements.High Performance Concrete (HPC)
HPC can be defined as concrete made with appropriate materials (super plasticizer, retarder, fly ash, blast furnace slag and silica fume) combined according to a selected mix design and properly mixed, transported, placed, consolidated, and cured to give excellent performance in some properties of concrete, such as high compressive strength, high density, low permeability and good resistance to chemical and environmental attack. Self-Consolidating-Concrete (SCC) is a subset of HPCs which has brought a revolution to the precast industry. SCC is a highly flowable mix that requires no vibration and is proportioned to eliminate segregation and voids.Corrosion Inhibitors and Crystalline Waterproofing Agents
Steel corrosion in reinforced concrete continues to be a major problem throughout the world; especially in regions where there is a heavy use of de-icing salts on the roads. Corrosion inhibitors can be deployed as an admixture of applied over existing concrete resulting in significantly reduced corrosion activity (typically up to 65%) without adversely affecting the properties of hardened concrete, such as compressive strengths, permeability, etc. This can be useful especially in precast structures where connection hardware is at risk of exposure to chlorides and other corrosive agents. Crystalline waterproofing agents effectively eliminate the permeability of concrete by introducing hydro-reactive micro-crystalline structures within the concrete that when exposed to moisture will seal the capillaries, effectively blocking the migration of water and soluble chlorides. When combined with corrosion inhibitors, waterproofing can prolong life more than double that of normal concrete.
Smog Eating Concrete
Concrete mixed with cement that is treated with titanium oxide and then exposed to ultra-violet (UV) light can produce an accelerated natural oxidation process and decomposes air-borne pollutants to promote better air quality. The reaction prevents bacteria and dirt from accumulating on a surface. It is easily removed with water or rain and keeps concrete clean and white. This technology has potential for barriers in the transportation sector as well as for buildings in smog-prone areas.Pervious Concrete
Pervious concrete is made using large aggregates with little to no fine aggregates. The concrete paste then coats the aggregates and allows water to pass through the concrete slab. Pervious concrete is traditionally used in parking areas, areas with light traffic, residential streets, pedestrian walkways, and greenhouses. Pervious concrete requires very precise mix control and conditions to ensure that the result is acceptable; coupled with the increased use of precast for roads and parking, this opens up the market to new opportunities.