Choosing the right pipeline, now and for the future
Concrete pipelines have been in use for over a century and, argues Stuart Crisp, business development director of the Concrete Pipeline Systems Association, they can help build a sustainable future
Pipelines can be considered structurally as rigid or flexible systems. Concrete is a rigid system and the pipe is a structural component, so the strength and structure of a concrete pipeline comes mainly from the pipe itself.
A flexible pipe acts only as a conduit; construction of the supporting structure takes place on site, where the system's structural integrity is largely reliant on the design and quality of the installation. Thus concrete is less vulnerable than flexible pipes to inadequate bedding design and installation.
There are several bedding design options for concrete pipes, and unlike flexible systems, a full granular surround is not usually required. This can result in a number of advantages:
Many long-term supply contracts are secured over several years, and the relative stability of concrete prices can be a benefit, particularly when compared with plastics pipes, which can be affected by surges in oil prices.
Concrete pipes have a proven service life exceeding 100 years. They are strong, robust and resistant to damage from impact, abrasion, sulphates, rodent attack, deformation, heat, fire and high-pressure jetting, so are not dependant on scientific extrapolation to predict future performance. And as concrete gets stronger with age, it may be less likely than other materials to experience progressive age-related defects.
A wide choice of standard sizes and cross-sectional shapes, along with the ability to manufacture bespoke solutions or make adjustments on site, provides enormous design flexibility. Products are available for conventional cut-and-cover techniques or trenchless jacking pipe solutions to minimise traffic disruption.
Special shaped units are ideal for constrained areas where buried services must be avoided, and where there are limitations to pipe gradient or minimal cover depth.
Concrete products can also be readily customised in the factory or in-situ, for example with cut-outs or additional components, while maintaining structural integrity.
Such modifications include junctions and bends, side-entry manholes and access chambers, plus a range of built-in hydraulic features such as weir walls, flow regulators and silt traps. This adaptability makes concrete systems the practical choice for drainage, sewerage, attenuation and storage applications.
Ten years ago, a life-cycle study conducted by Dutch consultant Intron, and critically reviewed to ISO 14040 by BRE, concluded that concrete pipes can be regarded as similar to clay, and are more environmentally sound than PVC, HDPE and PP sewer systems.
Recently, the embodied carbon in concrete and other pipe materials was updated following a study by the Concrete Pipeline Systems Association (CPSA). Using current methodologies and conversion factors, this included a comprehensive audit of the manufacture of concrete pipes and other pipe materials at CPSA members' factories.
It provided strong evidence that concrete compares favourably with other materials and highlighted the importance of benchmarking using recognised methodologies, of accurate data and the need for a consistent and clear definition of the boundary conditions. It also showed how alternative installation designs can make a significant difference to the environmental impact, and the importance of backing-up any claims with a full third-party accredited review by technical experts.
The study also highlighted deficiencies in carbon databases used extensively by the industry. It showed that the embodied carbon equivalent of concrete is up to 30-40% lower than industry databases and that the embodied carbon equivalent of plastic pipes can be up to around 50% higher than currently indicated.
Concrete drainage components are manufactured to a complete and consistent set of stringent European and British standards, ensuring that products are made to the highest requirements and are rigorously tested throughout the manufacturing process. BSI regularly assesses quality systems at all factories.
Advances in technology and increasingly demanding standards have led to consistent, high-performance of products. Concrete pipes are designed with flexible joints so they can tolerate ground movements, while modern durable, integrally-cast seals are available for strong, watertight joints.
Manhole systems are now available with watertight, precast bases, high-performance seals and thicker walls. This results in significant construction time saved on site, removes the problem of water ingress with potential overloading of sewers and treatment works, and means that a concrete bedding surround is no longer required to install the unit, saving even more time and money.