26 27 April 2019 M12 // Concrete & Precast Solutions S emi-precast is the core of our business, a hybrid between traditional in-situ concrete and traditional precast. Although sometimes seen as an under- developed off-site manufactured solution, the semi-precast design philosophy brings enormous improvement to cost and construction efficiency. The semi-precast approach aims to deliver solutions fully compliant with the operational design requirement. The ideal configuration is not adapted to prefabrication. Whereas we will identify cost and time saving opportunities during the design development phase, we can adapt to the most precise configurations for operational accuracy. In principle, any structure imagined in in-situ concrete can be delivered in semi-precast. Approving Authority confidence is engendered by implementing designs which cannot be disproved by failure to comply in any respect with the specified codes and standards, whether national, international or customer specific. We place wet concrete against hard concrete, the way it’s always been done. The difference is that some of the concrete was manufactured elsewhere and the location of joints and interfaces are unconventional. Regardless, the integrity of joints and interfaces remains uncompromised and verified by design. The Benefit of Prefabrication We complete the difficult parts of construction in our factory, under ideal conditions and under quality supervision. Features including pipe- fittings, nibs, corbels, launder-channels, formwork attachments and stability-footings (among others) are eliminated from the site works. Products are delivered to site on a just-in-time basis then taken from the delivery vehicle to their service position in one simple operation without fuss or temporary propping. Small crews achieve amazing productivity by following simple steps and using well designed components and delivery systems. Tolerance Precast concrete units can weight in excess of 20 tonnes. Under normal manufacturing tolerances, it could be very difficult to ensure the precision required to maintain accurate alignment and watertight fit. The in-situ joint provides a transition between elements which ensures a complete and perfect fit (in it’s liquid phase) and a completely ‘relaxed’ structure at introduction to service. We don’t stress pieces into alignment or position. The design assumptions are fully realised. Waterproofing Integrity At every interface a scabbled surface is prepared. In addition, a smooth dense slot is preserved for the application of hydrophilic strip. This provides ongoing self-healing capability in service. We use only one hydrophilic product; Denso Hydrotite. Hydrotite is resilient to inflation prior to encasement in concrete. It can compress against the surrounding concrete with a pressure of up to 3MPa on contact with water and has been approved by Tokyo Underground for design life up to 100 years. It is also DWI and Materials in Contact approved for potable water FLI Carlow are the premier total service provider of engineered structural solutions to the Water, Energy, Storm Attenuation and Bespoke markets. Our capacity to design not just the precast units, but the structure into which they integrate and the manufacturing tools used to make them has kept us at the forefront of innovation in our industry. Leaders in Semi-Precast Concrete Design for Manufacture & Assembly applications in the UK. That’s 100 years to first significant maintenance of the structure – no compromise. Sealants used at the mechanical interfaces of traditional precast concrete tanking structures rarely have a service life in excess of 20 years. These features are particularly relevant to storm attenuation, storage, treatment and basement applications, Structural Continuity Although relatively short, the in-situ joint is used to enable two-way bending of the structure. This capacity is not available using any other precast approach. Reinforcement lap lengths are designed on a bond-stress basis to ensure full capacity in smaller spaces. Even the interface between the in-situ concrete stitch and the precast unit is designed for the same crack-width control as the body of the structure. This ensures that all elements of the structure provide the minimum standard of waterproofing integrity and full compliance with concrete structures design standards. By bending in both orthogonal directions, structures are thinner, lighter, economical, require less transport, less craneage and have a lower carbon cost. Carbon Our particular concrete mix design delivers very high early strength for efficient production, typically, 25 Newtons at 16 hours. This ensures maximum safety and maximum value by extracting products daily. We use very high concentrations of GGBS (66%) which in conjunction with other energy and carbon saving measures has reduced our carbon cost from 278kg/tonne of concrete manufactured to 182kg/tonne. To ensure the high early strengths despite the use of GGBS we use thermal activation. By adding mixing water at up to 80°C the disadvantage of slow strength development of GGBS is eliminated. Sulphate Resistance High levels of GGBS when used in conjunction with limestone cement and limestone powders (for self-compacting behaviour) produce a design chemical resistance class DC4. That’s sulphate resistant concrete at no additional cost. Value The precast unit is delivered to site with projecting reinforcement oſten from five of it’s six faces. All components are 3D modelled prior to manufacture and assembled in model-space prior to fabrication. This eliminates the risk of clashing reinforcement and disruption to programme. Projecting reinforcement leaves very few bars to be placed on site. Typically the vertical in-situ stitches represent 30% of the volume of the perimeter and internal walls. While precast concrete products are relatively expensive (although value-adding), the concrete used in the joints is locally sourced readymix at approximately £40 per tonne. The formwork required is very light. Shuttering ply facing with vertical stiffeners is locked against the structure using steel braces and MKK cone anchors. The advantage in this low cost approach is that the formwork is torsionally flexible adapting easily to the surfaces on which they bear. Smooth transitions and tight interfaces are achieved. Through-ties are completely eliminated. These are oſten a problematic feature of conventional in-situ works. Length of Joints The number and length of joints in our solutions are oſten questioned. Our industry sees joints as the most problematic elements of waterproof concrete construction – more joints, more risk. The rebuttal is that it’s not the number of joints you fear, but the distance between them. Traditional construction methods utilise joints at 6m – 10m centres. Thermal and drying shrinkage accumulate over these lengths and are concentrated at a single interface. The precast unit has long completed its shrinkage when placed on site therefore the shrinkage to be addressed is that occurring over only 500mm. In addition, each interface has the benefit of a factory prepared scabble, reinforcement continuity designed to the higher standards for crack-width control and a self-healing strip at each end. The semi-precast interface is subject to only between 5% and 10% of the movement occurring at conventional joint. As a result, it is significantly better preforming than conventional concrete in this respect. Rate of Construction Semi-precast structures are typically completed in 60% to 40% of the time taken to deliver conventional structures. This is where the value lies, both in terms of reduced preliminaries and hugely increased productivity. During the conventionally difficult construction of vertical and suspended works, equivalent productivity per person on site is ten times greater. For more information, call us on +44 (0) 1279 423303 or email us at enquiries@flicarlow.com. You can find us on the web at the below address. www.flicarlow.com Bryn Colwyd RGF and DAF Structures Snowdonia Semi-precast structures are typically completed in 60% to 40% of the time taken to deliver conventional structures. This is where the value lies, both in terms of reduced preliminaries and hugely increased productivity.
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26 27April 2019 M12
// Concrete & Precast Solutions
Semi-precast is the core of our business, ahybrid between traditional in-situconcrete and traditional precast.
Although sometimes seen as an under-developed off-site manufactured solution, thesemi-precast design philosophy bringsenormous improvement to cost andconstruction efficiency.
The semi-precast approach aims to deliversolutions fully compliant with the operationaldesign requirement. The ideal configuration isnot adapted to prefabrication. Whereas we willidentify cost and time saving opportunities duringthe design development phase, we can adapt tothe most precise configurations for operationalaccuracy. In principle, any structure imagined inin-situ concrete can be delivered in semi-precast.Approving Authority confidence is engenderedby implementing designs which cannot bedisproved by failure to comply in any respect withthe specified codes and standards, whethernational, international or customer specific. Weplace wet concrete against hard concrete, theway it’s always been done. The difference is thatsome of the concrete was manufacturedelsewhere and the location of joints andinterfaces are unconventional. Regardless, theintegrity of joints and interfaces remainsuncompromised and verified by design.
The Benefit of PrefabricationWe complete the difficult parts of construction inour factory, under ideal conditions and underquality supervision. Features including pipe-fittings, nibs, corbels, launder-channels, formworkattachments and stability-footings (among others)are eliminated from the site works. Products aredelivered to site on a just-in-time basis thentaken from the delivery vehicle to their service
position in one simple operation without fuss ortemporary propping. Small crews achieveamazing productivity by following simple stepsand using well designed components anddelivery systems.
TolerancePrecast concrete units can weight in excess of20 tonnes. Under normal manufacturingtolerances, it could be very difficult to ensure theprecision required to maintain accurate alignmentand watertight fit. The in-situ joint provides atransition between elements which ensures acomplete and perfect fit (in it’s liquid phase) and acompletely ‘relaxed’ structure at introduction toservice. We don’t stress pieces into alignment orposition. The design assumptions are fullyrealised.
Waterproofing IntegrityAt every interface a scabbled surface is prepared.In addition, a smooth dense slot is preserved forthe application of hydrophilic strip. This providesongoing self-healing capability in service. Weuse only one hydrophilic product; DensoHydrotite. Hydrotite is resilient to inflation prior toencasement in concrete. It can compressagainst the surrounding concrete with a pressureof up to 3MPa on contact with water and hasbeen approved by Tokyo Underground for designlife up to 100 years. It is also DWI and Materialsin Contact approved for potable water
FLI Carlow are the premier total service provider of engineered structural solutions to the Water, Energy, Storm Attenuation and Bespokemarkets. Our capacity to design not just the precast units, but the structure into which they integrate and the manufacturing tools used tomake them has kept us at the forefront of innovation in our industry.
Leaders in Semi-Precast ConcreteDesign for Manufacture & Assembly
applications in the UK. That’s 100 years to firstsignificant maintenance of the structure – nocompromise. Sealants used at the mechanicalinterfaces of traditional precast concrete tankingstructures rarely have a service life in excess of20 years. These features are particularly relevantto storm attenuation, storage, treatment andbasement applications,
Structural ContinuityAlthough relatively short, the in-situ joint is usedto enable two-way bending of the structure. Thiscapacity is not available using any other precastapproach. Reinforcement lap lengths aredesigned on a bond-stress basis to ensure fullcapacity in smaller spaces. Even the interfacebetween the in-situ concrete stitch and theprecast unit is designed for the same crack-widthcontrol as the body of the structure. Thisensures that all elements of the structure providethe minimum standard of waterproofing integrityand full compliance with concrete structuresdesign standards.
By bending in both orthogonal directions,structures are thinner, lighter, economical, requireless transport, less craneage and have a lowercarbon cost.
CarbonOur particular concrete mix design delivers veryhigh early strength for efficient production,typically, 25 Newtons at 16 hours. This ensuresmaximum safety and maximum value byextracting products daily. We use very highconcentrations of GGBS (66%) which inconjunction with other energy and carbon savingmeasures has reduced our carbon cost from278kg/tonne of concrete manufactured to182kg/tonne. To ensure the high early strengths
despite the use of GGBS we use thermalactivation. By adding mixing water at up to 80°Cthe disadvantage of slow strength developmentof GGBS is eliminated.
Sulphate ResistanceHigh levels of GGBS when used in conjunctionwith limestone cement and limestone powders(for self-compacting behaviour) produce a designchemical resistance class DC4. That’s sulphateresistant concrete at no additional cost.
ValueThe precast unit is delivered to site withprojecting reinforcement often from five of it’s sixfaces. All components are 3D modelled prior tomanufacture and assembled in model-spaceprior to fabrication. This eliminates the risk ofclashing reinforcement and disruption toprogramme. Projecting reinforcement leavesvery few bars to be placed on site.
Typically the vertical in-situ stitches represent30% of the volume of the perimeter and internalwalls. While precast concrete products arerelatively expensive (although value-adding), theconcrete used in the joints is locally sourcedreadymix at approximately £40 per tonne.
The formwork required is very light. Shutteringply facing with vertical stiffeners is locked againstthe structure using steel braces and MKK coneanchors. The advantage in this low costapproach is that the formwork is torsionallyflexible adapting easily to the surfaces on whichthey bear. Smooth transitions and tightinterfaces are achieved. Through-ties arecompletely eliminated. These are often aproblematic feature of conventional in-situ works.
Length of JointsThe number and length of joints in our solutionsare often questioned. Our industry sees joints asthe most problematic elements of waterproofconcrete construction – more joints, more risk.The rebuttal is that it’s not the number of jointsyou fear, but the distance between them.Traditional construction methods utilise joints at6m – 10m centres. Thermal and dryingshrinkage accumulate over these lengths and areconcentrated at a single interface. The precastunit has long completed its shrinkage whenplaced on site therefore the shrinkage to beaddressed is that occurring over only 500mm. Inaddition, each interface has the benefit of afactory prepared scabble, reinforcementcontinuity designed to the higher standards forcrack-width control and a self-healing strip ateach end. The semi-precast interface is subjectto only between 5% and 10% of the movementoccurring at conventional joint. As a result, it issignificantly better preforming than conventionalconcrete in this respect.
Rate of ConstructionSemi-precast structures are typically completedin 60% to 40% of the time taken to deliverconventional structures. This is where the valuelies, both in terms of reduced preliminaries andhugely increased productivity. During theconventionally difficult construction of verticaland suspended works, equivalent productivity perperson on site is ten times greater.
For more information, call us on +44 (0) 1279423303 or email us at [email protected] can find us on the web at the below address.
www.flicarlow.com
Bryn Colwyd RGF and DAFStructures Snowdonia
Semi-precast structures aretypically completed in 60%
to 40% of the time taken to deliver conventional
structures. This is where the value lies, both in terms
of reduced preliminaries and hugely increased
productivity.
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