Concrete prefabrication, the right calculation to optimize construction sites

This campaign, via the expression Good Calculation, is based on the 5 advantages of concrete prefabrication, the role of ambassadors of the members of the federation to share the tools made available to them, on the organization of a road show in the regions and the creation of the Préfa Béton Les Trophées competition to promote their successes.

Less carbon-intensive systems in line with the environmental transition

Prefabricated concrete solutions with a low carbon footprint favor saving materials, the use of carbon-free concrete construction systems and the use of agro-sourced materials (plant aggregates, miscanthus, hemp, flax, etc.). They also make it possible to optimize sections and masses, the reduction of which directly contributes to reducing the carbon impact, as does the optimization of concrete formulas and the industrial control of manufacturing processes. Reducing the carbon impact of these solutions is also based on the use of cements with a lower quantity of clinker, more mineral additions to replace clinker and the use of carbon-free binders.

The systems for buildings meet the constraints of RE2020 and its three objectives: excellent thermal performance of the building, better comfort for occupants in summer, low carbon impact:

• by working on the thermal performance of the building envelope,
• by integrating thermal bridge treatment solutions,
• by significantly contributing to guaranteeing the freshness of buildings in the event of high heat, to promote comfort in the summer period, conferring thermal inertia on buildings and thus smoothing out heat peaks within them,
• by typically only contributing around 10 to 15% of the construction carbon indicator in both individual houses and collective housing.

To reduce the carbon impact of each part of buildings, concrete prefabrication offers several levers which can be illustrated by the following examples:

• 15 to 25% reduction - Switch from load-bearing separating walls and partitions to posts/beams (or posts/slabs)
• 55 to 65% reduction - Switch from solid sails to concrete block sails of different strengths depending on the building levels.
• 33% reduction - Switch from solid slab to hollow core slab
• 25% reduction - Switch from solid slab to joist/joist/compression slab

And on the scale of products and the construction system:

• 20% reduction - Increase the strength of concrete and reduce the sections of vertical or horizontal elements. Replacement of C25/30 posts with 110 kg of reinforcement by thinner C50/60 posts with 140 kg of reinforcement.
• 25% off - Switch from traditional masonry blocks to thin-joint glue-laid concrete blocks

Their carbon impact is calculated for a given functional unit over their entire life cycle. Reduced per tonne, the carbon impact of a B40 concrete block mounted with a thin joint is 10,34 kg eq. CO 2 /m 2 wall in functional unit and 57,1 kg eq. CO 2 /ton. That of a 5 cm reinforced pre-slab is 24,0 kg eq. CO 2 /m 2 floor and 187,7 kg eq. CO 2 /ton. That of a straight staircase is 334 kg eq. CO 2 /m height and 183,2 kg eq. CO 2 /ton.

Systems for public works make it possible to prevent, manage and adapt to climatic hazards and thus guarantee the performance of the structure and promote urban resilience. To do this, a whole arsenal of solutions makes it possible to limit and manage the risks of runoff, control pollution, preserve water and contribute to offering a longevity of more than 100 years to hydraulic structures. In a context where the intensification of rainy events requires waterproofing of soils, the use of draining paving stones helps to combat flooding, contributes to the cooling of cities and allows integrated management of the water cycle.

These solutions also support the greening of cities and contribute to the fight against the phenomenon of heat islands in cities, possible when we use reflective and/or clear materials, characterized by high albedos or when construction systems facilitate the evapotranspiration.

For prefabricated concrete products intended for civil engineering, the FIB and CERIB have just designed a Carbon footprint calculator: CIBLE-Génie civil, which allows manufacturers

to evaluate the carbon footprint of these products, based in particular on the composition of the concrete, the energy consumption devoted to manufacturing and data linked to the delivery of products from the factory to the site.

Frugality and optimized resource management

Concrete manufacturers are engaged in a dynamic of circular economy, eco-design and preservation of resources, to reduce the impact of their activity both on resources and overall on the environment. Their solutions are in line with new methods of building design/construction including selective deconstruction. The benefits of precast concrete also extend to the environment, as it reduces GHG emissions due to reduced vehicle movements and local purchases of materials.

Decarbonization takes place in a circular economy context, which results, for example, in the use of recycled concrete aggregates, secondary raw materials, including industrial co-products (biomass ash, paper mill sludge, etc.). .), or materials from re-use (shells, tires, etc.). Fewer materials used actually mean less GHG emissions, pollution and depletion of natural resources.

Manufactured by a local workforce in a logic of short circuits, prefabricated solutions, by promoting recycling and the integration of materials from deconstruction, make it possible to increase the reuse rate and reduce the production of waste in factories. and on site, minimize the quantities of material sent to landfill, shorten supply circuits, and ultimately optimize costs. With cutting precision down to the millimeter, factory prefabrication also reduces the quantity of waste and makes it possible to recover any production scraps.

Prefabricated concrete products use a natural resource available throughout France, limiting the environmental footprint of production, saving energy and transport. They are eco-designed from cold-manufactured products that consume very little energy and water, emit little CO 2 and are 100% recyclable at the end of their life to reduce material waste. Off-site manufacturing also allows for a 20 to 30% reduction in weight thanks to accurate sizing. Factory-controlled processes also offer strength gains and material savings. Performance on all levels and foolproof resistance to various attacks or risks make it possible to extend the lifespan and use of structures, thus reducing their carbon footprint and creating lasting value.

Guarantees and sustainability thanks to NF and FDES certifications

The energy and environmental performances of prefabricated concrete solutions to achieve the sobriety objectives of the structures are confirmed by the LCA, FDES and the configurator of collective FDES Environment IB established by the Concrete Industry.

60% of concrete prefabrication plants in France hold the NF or Qualif-IB mark. 70% of prefabricated concrete products have NF certification. The collective and verified FDES, available in the INIES database, cover the main prefabricated concrete products: 90% of those intended for buildings and the majority of road and sanitation products.

Maintaining the local industrial fabric and economic development of the territories

Concrete prefabrication is a local industry on a human scale, 96% of which is made up of French SMEs and SMIs anchored in local life. It forms a very dense territorial network with 700 production sites spread throughout the territory, manufacturing 100% French products, from the supply of raw materials to production and represents a source of 20.000 non-relocatable jobs in France, ensuring vitality economic of the territories.

Concrete prefabrication favors short loops, thanks to 100% local supply of materials production throughout the value chain as close as possible to the markets, promoting the traceability of materials throughout the production chain.

This 100% local network allows proximity to raw materials: within a radius of approximately 50 km around the site and thus a reduction in nuisance and savings in transport and energy. The proximity of delivery to construction sites: between 30 and 100 km on average for most products makes it possible to limit the flow and transport of materials and to offer local and sustainable supply.

Speed ​​of execution and safety of employees and local residents

Concrete prefabrication offers the guarantee of constant and controlled industrial quality, with proven assembly methods and installation systems, avoiding errors, requiring fewer workers on site, controlled production throughout the value chain and planning of the construction site and the implementation of safety measures, which makes it possible to:

• reduce the construction time by 40%, optimize its design and transport times, facilitate implementation,
• improve the working conditions and safety of employees and reduce risks, in particular by using less noisy mobile cranes,
• ensure safety and limit noise and visual nuisance for local residents during construction sites: less noise, dust, traffic disruption, equipment and materials on site and less waste to store,
• free ourselves from climatic hazards and labor shortages,
• offer the guarantee of constant performance with R&D resources to optimize the design of projects, from the most standard to the most creative,
• offer total control of production and production costs and deadlines and thus the best profitability.

Key figures for the precast concrete industry in France

• 461 companies
• 696 production sites
• €3,3 billion in turnover ex-factory, excluding taxes and transport, including:
  • 63,3% for building
  • 36,7% for public works and civil engineering
• 22 million tons of concrete products by volume
• 19.200 direct jobs
• 100% local network
• 1st employer in the quarrying and construction materials sector.

Concrete prefabrication in Europe

• Estimated consumption of cement in mainland France (source France Ciment): 19.147 thousand tonnes
• Estimated consumption of cement in mainland France for all prefabricated concrete products: 2.680 thousand tonnes, or 14% of overall consumption (source BIBM).

Year 2024: evolution in volume at the end of February

2/3 of prefabricated concrete products intended for buildings

• Building turnover: 166 billion euros of work (source FFB – 2022)
• Turnover expressed in value of prefabricated concrete products intended for buildings: 2,2 billion current euros (FIB source)
• Share of turnover of prefabricated concrete products in construction: 1,50%
• The change in volume of products intended for the building industry is around -20,8%.

1/3 of prefabricated concrete products intended for public works and civil engineering

• Turnover expressed in value of public works: 48 billion current euros (source FNTP – 2022)
• Turnover expressed in value of products intended for public works and civil engineering: 1,1 billion current euros (FIB source)
• Share of turnover of products in the public works and civil engineering sector: 2,50%
• The change in volume of prefabricated concrete products intended for public works at the end of February 2024 is down -6,9%

Illustrative image of the article via Depositphotos.com.