Technology of manufacturing road concrete slabs and their laying

Greetings and welcome to "All about Concrete," your one-stop shop for all things concrete technology. This article delves into the intricate details that guarantee our roads are safe, sustainable, and long-lasting. We explore the fascinating process of manufacturing and laying road concrete slabs.

Producing concrete slabs for roads requires a methodical process and a precise mixture of ingredients. The main components are cement, water, aggregates (like sand and gravel), and occasionally additives to improve particular qualities like workability or strength. To make concrete, these ingredients are combined precisely. Through the use of automated batching plants that precisely measure each component, modern technology ensures consistency and quality.

After mixing, the concrete is put through a rigorous testing procedure to make sure it satisfies specifications for strength and durability. At every stage, from batching to transportation to the construction site, quality control inspections are essential. This careful process ensures that the concrete slabs will endure the demands of frequent traffic and different weather patterns for the duration of their lives.

The methodical process of laying concrete slabs for roads is also followed. The subgrade, or the natural ground beneath the road, is carefully prepared to provide a stable foundation before pouring starts. Compaction of the soil and ensuring appropriate drainage may be part of this preparation to avoid problems later on, such as settling or erosion.

After that, the edges of the area where the concrete will be poured are prepared with forms or molds. These forms aid in containing the concrete during pouring and curing while also defining the slab’s dimensions. To improve the strength and flexibility of the slab, reinforcement—such as steel bars or mesh—may also be added, particularly in regions that are prone to shifting or cracking.

Coordination and timing are essential for the crucial concrete pouring step. The mixture is transported by concrete trucks to the location where it is poured into the forms. Contractors level the concrete and remove any excess with tools like floats and screeds to create a smooth, even surface. This guarantees that the final slab satisfies safety and aesthetic requirements.

To reach its maximum strength and durability, the concrete must cure after pouring. Curing entails keeping the environment sufficiently moist and warm for a predetermined amount of time. This is an important step because it keeps the concrete from cracking and guarantees that it lasts the entire duration of its design without degrading.

In summary, a combination of science, engineering, and real-world application goes into the technology used in the production and installation of road concrete slabs. We can appreciate the time, effort, and accuracy required to build dependable infrastructure that supports our daily lives by comprehending these processes. For additional information about the field of concrete technology, keep an eye on "All about Concrete."

Types of road concrete slabs

Products are classified as highway, airfield, or for the layout of city roads based on their quality and capacity to support loads.

1) Heavy concrete components that have non-stressed reinforcement. Temporary roads and different kinds of access roads are typically constructed from them. Reusing them after disassembly is feasible because they keep all of their features and can be used again.

2) Expensive and permanent highway road surfaces are made from pre-stressed reinforced concrete slabs. This kind of pavement is strong enough to support both heavy machinery and regular traffic loads. withstand H-10 and H-30 loads.

Concrete road structures come in the following shapes: trapezoidal, hexagonal, and rectangular (with one or two offset sides). GOST 219224.0-84 states that concrete grade M400 and above, with a mixture density between 2200 and 2500 kg/m2, is used to make factory-made concrete road slabs.

High-density Portland cement is used as the binder, crushed stone is used as the filler, and steel rods of classes A–I (prestressed) and A–III (non-prestressed) are used as reinforcement. Additionally, they can incorporate plasticizers, unique contaminants, and air-entraining elements. Hot-rolled or thermomechanically hardened steel reinforcing bars are used in the design of prestressed products.

Details regarding the form, kind, size, design load, and class of unstressed or stressed reinforcement must be listed on product labels.

This piece from "All about concrete" delves into the crucial steps involved in producing and installing road concrete slabs. We examine how cutting-edge technologies have transformed these processes, guaranteeing their robustness, economy, and sustainability. This article outlines the essential procedures and innovations that characterize contemporary concrete road construction, from the exact mixing of aggregates and cement to the minute details of slab installation. Knowing these techniques not only makes us appreciate infrastructure development more, but it also emphasizes how vital reliable and efficient road networks are to our day-to-day existence.

What are they for?

The process of constructing reinforced concrete roads is made much simpler by road concrete slabs. Because of their versatility, the canvas can be placed anywhere. With asphalt applied as the top layer, it provides protection from external factors and greatly prolongs its service life.

Reusing reinforced concrete components can result in significant cost savings, as long as the quality attributes are preserved. Both high and low temperatures can be used for operating conditions with concrete slabs. The products produce an aesthetically pleasing type of coating, expedite the installation process, and eliminate the need for intricate foundation preparation.

This kind of concrete structure arrangement has a number of benefits, chief among them being the elimination of the need for soil excavation or other associated work, which in turn reduces the time and expense of laying the roadbed. Road slabs are easy for cars to drive on right after they are laid because they are sturdy and long-lasting.

Design

A reinforced concrete slab is a level product with the proper form and thickness (140–240 mm), composed of concrete and reinforced with either stressed or non-stressed reinforcement. Products are frequently made with metal hinges cast into the structure’s plane rather than sticking out over the road surface to make installation easier.

Concrete, which is used to make road slabs, binds the reinforcement and shields it from environmental, mechanical, and other damaging forces. Use concrete that has a frost resistance of at least 150 cycles and a density of 2.2–2.5 t/m3.

Steel rods of grades AT-4, AT-5, and A-5 are chosen for prestressed frames. A-3, A-3C, A-1 rods, and VR-1 wire with a cross-section of 6–8 millimeters are used to create non-stressed structures. reinforced with reinforcement that is no longer than six meters, depending on the specifications of the product. Following production, they are placed in a warehouse on a sturdy, level base, spaced horizontally between wooden spacers and divided perpendicularly by wooden supports.

Marked in compliance with standards: all attributes are listed, along with length, width, and thickness in centimeters and meters (the slab’s width or length in millimeters is not taken into account; millimeters are typically only important for calculating thickness).

Classification

The form, weight, application, roughness, and load-bearing capacity of slabs vary.

Using shapes to mark:

• P – rectangular (the most commonly used)
• PT – trapezoid
• PSh – hexagonal elements
• PB and PBB – rectangular with 1-2 combined sides
• PShP, PSHD, PPSh, PPSh – different configurations of hexagonal road slabs

If the concrete structure can be reused, it is indicated by the first digit in the marking: 1) for long-term use, and 2) for constructing temporary roads. First and second graders can be used ones. Products of the first grade, with excellent geometry, were laying under construction trailers, on parking lots, etc. Second-grade goods are worn out, chipped, and frequently used with large loads.

Grouping based on technological attributes:

• 1P – unreinforced structures for road paving.
• PD and 2P – without reinforcement, which are chosen for creating sidewalks, pedestrian areas, temporary roads. Cannot withstand heavy traffic loads and severe frosts.
• PDP – the most common reinforced concrete products with universal characteristics, with non-stressed reinforcement, most often used for the arrangement of permanent paths with not very heavy traffic. Can be laid again after dismantling.
• PDN – products with pre-stressed reinforcement, suitable for use in difficult conditions: at a large minus, weight.
• PAG – very strong slabs weighing 4-5 tons, designed for the installation of canvases for large-sized vehicles, tracked vehicles, airfield runways.

Manufacturing technology

The need to strictly adhere to standards and established indicators explains why the production of slabs and their use in construction are subject to strict regulations.

Principal phases of manufacturing:

• Preparation of forms, cleaning all containers from mortar residues, lubrication with a special substance that reduces the adhesion of concrete to the metal of the container and simplifies the removal of the finished product.
• Reinforcement of the structure with metal meshes, which are fixed on special elements for stretching metal rods in the container, allowing to set the distance between the parts of the frame and to make a sufficient layer of concrete coating.
• Preparation of a solution from crushed stone, sand, cement, water. If it is necessary to increase the rigidity of the slab and reduce the consumption of cement, plasticizers are introduced into the solution.
• Uniform distribution of the solution in the container, compaction on a vibrating table.
• Heat treatment – containers are sent to a special chamber in which they are heated and treated with temperature.
• Removal of products by dismantling the structure.
• Checking for the required characteristics, marking.
• Shipment of finished products to the warehouse, stacking is carried out in stacks.

Two methods are used to create road slabs:

1) Aggregate-flow method: multiple product types can be produced simultaneously, moved by a lifting mechanism, and dried in dedicated thermal chambers.

2) Bench: this is for modest output. The product itself is stationary, but the mechanism is moved between the stands during manufacturing.

In order to produce reinforced concrete slabs, the following equipment is needed: lifting mechanisms, a vibration table, a steam chamber, mortar mixers, jacks for tensioning steel rods with prestressed reinforcement, and metal containers.

PDN slabs

The rectangular PDN (prestressed road slab) is the most widely used product in road construction and is a universal brand. It is six meters long, two meters wide, and fourteen to eighteen centimeters thick. Slabs of this type can withstand testing in arid climates, challenging soil, and unfavorable hydrological conditions.

Because the coating’s components have unique clamps on their longitudinal edges, welding is required to assemble the components. When using a crane to lift the slabs, the same clamps are required. Connecting plates at the end of the slab, along with the brackets, form a single reinforcement unit.

Because they were processed using tarpaulin tape, a nylon-bristled brush, and special knurling, slabs with the "up" type working surface have a slightly rougher surface. The corrugation on those with the working side "down" is at least one millimeter deep.

Similar slabs that are designated PDP and have prestressed reinforcement are also very common. Because of their corrugation, they have excellent adhesion to transport wheels, are waterproof, resistant to frost, and able to support loads of up to 30 tons.

About the technology of laying road slabs

Both large-scale road construction projects and private development frequently use reinforced concrete road slabs, whether they are paving garden paths or building paths alongside driveways.

Based on the intended use of the road and the length of time it will be in use, the base is prepared. A prepared and compacted sand cushion is laid without the use of a curbstone for temporary canvases, platforms, and driveways.

These layers are used when laying the foundation for roads intended for permanent use: a dense sand cushion, flooring made of non-woven geotextiles, and crushed stone for drainage. For rainwater to drain, the border stone must be installed with gaps of six centimeters every ten meters.

The top layer of soil in the future canvas’s width should be removed first, down to a depth of 30 centimeters. Subsequently, the drainage layer is introduced into the indentation, compacted, and covered with geotextiles. A layer up to 15 centimeters thick is then added to the sand. The road plate is then installed, and mounting grooves with loops filled in with cement mortar or fine-grained concrete are sealed. PBB or PB with combined on-board protrusions next to the curb stone should be the coating’s extreme elements.

In order to enhance the coating’s quality, either a concrete construction mixture or asphalt rolling is applied as the top layer.

To ensure dependable and effective infrastructure, it is essential to comprehend the technology involved in the production and installation of road concrete slabs. The procedure starts with the materials—cement, aggregates, water, and additives—being carefully chosen. The right amounts of these ingredients are combined to provide the required strength and longevity. Computer-controlled batching plants that guarantee consistency and quality in the concrete mix are a common feature of modern techniques.

After being mixed, the concrete is driven to the construction site in trucks specially designed to keep the concrete from hardening too soon. Concrete is poured onto forms or molds at the site to create slabs with precise dimensions. Depending on what the project requires, these molds can be modified to produce slabs in a variety of sizes and shapes.

Concrete is cured to maximize its strength development and durability after it is poured. In order to avoid cracking and guarantee uniform cement hydration, this process usually entails regulating the temperature and moisture levels. Depending on the environmental factors and the unique needs of the concrete mix, the curing process could take a few days to several weeks.

The concrete slabs are prepared for installation after they have dried. To create a solid foundation for the slabs, the subgrade must be leveled and compacted as part of the site preparation process. In accordance with the design specifications, the slabs are meticulously positioned and aligned, paying special attention to joint spacing and alignment to account for expansion and contraction brought on by variations in temperature and traffic loads.

In order to keep the integrity of the road surface intact and stop water infiltration, sealants are finally applied to the joints separating the slabs. In order to ensure the long-term performance of concrete slabs and minimize the need for repairs, proper installation and maintenance are imperative. Engineers and contractors can help create resilient and sustainable transportation infrastructure by learning about the manufacturing process and best practices for laying concrete slabs.

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