Laying concrete on old concrete

Although concrete is a strong and adaptable building material, even well-laid concrete may eventually show signs of wear. Older concrete surfaces can appear ugly and lose some of their functionality due to cracks, surface damage, and general wear and tear. Many choose to pour new concrete on top of the old surface rather than removing and replacing it. This method can cut expenses, save time, and lessen the mess that comes with demolition.

To ensure a solid and long-lasting bond between the new and old layers, however, pouring concrete over existing concrete calls for meticulous planning and attention to detail. The state of the existing concrete and the preparations made for it will have a major impact on how well this process goes. It takes careful surface preparation to get a long-lasting finish that stands the test of time.

It’s critical to evaluate the current concrete for any significant structural problems before beginning. Before applying a fresh layer, any serious cracks or instability in the old concrete must be fixed. The surface needs to be properly cleaned to get rid of any loose materials, dirt, and debris after any necessary repairs are completed. The key to ensuring proper adhesion of the new concrete is a clean, stable base.

The adhesion between the old and new concrete can be greatly enhanced by using a bonding agent in addition to cleaning. This procedure lessens the possibility of the new layer separating over time and helps to form a strong bond. The right bonding agent should be chosen for your particular project out of the many that are available, as they are all made for different kinds of concrete and environmental factors.

Lastly, it’s critical to mix, pour, and cure the new concrete according to best practices. Concrete that has been mixed and dried properly will have the highest strength and durability, guaranteeing the longevity of your new surface for many years. Resurfacing an old concrete surface with new concrete can be accomplished by carefully planning and carrying out each step, which will rejuvenate the surface and improve functionality.

Steps Description
Clean the surface Remove all dirt, debris, and loose concrete from the old surface.
Apply bonding agent Use a bonding agent to ensure the new concrete adheres to the old surface.
Mix new concrete Prepare the new concrete mix according to the manufacturer"s instructions.
Pour the new concrete Spread the new concrete evenly over the old surface.
Finish and cure Finish the surface as desired and allow it to cure properly.

Laying concrete on old concrete

When the previous layer of concrete is destroyed, fresh concrete must be poured. There is a chance of destruction for the following reasons:

  • impact on the concrete coating of water;
  • insufficient compaction of the mixture, which leads to the formation of cracks;
  • failure to properly care for the mixture during the hardening process;
  • the poured solution was not covered with a material that prevents moisture evaporation;
  • expansion joints were not performed when laying the mixture;
  • impact on the poured surface of a load exceeding the bearing capacity of the material;
  • improper preparation of concrete mortar.

To apply fresh concrete to an existing surface in a qualitative manner, you must follow the following technological order when applying the solution:

  • prepare the necessary materials and tools;
  • remove the top layer of concrete coating;
  • clean the surface from dust and dirt;
  • apply a primer impregnation;
  • carry out a floor screed;
  • lay a reinforcing mesh, which will strengthen the entire structure;
  • concrete is poured and compacted.

It is important to pour concrete continuously if you want high-quality results.

Preparation of tools and materials

The following supplies and equipment need to be ready before fresh concrete is placed over an existing concrete base:

  • building level;
  • water hose;
  • screwdriver;
  • beacons;
  • rule;
  • self-tapping screws;
  • nails;
  • trowel;
  • cement;
  • water;
  • sand;
  • waterproofing material;
  • gravel;
  • steel mesh;
  • plasticizer;
  • primer.

Removing the top part of the concrete

The old surface wears out and needs to be ground. Grinding makes it possible to remove covering materials from the previous base. Breaking up the solution is necessary to remove the upper part if grinding does not help and there are many defects on the surface.

Epoxy mastic is used to fill in cracks, potholes, and expansion and shrinkage joints. Rough grinding of the solution involves applying compounds that strengthen the materials to the surface. After that, polishing is done to smooth out the surface.

If the right preparations are done, laying new concrete over old concrete can be a useful technique to restore and revitalize existing surfaces. The life of your concrete can be prolonged by creating a strong, long-lasting overlay by carefully cleaning the previous surface, using a bonding agent, and making sure the layer is thick enough and cures properly. Without requiring total removal and replacement, this method provides an economical and effective way to enhance the look and usability of patios, driveways, and other concrete structures.

Cleaning from dirt and dust

It is worthwhile to remove all dust and debris from the old mortar before adding crushed stone cement mortar. Specifically designed steel wire brushes are used for cleaning. Grinding mechanisms are used when it’s necessary to remove dust and dirt from large areas. If large deformations or cavities are seen when working with old concrete, these surfaces can be cut down to the level of the reinforcement. The old surface is impregnated with a cement milk solution after the reinforcement has been cleared of rust and adhered particles. Following the completion of the impregnation, they start to pour a new mortar that is of a higher grade than the prior one.

Applying the primer

Following cleaning, they start impregnating the base with a deep primer. In order to improve adhesion and prevent the walls from crumbling and cracking, priming is required. Use the primer in a humid room to prevent the growth of mildew and mold. It is crucial to choose the primer based on the type of base in order to get the desired outcome. Only after the primer composition has completely dried can you begin subsequent work.

Floor screed

The floor is cleaned and primed before applying the floor screed. Installing beacons that are precisely level-matched is the first step in fortifying the base. Simultaneously, a distance is noted that must not be greater than twenty centimeters beyond the length of the utilized rule. The number of workers who will perform the floor reinforcement determines how long the rule will last. Place beacons on the gypsum adhesive cakes and smooth the screed all the way around.

Cement and sand mortar can be laid after the adhesive has dried. Divide the mixture amongst the beacons that were already installed. Next, use a rule pulled in a zigzag pattern to the screed’s edge to remove any excess mortar. The drying time of the cement-sand mortar is longer than that of the floor screed. After a month, the concrete mixture will exhibit its peak strength.

Reinforcement

Although concrete floors are very resilient, they can be reinforced by adding a layer of reinforcing concrete to ensure that this quality lasts for many years. Cleaning and clearing the work surface is the first step in the reinforcement process. After the surface has been cleaned and primed, metal or wooden beacons are installed, and the reinforcing mesh is fastened to them. After installing a mesh and applying a cement-sand mortar to the reinforcing layer, the necessary number of times is repeated. After the reinforcement is finished, the concrete mortar is laid.

Laying concrete

They start laying the mortar after putting in the beacons and strengthening mesh. The mixture needs to be spread uniformly and continuously. Subsequently, a rule is used to level and gather the mortar. After that, the mixture is manually or with vibrators compacted until no more air bubbles form on the surface.

The grade of concrete that is used for mortar installation is determined by the building’s intended use. You should check the passport, which is a warranty card for the ordered grade, if you use ready-made concrete composition, which is delivered straight to the construction site from a mortar and concrete plant or plant. If you are making the mortar yourself, you must follow the ratios of the ingredients in the concrete. You should familiarize yourself with the material costs in accordance with building codes and regulations before making the necessary portion mixture.

It is crucial to keep in mind that the prepared solution’s quality determines the structure’s overall strength, so keeping an eye on the mixture’s grade is worthwhile. In order to accomplish this, test cubes are created using the prepared solution and brought to the lab to be tested and their strength verified. When a new solution is laid on top of an old one, a high-quality monolithic surface should result; this can be accomplished by adhering to all norms and specifications for the production of concrete.

It is recommended to let the solution dry for a full day while maintaining the ideal humidity and temperature in the air. The solution is periodically misted with water to keep it from drying out and cracking in hot weather. The poured surface is covered with a protective material to keep atmospheric precipitation from penetrating it. The final hardening of a cement-sand solution takes one month; only then can it achieve its maximum strength and be used under heavy loads.

Compaction

Air bubbles that form during the laying process must be eliminated in order for the building mixture to reach its maximum strength. Compaction can be done manually or with the aid of deep vibrators, which displace air. Compaction is applied to the entire laid mixture area using a vibrator. When using a vibrator on a freshly laid layer, the tool is submerged so that the prior layer is not reached. The process of compaction is finished. when the building mixture starts to look like cement milk.

Acceleration of the hardening process

Excess water and air are drawn out of the working fluid to hasten the building mixture’s hardening. We refer to this process as vacuuming. It boosts the building mixture’s strength by twenty percent or more and doubles the pace at which it sets.

Vacuuming helps to improve frost resistance, quickens the process of strength growth, and strengthens the bond between freshly laid concrete and reinforcement.

For many projects, laying concrete over existing concrete can be a workable solution, but in order to assure longevity and durability, careful preparation is needed. You can forge a solid bond between the old and new concrete by thoroughly cleaning and preparing the existing surface. This entails clearing out any loose particles, oil, or debris that might erode the connection.

It is imperative to apply a bonding agent to the old concrete in addition to cleaning. This lessens the likelihood of future problems like separation or cracking by improving the new layer’s adhesion. To give the new concrete layer additional strength, you might also need to use reinforcing materials, such as wire mesh or rebar, depending on the particulars of the project.

Make sure to pour the new concrete quickly and effectively. To prevent any uneven spots that might later cause issues, level the surface and smooth it out. For the new concrete to set and harden under ideal conditions and maximize its durability, proper curing is also essential.

In the end, you can increase the longevity and aesthetic appeal of your structure by pouring new concrete over old. You can accomplish an outcome that satisfies your needs and is successful and long-lasting with careful planning and execution. Don’t forget to adhere to best practices and seek professional advice if you have any questions about the procedure.

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Marina Petrova

Candidate of Technical Sciences and teacher of the Faculty of Construction. In my articles, I talk about the latest scientific discoveries and innovations in the field of cement and concrete technologies.

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