Application of polymer coating on the sidewalk of the bridge

Elastic polyurethane pavement coating

Polyurethane coating

Application of polyurethane coatings

                                                                  Real Project                                                                           

Project Data

• G. Lozovaya, Kharkiv region

• Object: road bridge over the railway.

• Base: concrete footpath.

 

 Polyurethane concrete floors

A task

According to the project, it is necessary to install a waterproofing, wear-resistant, anti-slip, ultraviolet-resistant, elastic coating on the pedestrian sidewalk of the automobile bridge.

Solution

Design decision, apply a two-in-one system,  waterproofing + thick-layer, anti-slip, elastic coating, SikaCor Elastomastic TF.

SikaCor Elastomastic TF is a two component, chemically curing epoxy polyurethane resin used to create hard elastic coatings on steel and concrete.

• Thick coatings on steel and concrete, in areas with heavy traffic. 

• Sika Elastomastic TF is officially certified and approved for use as bridge pavement according to the German “ZTV-RHD-ST” standard. 

• Also approved as a protective coating for ballast troughs of railway bridges.

Benefits of applying polyurethane coating

• Good adhesion to steel and concrete.

• Good mechanical strength.

• Very high impact strength.

• Good chemical resistance.

• Hard elastic, not brittle.

                                                         

                           Polyurethane coating application                         

Stages of work on the application of polyurethane coating               

Background

• Running ahead. Outside, hot August 2019. Not the best time to work with polymer floors in nature, but there is no way out, you have to do it. Bridge commissioning schedule, until September 1.

• We go to the site and evaluate the project. We draw up a work schedule, get acquainted with our sidewalk and colleagues who work on the bridge in parallel.

• Builders are working on the next strip, preparing for pouring a monolithic concrete slab, and below, under the bridge, a team is restoring reinforced concrete columns and the ceiling, shotcrete, reinforce, paint.

• In this situation, we understand that the work will be exciting and we get extreme conditions for applying a polymer coating on the bridge.

Here's what you have to face during such work

• Across the bridge, in one lane, 50 cm from our workplace, our pedestrian crossing, the movement of vehicles is carried out, at different speeds according to the incomprehensible desire of the drivers, although speed limit signs are present.

• This I lead to the fact that everyone knows that when performing work on applying polymer coatings to a concrete base, it is necessary to dedust the surface as much as possible. 

• How to create such conditions on the bridge, with wind load, the movement of cars and help from neighbors, is not entirely clear and difficult. 

• Fortunately, we had a “duika” that constantly worked, removing and cleaning our surface. 

• They worked without an industrial vacuum cleaner.

 

Cleaning concrete floors

Ambient temperature

• Unfortunately, the weather was unbelievably hot. Not a cloud, not a shadow. It didn't rain and thanks for that.

• There is no opportunity to work at night, there are no conditions. Therefore, we tried to apply the polymer coating before lunch, although it was already hot in the morning and the concrete base was heating up. Under such conditions, the polyurethane resin sets faster, begins to thicken and must be worked quickly.

• Banks with polyurethane resin were covered so that the material would not heat up, kept in the shade.

• When they say that follow the technology, you must apply at a certain temperature, this is of course correct. But it's cool to talk about it in an air-conditioned office. Try it, create such conditions on the object, in the field.

• We were advised to apply the polymer coating after 17.00. Like, ahead of the night, it will be cool and the material will polymerize smoothly, there will be fewer bubbles.

• However, for us it was not acceptable.

• The concrete got so hot all day long that it was not very correct to apply the polymer on a hot base.

• Well, three hours later it was getting dark. How to create a quality seamless polyurethane coating in the dark is also not clear. 

• And then the cows go home, with a great desire to walk on a fresh expensive polyurethane coating.

• All in all it was fun and exciting!

 

Pavement preparation before polymer coating 

Foundation preparation

Preparing a concrete base is a very crucial moment in the installation of polymer floors.

The quality of the preparation will determine how long your polyurethane coating lasts and does not peel off.

First of all, a visual inspection of the concrete pavement is carried out, for the presence of shells, potholes and cracks.

If they are found, it is necessary to repair cracks in concrete.

Book foundation requirements

Concrete base, requirements	The base must be strong (compressive strength of concrete is not less than 25 MPa, tensile strength is not less than 1.5 MPa).
Base surface, requirements	It must be clean, even, dry, free from oil stains, loose particles, old coatings and cement laitance.
Moisture content of concrete, requirements	no more than 4%.
Foundation preparation, requirements	Loose particles, old coatings and cement laitance must be removed mechanically, e.g. shot blasting or milling.

What we faced before preparing the base of the sidewalk

• I would like a better concrete base device: good, smooth and vetted concrete, where the filler (crushed stone) is evenly distributed in the concrete, so that it does not stick out from above. To do this, you need to work a little vibrorail.

• It may be necessary to consider the option when the main preparation of concrete (sandblasting, grinding or milling) will be carried out before the installation of enclosing structures (fence, railings, mortgages, posts, etc.).

• Then after installation, once again update the base, run through the concrete, open the pores, but in general, it will be easier and faster.

• When you start grinding concrete, around the pillars, you have to go out onto the roadway along which cars move, a safety issue.

• Work with a manual machine, in an uncomfortable position (sitting, cancer). Hello back and joints.

• You can’t crawl under the fence with a grinder, a small distance.

• Therefore, it is difficult, long and inconvenient to prepare the sidewalk along the perimeter with high quality.

 

Mechanical preparation of concrete pavement

In our case, the building envelope has already been installed.

• The preparation was carried out with manual grinders, using a diamond grinding and cutting disc for concrete. 

• We did not have large grinding equipment.

• Removed cement laitance.

• Leveled concrete base.

 

 

• Repaired small bumps, sinks.

• Carried out sealing racks of the chipper, but that's another story.

• We pasted metal parts and the border with masking tape.

 

Concrete repair 

Ground application

• Dedusted the base, as it turned out.

• Correctly, by proportion, the two-component epoxy primer Sikafloor 161 was mixed.

Sikafloor-161  is an economical, two part, low viscosity epoxy resin.

Application

• It is used as a primer for concrete substrates, cement-sand and epoxy screeds.

• For slightly to medium absorbent substrates.

• Primer for coatings Sikafloor-263 SL (RU) and Sikafloor-264 (RU) economical flooring systems in warehouses, parking lots, car services, commercial and public buildings and structures; in enterprises: trade and public catering; food, chemical, engineering, pharmaceutical, alcohol and non-alcoholic industries, in sports, medical and educational institutions, offices, clean rooms.

• Binder for leveling mortars and screeds.

• Intermediate coat under Sikafloor-263 SL (RU) and Sikafloor-264 (RU).

Features / Benefits

• Low viscosity.

• Good penetrating power.

• High adhesion.

• Ease of application.

• Short dwell time before overcoating.

• Multifunctionality of application.

 

Soil application and sand filling

Application method

• Applied with a brush. 

• Carefully distributing the soil over the base, with a consumption of 0.5 kg / m / sq. 

• Paying attention to uneven areas and around mortgages, followed by backfilling of fine sand, fraction 0.40-0.7 mm, with a flow rate of 1 kg / m / sq., as they say in that sheet.

• But in fact, the consumption of sand and soil can vary.

• It all depends on the density of concrete, how it will pull the soil into itself.

• For example, there are areas with a thick layer of concrete milk, where the soil goes away, as if into dry ground. And there are areas where everything is fine, as in the book 0.3-0.5 kg / m / sq.

• When filling sand, you need to pay attention so that there are no wet spots left, so you go through these places again.

• Also during backfilling, this is without wind, sand flies from the sidewalk onto the roadway or down from the bridge. 

• Therefore, lay the sand consumption for backfilling more than indicated in the project.

• The next day, they picked up whatever sand that didn't set with the epoxy, blew it off, and got a sandpaper-effect base, a rough yellow finish.

 

 Pavement primer

Application of a carrier base polyurethane coating

We cleaned the base with brushes, spatulas, everything that flakes off, blew off the sand.

Preparation and application of the composition

• When mixing two components, sand 0.4-0.7 mm is added to the resin, as for backfilling the soil.

• We get a polymer mixture, a homogeneous mass, gray.

• Spread it over the surface with a notched trowel.

• The height of the spatula teeth was previously prepared for a certain size in order to obtain a layer of 3 mm.

• We planned to use a squeegee, with height adjustment and material consumption control, but since the sidewalk is 1.2 m wide, it is not convenient for her to work in such areas.

• Spatula, more mobile and more convenient, especially around posts and support mortgages.

• Three of us worked. One person applied and distributed the polymer mass over the base. The second rolled with a spiked roller, releasing air, eliminating bubbles and traces from the spatula. The third one, and it was me, covered it with sand and was in charge of mixing.

• A very exciting event, almost like in a laboratory. Everything through the scales, the exact ratio of proportions to the screams, come on ... .. faster.

 

 Polyurethane epoxy self-leveling floors

 A separate note for the use of personal protective equipment

• Headdress.

• Orange vest.

• Rubber gloves.

• Respirator - helps a lot, from not the most useful smell of the polymer and allergies to ragweed.

 

Bridge defense

• We controlled the consumption of the material, everything turned out clearly, 2.4 kg / m / sq., but the sand, as with the primer, took more.

• The next day, they removed the sand that had not set and got a rough, anti-slip coating.

 

 Elastic polyurethane pavement coating

Application of protective UV varnish Sikafloor 3570 

Sikafloor-3570 is a 2-component, hard-elastic, solvent-borne, colored, matt polyurethane top coat.

Application

• For making matt finish coats on Sikafloor glossy epoxy or polyurethane coatings.

• For making matt finish coats on Sikafloor systems sprinkled with quartz sand.

• For matt finishes on Sikafloor screeds.

• For matt finishes on concrete and cementitious screeds.

• Normal and medium mechanical and chemical stress for polymer floors.

Features / Benefits

• Rigid-elastic material.

• Good mechanical and chemical resistance.

• High color stability.

• Ease of application.

 Preparation and application of the composition

• We cleaned the base with brushes, spatulas, everything that flakes off, blew off the sand.

• Two components were mixed, a liquid homogeneous mass of gray color was obtained.

• The first layer was applied with a brush. 

• Since the surface is rough, it is good to fill and distribute the varnish with a maklovitsa. 

• At the same time rolling with a roller.

• The second layer is already easier, rolled cleanly with a roller. The easiest part of the job.

• Consumption received standard 0.8 kg/m/sq.

 

Resin flooring for pavement

The end of the project or "Tinted lips"

• Tape and trash removal.

• We paid attention to the high-quality interface of the polymer coating with the curb.

• Sanded and cleaned the curb.

• Dispose of used containers.

• We hope that this coating will serve the local residents for a long time and with high quality.

 

"Perform the installation of polyurethane coatings on the sidewalk, efficiently"