Dermasfalt - Technical Information

 

Introduction

Dermasfalt is a unique polymeric thin-layer paving product discovered after years of extensive research on polymeric binding composites. The final formula and the production process were perfected in 1982 and the first road application was done in 1984 in Brazil. Dermax holds the maufacturing exclusive rights for the product and its derivatives as well.

In view of the revolutionary properties of the product, Dermasfalt has been mostly used on highly technical paving jobs in Brazil, such as covering long orthotropic steel bridge decks where other paving materials failed or did not provide durable results. Average pavement thickness is as low as 5 mm and the product is installed in one step directly on the steel bridge deck with no need of binders or pre-treatments. The product is an ideal solution for reducing dead weight on old bridges or long decks. Average weight per square foot is 3.2 LB.

Over the years, on every new job accomplished, Dermasfalt has proven to be a unique paving product, exceeding expectances in terms of safety, durability and cost-benefit.

Dermasfalt may be briefly described as a material obtained by high temperature chemical processing using metal polymers generated in a maltene / asphaltene matrix, promoting agents, fillers and additives, resulting in a high temperature Hot-Melt type mastic.

Dermasfalt is a solid material at room temperature. Melting point is near 220C (450F).

Dermasfalt is applied as a seamless pavement in a layer that averages 8 mm (3/8") thickness directly on top of the substract with no need of additional binding materials or primers, as oppose to regular asphalt pavements that average 50 mm (2") thickness.

Dermasfalt adheres to any type of surface and allows a high anti-skid degree surface providing extremely safe pavements. It may also be applied at room temperature when used in the form of pre-molded sheets, which adhere at contact.

Dermasfalt pavements such as those installed on Metal Bridges do have a proven life expectance of over 30 years according with Brazilian Road Departments Engineers.

Types of Dermasfalt

 

Since Dermasfalt first came out in 1982 in Brazil, it has been employed in several specific areas, mainly in the paving industry, which required product adjustments to better fit each specific area requirements.

There are currently four types of Dermasfalt being produced in Brazil. Each type fits specific purposes from paving steel decks to crack sealing applications on old asphalt or concrete roads:

Type of Dermasfalt

Application

Dermasfalt GC

Maintenance Free Steel Bridge Decks paving

Dermasfalt ST/GC

Economic Anti Skid paving on Asphalt or Concrete surfaces

Dermasfalt WP

Thin layer paving on various surfaces

Dermasfalt CS

Crack sealing of asphalt or concrete pavements

 

Dermasfalt GC

 

Dermasfalt GC has been the most employed type up to date, used for special paving works whenever an area needs recovering or a new pavement is required.

This is the product recommended as a Maintenance Free pavement and has a life expectance of over 30 years on the road. The product incorporates mineral aggregate, which allows its application using slightly modified conventional paving equipment.

Additional top aggregate may be used to achieve specific pavement textures that will ensure traffic safety and may vary from one area to another.

Once the pavement is expected to last for a long period of time, special top aggregate is recommended to ensure the pavement will not lose its anti skid properties over the years.

 

Dermasfalt ST/GC

 

This is a recently developed version of the original Dermasfalt GC (above described) that has been engineered to compete against regular asphalt pavements in terms of cost and yet provide a thin layer (optionally anti skid) pavement that will last a minimum of 10 years.

This version of the product does not incorporate all technological advances of the original Dermasfalt GC however it provides a much lower manufacturing cost.

The product incorporates around 65%w of a mineral aggregate mix that may be added at the job site saving freight cost. The product without addition of the aggregate mix is called Dermasfalt ST.

  

Dermasfalt WP

 

This version of Dermasfalt consists basically of the same composition of the original GC product above without the incorporation of coarse mineral aggregate. It may be applied by airless spray or using a blade spreader. It may also be used as a protective casting layer on containers, pipelines, metal structures and platforms or whenever a thin layer of 1 to 3 mm (1/24 to 1/8") is required. It also allows use of top aggregate for improved anti-skid finishing.

 

Dermasfalt CS

Dermasfalt CS version is mostly used in crack sealing jobs and expansion joints on asphalt or concrete pavements.

This version also does not contain coarse aggregate and may be pumped into large cracks or expansion joints (at high temperature) providing deep sealing and locking lose pavement pieces.

Dermasfalt CS has been approved as a sealing material for traffic flow control sensors by the city of São Paulo in Brazil in 1996.

 

Main uses of Dermasfalt

 

In view of Dermasfalts extremely high aging resistance and durability as oppose to modified or polymeric asphalt, the product has been most applied on jobs that require improved safety and durability.

One of the main advantages of using Dermasfalt is the extremely low dead weight obtained once the final pavement averages a low 8 mm thickness (usually 5 to 12 mm), which allows its use for reducing dead weight in old bridges.

Dermasfalt has also provided amazing results when used to recover highly cracked pavements either on asphalt or concrete surfaces.

Below are listed the main uses for each specific type of Dermasfalt.

 

Steel Bridge Decks Paving

 

Ever since fist applied to a metal bridge deck early in 1984, Dermasfalt has proven advantages to other special asphalt or polymeric compositions providing a very safe and durable pavement.

It is applied as a thin layer pavement that may vary from 5 to 12 mm thick directly onto the steel bridge deck and does not require pre-treatments, primers or binding coatings, except for cleaning when the steel plate surface presents lose rust.

Dermasfalt allows a tremendous dead weight reduction on bridges because it weighs only 16 kg/m2 (3.52 LB/SQ.FOOT) as oppose to a 2 inches thick pavement that weighs 75 kg/m2 (16.5 LB/SQ.FOOT). All that is translated as safety.

Dermasfalt has been used as a maintenance free pavement for steel bridge decks in Brazil with remarkable results. It is not affected by intense traffic, wearing, weather or oxidation, maintaining its original properties over the years. It forms a seamless pavement that is actually alive, working on the surface of the steel deck allowing daily expansion and contraction without cracking or loosing adherence to the steel deck.. It has a tremendous resistance to constant traction and retaintion of the top aggregate.

These bridges have proven that Dermasfalt provides a seamless pavement that resists constant vibration, expansion and contraction without requiring expansion joints.

Picture 1 Bridge located at Av. dos Autonomistas in Osasco/SP - Brazil. Main steel metal deck has been paved with 3/8" of Dermasfalt and Sintered Aluminum Bauxite as the top aggregate in 1992. No maintenance required up to date.

Dermasfalt GC is the most usual type applied to metal bridge decks. It averages a low 8 mm thickness and may receive top aggregate for increased safety.

 

Old Pavement Recovering

 

Dermasfalt is also used for recovering old damaged pavements specially when cracks, superficial deterioration or bleeding are present.

Dermasfalt is applied directly onto the old affected pavement in liquid form, penetrating cracks, sealing and locking lose pieces, providing a new long lasting impervious pavement. Top aggregate may also be used for additional safety.

Applied to pavements that present foundation problems, Dermasfalt provides a new pavement that will resist constant abnormal flexion and vibration without cracking. Water penetration will not be allowed through the new pavement that will be stabilized.

 

Crack Sealing

 

Dermasfalt CS has been specially developed for crack sealing applications and may be applied using a special machine that melts the product and pumps it through a heat traced hose that allows fast and convenient sealing (seen on the right).

The product is melted at 220 C (450F) and may be injected into large cracks, deep penetrating, sealing and locking lose pieces. It may also be used for sealing expansion joints in bridges and asphalt or concrete pavements.

Picture 2 - Dermasfalt WP seen on top, installed on old cracked asphalt pavement at Rodovia dos Bandeirantes in the State of Sao Paulo - Brazil.

      

Anti-Skid Pavements

  

Dermasfalt is a permanent solution to slippery pavements caused either by aggregate wearing, bleeding, oil spillage, erroneous asphalt calculation or characteristic shape of the road.

For that purpose, the new Dermasfalt pavement should be covered by high hardness abrasive minerals such as sintered aluminum bauxite or Silicon Carbide, providing a high surface friction coefficient.

Dermasfalt GC may be used either on low friction coefficient pavements or dangerous areas where vehicles present difficulties slowing down for any reason such as dangerous intersections, curves or down grade areas.

The same type of pavement is also used on industrial areas that are constantly wet and require a chemical resistant pavement. Examples are milk or citric products industries.

Dermasfalt is also highly resistant to friction caused by tires or heavy equipment and may be used to repair or recover damaged industrial areas where large trucks, forklifts or equipment call for a long lasting solution. Shipping and receiving areas are a good example where trucks and forklifts maneuver all day long.

Picture 3- Finished pavement surface close-up picture taken from the Florianopolis Bridge - Anti-Skid Dermasfalt GC incorporating Sintered Aluminum Bauxite chips on top.

 

Paving on Stabilized Soil

 

Dermasfalt provided magnificent results when used to pave stabilized soil areas.

Some test installations done in certain industrial roads in Brazil have proven that the product resists intense heavy traffic when applied on stabilized soil. The pavement averages 10 to 12 mm thick and incorporates 8 mm diameter granite chip top aggregate.

 

Light or Colored Pavement

 

Dermasfalt may be used for chip-sealing roads and allows use of many different types of top aggregate including white dolomite or architectural stone chips.

The long-term adherence power of Dermasfalt ensures permanent retention of the aggregate over the years.

  

Dermasfalt Application Methods

  

Dermasfalt is a solid material at room temperature, which is melted at high temperature by using appropriate equipment and applied to the pavement in liquid form.

There are basically two application methods. The first method utilizes a modified asphalt spreader and the second uses a special airless machine. The first method may be used to apply any type of Dermasfalt and the spray machine is only able to apply the WP and CS types.

  

Dermasfalt GC Application Method Description

 

In this process, the Dermasfalt GC pellets are melted in a special reactor (seen on figure 6), which has a direct fired combustion chamber at the bottom that is capable of raising the temperature inside of the tank where the product is kept at around 250C (500 F).

The process of melting one batch of Dermasfalt (around 8,000 LB) takes about 3 to 4 hours depending on weather conditions.

The melting equipment is usually assembled on a truck that also pulls the application spreader on the rear end. Some units have four reactors on the same truck, which allows a large production (around 1,200 m2 or 12,000 Ft2) with a single whole discharge through the spreader.

The Application Spreader seen on picture 7 is a conventional towable asphalt spreader with light modifications to contain the fluid Dermasfalt in its hopper and a improved thickness adjustment device that allows a more accurate control of the amount of product being applied.

The application unit moves at a 40 meters per minute (120 feet/minute) average speed and puts down a layer of 8 mm of the product that may receive a top aggregate treatment (about 1 to 6 kg/m2 or 0.2 to 1.2 LB per square foot).

The aggregate is applied by another spreader that controls the output rate according with the thickness and finishing desired.

The pavement thus obtained is rolled to ensure aggregate retention and achieve the final superficial texture. The area is ready for the traffic after cooling, usually 20 minutes later.

Picture 4- Dermasflat GC being installed at the Florianopolis Bridge in 1994 - DER-SC.

   

Dermasfalt WP Application Method Description

 

Just as the GC type , Dermasfalt WP is supplied in pellets that require fusion in the reactor unit described before. It may also be applied by using the same type of spreader developed for the GC type.

A special airless spray machine has been developed to apply Dermasfalt WP, with advantages.

In this process, the melted product is transferred from the reactor unit into the spray machine that holds the material at an even temperature. The spray machine has a computerized pumping system that circulates the liquid Dermasfalt WP through a high temperature heat traced spray bar that has spray nozzles.     

The machine has an electronic device that controls the product output rate automatically according with the speed and ensures that the required pavement thickness is obtained.

An aggregate spreader may be connected to the rear of the spray machine.

Pavements made with Dermasfalt WP do require use of top aggregate. The same equipment has a manual hose used for crack sealing jobs

Picture 5- Dermasfalt WP high pressure and temperature spray machine working on asphalt pavement - Rodovia dos Bandeirantes km 134 Sao Paulo/SP -Brazil.

    

Dermasfalt CS Application Method Description

 

Dermasfalt CS is only used for crack sealing and expansion joints works that do not require large volume of product as oppose to the previous methods.

The ideal equipment for crack sealing jobs is the spray machine because it is able to melt and apply the product without any other additional equipment.

As seen on figure 3 the liquid Dermasfalt CS is pumped through a heat traced application hose that has a metal wand at the end that also allows use of a spray nozzle for thin coating jobs.

Liquid Dermasfalt CS is injected inside of cracks penetrating much deeper than polymer and rubber added asphalt products.

For small jobs a portable electric or propane-fired reactor may be used. A simple metal tool that is filled with melted product is used to fill the cracks manually.

     

Dermasfalt - Products Specification

   

PROPERTIES

Dermasfalt GC

Dermasfalt ST/GC

Dermasfalt WP

Dermasfalt CS

Physical State at 25 C

Solid

Solid

Solid

Solid

Specific Gravity at 25 C

1.95 g/ml

2.15 g/ml

1.65 g/ml

1.60 g/ml

Specific Gravity at 220 C

1.85 g/ml

2.10 g/ml

1.50 g/ml

1.45 g/ml

Softening Point

130 C

120 C

125 C

110 C

Color

Black

Black

Black

Black

Odor

Inodorous

Inodorous

Inodorous

Inodorous

Melting Point

200 C

210 C

190 C

180 C

Specific Heat

0,75 cal/gC

0,75 cal/gC

0.65 cal/gC

0.65 cal/gC

Penetration at 25 C (150g/0.1 / 20")

20

25

22

25

Flash Point (Cleveland open cup)

245 C

240 C

245 C

210 C

Thermo Molecular Degrading Point

285 C

260 C

280 C

270 C

Thermal Conductivity

Low

Low

Low

Low

Elongation

NA

NA

85 % a 120 C

110 % a 120 C

Oxidation Resistance

High*

High*

High*

High*

Boiling Weight Loss (48 hours)

0.05 %

0.25 %

0.1%

0.1%

Chemical Resistance to Inorganic Compounds

High

High

High

High

Traction Resistance (Tangent for a 8 mm film at 25C)

1750kg/cm2

1750kg/cm2

1750 kg/cm2

1400 kg/cm2

* Oxidation Resistance determined by Thin Film Method. DNER ME 01-72

Picture 6- Vitoria / Vila Velha Bridge view. Dermasfalt WP installed in 1989 - Usiminas Mecanica / Norberto Odebrecht.

Picture 7- Vitoria Bridge Metal Decks View - Five metal decks covered with 3/8 inch thick Dermasfalt WP using granite chips as top aggregate. Dermasfalt provides a monolitic pavement, which does not require expansion joints and resists daily heavy traffic, expansion and contraction.

Main Works in Brazil

 

 

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