More About Hot In-Place Recycling

In situ recycling systems for asphalt pavements have been developed over many years. In the 
1950's and 1960’s heating the pavement was used to reduce the energy required by cold 
planning machines that shaved off pavement material. This lead to specialized heater-
scarifying systems.

It is generally acknowledged that a deteriorated asphalt surface should be recycled to a 
minimum depth of 40 mm (1 ½ in.). If the asphalt surface is not being finished with a new 
virgin overlay, 50 mm (2 in) should be considered the minimum recycling depth.

ENVIRO-PAVE INC. has developed a 100% Hot In-Place Recycling (HIR) System that 
creates complete thermal bonding at the joints and between the layers in the asphalt, 
resulting in a sound, continuous and seamless asphalt pavement section and surface.
Patents have been applied for.

Core samples taken from the ENVIRO-PAVER®  HIR recycled asphalt pavements always 
show 100% bonding between the layers and at the joints. The quality of the finished 
recycled surface is equal to a completely new mix laid by a standard paving machine.


  Development of ENVIRO-PAVER® 100% Hot In-Place Recycling 
                                                  HIR Systems 

Asphalt pavement, whose basic structure is sound but has deteriorated and suffers from 
damage such as wheel track rutting, ravelling (loss of aggregates in the pavement surface), 
loss of coarse granular material, transverse and longitudinal cracks, lack of flexibility, 
deterioration through oxidation and the loss of skid resistance, is well suited to the 
HIR system.

ENVIRO PAVE INC.  the manufacturer of the ENVIRO-PAVER® 100% HIR equipment in 
North America, have designed, manufactured and developed a line of asphalt recycling 
machinery, that can heat and rework the asphalt to a recycling depth of 50 mm (2 in) 
or more. The existing asphalt pavement is recycled using liquid and aggregate additives, 
all controlled and monitored by on board computers.

Whilst other HIR systems have been developed and are available, they have shortcomings 
that have been eliminated by the ENVIRO-PAVER
® 100% HIR system as outlined in the 
tables on pages that follow.


            Benefits and Advantages of the ENVIRO-PAVER®  100% 
Hot-In-Place Recycling versus Other Methods


Single Stage 100% Hot-In-Place Recycling Process

Multiple Stage/Infrared Hot-In-Place Processes

Conventional Roto-Milling/



Traffic disruption


Traffic can pass close and around

processing equipment

Multiple stage process involves a long equipment train, operating at slow speeds.

Conventional mills and pavers require a large fleet of dump trucks to maintain constant material flow.

Machine noise

Low level: less engine horse power is required to rework the asphalt surface compared to Roto-milling

Higher level:

due to longer equipment train and multiple milling units

Noise levels are very high when Roto-milling. This creates a problem, especially in residential areas.

Mobilization of Equipment

Towable units do not require float. Fast hook up/set up.

Multiple towable units require additional tractors.

Heavy units require specialty transportation equipment.

Minimum Equipment Requirements

1 Recycling Unit

3 Pre-Heaters

2 asphalt rollers

Generally, 2 to 4 Pre-Heater/milling units; one paving machine;

2 asphalt rollers

One milling machine; one paving machine; fleet of dump trucks. Off site asphalt

2 asphalt rollers



Degradation of aggregate and wear on cutter teeth

The mill's carbide teeth are working with soft pre-heated asphalt. Mill teeth generally last for weeks. The larger aggregate in the asphalt is dislodged (by rakes) but not destroyed. Rake cutters generally last for months.

Multiple stage milling increases risk of aggregate degradation. Higher rate of wear on milling teeth due to lower heat penetration levels.

The carbide teeth used to mill the pavement under ambient conditions break down the larger aggregate. High rate of wear. Water is added to cool the teeth and help the cutting action. Carbide cutting teeth only last a few hours.

Loose aggregate

There is no loose aggregate. This is a major advantage when working on airport runways. One loose stone on the runway could cause catastrophic results in today’s jet engines.

There is no loose aggregate.

Large quantities of loose aggregates and dust at airports. Clean up is required immediately but not always done properly.

Transition joint

The joint between recycled material and existing pavement is fused together due to thermal bonding. This is especially important for highway pavement and airport runways. There is no unfinished surface. After rolling, traffic can drive on the surface immediately.

Lay-down asphalt temperatures are lower therefore less thermal bonding at joints.

Poor bonding. Tack coat used to bond hot asphalt (transported from off site asphalt plant) to the cold old pavement. Cracks appear at cold joints in the pavement at an early age.

Excessive emissions

Emissions are minimal. Asphalt is not recycled in a plant.

Fleet of dump trucks not required

Higher emissions due to longer equipment train and repeated heating/milling of asphalt pavement. Fleet of dump trucks not required

Excessive emissions. Asphalt recycling plants produce large volumes of blue smoke while heating recyclable material. Large fleet of dump trucks required

Manhole covers and iron castings

Scarification system is designed to automatically ride over this type of obstruction, providing full scarification.

Milling and scarification systems must be mechanically raised for obstructions, pavements either side of obstruction not recycled.

The milling drum must be raised otherwise serious damage will occur. Further milling is required by a small, manoeuvrable mill. Raised utility structures are left standing above grade.

Leaching into water table

There is no stockpiled material (RAP) therefore there are no chemicals to leach into the water table.

There is no stockpiled material (RAP) therefore there are no chemicals to leach into the water table.

Chemicals from reclaimed (milled RAP) leach into the water table as rain falls on the stockpile.

Productivity (50 mm/2 in depth)

Complete single-stage-single-pass process at speeds up to 9.0 m (30 ft) per minute.

Generally lower due to infrared heating and multiple stage process.

Comparable productivity but at much higher cost.

Road Profile (Crown/slope control)

Milled to uniform grade, provides uniform asphalt thickness and compaction.

Variable cutting depths result in possible irregular asphalt uniformity and compaction.

Milled to uniform grade, provides uniform asphalt thickness and compaction


The following equipment is recommended for most efficient operations and best profit structure:


Pre-Heating Units HM-16

3 Required


ENVIRO PAVER®  R1015 Hot-In-Place Recycler

1 Required


Dual Steel Drum Vibratory Roller, 8 – 12 tons

1 Required

4. Pneumatic Rubber Tired Roller, 10 –20 tons

1 Required


Rejuvenator Agent (Fluid) Supply Truck

1 Required


Diesel Fuel, Hydraulic and Engine Oil Supply Truck

1 Required


Mechanics Service Truck with Torches, Welder, Tools and more frequently required spare parts like bolts, filters, seals, etc.

1 Required


2.5 – 4.0 m3 Front End Loader for Sand

1 Required

Liquid Propane for Pre-Heaters and Recycling are ordered on regular 
basis from a local liquid propane supplier on as required basis



The following crews are required to efficiently operate the equipment train at lowest labour 

General Duties


1 – Foreman


1 – Mechanic (also operates the Front End Loader)


2 – Traffic control officers (Flag persons)

3 Pre-Heater


3 – Operators

ENVIRO PAVER®  R1015 Hot-In-Place Recycler


1 – Operator


1 – Screed operator


3 – General labour
1 Ground person
2 Rake men


1 – Dual Steel Drum Vibratory Roller Operator


1 – Pneumatic Rubber Tired Roller Operator

Thus a crew of 14 people are required to operate a 100% HIR system

Job Descriptions

Oversees all aspects of operations.
Is responsible for machine coordination including recording of data 
for records; amount of rejuvenator agent used, start station numbers 
where samples for testing are taken, air void materials, time cards, 
ordering propane and diesel fuel.  Needs to understand work to be 
executed, starting and finishing, traffic control items; cones, 
delineators, barricades signs.

ENVIRO PAVER®  R1015 100% Hot-In-Place Recycler
Needs to have general knowledge of hydraulic and electrical circuits and 
systems. Must be able to relay information on machine performance to 
mechanic and Foreman. 
Responsible for machine operation in general.
Responsible for daily maintenance; grease, engine and hydraulic oil levels.

Pre-Heater Operator
Needs to have general knowledge of hydraulic and electrical circuits and 
systems and air/gas systems. 
Must be able to relay information to the 
other Pre-Heater and Recycler operator, mechanic and Foreman.
Responsible for daily maintenance; grease, engine and hydraulic oil levels.
Keeps proper distance and speed.
Marks line for operator Recycler to follow.
Monitors heat system, checks tires, inspects gas and hydraulic system 
and hoses for leaks.
Monitors sand and aggregate spreading.
Informs Recycler operator or screed operator of upcoming obstacles.

Screed operator
Needs general knowledge of all Recycling machine functions.
Must understand and know specifications and job limits.
Responsible for Rejuvenator system, Aggregate Bin, Auger/Divider, Grade 
Controls and Screed operations.
Responsible for finished asphalt pavement product.
Directs rake men and roller operators.

Ground Person
Assists screed operator.
Responsible for Rakes, Mills, Pug Mill and Heater Box operations.
Helps other labourers when necessary.

Rake man
Manipulates asphalt mat where required.
Responsible for levelling and matching of joints.
Operates Front End Loader for sand when necessary.
Other duties as directed by Screed Operator or Foreman.

Roller operator – Dual Steel Drum Vibratory Roller
Breakdown operation – initial compaction of asphalt pavement.
Responsible to keep water on board machine.
Other duties as directed by Screed Operator or Foreman.

Roller operator – Pneumatic Rubber Tired Roller
Final compaction.
Other duties as directed by Screed Operator or Foreman.

Responsible for necessary maintenance and repairs of all equipment.
Assists with operations as directed by Foreman.

Traffic Control Officers
Sets up and moves/relocates traffic control devises.
Controls traffic flow where and when required.


                               Contractor’s Operations – Benefits and Profits

Contractors Benefits

The use of ENVIRO-PAVE®  100% HIR equipment gives a contractor a 
great number of operating benefits when compared to other HIR systems 
on the market. All the operating benefits translate into a highly profitable 
operation. The benefits are:


Faster operating speed than competing equipment under identical conditions. - ENVIRO-PAVE 100% HIR equipment has by far the most efficient pavement heating system; it combines proprietary radiant/hot air heating as opposed to infrared heating only used by others. No scorching of pavement surface by ENVIRO-PAVE 100% HIR equipment.


Single-stage, single-pass (SSSP)  process as opposed to multi-stage processes. Saves time, increases productivity and reduces traffic disruptions.


Single switch control All equipment features an on-board computer. Equipment can be stopped or started with one switch without having to reset operating parameters. Saves time, increases productivity and improves quality control.


Variable width scarification, milling and paving – The Pre-Heater and Recycling Unit are capable of on-the-go variable width scarification milling and paving. Permits more complex operations.


Rides over and around obstructions – others equipment's mills have to be raised mechanically to clear obstructions, leaving old asphalt. The resulting untreated areas must be recycled using manual methods.


Milling to uniform grade – provides uniform thickness and compaction of asphalt pavement, extends useful life and improves ride quality of pavement.


Uniform pavement surface – The geometric layout of the heater recycling unit results in averaging out all imperfections in the pavement surface.


High degree of quality control – The on-board computer control/monitoring system permits control and monitoring of all variables to a very high degree.


Low maintenance cost – The efficient heating of the pavement reduces wear to mill teeth and rake carbide cutters.


Low operating cost – The efficient heating of the pavement increases operating speeds and reduces operating costs.


Minimal emissions – The efficient heating of pavement prevents overheating of pavement surface and keeps emissions at a minimum. No scorching of pavement surface by ENVIRO-PAVE 100% HIR equipment.


Allows modification of existing pavement mix – The equipment design permits use of light and heavy rejuvenator fluid and Polymer liquids. The heating system permits the addition of moist or dry aggregates to change aggregate and air voids content.

Contractors profits

Even with greatly overestimated overhead costs and 100% financing for equipment 
with a payback period of three years, the contractor has considerable profit margins 
in operating the ENVIRO-PAVE 100% HIR equipment. The break-even point in
operations requires equipment utilization for 130 days during the first three years 
while the equipment loans are paid off (a loan interest rate of 18% per annum is 
used). During the fourth year after the loans have been retired, the break-even point 
occurs between 50 and 60 days of operations.


Independent third party information on 
Hot In-Place Recycling

In order to obtain independent third party information on Hot In-Place Recycling, we 
would recommend you visiting the website of the Asphalt Recycling and 
Reclaiming Association (ARRA)
at which is an 
independent trade association of members of the Asphalt Recycling Industry 
incorporated under the non-profit corporation law of the State of California.


Definition of Hot In-Place Recycling

From the homepage of ARRA i.e., click on “ARRA Industry 
and then on 
"Hot In-Place Recycling"  for a definition of Hot In-Place 


Hot In-Place Recycling - Frequently asked Questions

From the homepage of ARRA i.e., click on “FAQ” and then 
on “Hot In-Place Recycling” for Hot In-Place Recycling Frequently Asked Questions.


We believe the visit to the above sections in the ARRA website will be very helpful 
and educational for individuals who want to carefully study the method of 
Hot-in-Place Recycling.


Other useful websites


Asphalt Institute (The)
Canadian Strategic Highway Research Program
MIT Center for Transportation & Logistics
National Center for Asphalt Technology (The)
National Highway Institute (NHI)
Nottingham Centre for Pavement Engineering (The)
Pavement Research Center at Berkeley
Pavement Research Center at Michigan State
Recycled Materials Resource Center (The)
Rutgers Asphalt Pavement Laboratory
Texas Transportation Institute
Transportation Research Board
Turner-Fairbank Highway Research Center
Université de Montreal
Université Laval
US DOT National Transportation Library
Virginia Tech Transportation Institute
Western Research Institute


Canada's National Climate Change Process
Canadian Environment Industry Association
Environment Canada
Moving on Sustainable Transportation (MOST)
US Environmental Protection Agency (US EPA)

Government & Financial Institutions

Canadian International Development Agency
Centre for Surface Transportation Technology
European Conference of Ministers of Transport
European Union On-Line
Institute for Research in Construction
International Monetary Fund (IMF)
Transport Canada
United Nations
US Bureau of Transportation Statistics
US Federal Highway Administration
World Bank


Aggregates & Roadbuilding
Asphalt Contractor, The
Better Roads
Civil Engineering Magazine
Construction Europe
Demolition & Recycling International
Engineering News Record
ITS International
Journal of Transportation Engineering (ASCE)
Public Works Magazine
Recycling Today
Roads & Bridges
TecnoVial Mundial
World Highways

Road Safety

AAA Foundation for Traffic Safety
American Traffic Safety Services Organization
Canadian Automobile Association
Canadian Council of Motor Transport Admin.
National Highway Traffic Safety Administrators
Transport Canada Road Safety

Transportation Associations

American Highway Users Alliance
American Public Works Association
Asphalt Emulsion Manufacturers Association
Asphalt Institute (The)
Asphalt Pavement Association
Asphalt Recycling & Reclaiming Association
Association of Asphalt Paving Technologists
Australian Asphalt Pavement Association
BC Roadbuilders and Heavy Construction Assoc.
Canadian Automobile Association
Canadian Technical Asphalt Association (The)
Canadian Transportation Research Forum
Centre for Sustainable Transportation (The)
European Asphalt Pavement Association
Foundation for Pavement Preservation
International Road Federation
International Slurry Surfacing Association (ISSA)
International Society for Asphalt Pavements
National Aggregates Association (NAA)
National Asphalt Pavement Association
New Zealand Pavement & Bitumen Contractors' Association
Ontario Hot Mix Producers Association
Road Information Program (The)
Southern African Bitumen Association (SABITA)
Transportation Association of Canada
World Road Association (PIARC)