Detector Loop Installation Guidelines & Technical Specifications

PART 1: GENERAL

1.1 SCOPE

A. This work consists of the installation and encapsulation of traffic detector loops in Portland Cement Concrete (PCC) and Asphalt Concrete (AC) pavements. B. The installation shall be performed in accordance with Section [Insert Local Section] of the Standard Specifications, using a high-performance, rapid-setting urethane resin system.

1.2 SUBMITTALS

A. Installation Procedures: Submit detailed protocols for production, placement, and finishing. B. Safety Data: Maintain and follow Manufacturer Safety Data Sheets (SDS) for all chemical components.

PART 2: MATERIALS

2.1 LOOP SEALER (Percol® Elastic Cement AC Grade)

The loop sealer shall be a two-component, 100% solids, rapid-setting urethane resin mixed in equal volumes (1:1).

Physical Properties:

Property	Component A	Component B
Viscosity at 73°F (ASTM D2393)	70 cps	180 cps
Specific Gravity (approx.)	1.10	1.03
Appearance	Brown	Black

 

Mixed & Cured Performance:

Test Method	Property	Requirement
ASTM D-792	Specific Gravity	1.06 to 1.10
ASTM D-2240	Hardness (Durometer D)	45 to 65
ASTM D-412	Tensile Strength	1600 psi (min)
ASTM C-39	Compression Strength	800 psi (min)
ASTM D-412	Elongation at Break	140% (min)
ASTM D-624	Tear Strength	150 (min)
Pot Life	At 73°F	~60 Seconds
Cure Time	At 73°F	~10 Minutes

2.2 SKID-RESISTANT AGGREGATE

A. Sand: Commercial-quality dry blast sand (No. 4 to No. 16 mesh). B. Dryness: Aggregate must be 100% dry at the time of application to ensure proper adhesion to the polymer.

PART 3: EXECUTION

3.1 PREPARATION

Just prior to sealing, the saw-cut trench and adjacent surfaces must be cleaned by oil-free compressed air blasting to remove all dust, moisture, and loose debris.

3.2 PLACEMENT TEMPERATURE

A. Ambient Air: 0°F to 100°F. B. Material: Maintain resin components between 50°F and 85°F immediately prior to installation for optimal flow and reaction.

3.3 MIXING & DISPENSING

A. Mechanical: Resin must be mixed and dispensed using mechanical equipment designed for precise 1:1 metering. Hand mixing is not allowed. B. Calibration: Pump calibration must be verified to within 5% accuracy. Purge a minimum of one gallon of resin to test consistency before beginning the pour.

3.4 INSTALLATION

A. Encapsulation: Apply mixed sealer to the trench to completely fill the void and encapsulate the detector cable, ensuring no air is entrapped. B. Tooling: Tool the surface to provide a uniform, well-consolidated finish. C. Finishing: Broadcast skid-resistant aggregate immediately after tooling and before gelling occurs. D. Traffic: Resume traffic operations once the resin has cured (typically 10 minutes at 73°F).

PART 4: MEASUREMENT & PAYMENT

A. This work will be paid for at the contract unit price per lineal foot for DETECTOR LOOP INSTALLATION. B. Payment includes all labor, equipment, and materials (trenching, loop sealer, and aggregate) required for a complete installation.

 

 

 

 

 

 

 

 

 

 

 

Traffic Sensor Loop​ .pdf

2. Installation & Preparation

• Pavement Selection: Loops must miss existing joints and cracks if possible.

• Trenching: Saw cuts must be 1.5" minimum to 2.0" maximum deep. Width must be a minimum of 5/16".

• Corner Treatment: All corners must be drilled with 2" cores to the depth of the saw cut. Saw cuts across corners are NOT allowed.

• Cleaning: Use compressed air, wire brushing, and heat drying. Saw cuts must be free of debris, dust, and water residue immediately prior to sealing.

• Wire Positioning: Detector wire must be held 1.0" below the surface using form wedges spaced no more than 18" apart.

• Lead-in: Wire from the loop to the handhole must have six twists per foot.

3. Engineering Inductance Formulas

Calculations must be furnished to the Area Signal Engineer at the time of inspection:

• Single Loop (4-Sided): $L=\genfrac{}{}{0ex}{}{P}{4}(N+N^D)$

• Connected in Series: $L^T=L^{D1}+L^{D2}+L^{DN}$

• Lead-In Cable: $L^W=\text{Lead-in Length}\times 0.22\text{ mh/ft}$

• Inductance Ratio: Ideal ratio of total loop inductance to lead-in is 2:1 (Minimum allowable is 1:7).

4. Final Identification & Payment

4.1 Labeling

Each lead-in wire must be labeled in the handhole using a Panduit 250W1175C waterproof tag (or approved equal) secured with nylon ties. Tags must indicate location, rotation (CW/CCW), lead-in direction, loop cable number, and number of turns in waterproof ink.

4.2 Basis of Payment

This work will be paid for at the contract unit price per lineal foot for DETECTOR LOOP, which is payment in full for furnishing, installing, and testing. Measurement is taken along the raceway in the pavement. (Note: 6' round loops may be substituted for 6'x6' square loops and are paid as 24 lineal feet).

5. Reference Standards