A Falling Weight Deflectometer (FWD) is used to measure the vertical deflection response of a surface to an impulse load.
Precision load measurement and deflection sensors record the pavement surface characteristic, which is used to calculate pavement properties such as
• Bearing Capacity
• Layer Thickness
• E Moduli
• Expected Surface Life
A FWD can also be used in determining the actual material used and in what combination to build the pavement surface. It also identifies voids underneath the surface or how two surfaces, typically concrete slabs, are in contact with each other.
The sofware is user-friendly with an automatic self-check of results – data is easily transferred to PC via the USB memory key or by a direct connection.
A standard FWD system uses 7 deflection sensors that measure the load pulse over 60ms (0.06 of a second).
FWD is capable of measuring up to 23 deflection sensors over 240ms (0.2 of a second), giving greater resolution and increased measuring capability.
A standard test takes less than 30 seconds to perform,starting from when the FWD is stationary and finishing when the load plate is raised in to the locked and secured position. This makes the FWD the fastest deployable FWD available.
In addition to the basic configuration of the FWD, all machines are fitted as standard with Ambient,Ground and Sub Ground (Asphalt) temperature sensors.
The FWD can also be fitted with the following optional features:
• Up to 3 Camera System, for monitoring the Load Plate and to assist with vehicle positioning.
• Ground Penetrating Radar system
• Global Positioning System.
The FWD is used on highways, local roads, car parks and airport runways.
Complies with ASTM D4694 “Standard Test Method for Deflections with a Falling Weight Type Impulse Load Devices”.
A Deflectometer is used for the following applications :
• Pavement rehabilitation and overlay
• PCC joint sealing evaluation
• Pavement management systems
• Load transfer efficiency
• Void detection
• Spring load restrictions
• Utility cuts
• Experimental paving materials
• Project acceptance and evaluation
• ASTM D 4694 – 96 (Re-approved 2003): Standard Test Method for Deflections with a Falling Weight-Type Impulse Load.
• ASTM D 4695 – 03 (Re-approved 2008): Standard Guide for General Pavement Deflection Measurements
• ASTM D 5858 – 96 (Re-approved 2008): Standard Guide for Calculating In Situ Equivalent Elastic Moduli of Pavement Materials Using Layered Elastic Theory.
•ASTM D 4694 – 96 (Re-approved 2003): Standard Test Method for Deflections with a Falling Weight-Type Impulse Load.
• ASTM D 7228 – 06a Standard Test Method for: Prediction of Asphalt-Bound Pavement Layer Temperatures.
• ASTM E 1777 – 96 (Re-approved 2002): Standard Guide for Prioritization of Data Needs for Pavement Management.
• ASTM (for LWD) E 2835-11 – Measuring Deflections using a Portable Impulse Plate Load Test Device