The New Humboldt Overlay Tester is a dedicated cyclic cracking machine designed to perform the Overlay Test. A pill cut from a Superpave gyratory puck is glued to two platens and clamped into the frame. The actuator applies a fixed-displacement triangular waveform, repeatedly loading the specimen in tension, originally to simulate reflective cracking at joints and overlays, but now used to predict cracking performance in all mixtures. This Overlay Tester has been designed to overcome issues faced by other Overlay testers, making it easy to use, stiff, and accurate. An integrated displacement measurement (no LVDTs to insert) and a novel platen system that does not require high torque screw clamping, but does remove all slippage, combine to deliver repeatable, low-compliance results. Optional cameras allow users to film crack propagation and platen opening for advanced image analysis – making it a true testing machine of today and tomorrow. Specifications: • Load frame with one fixed and one moving plate • Software to perform standard and research-level tests • Image analysis option • Servo hydraulic actuator • 20kN load cell • 5mm precision LVDT • Thermo-electric heating/cooling system • PRT for precision temperature control • Temperature range 10°C to 30°C • Noise Level: less than 70db at 2mt • Power supply: 220V 50/60Hz • Dimensions: 920 x 1100 x 640 mm (36.22" x 43.31" x 25.20") (H x W x D) • Supports the following standards: TxDOT Tex-248-F (Texas Overlay Test) and the proposed ASTM overlay standard. Includes • Dedicated overlay load frame with one fixed and one moving platen • Hydraulic actuator and power unit (electromechanical drive option available) • High-accuracy load cell • Integrated displacement measurement (no external LVDTs required) • Overlay control and data acquisition software for PC • Mounting provisions for an optional camera system to record crack propagation and platen motion Features: • Realistic reflective cracking simulation • Dedicated, low-compliance design • No lvdt insertion or adjustment • Novel platen system to remove high-torque screws • Hydraulic drive with electromechanical option • Camera-ready for crack imaging • Made in the USA
