Pavement Vibration Made Simple
In the 1990’s concrete mix design changed and were being designed for strength and increased pavement life by reducing the amount of cement in the mix. While these mixes are more efficient, high frequency vibrators were becoming less compatible with the new mix designs. New variables created the demand for monitored vibration systems.
Monitored vibration like our Auto Vibe Systems gave the machine operator a way to control the vibrators frequencies and analyze placement results. The frequency of a hydraulic vibrator on a paver now has a uniform and measurable output. Vibrators are mounted horizontally on a paver and the vibrator centers are no more than 16 inches apart. This regulation was set by airport and highway officials and a vibrator’s influence is more than adequate at this spacing.Monitored vibration systems allow for a uniform and quantified force to be applied to the concrete being placed. A consistent output is used to analyze the frequencies of the vibrator and the effects that the vibration had on the concrete. A uniform frequency and force output allows for informed decisions on a vibrator’s effects on material separation and consolidation level during the process. Controlling the frequency of the vibrators has become a standard requirement with airport runway construction and the data has resulted in the development of DOT and airport authority frequency range specifications.
Here are a few things you should consider when using a control frequency vibrator:- Control Vibrator Frequency: the off-centered weight values are quantified at a set frequency. Use the known frequencies to analyze the results.
– Radius of Action: is set by the job specification or stay inside 16 inch centers.
– Machine Travel Speeds: with a forward machine travel speed of 4 feet per minute, you spend 10 seconds in a cubic foot. That is a lot of vibration.
– Pavement Surface: increasing vibrator speeds at the pavement surface may cause some unwanted material separation.
These considerations of the products behavior should be used for a better understanding of the process. An operator should always follow the job specifications and past best practices. A clearer picture of how a vibrator works though will help explain how the concrete is affected.
Better testing methods are now being developed to further the effectiveness of Controlled Frequency Vibrator Systems. Understanding vibration becomes less confusing when a vibration product is controlled and is constant. Most important, the operator can learn from the expected placement behaviors and determine how they can control the process.