The word Asphalt is usually thought of as the black, stony, hard material that is used to pave our roads, driveways, parking lots and paths, also known as Blacktop. One can envision the big dump truck that dispenses the steaming, oily material onto the ground, and the steam rollers that flatten it into its final form.
While this may seem very straightforward, it is not so simple. Even the word Asphalt has different meaning in different context. It is the very thick, black liquid that is present in crude oil before it is refined. Asphalt cement is another name for this liquid when it is used as a binder for the paving materials, which themselves are known as asphaltic concrete, or just asphalt. Many different types of materials are held together by the asphalt cement, resulting in paving materials for different applications. These adder materials are known as aggregates. The choice of aggregate and asphalt will produce paving that is smoother, with smaller particles, or rougher when larger particles are used. One type may be used for a base layer in road construction while another is used for the top layer. Different materials will provide different wear characteristics. What may be suitable for a residential driveway would not be appropriate for an interstate highway with extensive truck traffic. The aggregate material is often qualified by the size of the particles used. This is also the case with concrete. There are a number of different classifications for the aggregates, which may relate to the grid size of a sieve which will capture a specific size of particle. Sieve sizes are both by size, such as 3/8 inch, and by industrial standard numbers, such as number 4, number 16, number 50 or number 100. Contracts for road construction will often specify the amounts and types of aggregates that must be used. Municipalities require regular testing of the materials to insure that the proper ratio of aggregate materials are being incorporated into the asphalt. Industrial scales are the best devices for measuring the aggregates. But an appropriate electronic scale must be chosen to provide the accuracy and ruggedness that is required for this application. Those digital scales that are designed for this purpose are known as asphalt scales. Because of the wide range of aggregate materials, they must have a high weight capacity and fairly large platform. In order to measure each size properly, the asphalt scale must also have excellent accuracy and resolution. Because the application is quite harsh, with large containers of materials being roughly placed onto the scale, it must also be very rugged. Generally, the only type of industrial scale that qualified for this application utilized a type of technology known as Force motor, or Force restoration. As an over simplified explanation of this type of weighing, it consists of an electromagnet which varies the amount of current running through it to support the weight on the platform. This technology has been available for many years, and is able to provide both the capacity and the accuracy that is required. By its inherent design, it is not very rugged, so that care must be taken during use. It is also very expensive. A new type of industrial scale technology has become available from Arlyn Scales for use as asphalt scales. Their Ultra Precision Scale utilize surface acoustic wave transducers to accurately measure the deflection of a load cell within the scale. The transducers use a semiconductor material to produce a digital signal that is proportional to the weight on the scale platform. These electronic scales are also known by the initials of Surface Acoustic Wave, as SAW Scales. The SAW Scales are available in the range of capacities that are useful for asphalt scales. Some of the smaller models have capacities that range from ten pounds up to one hundred pounds. There is also a series of larger platform SAW Scales with capacities up to five hundred pounds. Arlyn Scales precision asphalt scales are much more rugged than the force restoration scales, or even the much less precise standard industrial scales that use strain gage load cells. They can accept instantaneous shock loads up to 500% of their rated capacity. This makes them much less likely to be damaged during use. As an added b benefit, the SAW scales are much less expensive than the force restoration scales, generally costing approximately the same as the strain gage scales. Additional features provide these asphalt scales with useful benefits. An optional USB memory stick allows data to be collected for later analysis. Thousands of readings may be stored on the stick, which can then be read by any standard computer. The data is formatted so that it can be directly loaded into an industry standard spreadsheet, or one of many different database programs. Another option allows the scale to be operated from its own internal, rechargeable battery pack.