I made a asphalt displacement gauge to measure how much it deflected while loading. The ring on the top was cut to set the gap. The outside rings were cut from a structural steel tubing. Then the holes were layed out using a protractor. They were drilled out with a #7 bit and tapped with a 1/4-20 tap. Allen head bolts were used to affix the rings to the specimen. The steel blocks were placed so that a dial gauge can be attached to measure the displacement between the rings. The asphalt cores were cut down to known dimensions and to get even loading.