Production of cellular concrete (foamcrete) units for use in arresting bed systems designed to decelerate large moving objects, e.g. aircraft

摘要

Vehicle arresting blocks of cellular concrete are usable to safely slow travel of an object and are used to construct an aircraft arresting bed at the end of an airport runway. For such purposes, cellular concrete blocks are fabricated to exhibit compressive gradient strengths of predetermined values to provide sufficient, but not excessive, deceleration forces on an object. Material uniformity characteristics must be met to avoid unacceptable drag force variations, so that arresting blocks exhibit a predetermined compressive gradient strength (e.g., a 60/80 CGS) over a depth of penetration of 10 to 66 percent of block thickness. A 60/80 CGS will typically represent an average compressive strength of 70 pounds per square inch over such depth of penetration. Methods described include parameter, ingredient and process controls and ranges effective to enable fabrication of arresting blocks having dry densities and compressive gradient strengths which can be specified in order to provide limited deceleration of aircraft and other large objects. Limited deceleration can avoid destructive effects inherent in excess rates of deceleration. One method for forming a section of a deceleration block to provide limited deceleration of a moving object comprises steps of: 1. forming a slurry of cement and water; 2. preparing a foam from water and a foaming agent; 3. admixing the slurry and foam to provide a cellular concrete; 4. placing a portion of the cellular concrete in a form to provide the deceleration block in a shape and size suitable for use in decelerating a moving object and; 5. including within the lower portion of the cellular concrete form a layer of material of higher strength than the cellular concrete after curing and the layer positioned so as not to interfere with the compressive failure of the block to a depth of penetration of 80 percent of the block thickness.