The focus of this work was to evaluate the use of commercially available matting systems to sustain C-130 and C-17 transport aircraft loads over soil bases having different California bearing ratio (CBR) ranges. Test sections were constructed using three range of CBR: high (CBR=40-50), medium (CBR=8-10), and low (CBR=5-6). Testing began with the C-130 load cart and six different matting systems. The C-130 was the lesser of the two aircraft loads examined and this initial testing was used as an "elimination round" for the various matting systems chosen. Matting systems deemed suitable for the C-130 were further tested under the C-17 load cart. Systems were evaluated based on logistical and assembly requirements, mat damage sustained during traffic, and accumulated deformation of the mats and soil during traffic. The latter are shown in line plots of passes versus plastic rut formation. Summary information on each matting system tested and the test sections themselves is presented. Conclusions on the matting systems tested and their application are discussed.

Non-traditional soil stabilization additives have been investigated for use in expedient construction of contingency airfields. Laboratory evaluations of several commercially available materials were performed to provide comparisons of the effectiveness of these materials for rapid stabilization. The laboratory investigation evaluated Portland cement (Type I and Type III), acrylic polymers, polypropylene fibers, and selected combinations of these materials for use in stabilizing silty sand. Two field test sections were constructed with test lanes of select stabilizers and trafficked with simulated C-130 aircraft wheel loading. The test sections were evaluated by measuring changes in surface profiles of the section with increasing traffic levels. Measurement was done by rod and level and by periodic measurements of surface deflections from a straight edge placed perpendicular to the traffic direction. The rut depths in Field Test 1 were plotted against unconfined compressive stress with reasonable correlation. In Field Test 2, the section stabilized with fibers and Type III Portland cement proved to be most resistant to permanent deformation under the defined traffic loading.

Blends of Type III Portland cement and select polymer emulsions were tested as potential soil stabilizers for airfield applications. The aim was to study increasing the early strength and curing time of emulsion polymer stabilization using blends of emulsion and Portland cement. Portland cement-stabilized specimens were prepared as conventional stabilizer controls. Each of the additives were added to a manufactured silty sand and compacted by a gyratory compactor at the optimum moisture content of 5% for the unmodified soil. Compacted specimens were cured in a controlled temperature and humidity environment for a maximum of 28 days. Samples were prepared at equivalent emulsion solids content of 2.75%. Portland cement was used at 6 and 9% dry weight for the control specimens and at 3% for the samples containing polymer/cement combinations. Stress-strain measurements were performed to determine the unconfined compressive strength and toughness under both wet and dry conditions. Results indicate that combinations of Type III Portland cement and polymer emulsions produce specimens with similar strengths and higher strains at yield compared to Type I and Type III cement alone. Cure time behavior indicates that the polymer-Type III soil cement blends build strength at a similar rate as Type III cement alone, yet may not have reached ultimate physical properties after 28-day cure times.

The need for rapid assessment tools as alternatives to traditional quality assurance/quality control (QA/QC) equipment has become evident over the past few years to determine the soil characteristics of stabilized, unsurfaced airstrips for military conctruction operations. These instruments must be sensitive to changes in strength properties and capable of measuring soil stiffness values well above those commonly encountered in subgrade or base course materials. The importance is apparent not only for in-theater airfields, but also for QA/QC of unbound and stabilized pavement layers. Commonly used QA/QC equipment such as the nuclear gauge is restricted by training and licensure. In this study, a stiffness gauge and a portable falling weight deflectometer were used to monitor changes in strength characteristics over time for a silty sand blend test section stabilized with type I portland cement, polymer emulsions, and combinations of both. The results were compared to values taken from unconfined compressive strength tests of the same material. The evaluation indicated the use of portable falling weight deflectometer to estimate the strength improvements of cement stabilized soils.