In this paper, several hundred specimens were compacted and tested to evaluate the potential of beam testing protocols to directly measure four mechanical properties from one beam. Mechanical properties measured through beam testing protocols were compared to properties of plastic mold (PM) device specimens and were found to be comparable once specimen densities were corrected. Mechanical properties were also used to quantify mechanical property relationships, often used as pavement design inputs. When compared to traditionally recommended mechanical property relationships, relationships between elastic modulus and unconfined compressive strength, as well as modulus of rupture and unconfined compressive strength, were overly conservative; however, indirect tensile strength and unconfined compressive strength relationships from the literature were accurate. This paper also assessed an elevated-temperature curing protocol to simulate later-life pavement mechanical properties on laboratory specimens. Mechanical properties of laboratory specimens that underwent accelerated curing were shown to be comparable to 10- to 54-year-old cores taken from Mississippi highways.

The current study analyzed a total of 28 flexible pavement sections for evaluating influence of cementitious stabilization of soil on pavement distresses under different climate, traffic, and reliability level conditions. A total of three stabilizers, namely, 3% lime, 15% class C fly ash (CFA) and 15% cement kiln dust (CKD) were selected. A total of six types of pavement distresses namely, total rutting, asphalt concrete (AC) rutting, AC bottom-up cracking, AC top-down cracking, AC thermal cracking and international roughness index (IRI) values were predicted for a period of 20 years (240 months) using AASHTOWare pavement mechanistic-empirical (ME) design software. It was found that cementitious stabilization is effective in reducing only total rutting, bottom-up cracking and IRI under different climate, traffic, and reliability levels. The amount of improvement was found dependent on resilient modulus values of stabilized soil layer. However, no effect of cementitious stabilization of subgrade soil was noticed on top-down cracking and thermal cracking of AC layer. On the contrary, cementitious stabilization increased AC rutting of pavement. The maximum percent increase in AC rutting was found 6.4% for CKD stabilization in WY climate, 5.5% for CKD stabilization under 1000 and 5000 traffic levels, and 5.6% for CKD stabilization at a reliability level of 80%. Among all six distresses, stabilization was found most effective in reducing bottom-up cracking (or fatigue cracking) of AC layer under different climate, traffic, and reliability level conditions. Further, the level of improvement in bottom-up cracking due to stabilization was found most effective under warmer climate region and highest reliability level. Specifically, the maximum percent improvement in bottom-up cracking was noticed 61.3% for CKD stabilization in TX climate, 70.5% for CKD stabilization under 10,000 traffic level, and 92.9% at a reliability level of 95%. The cementitious stabilization of subgrade soil showed highest percent improvement in reducing IRI values under coldest temperatures (1.8% for CKD stabilization in WY climate), highest traffic level (1.8% for CKD stabilization under 10,000 traffic level), and lowest reliability levels (1.1-1.5% at a reliability level of 80%).

This paper investigates the effect of subgrade soil stabilization on the performance and life extension of flexible pavements. Several variables affecting soil stabilization were considered, including subgrade soil type (CL or CH), additive type and content (3, 6, and 9% of hydrated lime, 5, 10, and 15% of class C fly ash (CFA), and 5, 10, and 15% of cement kiln dust (CKD)), three stabilization thicknesses (15, 30, and 45 cm), and four pavement sections with varying thicknesses. The effects of these variables were investigated using four different damage mechanisms, including the fatigue life of the asphalt concrete (AC) and stabilized subgrade layers, the crushing life of the stabilized subgrade soil, and the rutting life of the pavement, using a non-linear mechanistic-empirical methodology. The results suggest that the optimum percentage that maximizes the pavement life occurs at 3% of lime for subgrade soil type CL, 6% of lime for subgrade type CH, and 15% of CFA and CKD for both subgrade soil types. The maximum pavement life increase occurred in the with the lowest thickness and the highest stabilization thickness, which was 1890% for 3% of lime in the CL subgrade and 568% for 6% of lime in the CH subgrade. The maximum increase in the pavement life of subgrade stabilization with 15% of CFA was 2048% in a CL subgrade, and 397% in a CH subgrade, and life extension due to subgrade stabilization with 15% of CKD was 2323% in a CL subgrade and 797% in a CH subgrade.