Rigid pavements built on an expansive subgrade often sustain damage due to differential movement caused by variations in the subgrade moisture content and the resulting swelling pressure. This study aims to introduce an approach based on swelling pressure for analyzing the deformation of rigid pavements. The analysis takes into consideration the effect of soil matric suction on the modulus of subgrade reaction and potential swelling pressure. The numerical analysis was carried out using the pasternak foundation model, wherein the pavement was idealized as an Euler-Bernoulli beam, the pasternak shear layer represented the granular sub-base supporting the pavement, and the expansive soil was modelled using winkler springs. To demonstrate the practical applicability of the proposed model, a case study is presented for an Indian site and the outcomes are presented. The parametric study clearly illustrates that the modulus of subgrade reaction of expansive soil is the most sensitive and significant parameter for improving the flexural response of the pavement. A flowchart outlining the evaluation procedure is included to provide a visual representation of the analysis process.

One of the most successful techniques used to increase structural capacity and sustainability in highway construction is cement stabilization. Despite its reported advantages, some disadvantages such as sensitivity to overloading and reflection cracking normally accompany this technique. The aim of this paper is to investigate the effect of recycled steel fibers inclusion on compressive properties of cement-stabilized granular material and to identify the implications of such reinforcement on pavement responses and economic benefits in terms of pavement thickness. The study was undertaken from both laboratory and theoretical points of view. Laboratory investigation was conducted in terms of unconfined compressive strength (UCS), modulus of elasticity and Poisson's ratio. The results indicated that incorporation of fibers reduces density and UCS of the composite while stiffness modulus and Poisson's ratio were found to be increased as a result of such modification. The failure pattern observations revealed better intactness and integrity of specimens as fiber content increased. From a UCS point of view, the use of lower fiber content (0.25% by volume of aggregate) produced better properties. However, the reduction in the UCS due to reinforcement inclusion can be considered small compared with the reported improvement in tensile properties. Furthermore, incorporating fiber in a cement-stabilized base helps to reduce the tensile strains at the bottom of both asphalt surface and cemented base layers and also compressive strain on the top of subgrade. Finally, reinforcing cement-stabilized aggregate with fibers from consumed tires will ensure reduction of the required thickness of cemented base layer and/or overlying and underlying pavement layers.

Pavements subjected to high volume load require a robust structure. In Brazil, cemented base layer is usually used instead of asphalt concrete thick layer due to cost issues. Soil-aggregate-cement (SAC) mixture is an alternative in pavement application, but the lack of design and dosage protocols hinders the understanding of the parameters influencing its mechanical behavior. This study presents a mechanical characterization of SAC mixtures in terms of strength (UCS and ITS) and stiffness (Mr), focusing on integrating the needs of pavement design to dosage purposes. For this, different SAC mixtures are produced, varying the soil-aggregate proportion (30:70 and 20:80) and cement content (3, 5 and 7 %). Mechanical properties were measured on cured mixtures at 0, 7 and 28 days and compared to structural responses of hypothetical pavements computed by mechanistic analysis. The results indicate a potential for using SAC mixtures in base layers due to their higher strength and stiffness. Predictive models relating ITS x UCS, Mr x UCS, and Mr x ITS with good statistical fit were proposed to assist researchers and engineers in selecting mixtures more adequate and durable for pavement applications, based on the concept of limiting the tensile stress acting on the cemented base course.

Loess is a geological formation with poor geotechnical performances. To upgrade and allow use of this kind of material in civil engineering projects, it is common to add few percent of hydraulic binders. However, the mechanical properties of those materials are often estimated. Their performances are thus sharply downgraded during structure design processes of road structures and their uses are generally limited to the capping layer. However, it is possible to measure accurately mechanical performances of these materials to use them in subbase layers of pavements. Based on results, a design has been proposed and implemented on a real scale test section. The test has been instrumented with strain gauges and preliminary results are presented.

Using biopolymers for soil stabilization is favorable compared to more conventional methods because they are more environmentally friendly, cost-effective, and long-lasting. This study analyzes the physical properties of guar gum and laterite soil mixes. A comprehensive engineering study of guar gum-treated soil was conducted with the help of a brief experimental program. This study examined the effects of soil-guar gum interactions on the strengthening behavior of guar gum-treated soil mixtures using a series of laboratory tests. The treated laterite soil's dry density increased marginally, while its optimum moisture content decreased as the guar gum increased. Treatment with guar gum significantly enhanced the strength of laterite soil mixtures. For laterite soil with 2% guar gum, the unsoaked CBR increased by 148% and the soaked CBR increased by 192.36%. The cohesiveness and internal friction angle increased by 93.33% and 31.52%, respectively. These results show that using guar gum dramatically improves the strength of laterite soil, offering a more environmentally friendly and sustainable alternative to traditional soil additives. Using guar gum in T8 subgrade soil requires a 1395 mm pavement depth and costs INR 3.83 crores, 1.52 times more than laterite soil. For T9 subgrade soil, the depth was 1495 mm, costing INR 4.42 crores, 1.72 times more than laterite soil. This study introduces a novel approach to soil stabilization by employing guar gum, a biopolymer, to enhance the physical and mechanical properties of laterite soil. Furthermore, this study provides a detailed cost-benefit analysis for pavement applications, revealing the financial feasibility of using guar gum despite it requiring a marginally higher initial investment.

The present study aims to evaluate the possibility of perpetual pavement design with stabilized black cotton soil and polymer-modified bitumen for the major highways in India. Ground granulated blast slag (GGBS) was proposed as a potential material for use in pavements on weak subgrades, with proportions of 10%, 20%, 30%, and 40% added to the black cotton soil. Modified proctor compaction and California bearing ratio tests were conducted to determine the engineering properties of the soil and GGBS mixture. The study also aimed to design a high modulus bituminous concrete mixture for perpetual pavements using a combination of styrene-butadiene-styrene (SBS) polymer and viscosity grade 30 (VG 30) bitumen, with SBS added to the bitumen in amounts ranging from 1 to 4% by total weight. The physical and mechanical properties of both SBS-modified bitumen and neat bitumen were determined. Based on these results, 16 combinations of perpetual pavements were designed using the mechanistic-empirical methodology and according to Indian Road Congress (IRC 37: 2018) guidelines, with the aid of the IITPAVE software. These pavements included both treated and non-treated subgrades, as well as modified and unmodified mixes. The study found that the use of a sturdy foundation, treated subgrade, and high stiffness base materials is crucial in reducing the significant cost associated with using bitumen in a developing and oil-importing country like India. The designed pavements were also compared in terms of cost assessment and carbon dioxide emissions to determine the best option among the proposed combinations.