Subbase

Abstract: Changing material into a lightweight geomaterial such as EPSCS is one of the considerable methods to improve the geotechnical performance in the field. This material is already used in numerous construction projects due to its light characteristics. Lightweight Modular Block or LMB is a type of EPSCS composed of dredged Soil, cement, and Expanded Polystyrene (EPS). The amount of cement composition are 3%, 5%,7% and 9%. Meanwhile, Expanded Polystyrene (EPS) are 0.5% and 0.75%. This paper aims to briefly explain the performance of LMB as road foundation materials, such as subbase and base, through CBR laboratory tests. Based on the data, adding EPS can reduce density by 18% - 29% depending on the chosen mixture. Whereas adding more cement tends to increase the CBR value. All the test results will be analyzed and compared to SNI 03-3438-1994 for its qualification as a road foundation layer.

Abstract: Utilizing pond ash (PA) deposited in ash lagoons generated from thermal power plants (TPPs) as subbase material for hardstand foundation not only helps the cause of residual waste disposal problem but also solves associated shortcomings like, lower utility and degrading environmental impact for prolonged deposition. However, the property of the PA varies not only among various TPP but also within a single ash lagoon, depending on the point of deposition and subsequent settlement. This study presents detailed analysis of chemical, physical, morphological, and mineralogical properties of inflow and outflow PA within the same ash lagoon. Local sand (LS) has been used as conventional granular subbase material. A comparative analysis of the respective material properties has been drawn to access the feasibility of PA as subbase material, substituting sand. The results showed CBR ranging from 16.63 to 17.19% for standard compacted unsoaked samples, 23.55–24.17% for modified compacted-soaked samples of PA, compared to 25.08 and 32.96% of LS. Consolidated drained triaxial tests showed cohesiveness and φ value 32° for PA samples compared to 40° for LS. FESEM explained distinguished morphological forms of the mineral and showed the presence of microspheres in PA. XRD detected alumina-silicates, cristobalite, anorthite and showed PA particle size is directly proportional to its pozzolanic reactivity. FTIR detected presence of hydroxyl (–OH) stretches and (H–O–H) vibrations along with bond water molecule bending, revealing its pozzolanic nature. Finally, LFWD test provides 1.7% less peak surface deflection than LS predicting PA’s favorably as supplementary granular material for hardstand subbase layer.

Abstract: Abstract Flexible pavements consist of four main layers: subgrade, subbase, base, and surface layer. The surface layer is the impermeable layer of the pavement since it contains bitumen. The area the load is distributed over gradually increases in the Base, subbase, and subgrade layers. Subgrade layer is what represents the main foundation that supports the entire basement structure. Flexible pavements must have sufficient strength and stiffness to be able to withstand the subjected high stresses resulting from the applied wheel loads. the pavement layers materials are evaluated based on the soil classification and graduation, and the California bearing ratio. Generally, the main difference between subgrade soil and some beys and based soil is that the upper layers have more strict specifications since they are subjected to lower stress. As a result, if the existing subgrade soil is of sufficient strength, it could be modified in a way that increases its strength and makes it suitable to be used as subbase and base layers. This study aims to evaluate the subgrade soil existing in Sohar university campus and apply suitable modifications to create enhanced soil that is suitable to be used in the upper layers of the pavement. Such modifications are economically beneficial since it gives the opportunity of only having to transport the extra material instead of transporting the entire amount used for constructing the pavement leading to a significant reduction in the construction cost which is the main cost of the construction of the flexible pavement.

Abstract: Dowels are the most commonly used load transfer devices at joints in ground-supported slabs such as pavements and slabs-on-ground, to ensure a smooth ride across the joints and to minimize damage to concrete due to vehicular impact loads. Durability issues arising from corrosion and the consequent development of dowel looseness due to loss of material are some of the prevailing concerns when steel dowels are used. The past decade has seen rising popularity in the application of the corrosion-free glass fiber-reinforced polymer (GFRP) dowels at joints owing to its high tensile strength and ease of handling, and smooth exterior surface which negates the use of a bond-breaker mechanism. This paper presents the results of experimental and numerical works conducted to investigate the application of smaller diameter GFRP dowels at joints embedded in slabs-on-ground subjected to smaller infrequent loads. Based on the experimental results from four specimens of dimensions 1500 × 750 × 200 mm3 resting on an extruded polystyrene subbase simulating dense sand, with various types of dowels (GFRP 14 mm, GFRP 16 mm, GFRP 38 mm, and stainless-steel 12 mm), numerical models were developed and validated. Numerical parametric investigations were conducted to study the effect of parameters such as dowel spacing, concrete strength, slab width, slab thickness, modulus of elasticity of subbase material, and location of loading.