EFFECT OF WASTE MATERIALS ON CALIFORNIA BEARING RATIO FOR GRANULAR BASE

It is known that paving is a system with multiple layers and the strength of each layer is reflected on the entire pavement. Two kinds of materials are used as the base layer, and the materials are divided into ordinary traditional granular materials and recycled materials such as foundry sand. This paper presents the results of laboratory tests in the laboratory and discusses the effect of each of the materials and foundry sand and its effect as a stabilizer on the strength of the substrate and as a stabilizer. Also, a comparison is made between the changes that occur in the base layer Cast sand treated and compared with untreated. A mixture of foundry sand with graded natural aggregate according to certain sizes is used as a stabilizer in proportions (5, 10 and 15) %. The treated and untreated base layer is compared in terms of strength. The base layer material is a traditional base material taken from the Nabaie quarry. Samples are made of three replicates of each possible group. Samples were prepared and subjected to a compressive strength CBR test. The obtained results indicate an increase in the resistance of the base material when using FS at a rate of (5%) with a treatment period of 4 days, while a ratio of 10% gave the highest resistance in a treatment period of 14 days, and these ratios gave more resistance than the untreated samples without the additive.

Uso de polvo de alto horno para mejorar las propiedades de material granular para pavimentos

The granular base and sub-base materials used in the construction of road surface structures must comply with certain requirements. In some cases, the requirements are not complied with and it is necessary to search for alternatives to improve the properties of the materials and thereby enable the use of these materials in the construction of roadways. Blast furnace dust is a residue from the production of steel that is of little use and is causing a negative environmental impact due to its accumulation. This study was carried out to analyse the possibility of utilizing blast furnace dust to improve the properties of granular materials, as an alternative that mitigates the environmental problems caused by the disposal and accumulation of these residues, which affect the areas of influence of these companies. To achieve this goal, the chemical and physical properties of blast furnace dust were determined and a analysis was carried out on mixtures of granular base and sub-base materials with 0, 2, 4, 6, and 8 percent dust. The analysis took place of determined characteristics including optimum humidity, maximum dry density, resistance, plasticity, and expansion in the presence of water. The results indicate that with the incorporation of 6% of BFD the properties of the granular material are improved and it can be used as an optimal material in road construction.

Bender Element Field Sensor for the Measurement of Pavement Base and Subbase Stiffness Characteristics

Layer modulus values are important input parameters in mechanistic pavement design and evaluation methods. Direct measurement of the stiffness characteristics of pavement base/subbase has been a challenging task. Nondestructive testing methods that are commonly used based on surface deflection measurements not only require a backcalculation process, but also have limitations on measuring local stiffness within the layer. This paper presents the result of a recent research effort at the University of Illinois aimed to develop a new sensor for the direct measurement of the in-situ moduli of constructed unbound pavement layers. The new sensor employs bender element (BE) shear wave transducers embedded in a granular base/subbase to evaluate the layer modulus from shear wave velocity measured at any depth and any orientation. To provide appropriate protection for the BE sensor and its cable connections, a stainless-steel cable guide, a sensor protection module, and a protection cover for the sensor were designed and optimized. A laboratory calibration box containing sand-sized crushed aggregates was used in the development stage of the BE sensor design. The BE sensor results were also studied for a typical dense-graded base course aggregate commonly used in Illinois. Finally, the BE sensor was installed in a field trial in newly constructed airport pavement test sections, and its layer modulus measurements were compared with results estimated from Dynamic Cone Penetrometer testing. The new BE field sensor has proven to be a viable direct measurement technique in transportation geotechnics applications to monitor stiffness characteristics of pavement granular base/subbase layers.

Effect of Moisture Content on the Shakedown Limits of Base Course Materials

This paper summarizes the results of a laboratory testing program that was conducted to determine the effects of moisture content on the shakedown limits of unbound granular base materials. Two different types of granular base materials were investigated in this study, namely limestone and sandstone. Multi-stage repeated load triaxial tests were performed on these materials. The results of the tests were analyzed within the framework of the shakedown theory. The results indicate that the moisture content had an influence on the slope of the elastic and plastic shakedown limits lines. The effect of the moisture content was more pronounced on the slope of the elastic shakedown limit line, however. The moisture content affected the intercept of the elastic and plastic shakedown limits lines more significantly than the slope of these lines. The limestone material exhibited greater decrease in the intercept of the elastic and plastic shakedown limits with increase in moisture content compared with the sandstone material. This was explained by the limestone’s finer gradation.

Laboratory Evaluation and Design of Construction and Demolition Wastes for Granular Base

Using recycled aggregate from construction and demolition (C&D) wastes as a construction material is a potential method for solving the disposal of C&D wastes, which can reduce the exploitation of natural aggregate. In this study, extensive laboratory tests were carried out to investigate the reliability of the C&D wastes used as road base material. Meanwhile, the gradation design and the dominant aggregate size range were considered, and a physical disposal method was proposed to enhance the structural performance of the recycled material by replacing the skeleton of the recycled aggregate (RA) with high-quality limestone. The test results showed that (1) given the high absorbency and fragility of C&D wastes, its RA was not enough to provide the strength and stability required by the base; (2) the compaction characteristics of the RA are quite different from that of the limestone aggregate, but the final compaction effect is basically the same; (3) the replacement treatment proposed in this study is an effective approach to improve the performance of the recycled granular base because the breakage rate decreased by at least 28.2% and the mechanical properties increased by approximately 50% compared with that of the untreated specimen; and (4) when the limestone content reached 75%, the California bearing ratio and the resilient modulus of the graded B specimen exceeded 120% and 200 MPa, respectively, satisfying the pavement requirement in medium traffic.