Michéle Dal Toé Casagrande

Applicability of Municipal Solid Waste Incineration Ash on Base Layers of Pavements

AbstractThis study presents the characteristics of municipal solid waste (MSW) incineration ash obtained from an electric energy generation plant and evaluates the MSW ash applicability in base road pavement layers through the mixture of ash with a nonlateritic regional clay soil. Chemical, physical, and mechanical tests and the mechanistic-empirical design for a typical pavement structure were carried out on the pure soil and also in the soil mixture with the addition of different ash content (20 and 40%). Fly ash reduced the expansion of the material, showing an increase in the California bearing ratio (CBR) and resilient modulus value. The results are satisfactory, depending on the content and type of ash used, highlighting the positive work of MSW fly ash for its use in base road pavement layers.

Behavior of granular rubber waste tire reinforced soil for application in geosynthetic reinforced soil wall

Large quantities of waste tires are released to the environment in an undesirable way. The potential use of this waste material in geotechnical applications can contribute to reducing the tire disposal problem and to improve strength and deformation characteristics of soils. This paper presents a laboratory study on the effect of granular rubber waste tire on the physical properties of a clayey soil. Compaction tests using standard effort and consolidated-drained triaxial tests were run on soil and mixtures. The results conveyed an improvement in the cohesion and the angle of internal friction the clayey soil-granular rubber mixture, depending on the level of confining stress. These mixtures can be used like backfill material in soil retaining walls replacing the clayey soil due to its better strength and shear behavior and low unit weight. A numerical simulation was conducted for geosynthetic reinforced soil wall using the clayey soil and mixture like backfill material to analyzing the influence in this structure.

Application of Enzymes for Stabilization of Soils in Paving

In recent years, there was a great offer of patented additives (enzymes) to the road market as solution to soil stabilization. However, they are many times rejected because there are no theoretical foundation to prove such uses, and also because researches themselves don’t see research opportunities. Anyway, these products has been marketed, and frequently municipalities and states waste resources by choosing for a solution that is not yet well studied. This study aims to present a methodology to solve the problems that affects the use of additives in laboratory, because his use in conventional tests do not shown efficient for these purposes. For this, it was used a portable traffic simulator, easy handling and common in pavement laboratories. It is a standardized equipment, used to assess the effect of compression and the strain characteristics of asphaltic coating layers. It was developed a set with several accessories to mold samples in the shape of tablets (380 x 50 x 10 mm), may be easily adapted to the equipment selected as simulator. The soils used for the production of the tested tablets were lateritic soils from Rio de Janeiro–RJ, and the enzymatic products were imported. A rigorous care was followed in the production of each tablet to ensure equality and, after, compare results each other. These tablets were molded and tested in order to obtain a series of experimental results, comparing the soil treated with enzymes with the soil without any kind of treatment. The study concludes, in principle, that the equipment used and the developed accessories are appropriate for this purpose and that the use of enzymes showed effective for some applications, but lacks more studies, including with the use of other types of soil to prove such effectiveness.

Swelling Behavior Evaluation of a Lime-Treated Expansive Soil through Centrifuge Test

AbstractThe main objectives of this research are to investigate the effect of hydrated lime (HL) treatment on the swelling behavior of a natural expansive soil, Eagle Ford clay from Texas, through ...

Swelling Potential Behavior of Expansive Soils Treated with Hydrated Lime

This paper presents the results of an experimental program developed to investigate the effect of lime treatment on the reduction of swelling potential of an expansive soil. The swelling properties were determined using the new geotechnical centrifuge developed by The University of Texas at Austin. This new technology allows the infiltration water into the soil in shorter time than the conventional free-swell testing because of the high g-level acceleration applied in the specimens. The expansive clayey soil used in this study was Eagle Ford clay that was treated with different percentages of hydrated lime by weight of soil (between 0% and 4%). The compaction density of the specimens was varied between 94% and 100% of the maximum dry density, and the compaction moisture was varied between dry of optimum, optimum and wet of optimum moisture content. The centrifuge tests were carried out at three different g-levels acceleration in order to apply different vertical stresses during the swelling tests. The test results demonstrated that the effect of compaction density on the swelling potential is more significant when the specimens are compacted with low moisture content (dry of optimum) than specimens prepared at the optimum moisture content. However, most of the cases, higher potential swelling was observed in specimens prepared with densities near to the maximum than the specimens with lower density compaction. The results also allowed to conclude that the hydrate lime percentage required to avoid completely the swelling depends on the moisture condition and the effective stress. Samples compacted with wet of optimum moisture content required only 2% of lime to prevent the swelling behavior, whereas samples compacted at dry of optimum moisture content needed 4% of lime to avoid significant expansion at the same effective stress. The strong influence of the compaction moisture on swelling showed the same trend observed in untreated soils, where high potential swelling is produced when the specimens were compacted at dry of optimum moisture content than the compacted at optimum or wet of optimum moisture content. Higher compaction moisture than the optimum can be recommended for lime treated soils in order to allow the pozzolanic reactions taking place into the treated soil and to achieve the total elimination of swelling potential of expansive soils.

Static Compaction of Soils with Varying Clay Content

The use of compressed earth blocks (CEBs) is widespread in the field of earth construction. They present better mechanical performance than adobe and the equipment for their production is simple. Laboratory testing of compressed earth blocks requires large amounts of material. There are variations of unconfined strength testing procedures such as testing halves of the blocks with layers of mortar between them or testing whole blocks in diverse directions. This complicates the interpretation of test results as the shape factor and mortar characteristics influence the results significantly. Static compaction test can be used to produce cylindrical samples representative of CEBs. The water content of soil used for the production of CEBs is often determined in standard Proctor test while experimental data indicate that the optimum moisture content for static and dynamic compaction is different. The present article addresses the behavior of four soil mixes with varying clay content compacted statically with a constant rate of strain. Static compaction curves were compared with those obtained in standard Proctor test. For all the soil mixes the static optimum moisture content was found to correspond to the start of consolidation. The compaction curve presented no wet side of optimum in contrast to Proctor test. The energy needed to achieve a desired density by static compaction was analyzed for soils with varying clay contents. Static compaction was found to be more efficient than dynamic for clayey soils. An increase in water content was observed to help achieving higher densities at low pressures, which can improve the performance of manual CEB presses.

Mechanical Behavior of Reinforced Clayey Soil with Fine Crushed Polyethylene Terephthalate

Currently a lot of bottles of polyethylene terephthalate (PET) are discarded into the environment. In order to reduce the disposal of this polymer in nature, this study aims to evaluate the mechanical behavior of a clayey soil mixed with fine crushed PET. The potential use of this waste material in geotechnical applications may ultimately reduce the problem of improper disposal and improve the strength and deformation characteristics of the soil. This paper presents an experimental study to evaluate the mechanical behavior of pure soil and mixtures with different contents of PET waste by triaxial tests, in order to obtain the strength parameters of the Soil-PET mixtures. The clayey soil used was mixed with 10 and 20 percent of fine crushed PET by dry weight. Characterization tests such as grain size, Atterberg limits and compaction test were performed on the soil-PET mixtures. Triaxial tests at confining stresses of 50, 150 and 300 kPa were done on the soil and mixtures. The results show that the soil strength parameters are influenced by the addition of the fine crushed PET, thus improving characteristics such as friction angle and cohesion of the Soil-PET mixtures. This improvement also depends on the confining level which the samples were submitted. These mixtures may be used in pavement and other geotechnical works, so this paper proposes to contribute to a better understanding and interpretation of the behavior of reinforced soil with waste PET.