Nilo Cesar Consoli

Parameters Controlling Tensile and Compressive Strength of Artificially Cemented Sand

The enhancement of local soils with cement for the construction of stabilized pavement bases, canal lining, and support layer for shallow foundations shows great economical and environmental advantages, avoiding the use of borrow materials from elsewhere, as well as the need of a spoil area. The present research aims to quantify the influence of the amount of cement, the porosity, and the voids/cement ratio in the assessment of unconfined compressive strength qu and splitting tensile strength qt of an artificially cemented sand, as well as in the evaluation of qt /qu relationship. A program of splitting tensile tests and unconfined compression tests considering three distinct voids ratio and seven cement contents, varying from 1 to 12%, was carried out in the present study. The results show that a power function adapts well qt and qu values with increasing cement content and with reducing porosity of the compacted mixture. The voids/cement ratio is demonstrated to be an appropriate parameter to assess both qt and qu of the sand-cement mixture studied. Finally, the qt /qu relationship is unique for the sand-cement studied, being independent of the voids/cement ratio. DOI: 10.1061/ASCEGT.1943-5606.0000278 CE Database subject headings: Tensile strength; Compressive strength; Soil cement; Compacted soils. Author keywords: Tensile strength; Compressive strength; Soil cement; Compacted soils.

Fundamental Parameters for the Stiffness and Strength Control of Artificially Cemented Sand

The treatment of soils with cement is an attractive technique when the project requires improvement of the local soil for the construction of subgrades for rail tracks, as a support layer for shallow foundations and to prevent sand liquefaction. As reported by Consoli et al. in 2007, a unique dosage methodology has been established based on rational criteria where the voids/cement ratio plays a fundamental role in the assessment of the target unconfined compressive strength. The present study broadened the research carried out by Consoli et al. in 2007 through quantifying quantifies the influence of voids/cement ratio on the initial shear modulus ( G0 ) and Mohr-Coulomb effective strength parameters ( c′ , ϕ′ ) of an artificially cemented sand. A number of unconfined compression and triaxial compression tests with bender elements measurements were carried out. It was shown that the void/cement ratio defined as the ratio between the volume of voids of the compacted mixture and the volume of cement is an ap...

Influence of Cement-Voids Ratio on Stress-Dilatancy Behavior of Artificially Cemented Sand

The addition of cement is an interesting remediation technique when the project requires improvement of the local soil for the construction of pavement base layers, in slope protection of earth dams and canal linings, as a support layer for shallow foundations and to prevent sand liquefaction. The present study was carried out to quantify the influence of the amount of cement and the porosity in a cement- voids ratio, defined as the ratio between the volume of cement and the volume of voids of a mixture, on the stress-dilatancy behavior of an artificially cemented sand. A program of triaxial compression tests considering three distinct cement-voids ratios was carried out with two combinations of volumes of voids and volumes of cement at each cement-voids ratio. Results showed that the stress-dilatancy relationship is alike for a given cement-voids ratio and that the stress-strain behavior is also similar. The cement-voids ratio is therefore an appropriate parameter to assess stress-dilatancy of the sand-cement mixture studied. DOI: 10.1061/(ASCE)GT.1943-5606.0000565.

Variables Governing Strength of Compacted Soil–Fly Ash–Lime Mixtures

The practice of treating soil with fly ash and lime is an attractive technique when the project requires improvement of the local soil for the construction of stabilized bases under pavements, as a support layer for shallow foundations, to strengthen slopes in slope stability problems, and to prevent sand liquefaction. Currently, efforts are being made to develop dosage methodologies for improved soils based on a rational criterion as it exists in concrete technology, in which the water-cement ratio plays a fundamental role in the assessment of the target strength. This study evaluates the strength controlling parameters of a sandy soil treated with fly ash and lime and shows that the voids-lime (η=Lv) ratio (corresponding to porosity divided by the volumetric lime content) plays a fundamental role in the assessment of the target strength. The controlling parameters evaluated were the amount of fly ash, quantity of lime, porosity, and voids-lime ratio. A number of unconfined compression tests and suction measurements were carried out in the present work. The results show that the unconfined com- pressive strength (UCS) increased linearly with the amount of lime for soil-fly ash-lime mixtures. A power function adapts better to the relation UCS-porosity (η) for soil-fly ash-lime mixtures. The ratio η=Lv, in which Lv is adjusted by an exponent (in this case 0.12 for all soil- fly ash-lime mixtures studied), is shown to be a good parameter in the evaluation of the UCS of the soil studied (UCS varies nonlinearly with η=Lv in the case of fly ash-lime addition). Finally, it was found that a unique correlation controls the strength of the compacted soil-fly ash-lime mixtures studied; consequently, using this relationship an engineer (considering the specifics of each case such as price, availability, and cost of transportation of each material, among others) can choose the amount of lime, the quantity of fly ash, and the compaction effort appropriate to provide a mixture that meets the strength required by a project at the optimum cost. DOI: 10.1061/(ASCE)MT.1943-5533 .0000186.

Studies on the Dosage of Fiber-Reinforced Cemented Soils

This paper reports on the development of a dosage methodology based of compressive strength for artificially cemented fiber-reinforced soils. The controlling parameters evaluated were the fiber content (F), volumetric cement content (Civ), porosity (η), and cement/porosity ratio (Civ/η). To evaluate the influence of each parameter on the soil response, a number of unconfined compression tests were carried out. The results show that fiber insertion in the cemented soil, for all dry unit weights and for the whole range of cement dosages studied, causes an increase in unconfined compressive strength. The unconfined compressive strength (qu) increased linearly with the amount of cement (Civ) for both the fiber-reinforced and nonreinforced specimens. It was also shown that the cement/porosity ratio, in which volumetric cementitious material content is adjusted by an exponent (0.28 for all the fiber-reinforced and nonreinforced cemented soil mixtures) to give unique correlations for each mixture, is a good para...

Variables Controlling Stiffness and Strength of Lime-Stabilized Soils

Lime treatment is an attractive technique for soil improvement in the construction of rail tracks and pavement layers, in slope protection of earth dams, and as a support layer for shallow foundations. However, there are no dosage methodologies based on rational criteria as in the case of soil-cement technology, where the voids/cement ratio is shown to be a key parameter for the estimation of both strength and stiffness. The present study, therefore, was aimed at quantifying the influence of the amount of lime, porosity, and voids/lime ratio on the initial shear modulus (G0) and unconfined compressive strength (qu) of a lime-treated clayey sandy soil. From the results of unconfined compression tests and bender elements measurements, it was shown, for the soil-lime mixtures investigated, that the voids/lime ratio is an appropriate parameter to assess both initial stiffness and unconfined compressive strength. Also, a unique G0/qu versus voids/lime ratio relationship was established linking the soil-lime mi...

Voids/Cement Ratio Controlling Tensile Strength of Cement-Treated Soils

The improvement of locally available soils with cement can provide great advantages, including avoiding the need to borrow volumes of appropriate material and disposing of the local soil in deposits. This research aims to quantify the influence of the amount of cement, the porosity, and the voids/cement ratio in the assessment of splitting tensile strength (qt), also known as indirect diametrical tensile (IDT) strength, of three distinct soils from Brazil and Portugal. From Brazil, clayey sand derived from Botucatu sandstone and uniform Osorio sand were considered; from Portugal, silty sand derived from weathered Porto granite was studied. A number of splitting tensile strength tests were carried out. The results show that qt increased with the amount of cement (C) and decreases in porosity (η) for the three soil-cement mixtures. A power function was well-adapted to fit both qt-C and qt-η. Finally, the tensile strength was plotted against the porosity/volumetric cement content relationship (η/Civ), in whi...

High-Pressure Isotropic Compression Tests on Fiber-Reinforced Cemented Sand

High-pressure isotropic compression tests were carried out on reconstituted sand samples that were reinforced with cement, randomly distributed fibers, or both, making comparisons with the unreinforced sand and conducting tests from a variety of initial specific volumes. The results indicated changes in the isotropic compression behavior of the sand due to the inclusion of fibers and/or cement. Cementitious bonds are sufficiently strong relative to the particles to allow the cemented samples to reach states outside the normal compression line NCL of the uncemented soil, but the effectiveness of cemented fiber-reinforced specimens is even larger due to the control of crack propagation in the cemented sand after the inclusion of fibers. Distinct NCLs were observed for the sand, fiber-reinforced sand, cemented sand, and fiber-reinforced cemented sand. Both fiber breakage and fiber extension were observed in fibers measured after testing indicating that fibers individually have worked under tension, even though in the macroscopic scale, isotropic compressive stresses were applied. Fiber reinforcement was found to reduce the particle breakage of both the uncemented and cemented sands.

Parameters Controlling Tensile and Compressive Strength of Fiber-Reinforced Cemented Soil

AbstractEnhancement of local soils with fibers and cement for the construction of stabilized pavement bases, canal lining, and support layers for shallow foundations shows great economical and environmental advantages, avoiding the use of borrow materials from elsewhere, in addition to the need of a spoil area. In previous studies, a unique dosage methodology for cemented soils has been established based on rational criteria in which the porosity-to-cement ratio plays a fundamental role in the assessment of the target unconfined compressive strength (qu). The present paper extends previous work by quantifying the influence of the amount of cement, the porosity, and the porosity-to-cement ratio in an assessment on tensile strength (qt) and compressive strength of a fiber-reinforced artificially cemented sand, in addition to the evaluation of the qt/qu relationship. A program of splitting tensile tests and unconfined compression tests considering four distinct dry densities and five cement contents, varying...

Variables Controlling Strength of Artificially Cemented Sand: Influence of Curing Time

The present research aims to quantify the influence of the curing time period, amount of cement, porosity, and voids/cement ratio in the assessment of unconfined compressive strength (qu) of artificially cemented sand. A program of unconfined compression tests considering distinct curing time periods (t), porosities (η), and cement contents (C) was carried out in the present study. It has been found that a power function adapts well unconfined compressive strength values with increasing cement content and with reducing porosity of the compacted mixture. As expected, the unconfined compressive strength of the cemented sand increases with an increasing curing time period. It was also shown that the voids/cement ratio (η/Cv) is a good parameter in the evaluation of the unconfined compressive strength of the cemented sand studied, for the whole range of cement and porosities studied, at each specific curing time period studied. Finally, a unique relationship can be achieved linking the unconfined compressive ...