The soil of the Guabirotuba geological formation (Paraná Basin, Brazil) has physico-mechanical properties which are not suitable for its utilization in pavement construction, in protection of hillsides and slopes, or as shallow foundation support. Treatment of this soil by lime addition would improve its usability. The present context intends to determine the ratio between the splitting tensile strength (qt) and the unconfined compressive strength (qu) of clayey soil in the metropolitan region of Curitiba City, which has been treated with different lime contents and curing times. The control parameters evaluated include lime content (L), curing time (t), moisture content (w), and ratio of porosity to volumetric lime content (η/Lv). It was observed that the qt/qu ratio is between 0.17 and 0.2 in relation to the curing time, and an exponential relation exists between them. Meanwhile, the unconfined compressive strength of lime-treated soil was found to be approximately four times the initial value.

Failures of tailings dams, primarily due to liquefaction, have occurred in Brazil in recent years. These events have prompted the Brazilian government to place restrictions on the construction of new dams, as iron ore tailings deposited behind upstream dams by spigotting have been shown to have low in situ densities and strengths and are prone to failure. This work proposes a new trend for tailings disposal: stacking compacted filtered ore tailings–Portland cement blends. As part of the proposal, it analyses the behaviour of compacted iron ore tailings–Portland cement blends, considering the use of small amounts of Portland cement under distinct compaction degrees. With the intention of evaluating the stress–strain–strength–durability behaviour of the blends, the following tests were carried out: unconfined compression tests; pulse velocity tests; wetting–drying tests; and standard drained triaxial compression tests with internal measurement of strains. This is the first study performed to determine the strength and initial shear stiffness evolution of iron ore tailings–Portland cement blends during their curing time, as well friction angle and cohesion intercept. This manuscript postulates an analysis of original experimental results centred on the porosity/cement index (η/Civ). This index can help select the cement quantity and density for important design parameters of compacted iron ore tailings–cement blends required in geotechnical engineering projects such as the proposed compacted filtered iron ore tailings–cement blends stacking.

Fine-grained soils have a low load-bearing capacity that hinders their use in pavement construction, slope protection, or foundation support. Therefore, the chemical stabilization of a soil with the addition of lime is a viable technique that could enable its use in civil construction. Unconfined compressive strength (UCS) and split tensile strength tests were performed to evaluate the improvement of a soil with lime and the existing correlation between these two tests. This study aims to determine the empirical relationships between the split tensile strength ($q_t$ ) and UCS ($q_u$ ) of a silty soil artificially cemented with hydrated lime ($L$ ). To calculate the $q_t/q_u$ ratio, soil–lime specimens are molded by controlling the dry unit weight, lime content, porosity, and water content, followed by curing for 15, 30, 60, 90, and 180 days. The voids/lime relationship determined by the porosity/volumetric lime content ratio ($\eta /L_v$ ) plays an essential role in this study, and it is the principal parameter used to assess the increases in $q_t$ and $q_u$ and determine their empirical relationship. The results demonstrate that $q_t/q_u=0.16$ for all curing times (15–180 days), so that it is an overall constant relationship ($q_t/q_u$ ). Moreover, with the addition of 9% lime, maximum resistances of $q_t$ (700 kPa) and $q_u$ (3,750 kPa) are obtained for the soil–lime mixtures after 180 days of curing. Moreover, two dosage equations that can be used as mix design relationships are obtained to determine the $q_t$ and $q_u$ of the lime-treated soils.

Sulfate-rich dispersive soils are worldwide responsible for damaging earthworks, such as roadway roadbeds and embankments. One of the causes for such behavior is the high amount of exchangeable sodium ions adsorbed on their clay particles vastly increasing erosion susceptibility, being responsible for problems as piping, ravines, and water turbidity. In order to reduce the erodibility, it is usual to treat such soils with calcium-based stabilizers. However, in the presence of sulfates, when combined with calcium-based stabilizers in the soil, reactions take place between stabilizers and sulfates to form expansive minerals. Namely, these minerals are known as ettringite and thaumasite and are responsible for excessive volumetric swell. In this context, the present research aims to develop alternative soil stabilizers (industrial byproducts plus artificial pozzolans) and reinforcements (fiberglass) to solve problems associated with sulfate-rich dispersive soils. Thus, a binder composed of carbide lime and ground glass was used. In addition, fiberglass was applied to look for enhanced mechanical properties of the materials. To assess the efficiency of the proposed stabilization and reinforcement, unconfined compressive and splitting tensile strength, ultrasonic pulse velocity, wet and dry durability, and fatigue life tests were carried out. Soil–ground glass–carbide lime-fiberglass blends were molded at different porosities, carbide lime, ground glass, and fiberglass contents. Results show that unconfined compressive and split tensile strength and initial shear modulus are highly dependent on changes in porosity and lime content. Durability, expressed as the accumulated loss of mass, could be assessed through the adjusted porosity/lime index ($\eta /L_{iv}$ ). Fiberglass inclusion resulted in higher tensile strength. The fatigue life was correlated to the $\eta /L_{iv}$ index through a negative exponent. The greater the carbide lime level, the smaller was the fatigue life for all treated specimens. An increase in porosity results in fewer contacts between particles, whereas an increase in carbide lime content enhanced the specimen’s rigidity.