Abstract
The increasingly strong search for alternative materials to Portland cement has resulted in the development of alkali-activated cements (AAC) that are very effective at using industrial by-products as raw materials, which also contributes to the volume reduction in landfilled waste. Several studies targeting the development of AAC—based on wastes containing silicon and calcium—for chemical stabilization of soils have demonstrated their excellent performance in terms of durability and mechanical performance. However, most of these studies are confined to a laboratory characterization, ignoring the influence and viability of the in situ construction process and, also important, of the in situ curing conditions. The present work investigated the field application of an AAC based on carbide lime and glass wastes to stabilize fine sand acting as a superficial foundation. The assessment was supported on the unconfined compressive strength (UCS) and initial shear modulus (G0) of the developed material, and the field results were compared with those prepared in the laboratory, up to 120 days curing. In situ tests were also developed on the field layers (with diameters of 450 and 900 mm and thickness of 300 mm) after different curing times. To establish a reference, the mentioned precursors were either activated with a sodium hydroxide solution or hydrated with water (given the reactivity of the lime). The results showed that the AAC-based mixtures developed greater strength and stiffness at a faster rate than the water-based mixtures. Specimens cured under controlled laboratory conditions showed better results than the samples collected in the field. The inclusion of the stabilized layers clearly increased the load-bearing capacity of the natural soil, while the different diameters produced different failure mechanisms, similar to those found in Portland cement stabilization.
Highlights
A recurrent problem found in engineering works is the poor geomechanical properties and, especially, the low strength and stiffness of soils, which is responsible for the structural problems associated with the installation of superficial foundations or pavement layers, for example, often made unfeasible
FigFigure 9 shows the unconfined compressive strength tests (UCS) of the samples recovered from the field after 14 and 120 days ure 9 shows the UCS of the samples recovered from the field after 14 and 120 days and and compares these values with those obtained in the laboratory
As is usually the case, the case, the field results are lower than those obtained with the specimens fabricated in the the field results are lower than those obtained with the specimens fabricated in the concontrolled environment of the laboratory. Such difference is more significant after 120 days trolled environment of the laboratory. Such difference is more significant after 120 days since the material spent more time exposed to the environment and, was less capable since the material spent more time exposed to the environment and, was less capable of developing higher UCS levels
Summary
A recurrent problem found in engineering works is the poor geomechanical properties and, especially, the low strength and stiffness of soils, which is responsible for the structural problems associated with the installation of superficial foundations or pavement layers, for example, often made unfeasible. [39], through compressive strength and durability tests, concluded that the compacted mixture of finely ground waste glass-carbide lime with an alkaline sodium hydroxide solution of 3 molal concentration has proven to be a viable material to be used in engineering applications as an alternative and sustainable replacement geomaterial for earthworks, pavement and soil stabilization. After the laboratory evaluation of the binders, several layers of fine sand were stabilized with two different types of binders— Both based on GWG and CL, which were alkali-activated in one case and hydrated with water in the other—and analyzed after 14 and 120 days of curing, through their unconfined compressive strength (UCS) and initial shear modulus material stiffness (G0 ). The results of in situ plate load tests are presented
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