Influence of base material particle features on petrophysical properties of synthetic carbonate plugs.

Rocks with representative physical and chemical properties are essential to understanding fluid-solid flow behaviors at the pore scale. In this way, studying the pore space characteristics is a key point for evaluating and providing petrophysical properties for distinct rock types, such as synthetic rocks, with controlled and representative properties like natural ones. This work studies the petrophysical properties of synthetic carbonate plugs with a novel approach by correlating particle size, particle size fraction, and the morphology of particles with porosity and permeability, which could guide the scientific community to further forming of carbonate rocks with a controlled pore network. Results indicated that particle shape influenced the accommodation of particles in the porous space and, therefore, in the petrophysical properties, where an increase in particle size decreases porosity and increases permeability. Also, the obtained plugs showed the following petrophysical features: gas porosity from 10% to 17%, mercury porosity from 11% to 19%, gas permeability from 0.07 mD to 0.70 mD, and mercury permeability from 0.02 mD to 0.35 mD, providing important insight on controlling pore space in synthetic carbonate rocks.

Effects of acidic attack on chemical, mineralogical, and morphological properties of geomaterials.

Exposure of geomaterials to acidic leachates may compromise their structure and functionality due to changes in physicochemical, mineralogical, and hydraulic behavior. The literature identifies the need to evaluate changes in a pure state and in conditions of extreme acidity. This study aimed to evaluate changes in the chemical, mineralogical, and morphological properties of Osorio fine uniform sand (OFS), basalt residual soil (BRS), kaolin (KAO), and bentonite (BEN) exposed to sulfuric acid in concentrations of 0.00 mol/L (distilled water), 0.01 mol/L, and 1.00 mol/L. The tested samples were characterized using X-ray fluorescence spectrometry, X-ray diffraction, thermogravimetry, differential scanning calorimetry, and scanning electron microscopy. The acid attack on geomaterials by contact with the solution 1.00 mol/L has resulted in the solubilization of some constituent minerals, as well as the formation of sulfate minerals, changes in the water dehydration peak in the pores, and mass loss. The morphology of the sand and bentonite particles did not change with exposure to sulfuric acid. The acidic attack resulted in changes in the morphology of the particles for BRS and KAO. The results of this study are important for determining operational parameters of waste containment systems and contaminated areas, as well as for applying geomaterials as founding materials.

Separability studies of construction and demolition waste recycled sand.

The quality of recycled aggregates from construction and demolition waste (CDW) is strictly related to the content of porous and low strength phases, and specifically to the patches of cement that remain attached to the surface of natural aggregates. This phase increases water absorption and compromises the consistency and strength of concrete made from recycled aggregates. Mineral processing has been applied to CDW recycling to remove the patches of adhered cement paste on coarse recycled aggregates. The recycled fine fraction is usually disregarded due to its high content of porous phases despite representing around 50% of the total waste. This paper focus on laboratory mineral separability studies for removing particles with a high content of cement paste from natural fine aggregate particles (quartz/feldspars). The procedure achieved processing of CDW by tertiary impact crushing to produce sand, followed by sieving and density and magnetic separability studies. The attained results confirmed that both methods were effective in reducing cement paste content and producing significant mass recovery (80% for density concentration and 60% for magnetic separation). The production of recycled sand contributes to the sustainability of the construction environment by reducing both the consumption of raw materials and disposal of CDW, particularly in large Brazilian centers with a low quantity of sand and increasing costs of this material due to long transportation distances.