Abstract
For several decades, constant research has been performed in the world in order to obtain more durable, tighter, or less environmentally harmful binding materials which could be used to seal casing strings in boreholes. There is an increasing search for innovative solutions allowing the production of the highest possible class of binding cements. Since the beginning of the 21st century, one thing which has become synonymous with development is nanotechnology—a dynamically growing branch of science involving both the design, production, and testing of structures with the size of billionths of a metre. Among other things, a set cement stone is made of the grains of hydrated calcium silicates and calcium aluminates, between which there are pore spaces. Fine grains of nanoparticles can successfully settle inside these spaces, causing a decrease in the porosity and permeability of cement matrix. The paper presents the results of laboratory tests performed for formulas of cement slurries containing between 0.5% and 1% of nanosilica, between 1% and 3% of nanosized alumina and approximately 0.1% of carbon nanotubes. The resulting slurries had a density of approximately 1830–1920 kg/m3 and zero water settling. The thickening times of slurries were selected in accordance with the given geological and technical conditions. Early compressive strength amounting to 3.5 MPa (based on a test using an ultrasound cement analyser) was achieved by slurries after times between approximately 7 and 14 h. Upon setting of samples, cement stones produced from slurries featured a very low share of capillary pores. After 28 days of hydration, the compressive strength of the resulting cement stones took on very high values, reaching even up to 50 MPa. Photographs of cement stones containing nanomaterials (taken by means of scanning microscopy) are a confirmation of the exceptionally compact microstructure of the resulting samples.
Highlights
Nanotechnology is listed as a field of science focused among other things on testing, designing and producing components of very small sizes
Compositions marked with the symbols II and III were prepared for a temperature of 40 ◦ C and a pressure of 14 MPa, and subsequent formulas marked IV and V were prepared for 60 ◦ C and a pressure of 21 MPa
Upon performing a series of tests, it can be concluded that these components cause an improvement in the parameters of liquid and set cement slurry
Summary
Nanotechnology is listed as a field of science focused among other things on testing, designing and producing components of very small sizes. These components have grain sizes of several dozen nanometres, which allows them to constitute a basis for products with specific technological properties. The use of nanosilica, nanosized alumina or carbon nanotubes in the composition of cement slurry is a considerable step in the technological development of this branch of industry [3,4,5,6]. Nanoparticles (including n-SiO2 and n-Al2 O3 or carbon nanotubes) fill empty spaces between cement grains, resulting in the closure of pore channels in the cement matrix [7,8,9]. Nanoparticles participate in pozzolanic reactions or accelerate them, due to which some of the chemically unstable portlandite Ca(OH) is “used up” in cement during setting, and “additional” gel of the
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