Construction materials science. Рубрика в журнале - Nanotechnologies in Construction: A Scientific Internet-Journal
The strength and deformability of cement stone and powder-activated concrete. Part I
Статья научная
Introduction. During the operation of buildings and structures, reinforced concrete structures are subject to various loads that can cause deformation and destruction. The strength and elastic-plastic properties, as well as the durability of modern concrete, are controlled using superplasticizers, nanoadditives, fillers, and aggregates. The potential of using nanohydrosilicate technologies is demonstrated. This article examines the physical and mechanical properties of cement stone and powder-activated concrete – one type of next-generation concrete. Materials and methods. The influence of the water/cement ratio, the presence of a carboxylate superplasticizer, and a modifying additive were considered as structure-forming factors for cement stone, and the influence of the water/cement ratio, modifying additive, superplasticizer, finely dispersed filler, rheological fillers and reactive fillers were considered for concrete. Results. The article presents the results of a study establishing the relationship between the density of cement stone and powder-activated concrete with the porosity and strength indicators under static and dynamic loads. The rational compositions of the developed composites are characterized by a set of improved physical and mechanical properties. It was found that an increase in the W/C ratio from 0.267 to 0.35 causes a decrease in the compressive and tensile strength of cement stone when splitting by 22–30%. The addition of the superplasticizer ”Melflux 1641F“ led to a significant decrease in the water-cement ratio – from 1.56 times compared to the composition of normal consistency and by 2.04 times – compared to the composition with an increased W/C ratio, as well as a corresponding increase in compressive strength properties – by 1.20 times and 1.72 times – in flexural tensile strength. Conclusion. It was found that the introduction of finely dispersed fillers into the composition of sand concrete led to an increase in compressive, flexural, and tensile strength when splitting by 1.62 to 2.55 times, which is explained by a denser packing of quartz filler, causing an increase in the density of such samples by 9.5%, the plasticizing effect of microquartz, and the high activity of microsilica. The impact strength of the cement composite was studied. It was found that plasticized highly filled compositions of the new generation demonstrated high values of the maximum contact force, contact duration, and impulse magnitude. The composite containing microquartz, quartz filler, fine aggregate, and Melflux 1641F superplasticizer has a maximum contact force of 4.530 N, compared to a similar value of 2.073 N for a cement stone composition made from normal consistency paste. Moreover, the contact duration and impact impulse magnitude are approximately twice as high. The addition of microsilica to the highly filled compositions caused even better results. The maximum contact force at which the samples failed was 4.530 N. This is more than twice that of cement paste based on normal consistency.
Бесплатно
Use of pulp and paper industry waste in binding and cementitious materials technology
Статья научная
Introduction. Utilization of chemical cellulose fillers in construction industry is one of the ways of processing unused wastes from pulp and paper industry. Decorative, finishing, and heat insulation materials are widely used as construction materials. This paper proposes various compositions and insulation materials characterized by compressive strength of not less than 10 MPa, water tightness of 0.8, and density of not over 600 kg/m3. The likely curing mechanism is studied for cement systems. The possible mechanism of hardening structures formation in the systems is discussed. Methodology. Corrugated fibreboard МS-5B waste is used as a filler, high-early strength cement М-500 (CEM 47.5) – as inorganic binder, and elemental sulfur, polyethylene terephthalate, cementmodified polyurethane (PU) with the addition of nanosized silicon oxide are used as a polymeric matrix. Infrared spectroscopy, terahertz time-domain spectroscopy (THz-TDS), and scanning electron microscopy are used for investigations. Cement samples undergo compressive strength, water tightness and water absorption testing. Results and discussion. Physical and mechanical properties obtained for composites with the paper filler and polymeric matrix based on cement-modified PU, are described, and testing results are compared with the experimental data obtained for materials based on other binders. It is found that the paper filler–cement-modified PU composition is consistent with the purposes of this research. The understanding is improved for the curing mechanism of the polymeric matrix–paper filler system. The THz-TDS data demonstrate a correlation between the spectral transmission and thermal conductivity and density of synthesized heat insulation materials. Conclusion. Synthesized is the effective heat insulation material with relatively high compressive strength, low density, and high tightness to water. Scientific understanding of the curing mechanism is improved.
Бесплатно
