Efficient use of recycled resources. Рубрика в журнале - Nanotechnologies in Construction: A Scientific Internet-Journal
Circular economy in recycling concrete and reinforced concrete waste
Статья научная
Introduction. In the process of demolition and dismantling of emergency buildings, as well as during construction and reconstruction, more than 70 million tons of construction waste are generated annually in Russia. The circular economy is based on the principle of resource renewal, recycling of secondary raw materials, technological measures to return waste to the repeated economic turnover. Nowadays the problem of saving natural resources and reducing construction waste is especially urgent. About 80% of construction waste is heavy and light reinforced concrete, from which can be produced secondary crushed stone, increasing the use of which is one of the tasks in the transition of linear economy to a circular economy. Materials and methods. The study of the implementation of a set of organizational, economic and technological solutions aimed at the reuse of construction waste was carried out. The analysis was carried out on the example of using secondary aggregates obtained from concrete scrap. Results and discussions. In the course of the research the necessity of concrete scrap involvement into repeated economic turnover was proved, as its use in construction fully meets the requirements of the set tasks in the field of energy and resource saving and environmental safety. Conclusion. Recycled crushed stone is a valuable resource that contributes to the sustainable development of the economy as a whole and reduces the harmful impact of the construction industry on the environment.
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Microstructural and micro-mechanical characteristics of cement paste incorporating cuttlebone powder
Статья научная
Introduction. Marine bio-waste provides a sustainable calcium-rich resource for cementitious materials, but its role in hydration control remains limited. Cuttlebone powder (CBP) is a marine bio-calcium with a porous hierarchical structure, and it forms a nanostructured calcium carbonate system. This system influences phase evolution and structure–property relationships in cement paste. This study evaluates its effects on phase composition, Ca/Si balance, microstructure, and structure–property relationships. Materials and Methods. The study prepares plain and CBP-modified cement paste. CBP replaces cement at 10–50% by weight. All mixtures use a constant w/b ratio of 0.5 and cure for 28 days. TGA evaluates phase composition, EDS determines Ca/Si ratio, SEM and mapping examine microstructure, and Vickers hardness measures micro-mechanical properties. Results. CBP modifies the phase composition of cement paste. Calcium hydroxide decreases from 18.68% to 13.13%, while calcium carbonate increases from 2.80% to 15.05%. The Ca/Si ratio increases and indicates a Ca-rich system. The microstructure becomes heterogeneous, and Ca distribution becomes more localized, while Si remains relatively stable. Micro-mechanical properties increase up to CBP40 and decrease at higher replacement levels. Discussion. CBP influences hydration through its porous hierarchical structure and calcium carbonate composition. This structure controls ion distribution and phase development and governs Ca/Si balance and microstructural evolution. The results establish a structure–property relationship and define the micro-mechanical response. Conclusion. CBP acts as a nanostructured calcium carbonate and alters phase composition, Ca/Si balance, and microstructure. This modification improves micro-mechanical performance at moderate replacement levels but reduces matrix continuity at higher levels.
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Статья научная
Introduction. The volume of industrial, agricultural, and household waste generated annually in Vietnam has been steadily increasing, while the demand for building materials is growing. This study evaluates the feasibility of using cement-free "green" concrete based on thermal power plant fly ash, blast furnace slag, and glass waste to produce translucent decorative elements. Materials and methods. The study used research methods that comply with current Vietnamese standards, as well as a specially developed experimental setup to determine the light transmittance coefficient of decorative “green” concrete samples. Cement-free binders were produced using fly ash from the Pha Lai Thermal Power Plant and finely ground granulated blast furnace slag from the Hoa Phat Steel Plant, combined with an activator consisting of a 1:1 mixture of aqueous solutions of NaOH and Na2SiO3. The concrete mixtures also included glass waste of various colors, crushed to particles sized 5.0–20.0 mm, decorative fine aggregate with a fraction of 2.5–5.0 mm, and a superplasticizing admixture under the trade name MVN-SR manufactured by Silkroad Hanoi. Synthetic polypropylene fibers in the form of individual filaments and steel mesh fiber were used to provide dispersed reinforcement for decorative translucent products to improve their crack resistance and mechanical properties. Additionally, various pigment powders in red, yellow, blue, and other colors were used to impart the desired color range and aesthetic properties to the decorative products. Results. Four compositions with waste glass contents ranging from 5 to 20% by weight were developed to analyze their effect on the workability of concrete mixes, as well as the physical and mechanical properties and light transmittance of decorative products. The obtained results showed that with an increase in the glass content, the workability of concrete mixes according to the cone flow decreased from 25 to 19 cm, while their average density increased from 2068 to 2169 kg/m 3. After curing for 28 days, the compressive strength of concrete samples was 38–46 MPa, tensile strength in bending was at least 4.9 MPa, wear resistance was 0.3–0.51 g/cm3, water absorption by weight was from 7.3 to 8.5%, and the light transmittance coefficient increased from 11.8 to 20.5%. Conclusion. The resulting light-transmitting decorative products are suitable for interior and exterior decoration, simultaneously providing the required performance characteristics and creating a soft light diffusion effect indoors. Furthermore, the use of high-volume industrial waste helps reduce natural resource consumption and carbon dioxide emissions, confirming the potential of this decorative finishing material to enhance the architectural expression of residential and public building interiors.
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