Key Engineering Materials Vol. 930

Abstract: Increasing the durability of brick structures is a current requirement for reducing damage in particular natural disasters, over-pressure wind effects and extraordinary loads.The structures are designed today according to valid standards and on the basis of empirical experience. They are designed for extraordinary effects only in cases where this is required by regulations, especially fire regulations. For brick structures, it is often followed by established procedures and catalogue recommendations, and the solution of these structures is often considered banal. However, what if the damage exceeds the effects set by the standards. Therefore, this contribution is devoted to simple instructions for increasing the durability of low-floor masonry buildings above the normal limit given by the current construction and the applicable regulations.

Abstract: Design of concrete columns subjected to axial force and uniaxial bending moment from the point of view of prepared prEN1992-1-1/2021. A comparison by interaction diagrams for concrete strength classes C30/37 and C90/105 for symmetrically and asymmetrically reinforced cross-section and for symmetrical cross-sections only to one axis, respectively.

Abstract: Cement panels are industrial products that are widely used as construction and insulation materials. In general, cement panels are reinforced with synthetic fibers. In this study, a cement panel reinforced by natural fibers, namely abaca fiber, was developed. Abaca fiber has advantages over other natural fibers in terms of availability, mechanical properties and physical properties. Cement panels were made in several levels of abaca fiber content (0%, 1%, 2%, 3% and 4%) to study the effect of fiber content on the flexural strength and physical properties of cement panel. The material and experiment were prepared and carried out according to Indonesia standard SNI 01-4449-2006. The result of the experiment showed that the fiber content significantly affected the flexural strength, density, moister content, water absorption and thickness development of abaca-cement panels. The maximum flexural strength was 71.88 MPa, produced by cement panel with 3% fiber content, and it was 2.15 time higher than cement panel without fiber. The result of the experiment indicated that the abaca fiber was potential inforcement for cement panel with respect to its flexural strngth and physical properties.

Abstract: Rice husk (RH) is an agricultural waste transformed to produce secondary by-products and is widely accepted as a substitution of cement or concrete mixtures. This paper deals with the optimal level of SiO₂ content due to various incineration conditions of rice husk grown in Perlis, Malaysia. RH was burnt in a controlled environment with a targeted temperature of 650, 750 and 850 °C at various incineration period between 1 and 6 h. All the ashes were assessed for visual inspection and physiochemical and mineralogical properties using X-ray fluorescence (XRF) and X-ray diffraction (XRD). From the analysis, a significant amount of SiO₂ in the range of 89–93 wt % was successfully obtained with the preferable properties of supplementary cementitious materials: amorphous silica with high reactivity, ultrafine size, and large surface area. Contrary, the burning temperature of 850 °C greater than 4 h incineration period is not advisable to be used as it transformed into a crystalline phase. No obvious color changes were observed for the ashes as the amount oxide compound of K₂O causes carbon entrapped in surface melting. To sum up, 650 °C incineration for 1 h shows an optimum result, and the RH is bearable to reduce the negative impact on the environment.

Abstract: Generally, reinforcing steel in concrete is protected from corrosion. This happens because the cement content in the concrete has an alkaline effect. It can reduce the risk of corrosion, but the reinforcing steel may still corrode if exposed to a corrosive environment. One method of providing a high protection value against corrosion is the sacrificial anode cathodic protection system. This study aims to evaluate the effectiveness of the sacrificial anode cathodic protection on reinforced concrete. Three types of specimens were used in the study. The specimens were (a) unconnected anode-cathode specimen, (b) connected anode-cathode (design 1), and (c) connected anode-cathode (design 2). The dimensions of the concrete specimen are 1000 mm in length, 100 mm in width, and 100 mm in height. Profometer 5+ was used to locate the reinforcing steel in the concrete. In this study, the condition of the protected criteria of reinforced concrete was achieved within 30 weeks in 2019 after wet-dry cycle treatment in 3.5% NaCl media, and thus, the specimen was exposed in an open air for one year. In 2020, all of the specimens were treated again with a wet-dry cycle for 3 weeks to measure the potential value of the reinforcing steel after a year. The measurement result of the corrosion potential value after one year showed that the specimen (c) had a potential value of -884.67 mV. While the specimen (b) had a potential value of -689 mV. These results show that the specimen (c) still within the protected criteria based on the NACE standard after one year of exposure, whereas the specimen (b) is no longer protected after one year of exposure.

Abstract: The need of returning millions of tons of previously used materials to the production process is already a globally addressed fact. This also applies to building construction, where the construction materials can also be used repeatedly. The use of recycled materials is a crucial tool for sustainable development and reaching a compromise between economic progress and the preservation of the environment. Notable improvement has been recorded in the use of recycled material on road communication. There, the optimal solution is to use the „old surface“ to create a new one – this is advantageous for roads with concrete surfaces, as well as for the ones with bituminous surfaces. Though the effort is to use 100% of the recycled material, there are many cases where it is only possible to use a certain portion of the materials, depending on the type of processing. The remaining volume of milled material is either used to strengthen the subsoil of roads or for service roads. Recycled concrete is suitable as a low-cost alternative of gravel on less stressed structures and places, or as a replacement for quarry stone. The processes of using recycled concrete are actively being studied and improved on in laboratories. However, the portion of recycled concrete affects the consistency of the concrete mix and in order to maintain the required consistency, it is necessary to increase the dosage of mixed-in water, which results in reduced concrete strength. The use of recycled concrete must be assessed for each case according to the grading curve and with the impact on the values of load-bearing capacity, water absorption and frost susceptibility. The economic assessment must also be addressed, with an emphasis on traffic requirements and impact on the environment. The first important step is to offer the investor, architect or supplier a decision-making model which allows one to evaluate the usability of the recycled material, including the consideration of possible risks.

Abstract: The article deals with the role and importance of supervision in the Czech construction industry. It accentuates its role in public procurement and provides a comprehensive view of its activities. The article also clarifies the function, content and duties of supervision with regard to concrete structures or the importance of supervision of the construction life cycle.Currently, during the time the Czech construction industry is almost at the peak of its staff and material capacities, the main topic between the Employer and the Contractor is the ratio of quality and price of construction. This ratio can never be determined exactly, but it can be checked and monitored during the actual course of construction. Among other things, the position of technical supervision is included between these two entities. Emphasis should be placed on independence, technical expertise and competence in the performance of supervision. If these requirements are to be fulfilled, it is mainly external supervision, i.e. supervision by external persons (legal entity).

Abstract: The paper is focused on diagnostics and calculation of load-carrying capacity of the two atypical girder bridge objects on the railway line between Púchov and Považská Bystrica in Slovakia. These are skewness reinforced concrete (RC) girder bridges with three girders. The non-typicality is given by the fact that the spandrel girders are in the longitudinal direction, but the middle girder is relatively wide and is perpendicular to the clearance (not in the longitudinal direction). The diagnostics was performed on the objects aimed at determining the material and geometric characteristics, which served as a basis for the numerical model. A 3D scanner was also used to determine the geometric dimensions. The load-carrying capacity was subsequently determined on the bridges. The recalculation and diagnostics revealed the fact that bridge structures can still be used, but have to be reconstructed. This is a prime example of reusing in practice, i.e. how the old bridges can be further used, which means a significant saving of CO₂ emission that would be produced by demolishing the old bridges and building new ones

Abstract: The paper deals with diagnostics, recalculation, and determination of the current load capacity of three concrete arch bridges on the original railway line Bratislava - Žilina. This was built in 1954 in connection with the relocation of the line, caused by the exhibition of the Nosice reservoir. At present, the railway line has been relocated to a new location and the existing original line, including the existing engineering facilities, will be used for the construction of a new road connecting the district towns of Púchov and Považská Bystrica. The task was solved within the cooperation of Faculty of Civil Engineering with the Railways of the Slovak Republic (ŽSR in Slovak) and the Research and Development Institute of Railways (VVÚŽ in Slovak). The conclusions from the recalculations and the subsequently determined load capacity show that the bridge structures in question are suitable for further use, however, their reconstruction is necessary.