Hasil untuk "Systems of building construction. Including fireproof construction, concrete construction"

Kaniaw Marof, Lidija Šiller

Abstract This study develops a sustainable masonry mortar incorporating a low dosage of KH-570 surface-modified silica aerogel and basalt fibre to improve thermal insulation while maintaining mechanical compliance suitable for non-load-bearing applications. This work, to the authors’ knowledge, is the first to combine KH-570 functionalised aerogel with basalt fibre to overcome the insulation–strength trade-off at low aerogel dosages. Two mortar series were prepared: (i) mortars containing 3, 5, and 7 vol. % unmodified aerogel as partial sand replacement and (ii) mortars with the same aerogel contents combined with 1 wt% cement-chopped basalt fibre. The setting time, flow of fresh mortar, dry bulk density, mechanical strength, and thermal properties were evaluated. Basalt fibre-reinforced samples demonstrated compressive strength increases of 8.0%, 7.2%, and 7.6%, and flexural strength gains of 6.0%, 8.0%, and 6.6%, respectively, compared with non-reinforced aerogel mortars while meeting the requirements of ASTM C270. Standard Specification for Mortar for Unit Masonry. ASTM International, West Conshohocken, PA, USA. (Type N), EN 998-2 (Class M5), and AS 4456.10 (Class M2). Thermal conductivity was reduced by up to 65% relative to conventional mortar, reaching its lowest value at 7 vol% treated aerogel combined with basalt fibre. The results demonstrate a material-efficient route to thermally insulating mortars that retain mechanical performance suitable for non-load-bearing masonry.

Juan C. Reyes, Diego A Peñaranda, Nathalia Ceron et al.

To reduce disaster impacts, initiatives have been promoted to assess seismic risk in developing countries like Colombia. To achieve this, it is crucial to develop exposure models that consolidate parameters of assets that may be affected by a seismic event, including their geographic location, material, structural system, and economic value. This last parameter is often assessed by using the asset replacement cost. Replacement cost valuations are often based on rough estimates that overlook factors like demolition, material transport, land suitability, structural typology, and regional socioeconomic dynamics. This study focuses on developing a simplified national replacement cost model for residential buildings in Colombia, a country that exemplifies the complexities and unique characteristics among developing nations. Colombia’s diverse seismicity, topography, socioeconomic disparities, and varied climatic conditions present an ideal case for examining how a streamlined approach for cost estimation can be implemented and effectively used. Within the framework of the open National Seismic Risk Model (MNRS), the proposed methodology includes over 50 representative combinations of materials and structural systems obtained from the available exposure models of the country. The model integrates traditional construction costs of common building types with variables reflecting current socioeconomic conditions and regional transportation dynamics. The research highlights the importance of including indirect costs and transportation dynamics for accurate nationwide replacement costs. The regional models, calibrated to reflect local socioeconomic and logistical dynamics, demonstrate a range of fit that varies significantly across regions. This variability highlights the importance of calculating replacement costs using a regional approach rather than assuming a homogeneous national model. The study also shows that reinforced concrete systems, especially moment-resisting frames, are costlier than masonry-based systems. The model updates Colombia’s exposure models in the MNRS, providing a crucial tool for decision-makers in a seismically active country.

Ziwei Wang, Dongping Huang, Minjuan He et al.

Abstract There are many engineering applications of prestressed concrete tower as the wind turbine support structure, and the concrete tower has the advantages of applicability and economy with good prospects. This paper proposes a grout layer replacement scheme for the problem of grout missing in the horizontal joint of concrete tower segments, and conducts a series of numerical simulation and fatigue analysis. The simulation results show that, for the case of grout missing, there is an obvious stress unevenness in the local area of severe grout missing. The concrete compressive stress decreases, tensile stress increases, tensile damage zone develops, and steel rebars stress increases, which can lead to local concrete cracking and blocks falling. For the case of grout filling and replacement completion, using no expansion grout for repair makes little contributions to the recovery of concrete stress, while using slight expansion grout can restore the concrete local stress to an even state. The fatigue analysis results show that, for the case of grout missing, the fatigue damage factors greatly exceed the limit, indicating a short fatigue life and the potential risk of local failure. For the case of grout filling and replacement completion, using no expansion grout cannot decrease fatigue damage, while using slight expansion grout can decrease fatigue damage and improve fatigue life. This paper provides the investigation into the effectiveness of grout layer replacement for horizontal joint, and the presented results can provide technical supports for the analysis and solution of grout missing problems.

Suthisa Onthong, Wilasinee Hanpongpun, Sakprayut Sinthupinyo et al.

Abstract Multiwall carbon nanotubes (MWCNTs) significantly enhance hydration reactions and properties of cement composites, expanding their applicability. Interest has grown in the use of multifunctional composites with MWCNTs being a popular filler material to impart additional features. Dispersing MWCNTs in the cement matrix creates an electrical network and replaces pore areas to enhance cement performance. This work compares two novel methods by admicellar polymerization (AP) and grafting polymerization (GP) for preparing bifunctional MWCNTs. Both techniques utilized polyindole (PIn) to enhance electrical conductivity and polyvinyl acetate (PVAc) for better dispersion. Isothermal calorimetry was used to observe the hydration of the cement composites. Results showed that AP-MWCNT/cement and GP-MWCNT/cement increased exothermic heat by 8.4% and 12.1%, respectively, compared to bare MWCNT/cement with the same nanotube content (0.3 wt%). Moreover, both modified MWCNTs improved mechanical properties and electrical conductivity. When comparing AP-MWCNTs and GP-MWCNTs in cement, AP-MWCNT/cement exhibited higher electrical conductivity, while GP-MWCNTs demonstrated superior embedding within the cement matrix, which led to a reduction in pore area and the higher mechanical strength of the two modified MWCNTs.

O. A. Mohamed, Ahmed Hassan, Nesreen R. Abdelwahab

Abstract This research aims to assess the effectiveness of incorporating thermally treated alumina sludge ash (ASA) as a partial replacement for slag-based geopolymer (SG-Geo) at various ratios (5%, 10%, and 20% by mass) and the integration of cost-efficient CuFe₂O₄ spinel nanograins (CF-NGs) at different addition levels (0%, 0.5%, 1%, and 1.5% by weight). The study focuses on enhancing the physico-mechanical features and durability of the geopolymer in aggressive environments, particularly against sulfate (SO₄2−) and chloride (Cl−) attacks. Key performance indicators include compressive capacity, and non-evaporable water content, to improve the ionizing radiation shielding properties of these eco-friendly geopolymer pastes to advance sustainability objectives. The fabricated samples were tested at 0.662 MeV, 1.17 MeV and 1.33 MeV photon energies as radiation shielding material to achieve sustainability goals. Gamma attenuation parameters (MAC, LAC, MFP, HVL and TVL) were determined experimentally and calculated theoretically using Phy-X/PSD software. The findings indicate that both theoretical and experimental results are consistent, with the radiation protection efficiency improving as ASA content increased up to 20%. The addition of 1.5% CF-NG notably enhanced the compressive strength at 28 days, as well as the gamma attenuation efficiency. Among the various SG-ASA hardened nanocomposites, Mix PS3CF1.5 exhibited superior physical and mechanical properties, along with the most effective gamma radiation shielding performance.

Mohammed Rihan Maaze, Sourav Kumar Das, Nikhil Garg et al.

Abstract India, as the world's second-largest cement producer, faces significant environmental challenges due to high carbon emissions from cement production. This study investigates the potential of using waste cement concrete (WCC) powder as a sustainable precursor in geopolymer concrete, aiming to advance sustainable development and effective waste management. Utilizing a central composite design (CCD) approach, the research optimizes molarity (M) and alkaline mix (AM) ratios to enhance the material's properties. Findings reveal that heat curing increases the 28-day compressive strength by 15–20% compared to room-temperature curing. Moreover, environmental impact assessments indicate a 15% reduction in Global Warming Potential (GWP) and a 12% reduction in Acidification Potential (AP), despite a 30% higher fossil fuel (FF) impact due to alkali use compared to traditional Portland cement mortar. Multi-response desirability analysis identifies the optimal molarity (10) and alkaline mix ratio (2.5) for achieving balanced performance across compressive strength, water absorption, shrinkage, tensile bond strength, and GWP. The confirmation experiments validate these predictive models, showing close alignment between predicted and observed values, ensuring the reliability and accuracy of the optimization approach. The study concludes that geopolymer mortars, particularly those cured at 60 °C with a 10 M NaOH solution and the optimal alkaline ratio, offer an environmentally friendly and mechanically superior alternative to conventional cement mortars. This approach supports sustainability by reducing environmental impact, promoting effective waste management, and contributing to sustainable development in the construction industry.

Seung-Hee Kwon, Jung-Soo Lee, Gi-Beom Ji et al.

Abstract To comprehensively explore the utility of non-destructive tests (NDT) results for structural diagnosis, this study collected NDT results and core compressive strength test results from aged bridges. Girders and slabs were obtained from seven such bridges, and after sectioning, rebound hardness test (RHT) or ultrasonic pulse velocity test (UPVT) were conducted alongside coring. The standard equations for estimation in South Korea were applied and a comparison between core strength and strength estimated using NDT results was conducted. In addition, the relationship between the static modulus and core specimen strength was determined to assess the soundness of the concrete cores, a factor that influences NDT signals. Based on the experimental results, this study deliberates on the practical applications of NDT results in structural diagnosis. A protocol for calculating the characteristic in-situ compressive strength using NDT results without coring was proposed and statistically validate this protocol via a probabilistic simulation.

Yi Li, Jiong Zhang, Jie Ding et al.

Abstract Solid waste materials (SWM) are commonly used in the preparation of building materials due to their structural characteristics and chemical composition. Pervious concrete (PC) is a green infrastructure material that offers advantages such as reducing surface runoff and purifying water quality, making it an important component of sponge cities. This study aims to investigate the physical properties and micro-structure of PC prepared from various SWM and determine the optimal mix proportion. In this study, three common SWM, including muck, steel slag (SS) and fly ash (FA), are used as raw materials. The chemical composition and physical properties of SWM are analyzed. A five-level and five-factor test scheme is developed using the orthogonal test method. This scheme considers the target porosity, water–cement ratio, muck content, SS content, and FA content as variables. The mechanical properties and permeability of PC, including compressive strength, porosity and permeability coefficient are evaluated. The internal structure of PC is observed using a scanning electron microscope (SEM). The results indicate that the optimal mix proportion for preparing PC is determined through efficiency coefficient method analysis: target porosity of 25%, water–cement ratio of 0.36, muck content of 10%, SS content of 10%, and FA content of 12.5%. The corresponding performance indicators of the PC sample are measured as follows: porosity of 24.67%, compressive strength of 15.78 MPa, and permeability coefficient of 2.23 mm/s. This study provides valuable insights for the rapid and flexible batching and performance optimization research of PC based on SWM.

Ebrahim Ashrafi, Masood Farzam

Abstract This study examines the mechanical behavior of structural lightweight aggregate concrete (LWAC) through uniaxial, cyclic, and biaxial compressive testing on cubic specimens at the macro level. The research focuses on mapping the biaxial failure stress envelope in the compression–compression domain and calibrating the Kupfer and Gerstle biaxial failure criterion specifically for LWAC, enabling its application in numerical simulations. A quadratic failure model is also proposed to predict LWAC's biaxial failure stress envelope. In addition, uniaxial cyclic compression tests were performed, allowing the determination of the cyclic stress–strain relationship and the calculation of the elastic damage index for LWAC under repeated loading. Tests on cylindrical and prismatic specimens further explored how increased uniaxial compressive strength influences key mechanical properties, such as the elastic modulus, splitting tensile strength, modulus of rupture, and axial stress–strain response. The biaxial tests revealed that LWAC has a biaxial compressive strength that is, on average, 21% greater than its unconfined uniaxial compressive strength at a stress ratio of 0.51 ( $$\alpha = 0.51$$ α = 0.51 ). The uniaxial cyclic tests show that LWAC experiences less post-peak damage compared to normal-weight aggregate concrete (NWAC), with the residual strength-to-peak stress ratio ( $${\sigma }_{res}/{\sigma }_{peak}$$ σ res / σ peak ) being 1.85 times greater in LWAC than in NWAC.

Alena Sičáková, Jeonghyun Kim, Magdaléna Bálintová et al.

Abstract When processing construction and demolition waste, determining the most effective waste management, potential use and recycling method for the identified materials is a key element. To do this, it is necessary not only to determine the type of materials, but also knowledge which aspects of the quality of the original materials are relevant for recycling and the ability to determine the values of these parameters as easily and quickly as possible, directly during demolition activities, is highlighted as an effective tool. This paper, intended as a case study, focuses on the evaluation of the effect of finely ground parent concrete as a cement component, the main objective being to find out whether the differentiation of the quality of the parent concrete, by compressive strength, plays a significant role. The parent concrete, the powder prepared from it, and the new standard mortar mixes, were analysed to obtain a comprehensive picture of the possibility of predicting the properties of the mixes based on the strength of the parent concrete. In general, no clear effect of the parent concrete strength on the flexural strength, compressive strength, water absorption, and ultrasonic pulse velocity values of the new generation mortar was observed. However, finely ground recycled concrete have shown a nice potential to be incorporated in Portland fine-grain cements, reaching strength classes 32.5 and 42.5. Care and precise verification require a 25% replacement, especially in the case of low strength parent concrete.

Wanheng Li, Tingyu Wan, Xiaohui Wang et al.

: As is well known, prefabricated concrete structures have the advantages of reducing on-site wet work volume, fast construction speed, saving materials, being conducive to building industrialization, and having good economic and social environmental benefits compared to cast-in-place concrete structures. Therefore, experts in the engineering industry actively advocate the application of prefabricated concrete structures. From the perspective of its structure, the hybrid prefabricated frame system has the characteristics of light weight, convenient construction, and large span, and has excellent seismic performance. According to the current specifications, propose reasonable seismic performance goals and measures, and conduct dynamic elastic-plastic supplementary analysis. The seismic performance can meet the needs of earthquake resistance, and the corresponding point is defined as the characteristic point of structural seismic performance, which can be based on the corresponding structural base shear force, vertex displacement, interlayer displacement, and crack development situation. Conduct performance testing and research on the seismic performance of the specimen, including hysteresis curve, load-bearing capacity, displacement ductility, strength degradation, and energy dissipation capacity.

Maciej Cwyl, Stanisław Wierzbicki, Rafał Michalczyk

: This article presents a study of a wall cladding system composed of stainless steel sub-frame and composite, fibre-reinforced concrete cladding panels, which was been installed on a high-rise public building. The study focused on the assessment of strength, safety and durability of design through laboratory tests and numerical analyses. The laboratory tests were conducted using a threedimensional tests stand and a full-scale mock-up of the wall cladding system built at the laboratory using the actually used materials and cladding panels. The boundary conditions and the test loads corresponded to the values of actions determined during the engineering phase of the high-rise building under analysis. Noteworthy, wind actions were verified by supplementary wind tunnel testing. In addition, the stainless steel was also tested to determine the strength properties of the material actually used in construction. These test were carried out just before commencement of the curtain wall installation. The 3D model was constructed with the application of the finite element method (FEM) to obtain adequate representation of geometry, material performance and structural behaviour of the analysed wall cladding system. Particular attention was paid to determination of the parameters defining the behaviour of the cladding system sub-frame from the angle of plastic deformations of the stainless steel and the resulting failure mechanisms of the members of the structure itself. To this end, the stainless steel was subjected to appropriate performance tests to determine material properties including the values of the proportionality limit and yield strength.

Najib Gerges, Camille A. Issa, Elias Sleiman et al.

Highlights Shear Strengthening of RC beams by HPFRC plates utilizing two methods. Precast HPFRC plates bonded by epoxy adhesive and anchored. Continuous shear strengthening resulted in high-capacity enhancement and ductility.

M. Laissy

Several factors have been affecting the urban design areas, leading to the construction of reinforced concrete (RC) buildings. Buildings on sloped terrains have been gaining increased popularity, especially from architectural peers. The vulnerability of constructions to seismic loads on sloped terrains increases due to mass and vertical irregularity, which in turn increases the torsional moments as well as shear forces. To control the effect of the seismic loads, many systems have been implemented, including shear walls and bracing systems. The objective of this work is to evaluate the effects of different strengthening systems and to identify the most suitable one for seismic load resistance. This paper studies the behavior of buildings with different strengthening systems applied to seismic loads using ETABS V18.1 and response spectrum analysis. A parametric study for these buildings has been performed to evaluate the effect of seismic loads on them. A dynamic analysis of the buildings in terms of shear forces, displacement, drift, fundamental time period, base shear, and story stiffness was carried out. The results demonstrated that the use of a combined strengthening system increased the stiffness and stability of the models and the resistance of RC buildings to seismic loads on sloped terrains. Doi: 10.28991/CEJ-2022-08-09-014 Full Text: PDF

Hua Chai, Zhixian Guo, H. Wagner et al.

. While current approaches in timber construction stress the advantages of off-site prefabrication, glued laminated timber(glulam) structures is limited to the constraints of standardized, prefabricated mostly linear elements, which also lends itself only to building typologies that offer an increased level of standardization and regularity. The design freedom of timber structures is incomparable to that of reinforced concrete structures, which mostly gains from the in-situ fabrication process. An in-situ robotic timber fabrication platform allows the on-site construction of glulam structures with highly differentiated networks of beams composed of robotically assembled discrete linear elements. Based on the possibilities of such mobile robotic fabrication process, this paper explores novel architectural typologies of spatial glulam structures. The research is conducted from several aspects including joint tectonics, design method, and robotic fabrication process. A large-scale pavilion is designed and fabricated to verify the feasibility of the proposed system. This research could provide a novel mode of in-situ robotic timber fabrication and corresponding glulam structure system for timber construction.

Seungchan Kim, Yangwoo Lee, J. Plank et al.

Abstract Tricalcium oxy silicate (C3S) and dicalcium silicate (C2S) are the major constituents of cement. In this study, the reactivity of polymorphs of calcium silicates is quantitatively investigated using Density Functional Theory. The result of combining the DFT calculation and the Bader charge analysis elucidates that the main difference in reactivity between C3S and C2S is the presence of oxy ions in C3S which has smaller partial charge compared to that of other oxygen in the crystals. For the C3S, the reactivity of among different C3S polymorphs is decisively affected by the Bader charge of oxy ions. In contrast, total internal energy of C2S determines the quantitative chemical reactivity of C2S polymorphs. This result suggests that oxy ion has more dominant impact on the thermodynamic stability of calcium silicates. Furthermore, total energy can be used to estimate the chemical reactivity of calcium silicates, where there is no oxy ion exists.

Hai-feng Lu, Kai Zhang, Jin-long Yi et al.

Abstract With the continuous development of economy, engineering construction is developing towards deep high-stress area, and the problems of large-deformation engineering are becoming more and more serious. Anchoring grouting is a very effective support reinforcement method. The anchoring grouting materials used in the project are mainly cement paste and cement mortar. The characteristics of the grouting material have a decisive influence on the grouting effect. However, it is difficult for the existing grouting materials to satisfy the requirements of strength and deformation at the same time, and improvement is urgently needed. Polycaprolactone (PCL) is an organic polymer material of good engineering properties, including high ductility, good stability and strong impact resistance. In this paper, PCL was added as an auxiliary additive to cement-based materials innovatively, and the mechanical test and micro-test of PCL-cement-based materials were carried out. The results show that adding PCL can significantly increase the compressive strength of cement paste. By adjusting the content of PCL, the strength and ductility of cement mortar can be effectively improved. When the content of PCL is 15%, ideal high performance cement mortar material can be obtained. Anchor grouting is a very effective reinforcement and support method.

In-Deok Han, Dongyeop Han

Abstract The aim of this research is to provide a quantitative method for evaluating concrete segregation. Because of various conditions of concrete materials, mix proportions, and delivery, concrete can be segregated. The acquisition inspection executed in construction field for supplied ready-mixed concrete is an important quality control process for concrete. Among the inspections conducted at the project site, segregation of concrete mixture should be evaluated before placing the concrete mixture, currently a qualitative inspection on concrete segregation was conducted. For a normal concrete mixture with slumping behavior, shear slump or collapse slump often occur as an indication of segregation. The suggested evaluation index of segregation for normal concrete (EISN) was induced from the shape of the concrete slumping: relation between the maximum distance of flow and the minimum distance of flow. To evaluate the feasibility of EISN, two different concrete mixture conditions were tested. The recommended EISN parameter of segregation is 1.09 using the three grades of concrete quality. This new quantitative method of evaluating segregation of the concrete mixture is expected to contribute to a more efficient quality control in concrete construction.

Eskinder Desta Shumuye, Jun Zhao, Zike Wang

Abstract In this study, the effect of curing temperature on the properties of slag cement concrete after high-temperature exposure was studied, and elevated curing temperature (45 ± 2 °C and 95% relative humidity (RH)) was selected to compare with the standard curing temperature (20 ± 2 °C and 95%RH). Four different concrete mixes with the same mix proportion, except for different slag replacement ratios, were used: 0% (reference), 30% (slag), 50% (slag), and 70% (slag). After high-temperature exposure at 200, 400, 600, and 800 °C, the effect of slag replacement, high temperature, and curing temperature on the compressive strength and mineralogical and microstructural properties of slag cement concrete were studied. Test results indicated that the compressive strength of concrete cured for 7 d at elevated temperatures increased by 28.2, 20.7, 28.8, and 14.7% compared with that cured at the standard curing condition at slag percentages of 0, 70, 50, and 30%, respectively. X-ray diffraction (XRD) and Scanning electron microscope (SEM) results revealed that concrete cured at elevated temperatures exhibited a more condensed phase and contained a higher percentage of hydrates than that cured for 7 d in the standard curing condition. However, after 56 d of curing, concrete in the standard curing condition exhibited a more stable phase and a higher concentration of hydrates.