Search

Seismic occurrences have caused severe damage and even the collapse of fragile unreinforced masonry structures. New technologies are replacing these conventional methods of construction; concrete sandwich panels (CSP) are one such technique gaining popularity. In-plane diagonal shear strength of concrete sandwich panels is studied experimentally, and the effect of incorporating geogrids on the deformation capability and load-bearing capacity is reported. Two forms of geogrid material, plastic uniaxial geogrid (PUG) and polyester biaxial geogrids (PBG2 and PBG3) are used to improve the strength and ductility of concrete sandwich panels. Diagonal compression tests have been carried out better to understand the behavior of CSP under in-plane strength. This paper also discusses the effect of the different mixes, the effect of geogrids, load-deformation behaviour, shear capacity, deflection ductility factor, mode of failure, shear strength, and energy dissipation. In contrast to the control specimen, specimens cast with plastic geogrid had a 13.7% and 26% improvement in shear capacity and load-bearing capability for the two types of micro-concrete mixes used in this study. The conclusion reached is that plastic uniaxial geogrid is effective in improving the concrete sandwich panels' load-bearing capacity, shear capacity, and deformation ability. Polyester biaxial geogrids enhanced the ductility of the concrete sandwich panels. [ABSTRACT FROM AUTHOR]

Construction operations, particularly concrete formwork, pose significant risks of musculoskeletal disorders (MSDs) to workers. Previous studies have examined the MSDs associated with conventional job-built formwork. In light of the growing popularity of modern ready-made formwork systems, and the claim that such systems reduce MSDs, it is imperative that researchers characterize the activities associated with the use of these systems and offer empirical insight into their relationship with MSDs. In response to this need, this study aims to assess and compare MSD risks related to different modern formwork systems. Specifically, the Rapid Entire Body Assessment (REBA), a method for full-body postural ergonomic risk assessment, was used to study the ergonomic hazards of form workers during the installation and removal of horizontal modular and prefabricated or engineered formwork systems. The findings indicate that most formwork tasks and activities subject workers to medium to high MSD risks, necessitating preventive actions or imminent preventive actions. Modular formwork systems may subject workers to fewer hazardous ergonomic working conditions compared with prefabricated or engineered formwork systems. The findings provide an improved understanding of formwork activities and the MSD risks associated with ready-made formwork system construction, and provide a valuable resource for formwork designers and constructors dedicated to improving worker health and safety in formwork construction. [ABSTRACT FROM AUTHOR]

Compared with traditional portland cementitious material, alkali-activated material (AAM) had the advantages of low carbon emission, energy saving, excellent durability, strength, and high temperature resistance. It has been proved that the addition of a fiber or nano-particle could improve the mechanical properties of AAM. The fresh and hardened properties of nano-CaCO3 (NCC) and polypropylene fiber (PPF) reinforced AAM were studied in this paper. The hybrid effects of PPF with various volume fractions (0%, 4%, and 8%), aspect ratios (0–464.52), and NCC with various content (0%, 1%, and 2%) on the slump spread, flow rate, flexural strength, compressive strength, and ultrasonic velocity of AAM were investigated. For flowability, the mixture with 0.4% 6 mm and 0.4% 12 mm PPF was the optimal, showing a positive hybrid effect. The hybrid use of PPF and NCC significantly improved the flexural strength, but the compressive strength was not significantly improved. The hybrid effect factors for compressive strength were lower than those for flexural strength. The positive hybrid effect of strength was most obvious when the nano-CaCO3 was 1%. The threshold for fiber factors was 200. Microstructure studies showed that the bridging effect of PPFs can limit the crack development and enhance the strength of AAM. Nano-CaCO3 promoted the denseness of AAM and bond between fiber and matrix. The hybrid of PPF in different lengths and NCC could decrease fiber consumption, reducing the cost and promoting the engineering application of fiber-reinforced AAMs. The effect of hybridization of calcium carbonate nano-particles with polypropylene fibers on the fresh and hardening properties of alkali-activated materials has practical applications in the construction industry. One of its main advantages is its excellent flowability, which allows the material to be self-consolidating. This property allows it to be used effectively in areas such as post-tensioned grouting, pipe concrete, and other grouting processes, where the material flows effortlessly and fills voids efficiently. In addition, the mixing effect of the CaCO3 -nano-particles and the polypropylene fibers enhances the stability and strength of the material, which further enhances the durability and structural stability of the concrete elements. Overall, this blend has excellent flow and self-consolidation properties, making it an important choice for applications such as postgrouting and reinforced concrete construction. [ABSTRACT FROM AUTHOR]

The discrete-like crack model (DLCM), a crack-analysis scheme incorporated with the nonlinear finite element method, is redeveloped for parallelism. The algorithm of the new DLCM based on the theory of bond redistribution is implemented through the OpenMP interface and enables analyses of a 50-story building with more than four million degrees of freedom. The analysis considers the drying shrinkage and creep during the construction and service periods, static pushover loading, and a time history of a near-fault strong ground motion. The amount of cracks is quantified as the total length that occurs on the concrete surfaces. The structural damage due to compression softening exhibits a strong correlation with the length of cracks with opening widths larger than 2 mm. The analyzed building becomes unrepairable when the total length of the >2 mm wide cracks exceeds 50 m. However, the occurrence of such serious damage induced by any seismic vibrations ever recorded is unlikely. "There's no art to find the mind's construction in the face," so King Duncan said. However, we can consider the search for structural damages on concrete surfaces a form of art. The presence of cracks proves the life of a reinforced concrete building, similar to a person's history engraved as wrinkles and scars on their face. Our novel parallel numerical scheme, namely, the discrete-like crack model (DLCM), traces not only the long history of a building starting from its construction but also resolves the issue of unexpected near-fault pulse-type earthquakes into detailed profiles. In this case study, DLCM is employed to assess structural damage using a percentage of cracks that extend up to 100 km on the entire concrete surfaces of a 50-story residential building. The profiles of cracks, stresses, and strains articulate the building's past and current status and render the possibility to improve the quality of living in the future. [ABSTRACT FROM AUTHOR]

Sustainable development and the preservation of the natural environment are two concepts that are becoming increasingly important in the construction sector, leading to a growing interest in the development of ecofriendly building solutions. In this regard, the use of waste polyethylene terephthalate (PET) bottles as a construction material is an interesting alternative that can help to reduce the environmental impact of the building activity at little or no cost, while providing a second life to a material that is one of the main sources of pollution. The present study analyses the mechanical behavior of PET bottles for their use as construction materials, carrying compression tests to assess the elastic properties of PET bottles filled with sand or plastic waste, both alone and embedded in a concrete matrix. In a second part of the study, a finite-element method model of an existing water tank built with PET bottles in Tanzania is developed and tested. The results obtained show the suitability of the composite bottle-and-concrete samples as a sustainable construction technique. Environmental sustainability is an increasingly important aspect in our society and all its productive sectors, and the construction industry is no exception. In this regard, diverse initiatives have been proposed to introduce waste polyethylene terephthalate (PET) bottles as a construction material, which provides three direct benefits: offering a low-cost construction material, reducing the consumption of new resources, and giving a second life to waste material that would otherwise end up in landfills or in the environment. However, to use these new sustainable materials in safety conditions, it is necessary to understand their mechanical and structural behavior and treat them with the same rigor as we treat conventional construction materials such as concrete or steel. In this sense, in the present study, a testing campaign is conducted to assess the compressive strength of PET bottles filled with sand or plastic, as well as their combined use with concrete to form walls in buildings or water tanks. [ABSTRACT FROM AUTHOR]

Numerous techniques and technologies exist to automate construction-related tasks, which include the latest three-dimensional concrete printing (3DCP) methodology. These automation techniques seek to solve the entrenched problems in construction, such as declining productivity, shortage of skilled workers, ineffectiveness in project management, unsustainability, and the increase in construction demand. The 3DCP has further benefits, such as quicker construction times, design freedom, and more predictability. However, there is resistance to adopting 3DCP in the industry and by the market. With experience from a 3DCP organization and a case study on a 3DCP villa, this paper presents the major challenges that hinder this technology's adoption and use, important lessons learned from the villa construction, and highlights of the local community's critical feedback. [ABSTRACT FROM AUTHOR]

This review focuses on recent advances in concrete durability using graphene oxide (GO) as a nanomaterial additive, with a goal to fill the gap between concrete technology, chemical interactions, and concrete durability, whilst providing insights for the adaptation of GO as an additive in concrete construction. An overview of concrete durability applications, key durability failure mechanisms of concrete, transportation mechanisms, chemical reactions involved in compromising durability, and the chemical alterations within a concrete system are discussed to understand how they impact the overall durability of concrete. The existing literature on the durability and chemical resistance of GO-reinforced concrete and mortar was reviewed and summarized. The impacts of nano-additives on the durability of concrete and its mechanisms are thoroughly discussed, particularly focusing on GO as the primary nanomaterial and its impact on durability. Finally, research gaps, future recommendations, and challenges related to the durability of mass-scale GO applications are presented. [ABSTRACT FROM AUTHOR]

The Berus television tower in Überherrn – a building archaeology on a high modernism building The knowledge of planning and realization on the basis of building archaeology represents a benefit in the research field of the construction history for concrete structures of the high modernism. It also forms the basis for sensitive and conservation‐oriented maintenance; in particular, the identification of concrete surfaces at the time of construction or later renovation measures can be determined in this way. Built in 1954, the expressionist‐looking transmission tower of the Berus transmitter in Überherrn is one of the first television towers in Germany. The Béton brut surface of the three concrete pillars with their formwork board imprints have been preserved in large parts. As part of the building archaeology, new high‐precision survey methods were used to create a detailed survey of the building, which was analyzed from various points of view and compared with the craftsmanship techniques used at the time of construction, also with a view to the question of what conclusions can be made if the building itself is considered as a source. In summary, the article provides a comprehensive view of the construction and construction history of a building which, together with the transmitter hall, which has been awarded the title "Historic Landmark of German Engineering", forms a successful overall architectural and engineering composition. At the same time, the described approaches and methods are intended for a transfer and future use on comparable concrete structures. [ABSTRACT FROM AUTHOR]

This paper aims to study the influence of novel macro encapsulated phase change materials (PCMs) on the mechanical and thermal properties of concretes. Thermal energy storage aggregates (TESAs) were prepared using vacuum impregnation. The PCMs were a lauric-myristic acid (LA-MA) eutectic mixture and coconut oil, pure or mixed, and are impregnated in diatomite as a supporting material. Thermal energy storage concrete (TESC) was made by replacing gravel in ordinary concrete with TESAs. Thermal and mechanical properties of prepared TESC were studied using differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, compressive strength, and thermal performance analysis. The results showed that the melting temperature of coconut oil and the eutectic mixture of LA-MA were 25.2°C and 34.5°C, respectively. TESC with 80 wt.% of gravel replaced with TESA had a compressive strength of higher than 17 MPa, which indicates its usability as structural concrete. The results of thermal performance analysis also revealed that prepared TESC had the capability of storing thermal energy and can reduce energy consumption by damping temperature fluctuations caused by the outside environment. In this paper, a thermal energy storage concrete (TESC) was prepared by embedding phase change materials (PCMs) in diatomite used in TESC. Using this type of concrete in the building will reduce the energy consumption of the building and increase its thermal comfort. The produced concrete containing 80 wt.% of gravel replaced with diatomite saturated with PCM had a desirable 28-day cylindrical sample strength of 21 MPa. In the designed thermal test, the time required for this concrete to reach 40°C is almost twice that of concrete without PCM. The results show a reduction of the influence of outside temperature on the temperature inside the buildings made with this type of concrete. [ABSTRACT FROM AUTHOR]

A geopolymer is an inorganic amorphous cementitious material, emerging as an alternative sustainable binder for greener concrete production over Ordinary Portland Cement (OPC). Geopolymer concrete production promotes waste reuse since the applicable precursor materials include agricultural and industrial waste that requires disposal, helping to reduce waste in landfills and ensuring sustainable environmental protection. This study investigates the development of an environmentally friendly sodium silicate alternative (SSA) derived from pumice powder (PP) in place of a commercial Na2SiO3 solution at a 10 M concentration. Six concrete batches were produced at alkaline/precursor (A/P) ratios of 0.1, 0.2, 0.3, 0.4, and 0.5. The geopolymer mix AF4, with an A/P ratio of 0.4, became the optimum geopolymer concrete design; however, it recorded lower compressive, tensile splitting, and flexural strengths, respectively, against the control OPC concrete. The geopolymer formulations, however, obtained 28-day-hardened concrete densities comparable to the control concrete. The 28-day compressive strength of the OPC concrete was 29.4 MPa, higher than the 18.8 MPa recorded for AF4. However, the 56-day strength of AF4 improved to 22.4 MPa, an around 19% increase compared to the 30.8 MPa achieved by the control mix on day 56, having experienced only a 5% strength increase. The low mechanical performances of the geopolymer formulation could be attributed to extra water added to the original geopolymer design to improve the workability of the geopolymer mix. Therefore, the SSA alkaline solution using PP showed some potential for developing geopolymer concrete for low-strength construction applications. [ABSTRACT FROM AUTHOR]

A large number of post-tensioned concrete bridges were built in the second half of the last century. They have often been insufficiently maintained during their lifetime (usually around 50 years). Nowadays, these structures exhibit significant deterioration, mainly due to leakages and also due to various other deficiencies such as a small concrete cover. Their load-bearing capacity needs to be verified. This paper focuses on estimating the load-bearing capacity calculation of existing post-tensioned concrete bridges. In the engineering practice, this is carried out using the partial factor method according to the currently valid standards (Czech standards ČSN and the Eurocodes), which often impose more stringent requirements than the original standards. The partial factor method then often leads to low load-bearing capacities. This study deals with the bridge for which a very low load-bearing capacity has been determined. For this reason, a comparative probabilistic analysis was performed, allowing for a better description of the uncertainties in the resistance and load effect variables. The probabilistic approach appears to be less conservative and yields a higher load-bearing capacity. [ABSTRACT FROM AUTHOR]

Five different design approaches are compared on a single mid-rise reinforced concrete building, pitting two performance-based designs against three conventional methods in delivering a solution that satisfies different sets of performance objectives. Two of the conventional designs stem from the literature, and they represent 2003 IBC compatible solutions. Another employs the yield point spectra to deliver a code-like solution, satisfying the design norms without needing iterations. The final two are based on the yield frequency spectra to offer a design that can satisfy more detailed performance objectives in a single step. Overall, all five methods are shown to deliver what is expected. Conventional methods can safely capture the code requirements, yet they are disadvantaged when treading in beyond-life-safety territory, where Immediate Occupancy or Collapse Prevention objectives cannot be easily satisfied, a problem that is not shared by performance-based approaches. [ABSTRACT FROM AUTHOR]

The cracking of ultra-long and large concrete structures with strong constraints is a key issue under the action of shrinkage and hydration heat. The length of section pouring during construction is one of the main parameters to control the cracking of concrete. In this paper, the shrinkage test of concrete specimens under the condition of coculture is carried out under the background of the landing gear slide test platform of large aircraft. The measured early shrinkage curve of the expanded concrete is obtained, and the finite element model is established. The effects of the casting thickness, mould temperature, and limited expansion rate on the stress and cracking of super-long and large concrete are studied. The results show that factors such as the casting thickness, mould temperature, and limited expansion rate have significant effects on the limited length of the section after pouring. When the casting thickness is increased by 200%, the limit of the section length is reduced by 42%. When the mould temperature increases by 66.7%, the section length limit decreases by 28.2%, while the value increases by 24.2%, with an increasing expansion rate of 75%. The relationship between the three parameters and the piecewise pouring length is approximately linear. The exact calculation of the section length limit of strongly constrained ultra-long mass concrete under different pouring thicknesses, mould temperatures, and limited expansion rates is derived, and a simplified calculation formula is also proposed through data regression analysis. The errors between them are less than 1.7%, which provides a basis for calculating the section length of strongly constrained ultra-long mass concrete construction. [ABSTRACT FROM AUTHOR]

Additive manufacturing with concrete – guidance for planning and implementation of projects This guideline, created by the DAfStb Working Group "Digital Concrete Construction through Additive Manufacturing," serves as a comprehensive resource to support the planning and implementation of additive manufacturing projects in concrete construction. It is intended for architects, planners, applicants, material manufacturers, construction companies, and other parties involved in construction. After a brief introduction to the classification, terminology, and methods of additive manufacturing, legal aspects and approval procedures are highlighted to ensure seamless integration of this technology into construction practice. The guide addresses the integration of additive manufacturing methods with concrete into construction law, explains the approval process, and offers assistance for coordinating responsibilities in projects. It addresses technical rules for the design and construction of structures, particularly for walls produced by additive manufacturing, and covers constructive aspects of reinforcement. An important component is concrete and component testing, including methods for sample preparation and testing procedures for fresh and hardened concrete, making the guide a useful tool for professionals in the field of digital concrete construction. [ABSTRACT FROM AUTHOR]

The unique physical and chemical properties of silica fume enhance the compressive strength and water resistance of cement mortar. The study aims to investigate the effect of silica fume in cement mixes in terms of strength-gaining characteristics and water-resistance attributes. The silica fume was added in amounts of 0%, 10%, 20%, and 25% as a partial cement replacement for the production of mortar. A total of 120 mortar cubes were prepared with steel molds of 50 × 50 × 50 mm dimensions. Two water-cement ratios (w/c) of 0.4 and 0.5 were utilized to investigate the water-resistance properties. A water-resistant property was calculated using the compressive strength ratio in the saturated surface dry (SSD) state to the oven-dry condition. The compressive strength ratios in SSD and the oven-dry state were measured after curing in water for 3, 7, 28, 45, and 90 days. After 90 days of curing, the sample with a water-cement ratio of 0.4 exhibited the greatest compressive strength and the highest ratio of SSD to the oven-dry state. The higher SSD to oven-dry strength ratio shows the silica fume possesses superior water resistance. This study concludes that silica fume possesses great pozzolanic activity and excellent resistance to water. The incorporation of silica fume creates a concrete composition that enables the construction of durable concrete structures. [ABSTRACT FROM AUTHOR]

This investigation focuses mainly on the failure behaviour and performance of angle and channel shear connectors in composite structures made with steel and brick aggregate concrete. It was observed that both angle and channel shear connectors did not fail themselves. However, in some specimens, localised connector yielding was observed in channel shear connectors. In both cases, concrete strata failed as either concrete crushing and shearing, combined splitting and bending, or complete splitting mode of failure. Crushing and shearing failure was noticed in specimens having smaller web and flange and were brittle in nature as compared to the failure of specimens with larger web and flange. Other parameters, such as shear resistance, energy absorption, and load-slip behaviour, were also investigated. Web height and flange width of both connectors significantly affected the ultimate shear capacity and slip of the brick aggregate concrete specimen. Channel connectors were found more flexible and carried more shear than angle connectors. Channel connectors had an average of 32.41% and 116.17% more ultimate load and slip capacity than the angle connectors in brick aggregate concrete, respectively. The load-carrying capacity, slip, and failure behaviour of the brick aggregate concrete were found similar to those of stone aggregate concrete. [ABSTRACT FROM AUTHOR]

In this paper we present a concrete algebraic construction of a novel class of convolutional codes. These codes are built upon generalized Vandermonde matrices and therefore can be seen as a natural extension of Reed–Solomon block codes to the context of convolutional codes. For this reason we call them weighted Reed–Solomon (WRS) convolutional codes. We show that under some constraints on the defining parameters these codes are Maximum Distance Profile (MDP), which means that they have the maximal possible growth in their column distance profile. We study the size of the field needed to obtain WRS convolutional codes which are MDP and compare it with the existing general constructions of MDP convolutional codes in the literature, showing that in many cases WRS convolutional codes require significantly smaller fields. [ABSTRACT FROM AUTHOR]

In order to improve the mechanical properties and durability of lightweight aggregate concrete in extreme environments, this study utilized Inner Mongolia pumice as the coarse aggregate to formulate pumice lightweight aggregate concrete (P-LWAC) with a silica powder content of 0%, 2%, 4%, 6%, 8%, and 10%. Under sulfate dry–wet cycling conditions, this study mainly conducted a mass loss rate test, compressive strength test, NMR test, and SEM test to investigate the improvement effect of silica powder content on the corrosion resistance performance of P-LWAC. In addition, using grey prediction theory, the relationship between pore characteristic parameters and compressive strength was elucidated, and a grey prediction model GM (1,3) was established to predict the compressive strength of P-LWAC after cycling. Research indicates that under sulfate corrosion conditions, as the cycle times and silica powder content increased, the corrosion resistance of P-LWAC showed a trend of first increasing and then decreasing. At 60 cycles, P-LWAC with a content of 6% exhibited the lowest mass loss rate and the highest relative dynamic elastic modulus, compressive strength, and corrosion resistance coefficient. From the perspective of data distribution, various durability indicators showed a clear mirror symmetry towards both sides with a silica powder content of 6% as the symmetrical center. The addition of silica fume reduced the porosity and permeability of P-LWAC, enhanced the saturation degree of bound fluid, and facilitated internal structural development from harmful pores towards less harmful and harmless pores, a feature most prominent at the 6% silica fume mixing ratio. In addition, a bound fluid saturation and pore size of 0.02~0.05 μm/% exerted the most significant influence on the compressive strength of P-LWAC subjected to 90 dry–wet cycles. Based on these two factors, grey prediction model GM (1,3) was established. This model can accurately evaluate the durability of P-LWAC, improving the efficiency of curing decision-making and construction of concrete materials. [ABSTRACT FROM AUTHOR]

Prefabrication of reinforced concrete during the First and Second World Wars – the work of Benno Löser between the TH Dresden and Auschwitz The book on "Design methods for concrete and reinforced concrete components" shaped practical reinforced concrete construction like no other, and not just in Germany. However, little is known about its author, the building contractor and university professor Benno Löser (1878–1944). Early on, he dealt with questions about prefabrication and assembly logistics in concrete construction, and a large number of the buildings he constructed are now architectural monuments with a pioneering constructive character. This also applies to his work during the First and Second World War, where he focused on the topic of prefabrication of prefabricated concrete parts for various instances and ultimately became entangled in the unjust National Socialist state. He also used his professional expertise in places of destruction, such as Auschwitz and Dyhernfurth. The first research results from the current research project on the history of composite materials in construction by the Chair for the History of Natural Sciences and Technology at the University of Stuttgart are presented here. Based on previously completely unknown image and written documents from the estate of Benno Löser, who commuted between university operations and the practical challenges of construction, an insight into prefabricated reinforced concrete construction during two world wars is provided. [ABSTRACT FROM AUTHOR]

With the continuous construction of urban traffic roads, more and more new roads are cut off by existing roads to form "dead end roads". There is an urgent need for a trenchless method suitable for urban ultra-shallow overburden to build the undercrossing tunnel. To solve this problem, this paper proposed the micro pipe jacking and joint assembly structure (MPJ & JAS) method, which has the characteristics of shallow burial depth, low cost, short construction time, flexible cross-section setting and high space utilization. The MPJ & JAS method construct a large cross-section tunnel through assembling small cross-section elements, quite different from traditional methods. Therefore, this paper designed a CT-shaped integrated joint, the mechanical performance of which was verified and clarified by tensile test. The bending test and finite element (FE) analysis proved the reliability of MPJ & JAS tunnel structure, and confirmed the structure performances such as the failure models, crack behaviors, load–deflection response and stress–strain distribution. Moreover, the influences of the steel plate thickness, concrete strength and shear connector spacing were determined by the FE analysis. On the basis of test results and reasonable assumptions, a theoretical design method considering the influence of the CT-shaped integrated joint was proposed, which can effectively predict the bending strength of the MPJ & JAS tunnel structure with an error of less than 10%. Finally, in view of the characteristics of the MPJ & JAS method, the suitable micro pipe jacking machine, soil reinforcement measure, hydraulic traction construction technology, high-precision guidance system and concrete construction quality detection method based on the phased array ultrasonic imaging technology were developed, supporting the accurate and efficient construction of the MPJ & JAS tunnel. [ABSTRACT FROM AUTHOR]

One of the main approaches to reducing the environmental impacts of the construction industry is the use of mineral additives reducing the use of cement in mortars and concretes for construction. The objects of this research are different cement composites with high content of inert mineral fillers (marble and quartz sand), the influence of zeolite incorporation on the microstructure, and low water-cement ratio, obtained after the hydration of white portland cement. In this study, the evolution of the curing processes and the crystal formation during up to 120 days of water-curing are investigated. Moreover, the effects of replacing up to 10 wt. % of white cement with natural zeolite are studied. Attention was focused on the general microstructural development during curing with special attention on the evolution and morphology of pore space and the observed calcium silicate hydrates (C–S–H), portlandite, and carbonate-containing phases. The phase composition (newly formed phases as well as the formation of C-S-H gel) is defined by using powder X-Ray diffraction and SEM. The experimental data shows that the cement composites with the inert marble filler as an additive lead to the creation of carbo-aluminates. The incorporation of up to 10 percent of clinoptilolite in concrete mixtures by mass of the total cementitious components is more efficient when used in lower strength mixes. A significant reduction in the workability of the fresh mortars is not observed, but the high surface area of zeolite reduces bleeding and accelerates setting without any strong effects on the other physical and technological properties of fresh mortars. [ABSTRACT FROM AUTHOR]

The most extensively utilized material in construction is concrete, decreasing life of structure pointing toward loses in structural health. The crack is the major problem faced in the concrete construction. This causes the corrosion in the steel reinforcement. The structure gets deteriorated with the developing cracks; therefore need the proper attention toward this problem. The present work consists of the different self‐healing techniques used by the researchers to inhibit the crack and prevent further deterioration in the structure. The self‐healing mechanism proves advantageous in use of natural fibers to inhibit the corrosion process, to increase compressive strength, and to decrease water absorption is present in this study. The maximum strength increased and the width of crack get healed with the help of these techniques is also mentioned in the study. [ABSTRACT FROM AUTHOR]

3D Concrete Printing (3DCP) is a rapidly evolving technology that allows for the efficient and accurate construction of complex concrete objects. In this paper, a numerical modelling approach is presented for the simulation of the printing process of cementitious materials, based on the homogeneous fluid assumption. To cope with the large deformations of the domain and the nonlinearity resulting from the use of a non-Newtonian rheological law, the Navier–Stokes equations are solved in the framework of the Particle Finite Element Method (PFEM). Furthermore, tailored solutions have been formulated and implemented for the time-dependent moving boundary conditions at the nozzle outlet and for the efficient handling of the inter-layer contact in the same PFEM framework. The overall computational cost is decreased by the implementation of an adaptive de-refinement technique, which drastically reduces the number of degrees of freedom in time. The proposed modelling approach is finally validated by simulating the printing process of six rectilinear layers and one multi-layer "wall". The results show good agreement with the experimental data and provide valuable insights into the printing process, paving the way for the use of numerical modelling tools for the optimization of materials and processes in the field of 3D Concrete Printing. [ABSTRACT FROM AUTHOR]

The article discusses the challenges and management of post-tensioned bridges, particularly those built in the 1950s, 1960s, and 1970s. It emphasizes the importance of inspections, diagnostics, and reconstruction to address durability issues and maintain the intended service life of these bridges. The article also provides information about upcoming events and conferences related to concrete sustainability and PhD symposia in civil engineering. It mentions specific structures, such as the Vila Franca de Xira Bridge and the ongoing seismic retrofitting of the Duarte Pacheco Viaduct in Lisbon. The text acknowledges the support of national member groups and sponsoring members of the International Federation for Structural Concrete (fib). [Extracted from the article]

Evacuation zone recommendations are determined for potential asteroid impacts. In most impacts on land, the dominant damage mechanism is the blast wave. Hurricane evacuations in the United States show that on average people evacuate to a 1 in a million risk of fatality level. To achieve the equivalent risk from a blast wave, preliminary estimates show that everyone within the 1–2 psi (≈0.07–0.14 atm or bar) blast radius should evacuate as, even when taking shelter, the risk threshold is probably exceeded. From there out to the 0.4–0.5 psi radii, seeking shelter in the basement of a reinforced concrete building or storm shelter, or in a home-built shelter in the basement of a house would suffice as alternatives to evacuation while keeping the fatality risk below 1 in a million. From 0.4 down to 0.1–0.2 psi, windows may break but little to no structural damage to buildings is expected, so simply staying away from windows and doors would be sufficient. • Evacuation and shelter zones for asteroid impacts assuming sufficient warning time. • Hurricanes show risk tolerance of about 1 in a million fatality. • Nuclear tests show risk due to blast waves and effect of shelters. • Example calculations with poorly constrained and well characterized asteroids. [ABSTRACT FROM AUTHOR]

"Concrete City: Material Flows and Urbanization in West Africa" by Armelle Choplin explores the production, sale, circulation, and use of concrete in West Africa, focusing on the neighborhood of Misra in Saint-Louis, Senegal. The book examines the political economy of concrete, its contribution to national identity, and its role in urban development. It also explores the social and cultural significance of concrete in the lives of individuals and communities. The author discusses the challenges and potential alternatives to concrete construction, as well as the need for a post-concrete world. The book offers a comprehensive analysis of the material and social aspects of urbanization in West Africa. [Extracted from the article]

A total of 9 real scale reinforced concrete shear walls were produced, 3 of them being the reference, representing the basement floor of a reinforced concrete building. These 9 shear walls produced, 3 wall are fully filled, 3 of them have window openings and 3 of them have door openings. The RC shear walls were exposed to displacement-controlled reversed cyclic lateral loading. In the experiments that damaged the experimental specimens, loads up to 0.5% story drift ratio for moderate damage and 1.0% story drift ratio for heavy damage were applied. Within the scope of the experimental study, the damage distributions of the tested nine RC shear walls were examined in detail, and the strengthening technique was developed using CFRP strip and CFRP fan-type anchors. The performance of damaged RC shear walls after using the devised repair method was analysed. The study's findings revealed that the repair method created by employing CFRP strips to restore moderately damaged RC shear walls with and without apertures was well enough successful in restoring the shear walls' performance levels. [ABSTRACT FROM AUTHOR]

Filling ability is one of the prominent rheological properties of the self-compacting concrete (SCC), which has been studied in this research work deploying the functional behavior of the concrete through the studied funnel apparatus using the coupled ANSYS-SPH interface. Seven (7) model cases were studied and optimized. The aim of this numerical study is to propose a more sustainable mix of coarse and fine aggregates proportion that allows for most minimum flow time to enhance a more efficient filling of forms during concreting. The maximum size of the coarse aggregates considered is 20 mm and that of the fine aggregates is below 4 mm. The Bingham model properties for the multiphysics (SPH)-ANSYS models' simulation are; viscosity = 20 ≤ μ ≤ 100 and the yield stress = 50 ≤ τ 0 ≤ 200 , standard flow time, t (s) ranges; 6 ≤ t ≤ 25 and the funnel volume is 12 L. The minimum boundary flow time, which represents the time it takes for the SCC to completely flow through a specified distance, typically measured in seconds was modeled for in the seven (7) model cases. The second case with 40% coarse mixed with 60% fine completely flowed out in 16 s, thus fulfilling the minimum flow time. This minimum flow time was considered alongside other relevant parameters and tests, such as slump flow, passing ability, segregation resistance, and rheological properties (stresses), to comprehensively assess the filling ability of SCC in this model. By considering these factors and the optimized mix (40%C + 60%F:16s), engineers and researchers can optimize the SCC mix design to achieve the desired flowability and filling performance for their specific construction applications. The multiphase optimized mix was further simulated using the coupled interface of the ANSYS-SPH platform operating with the CFX command at air temperature of 25 °C. The results show energy reduction jump at the optimized flow time. Ideally, the mix, 40%C + 60%F:16s has been proposed as the mix with the most efficient flow to achieve the filling ability for sustainable structural concrete construction. [ABSTRACT FROM AUTHOR]

This paper aims to summarize the findings of a comprehensive study on the correlation of displacement and deformation demands estimated using various code-compliant nonlinear modeling approaches commonly used in real-life performance-based seismic design and assessment applications, with experimental results obtained from the full-scale shake table tests on the 10-story reinforced concrete building performed at the E-defense testing facility in 2015. Nonlinear response history analysis results obtained using ASCE-41 and Turkish Building Earthquake Code model configurations with the lumped plasticity modeling approach adopted for beams and columns, as well as an additional configuration adopting the distributed plasticity approach, were compared with test measurements. Analysis sets were also conducted to evaluate the sensitivity of the analytical predictions to specific modeling assumptions that incorporate varying degrees of uncertainty, including consideration of beam effective flange widths, modeling of the floor slabs, adopting a tensile strength for concrete, selecting alternative effective shear moduli for structural walls, consideration of the vertical component of the ground motion, and selection of the damping ratio. Analysis results were compared with experimental measurements in terms of various global displacement and local deformation demands on the structure, including story displacement time-histories, peak interstory drift ratios, flexural and shear deformations on structural walls, and flexural deformations on beams and columns. The relative effectiveness of different methodologies and assumptions in replicating the experimentally-measured deformation demands on the test building are discussed in detail. Limitations of the adopted modeling approaches in simulating salient experimentally-observed response characteristics of the building are also identified. [ABSTRACT FROM AUTHOR]

This study develops an end‐to‐end deep learning framework to learn and analyze ground motions (GMs) through their latent features, and achieve reliable GM classification, selection, and generation of simulated motions. The framework is composed of an analysis workflow that transforms and reconstructs GMs through short‐time Fourier transform (STFT), encodes and decodes their latent features through convolutional variational autoencoder (CVAE), and classifies and generates GMs by grouping and interpolating latent variables. A benchmark study is established to confirm the minor difference between original GMs and the corresponding reconstructed accelerograms. The encoded latent space reveals that certain latent variables are directly linked to the dominant physical features of GMs. Resultantly, clustering latent variables using the k‐means algorithm successfully classifies GMs into different groups that vary in earthquake magnitude, soil type, field distance, and fault mechanism. By linearly interpolating two parent latent variables, simulated GMs are generated with consistent class information and matching response spectra. Furthermore, seismic fragility models are developed for a steel frame building and a concrete bridge using different sets of GMs. Using five classified, top‐ranked motions, regardless of recorded or simulated accelerograms, can achieve reasonable and efficient fragility estimates compared to the case that adopts 230 GMs. The proposed deep learning framework addresses two compelling questions regarding seismic fragility assessment: How many GMs are sufficient and what types of motions should be selected. [ABSTRACT FROM AUTHOR]

Massive concrete caps usually adopt cooling pipe water cooling to reduce the negative impact of the hydration heat of cement in construction. However, unreasonable cooling pipe layout, water temperature, and water speed often lead to low cooling efficiency of caps and concrete cracks caused by the excessive temperature difference between the surface and the inside, which can affect the safety and durability of structures. An improved calculation model for massive concrete caps was proposed to reveal the relationship between the transient temperature field of massive concrete caps and the cooling pipe layout and the value of relevant parameters. The proposed model considered the heat of cement hydration, solar radiation, air convection, and the heat exchange of cooling pipes through water. The boundary value conditions were identified through the least-squares method and physical test data, and a prediction model for the transient temperature field of massive concrete based on water cooling through cooling pipes was established. On this basis, the cooling pipe layout and cooling pipe parameters such as spacing, water temperature, and water flow rate were analyzed in accordance with the basic principles of heat conduction. Results demonstrate that, the influence of solar radiation cannot be ignored in the prediction of the transient temperature field of massive concrete caps. The single-circulation side-byside arrangement of cooling pipes is better than other layout methods. The internal temperature of caps is negatively correlated with the spacing of cooling pipes, but a considerably small spacing of cooling pipes can increase the amount of cooling pipes and the cost of temperature control. Lowering the water temperature can effectively control the temperature difference between the inside and the outside and reduce the risk of concrete cracking. Changing the water flow rate of the cooling pipes can reduce the maximum temperature inside the caps. However, when the water flow rate of the cooling pipes exceeds 2.4 cubic meters per hour, continuing to increase the cooling pipe water flow rate is not effective in reducing the maximum value of the transient temperature field of the caps. This study provides a good reference for temperature control in the construction of massive concrete caps for bridges. [ABSTRACT FROM AUTHOR]

A bilinear map whose domain and target sets are identical is called a self-bilinear map. Original self-bilinear maps are defined over cyclic groups. Since the map itself reveals information about the underlying cyclic group, the Decisional Diffie–Hellman Problem (DDH) and the computational Diffie–Hellman (CDH) problem may be solved easily in some specific groups. This brings a lot of limitations to constructing secure self-bilinear schemes. As a compromise, a self-bilinear map with auxiliary information was proposed in CRYPTO'2014. In this paper, we construct this weak variant of a self-bilinear map from generic sets and indistinguishable obfuscation. These sets should own several properties. A new notion, One Way Encoding System (OWES), is proposed to summarize these properties. The new Encoding Division Problem (EDP) is defined to complete the security proof. The OWES can be built by making use of one level of graded encoding systems (GES). To construct a concrete self-bilinear map scheme, Garg, Gentry, and Halvei(GGH13) GES is adopted in our work. Even though the security of GGH13 was recently broken by Hu et al., their algorithm does not threaten our applications. At the end of this paper, some further considerations for the EDP for concrete construction are given to improve the confidence that EDP is indeed hard. [ABSTRACT FROM AUTHOR]

Manufactured sand, known for its artificial production, eco-friendliness, cost-effectiveness, and sustainability, serves as an excellent alternative to natural sand. Stone powder content plays a crucial role in determining the performance of manufactured sand, significantly enhancing concrete compaction and its ability to withstand environmental degradation. This study aims to explore the feasibility of using environmentally and economically advantageous manufactured sand in the construction of subway tunnel segments in coastal areas. It investigates the impact of stone powder content on the corrosion resistance of concrete made with manufactured sand under the combined influence of chloride salts and stray currents. The analysis covers corrosion tendencies, the post-rusting performance of reinforcement bars, the resistance of concrete to chloride transport, and microstructure properties, which are assessed through electron microscope scanning and mercury compression testing. The findings indicate that the corrosion resistance of manufactured sand concrete generally surpasses that of river sand concrete. Furthermore, stone powder content within the 3–8% range leads to a denser concrete microstructure, reduced porosity, lower free-chloride ion levels, increased polarization resistance of post-corrosion reinforcements, lower corrosion current density, and reduced mass loss of reinforcing bars. This research provides valuable theoretical support for promoting the use of environmentally friendly manufactured sand concrete in subway construction projects. [ABSTRACT FROM AUTHOR]

Perfect state transfer has attracted much interest recently due to its significant applications in quantum information processing and cryptography. In this paper, we investigate perfect state transfer on Cayley graphs over dicyclic groups. Utilizing the representations and characters of dicyclic groups $ T_{4n} $ T 4 n , some necessary and sufficient conditions for Cayley graphs over dicyclic groups admitting perfect state transfer are provided. By those results, some concrete constructions are presented. [ABSTRACT FROM AUTHOR]

Durability plays a crucial role in maintaining the service life of a structure. This paper focuses on examining the durability of a building with a reinforced concrete structure that has been exposed to an offshore environment for 35 years. The study involved on-site inspections to assess external damage, including testing parameters such as the compressive strength of the concrete material and the overall tilt of the building. Additionally, microscopic inspection techniques, such as X-ray fluorescence (XRF), thermogravimetry-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM), were employed to analyze the corrosion products and microstructure associated with the damage mechanism. Based on the data obtained from the on-site inspections, structural calculation software was used to calculate and verify the overall load-bearing capacity of the building, aiming to determine its safety level. The evaluation results revealed severe safety issues within the building, despite it not having reached its designed service life, particularly in relation to reinforcement corrosion. [ABSTRACT FROM AUTHOR]

This study explores the possibility of partially replacing cement with crushed brick powder (CBP) and 6% hydrated lime (HL) in concrete. The results showed an increase in compressive strength compared with the control at the intermediate age of 56 days. Adding HL to the cement and CBP paste samples resulted in a 22% reduction in capillary pores and a 23% increase in gel pores. Although the control samples had less carbonation penetration, the corrosion rate was higher than that of blended cement concrete with HL. The half-cell potential measurement on carbonated samples indicated that, unlike chloride-induced corrosion, the depassivation of steel could not be identified by a stable demarcating half-cell potential value. Moreover, blended cement concrete with HL exhibited higher resistivity. Visual inspection of corroded bars revealed that the assumption of uniform corrosion by carbonation might not be entirely accurate. The use of HL with a cement-CBP binder improved the concrete's characteristics and reduced the risk of carbonation-induced corrosion. The study provides supplementary information on the feasibility of using a blend of crushed brick powder and hydrated lime as sustainable alternatives in the field of concrete construction with environmental considerations. [ABSTRACT FROM AUTHOR]