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Additive manufacturing is becoming increasingly important in the construction industry. Wire arc additive manufacturing (WAAM) can be integrated into the selective paste intrusion (SPI) to enable the simultaneous printing of reinforced concrete. The bond behavior of a WAAM reinforcement was investigated with pull-out tests and compared to alternative reinforcement types to analyze the stress transfer between the different components. In the first step, the surface of all the reinforcement types was recorded using a laser-based line scan measuring system. This permits the evaluation of the surface parameters, such as the surface roughness Rq, or the related rib area fR. The WAAM reinforcement showed a bond behavior in the pull-out tests that was comparable to a reinforcing steel bar. Both the bond stresses achieved, and the occurring scatter of the measurement results at the characteristic slip values were almost the same. Even without existing transverse ribs, the WAAM reinforcement reached maximum bond stresses similar to the reinforcing steel. An evaluation of the surface roughness revealed a linear relationship with the maximum bond stress achieved with a logarithmic scaling of Rq. The bond work Wτ, which is a measure of the system stiffness, showed that WAAM reinforcements and reinforcing steel bars have approximately similar behavior.

At present, the large quantity of wastes generated by the ceramic industry is not reused in any significant quantity. Research has shown the feasibility of incorporating these wastes into concrete production. This will benefit both the ceramic and concrete industries. However, not much research data is available on the use of ceramic wastes as fine aggregate material compared to their use as coarse aggregate material. Moreover, there are presently no models for predicting the properties of ceramic waste aggregate concretes. In this study, a modified regression theory based on Taylor’s series was adopted to formulate mathematical model for predicting compressive strength of concrete into which Recycled Ceramic Tile (RCT) is incorporated as fine aggregate. Preliminary tests on RCT indicate that it is a suitable fine aggregate material for concrete production. It has also been established that addition of RCT improves compressive strength of concrete and reduces concrete’s workability. The formulated model is a function of the mix proportions of its constituents and its predicted responses are in good agreement with experimentally observed data. The model has been tested using student’s t-test and analysis of variance and has been confirmed to be adequate and hence is validated.

Dredged river sediments produce a huge volume of mineral materials, which could be incorporated into building materials. Considering the raw sediment preparation, mineral processing techniques fit perfectly to this purpose. This work describes two procedures to prepare river sediments, according to the final beneficial use. The first is a dry procedure of deagglomeration to prepare river sediments with the aim of being incorporated into a concrete formulation to build a bicycle path. A large amount of deagglomerated sediment was prepared, requiring upscaling of the deagglomeration process. Successive steps of sieving and roll crushing were used to obtain deagglomerated sediments. To use it as raw material to produce pozzolanic materials and lightweight aggregates, a second procedure consisting of a wet classification at 63 µm was carried out. Steps of wet sieving, followed by hydrocycloning and screw classifying, were used to prepare several silt fractions under 63 µm.

This study presents analysis of two types of experimental test related to the crack propagation in concrete specimens subjected to high-sustained loading levels and quasi-static loadings. The concept of the equivalent crack length is introduced to perform this analysis. Even though this analysis is partial, it shows the influence of loading rate conditions on the crack process rate. This result shows that, in the domains of low and very low loading rates, the concrete mechanical characteristics linked to the cracking process (for example, tensile strength, post-cracking behaviour, etc.) are dependent on the loading rates applied to the specimens for determining them.

Current research paper deals with reinforced concrete (R.C.) beams numerical modeling and suggested strengthening procedure if it is required to create an opening within their shear zones. Strengthening is assumed to be achieved during different service load application conditions. Reinforced Concrete beams with rectangular or circular opening in shear zone; as critical regions; sustain two concentrated system of loads are tested till failure before and after performing suggested opening assessing technique by means of Carbon Fibers Reinforced Polymer sheets (CFRP). The main aim of this research is simulating real practice situation where the beam is subjected to service loads, supported temporary by means of hydraulic jacks, opening is created and strengthening is performed then jacking supports are released. Results of achieved numerical nonlinear modeling are introduced and influence of strengthening achieving on improving assessed beams almost structural behavior such as initial cracking loads, load deflection curves, cracking patterns, failure loads & modes for reference (without opening), main un-strengthened control beams, and CFRP strengthened opening beams are introduced and analyzed in details. Some important conclusions & recommendations for designer and executive engineers are stated.

Besides the fact that concrete recycling allows to avoid landfills disposal and contributes to a closed-cycle economy, such option may be very much in demand in war struck regions such as Ukraine, which after the end of the war, are faced with the problem of rebuilding and reconstructing. Beyond this emergency, even in peacetime extensive parts of the building stock will sooner or later need to be replaced and concrete recycling is called to play an increasing role there. However, depending on the technology and degree to which aggregates are recycled, concrete may be characterized by poor workability, reduced mechanical properties, increased shrinkage and reduced durability. This deterioration in the properties of recycled concrete is usually attributed to the characteristics of the old cement mortar remaining on the surface of the recycled aggregates, which is best considered as an additional volume of hardened cement paste with fine aggregate and additional porosity. This article attempts to underline how such key concepts help frame the current state of knowledge about concrete recycling, understand the implications of existing regulations, in order to define pragmatic and efficient routes for broadening the use of concrete recycling in war struck regions, with specific examples regarding Ukraine., RILEM Technical Letters, 7, ISSN:2518 -0231

The need for partial replacement of cement in concrete production has become inevitable because of adverse environmental impact of cement production, increasing cost of cement and financial benefits of utilization of waste products. This paper presents laboratory investigation of the properties of Olive Seed Ash (OSA) as partial replacement of cement in concrete. Concrete mix of 1:2:4 (Binder: Fine aggregate: Coarse Aggregate) and water-cement ratio of 0.44 were adopted in this study. Olive seed ash was used to replace cement at various levels of 0%, 5%, 10% and 15% by mass. Partial replacement of cement with OSA resulted in decrease in initial and final setting times of concrete but the values are still within acceptable limits. The results show that compressive strength, flexural strength and split tensile strength of the concrete decreased as the percentage of OSA increases. However, at 10% replacement level, the 28 days compressive strength achieved was 28N/mm2 and this value surpasses the minimum compressive strength of 25N/mm2 recognized by BS EN 1992-1-1 (2004) for reinforced concrete design. The results also showed that the water absorption decreased with increase in percentage replacement of cement with OSA portraying that replacement with olive seed ash has higher durability potentials. It is recommended that cement can be replaced with at least 10% OSA in concrete. This will reduce the cost of construction in addition to environmental advantage.

[EN] The existing shop is a former dwelling which seems odd amongst the commercial area big boxes. The program of the operation is no less ambiguous, as it merges commercial and ritual purposes. A generic box wraps the dwelling and its extensions, doubling the former surface. Its volume copies the surrounding ones while its shade refers to the conspicuously neutral grey suits of the profession. The public funeral home is located within the cemetery enclosure. It opens the surrounding wall with a timeless colonnade which sinks into the darkness of the building, below the natural sloping ground level. Seen from the cemetery, the new building surfaces like a large slab among the graves., [ES] La tienda existente es una antigua vivienda que parece extraña entre las grandes cajas del área comercial. El programa de la operación no es menos ambiguo, ya que fusiona fines comerciales y rituales. Una caja genérica envuelve la vivienda y sus anexos, duplicando la superficie anterior. Su volumen reproduce los alrededores, mientras que su tonalidad hace referencia a los trajes grises claramente neutros de la profesión. El tanatorio público se encuentra dentro del recinto del cementerio. Abre el muro circundante con una columnata atemporal que se hunde en la oscuridad del edificio por debajo del nivel del suelo en pendiente natural. Visto desde el cementerio, el nuevo edificio emerge como una gran losa entre las tumbas.

[EN] The crematorium building sits close to the chapel, right on the top of a hill and in such a way that from the cemetery the new building is not visible, yet from the building one can perceive the atmosphere and the beauty of the cemetery. The project acts on the desire to blend into the cemetery without distorting the poetry that emanates from it. The main idea in the crematorium was to sensitively understand the situation the program involves. It wants to connect with the nature around and strike a dialogue between visitors and the distant landscape discernible through the windows, a dialogue between life and death., [ES] El edificio del crematorio se asienta cerca de la capilla, justo en lo alto de una colina, de tal forma que desde el cementerio no se ve el nuevo edificio, pero desde el edificio se percibe el ambiente y la belleza del cementerio. El proyecto actúa sobre la voluntad de mimetizarse con el cementerio sin desvirtuar la poesía que de él emana. La idea principal del proyecto de crematorio fue comprender con sensibilidad la situación que implica el programa. Quiere conectarse con la naturaleza que lo rodea y entablar un diálogo entre los visitantes y el paisaje lejano, el cual se percibe a través de las ventanas, un diálogo entre la vida y la muerte.

[EN] The project arose from the need to build a columbarium in the extension of the Robregordo Cemetery, in the mountains of the Sierra de Madrid, whose first extension had been completed a few years earlier. The access, from the new extension, has no covered area in which to mourn the arrival of the coffin or ashes; a gate-like door, a perimeter wall of irregular granite ashlars that separates the interior from the exterior and two cypress trees placed symmetrically to serve as a reference from a more distant position are the pre-existing elements on the site., [ES] El proyecto nace desde la necesidad de ejecutar un grupo de columbarios en la ampliación del Cementerio de Robregordo, en la Sierra de Madrid, cuya primera ampliación se había finalizado unos años antes. El acceso, desde la nueva ampliación, no presenta ningún ámbito a cubierto en el que poder realizar la espera de duelo a la llegada del féretro o las cenizas; una puerta a modo de cancela, un muro perimetral de sillares de granito irregulares que separa el interior del exterior y dos cipreses colocados de manera simétrica que sirviese de referencia desde una posición más lejana son las preexistencias en el lugar.

[EN] Of all architectural typologies, a funeral parlor is one of the most difficult to design due to its profound symbolism. Death is represented in many ways by different cultures. In the Mexican tradition, death is not only a process of respect, grief, and fear, but has been culturally defined as a major social event. To give the project spatial definition we always came back to the concepts of limits, transitions, permanence, temporality, and thresholds that define death s social and cultural dimension., [ES] De todas las tipologías arquitectónicas, una funeraria es una de las más difíciles de diseñar debido a su profundo simbolismo. La muerte se representada de muchas maneras por diferentes culturas. En la tradición mexicana, la muerte no es solo un proceso de respeto, duelo y miedo, sino que ha sido definida culturalmente como un evento social importante. Para dar definición espacial al proyecto siempre se vuelve a los conceptos de límites, transiciones, permanencia, temporalidad y umbrales que definen la dimensión social y cultural de la muerte.

Recent engagements with deep time within anthropology have urged an expansion of our time horizons in order to confront the contemporary ecological crisis. Here, we explore this theme by considering concrete’s material properties as a substance that reveals the troubled relationship between the present and deep time. We combine discussion of the life cycle of concrete in Orkney, Scotland, with reflection on sculptural interventions that seek to capture concrete’s character as both solid and fluid—the pouring of concrete has the potential to congeal a fleeting moment in time. Yet, recognising the impact of the production of concrete, understood at the geological level, we see a pernicious feedback loop: attempts to secure the land/water boundary contribute to the climatic changes which threaten those very environments. The task of tracing concrete’s place within the geological record illustrates both the challenge and the necessity of recognising humanity within deep time.

The process of depleting the natural sources of virgin sand and aggregate makes it challenging to satisfy the demand for construction work. Therefore, in a context of sustainable construction, this study examined the feasibility of utilizing dredged sediments (DS) as a substitute for sand in non-structural controlled low-strength materials (CLSM). A total of two types of dredged sediments, coarser and finer, were collected from two different sources. Then, nine CLSM mixtures were prepared by using different proportions of natural sand (virgin sand) and dredged sediments. Each mixture was tested for flowability, unconfined compressive strength, density and excavatability. Flow consistency decreased with the amount of dredged sediments and presence of finer material in CLSM. Strength results were found within required specification for all nine CLSM tested in this study. Overall, flow consistency, strength and excavatability were found dependent on the characteristics of dredged sediments. This study showed that up to 50% of substitution of sand with DS in CLSM improved strength and density. Furthermore, flow consistency was found to decrease with increase in the amount of DS in CLSM mixtures.

For more than two decades, the construction technique using concrete filled steel tube (CFST) has been widespread throughout the world. Indeed, it has been demonstrated that the use of normal or high strength concrete, confined in a steel tube of circular shape can considerably improve its ductility as well as its load capacity, owing to the combination of the qualities of the two constituent materials; these tubes have an effortless execution, indeed, the concrete used in the CFST does not require formwork nor reinforcement, a durability of the two materials as well as a good behavior to fire, which was the effect desired at the origin of their elaboration. In this paper, we study the axial compression behavior of short circular steel tubes filled with concrete; their modelling will be performed using the ABAQUS/Standard calculation program. In order to accurately determine their behavior, we have created different models. Indeed, these tubes will be modeled in order to simulate different plastic state behaviours, namely a perfect elasto-plastic state, an elasto-plastic state with multilinear strain hardening and a third elasto-plastic behavior with strain hardening proposed by Tao et al. The tested columns consist of circular hollow sections which are designated in the literature as Concrete Filled Steel Tube (CFST), for which we vary the diameters, heights as well as the wall thicknesses, and which we fill with concrete of different qualities. The compressive behavior, including ultimate loads, confinement, load-deflection relationship and failure modes, was obtained from numerical models and compared with experimental and theoretical results based on Eurocode 4. All these results showed a good agreement and a satisfactory correlation, allowing us to assume that a correct modelling can be sufficient to simulate the behavior of CFST.

The reuse of concrete waste as a secondary aggregate could be an efficient solution for sustainable development and long-term environmental protection. However, the variable quality of waste concrete, especially with various compressive strengths, can have a negative effect on the final compressive strength of recycled concrete. In this approach, the major goal of this research is to study the effect of parent concrete qualities on the performance of recycled concrete. To accomplish this task, three grades of different compressive strengths (10 to 15) MPa, (20 to 25) MPa, and (30 to 40) MPa have been analyzed in an experimental test program, in which an unknown compressive strength is introduced as well. The experimental mix use 40% of secondary aggregates (both course and fine) and 60% of natural aggregates. This led to the decreasing of the compressive strength of the test concrete between 14% and 23.7% compared to the normal concrete. This loss was improved by adding an amount of cement equivalent to 4% of the weight of the recycled aggregate used. The achieved results prove that the strength properties of the parent concrete have a limited effect on the compressive strength of the recycled concrete. Additionally, low compressive strength parent concrete, when crushed, generates a high amount of fine aggregate and large percentage of recycled coarse aggregates with less attached mortar, and presents the same compressive strength as an excellent parent concrete.

The valorization of local by-products in the manufacture of a new range of sand concrete and the improvement of their properties, will lead to seek an arrangement between performance and cost in order to achieve a resistant material. Waste recycling affects two very important affect namely the environmental impact and the economic impact. The main objective of our work is to contribute to optimize the formulation of sand concrete as part of the recovery of waste, which is harmful to the environment given its bulky and unattractive nature, it is waste plastic. Most PET bottles become waste after use, causing environmental problems. To solve this problem, a method for recycling PET bottles as fibers to strengthen concrete is proposed. Two types of plastic waste are added to sand concrete; the first concerns the recycling of post-consumer bottles in PET, in the form of polyester fiber supplied by the company RET-PLAST and the second type concerns the packaging belts made of polyethylene terephthalate (PET). The properties in the fresh state (workability and density) and in the hardened state (compressive strength, tensile strength and water absorption) of the various produced concretes are analyzed and compared against their respective controls. From the experimental results, it can be concluded that the reinforcement of the cement matrix with PET fibers with a rate of 1% improves the mechanical properties of sand concrete as well as a remarkable decrease in its water absorption capacity.

Eight thin iron wires were embedded in a cement test block to evaluate corrosion behavior during cement carbonization by CO2 absorption. The gases supplied sequentially to the chamber containing the cement test block were air, CO2, and then air. Electrical resistance measurement of the thin wires revealed that the iron wires remained passivated during the supply of air and uncorroded during the supply of CO2 to promote carbonization. The iron wires started corroding from the surface when the air was resupplied after carbonization due to the presence of O-2 in the air as an oxidizing agent. A set of two-electrode impedances between two selected iron wires was measured as a function of depth from the surface. The impedance of all electrodes dropped considerably several hours after the CO2 supply due to the difference in the immersion potential of the iron wires as a function of depth, that is, the pH transition from alkaline to neutral. Consequently, the iron wires were polarized when electrically connected to each other during carbonization. After carbonization, each iron wire showed an impedance response corresponding to its corrosion condition, which depended on its depth.

This study includes the assessment of all possible combinations of ready-mix concrete encompassed in a reference construction database of building materials for Valencia (Spain). All concrete components are considered in the calculation: cement, water, aggregates, and admixtures. The life cycle assessment methodology was used to calculate the environmental impacts of each material, including the modules A1-A3, i.e. production of raw materials, transport, and manufacturing, and impact categories in accordance with EN 15804:2012 + A2:2019. This study shows that cement is the concrete component with the greatest overall impact on the environment. Furthermore, the impact for the Global Warming Potential (stages A1-A3) can double depending on the type of cement; with CEM I and CEM II types having the highest impact. The regressions obtained for each impact category allow to predict the environmental impacts of every ready-mix concrete and also to analyze the relative importance of each concrete component in each impact category.

[EN] The present investigation focuses on the creation of a geopolymer, using pumice stone from Ecuador as a precursor material. The chemical composition of the pumice and the alkaline activation of the geopolymer with NaOH and Na2SiO3 were validated through a multi-criteria analysis that was used to identify the best mine among the ones located in Cotopaxi, Chimborazo, and Tungurahua states. Through laboratory tests, it was obtained that the best pumice stone had the presence of aluminum oxide and silicon in its composition, as well as amorphous particles, with a size of 40 to 50µm. The percentage of aluminum that was found in the mines of Cotopaxi, Imbabura, and Tungurahua states was 0.60%, 0.68%, and 1.50% respectively. In the fineness modulus tests, it stands out that more than 80% passes the 75µm sieve. In regards to the activation of the geopolymer, the average resistance of the deposits was Cotopaxi 22.60 MPa, Imbabura 23.03 MPa, and Tungurahua 23.03 MPa. In the geopolymer concrete, the average resistance values of each of the deposits were: Cotopaxi 4.21 MPa, Imbabura 8.05 MPa, and Tungurahua 8.67 MPa. The multicriteria analysis showed that the best option to create geopolymer concrete comes from the mine located in Tungurahua. It should be noted that the increase in NaOH concentration, maintaining the ratio of 2.4 in geopolymer cubes between Na2SiO3/NaOH as an activating solution, induces an increase in compressive strength. The concrete made from the Tungurahua mine, made up of 50% geopolymer and 50% aggregates. It is the one that showed the best properties with a compressive strength of 16.16 MPa, cured in an oven for 24 hours and at a temperature of 80°C. The design of geopolymer concrete that replaces the use of portland cement is the first step to reduce the pollution produced by hydraulic cement.

The influences of mechanically activated fly ash on the microstructure and thermal behaviour of atmospheric-cured concrete panels have been evaluated. For this purpose, comparative analyses of concretes prepared with and without addition of raw and milled fly ashes were performed. The raw fly ash was activated with an attrition mill for 1 h. Cylindrical concrete specimens with and without 20% fly ash substitution and large concrete panels with the same compositions were prepared. Mechanical properties of the concrete specimens were measured after 3, 7, 28 days, 2 and 4 months. After preparation the cylindrical specimens were cured in water while the concrete panels were kept in an open atmosphere outside the building for 1 year. The 28-day compressive strengths of the non-fly ash added cylindrical concrete specimen was 61.1 MPa, raw and mechanically activated fly ash added specimens were 54.4 and 64.7 MPa, respectively. Microstructural and thermal studies of the concrete panel were performed in the core drilled specimens after 1 year curing. The compressive strength of the core drilled specimens was 26.6, 25.4 and 35.9 MPa for the non-fly ash added, raw and mechanically activated fly ash added concrete panels. A beneficial pozzolanic reaction and improved mechanical properties of the milled fly ash-substituted concrete cured under harsh weather conditions were observed and determined by differential thermal analysis-thermogravimetry and mercury intrusion porosimetry. Improved mechanical properties of the milled fly ash added panel indicates its potential applicability in industrial practice due to the simplicity of the process.

The response of vaulted structures with dry-joints such as arches and shells can be predicted using graphical methods, limit state analysis, and rigid block analysis. However, these approaches assume material deformations are negligible. While acceptable for conventional masonry structures, there is a growing body of work investigating segmented vaulted structures where the segments comprise a large portion of the overall span. In such cases, material deformations and non-linearities can play a significant role. Typical analysis tools available are usually difficult to use and are not widely used by industry practitioners. In this paper, a modelling approach using a widely used finite element analysis package (LS-DYNA) is presented, using an ‘out-of-the-box’ approach for parameter tuning and modelling. This was then benchmarked against five experimental tests of dry-joint arches undergoing support displacements and a segmented concrete shell with large segments tested under a central point load. Crucially, the segmented shell exhibited imperfect dry-joints, with gaps occurring throughout various locations. A method of modelling and assessing such imperfections in a simple and practical manner is investigated through the use of a positive penetration allowance in the contact surfaces. The results show that the modelling approach is able to predict the collapse mechanism and failure support displacement for arches well, with further experimental tests required for 3D systems. It is envisioned that this work will add to the number of tools designers will have for analysing segmented vaulted structures with dry-joints.

Most non-destructive tests of concrete require sophis-ticated equipment and training; in this work we aim to develop a simple method to estimate the strength class of cylindrical con-crete samples based on vibrations signals that are collected after striking a concrete cylinder with a hammer. The vibration signals were collected by attaching a smartphone to the concrete cylinder and logging the vibrations registered via the smartphone’s built-in accelerometer. The acquired 1-D vibration signals are trans-formed to 2-D scalograms using continuous wavelet transform. Scalograms are then used to train a deep learningmodel to predict the strength class. Preliminary findings show that the model is capable of classifying the strength of concrete to low, high, or me-dium. The developed model achieved a high accuracy of 91.67%. The promising results of this work shed light into the future of smartphone-based measurements of construction materials’ properties.

This paper deals with the effect of the character of the water used for the water storage of concrete test specimens on the results of tests for resistance to de-icing chemicals. Two experiments were conducted to investigate the effect of the content of free CO2 in water and leaching of calcium hydroxide from concrete on the test results. In the first experiment, the resistance of mortars to water and de-icing chemicals was investigated. It was found that the character of the water storage, i.e., fresh water vs. previously used water, can significantly affect the test results. The second experiment focused on investigating the effect of the content of free CO2 in water on the test results. It was found that the content of free CO2 in the water can statistically significantly influence the test results. In conclusion, the paper shows that the character of the water used for water storage of concrete test specimens and the content of free CO2 in water are essential factors that can significantly affect the results of concrete resistance tests to de-icing chemicals. Further research is needed to understand these influences and their potential use to improve the resistance of concrete.

After high-temperature treatment, both nano-titanium dioxide-modified concrete and ordinary concrete exhibit typical splitting failure. High-temperature heating reduces the mechanical properties and brittleness of concrete and improves the ductility of concrete. The stress–strain relationship of the specimens was obtained through the uniaxial compression test of ordinary concrete and nano-titanium dioxide-modified concrete cube specimens under normal temperature and high-temperature conditions. In addition, the relationship between temperature and damage variables was established, and the unified constitutive model containing damage variables after room temperature and high-temperature treatment of ordinary concrete and nano-titanium dioxide-modified concrete were established. It provides a reference for future research on the mechanical properties of high-performance concrete structures after high temperatures (fire).

V diplomski nalogi na kratko predstavimo zgodovino betona in zgodovino izdelave betonskih elementov. V prvem delu naloge je predstavljen postopek izdelave predizdelanih betonskih elementov - tehnologija izvedbe del. Preučili smo proces od tehnološke priprave in načrtovanja elementov do končnih izvedenih betonskih elementov. Za ta proces so potrebne velike tehnološke kapacitete in delovni kader, ki omogoča, da priprava opaža, armature in betona za produkte poteka nemoteno. Zaradi boljšega vpogleda v proces izdelave elementov smo obiskali enega od proizvodnih obratov v Sloveniji in na praktičnem primeru prikazali, kako se dela izvajajo. Sledi opis vseh korakov tehnologije izvedbe, vse do transporta in vgradnje elementov na gradbišču. Drugi del naloge se osredotoči na kontrolo kakovosti izdelave predizdelanih betonskih elementov, kar je ena od prednosti tovrstne izvedbe del. Pregledali smo, kako je potrebno v samem procesu priprave elementov kontrolirati kakovost izvedbe in kako se kasneje kontrolira izdelane končne produkte. Kontrola kakovosti sledi predpisanim standardom, ki smo jih za posamezne produkte tudi pregledali. V tem poglavju so zbrane informacije in izkušnje, pridobljene z opazovanjem dela v obiskanem proizvodnem obratu. Ponovno so prikazani koraki izvedbe elementov iz prvega dela naloge, tokrat s poudarkom na kontroli kakovosti. S tem je pripravljen pregled, na kaj vse je potrebno biti pozoren in kaj vse je potrebno nadzorovati v postopku izvedbe elementa, da je le ta pripravljen v skladu z zahtevami ter posledično primeren za vgradnjo in uporabo. This thesis gives a brief overview of the history of concrete and the history of the production of concrete elements. In the first part of the work, the process of making precast concrete elements is presented - the technology of performing the work. The process from the technological preparation and design of the elements to the finished precast concrete elements is examined. This process requires a large technological capacity and manpower to ensure that the preparation of formwork, reinforcement and concrete for the products runs smoothly. To gain a better insight into the process of manufacturing the elements, one of the production facilities in Slovenia was visited and a practical example was used to show how the work is carried out. Subsequently, all steps of the production technology up to the transport and installation of the elements on site are described. The second part of the thesis deals with quality control in the production of precast concrete elements, which is one of the advantages of this type of work. An overview is given of how the quality of workmanship must be controlled during the preparation of the elements and the subsequent inspection of the final manufactured products. Quality control is carried out according to the prescribed standards, which have also been reviewed for each product. This chapter summarises the information and experience gained during the observation of the work in the visited production facility. It repeats the steps of implementing the elements from the first part of the thesis, this time focusing on quality control. This gives an overview of what to look for and what needs to be checked during the production of the element to ensure that it meets the requirements and is therefore suitable for installation and use.

Nowadays, admixtures are used with the aim to provide strength and durability to concrete with less water use. New and low-cost admixtures gained a large amount of consideration to mitigate the problems associated with concrete’s durability and service life without upsetting its strength properties. The current work investigates the effect of three types of acetates on the workability, density, and compressive strength of concrete, which is used in structures of the Iraqi ports that suffer from corrosion damages and deterioration owing to the aggressive marine environments. Potassium acetate (KA), calcium acetate (CaA), and ethyl acetate (EA) are incorporated with different doses (1.38–5.6 wt.% of cement) in concrete mixtures using different water/cement ratios (0.48–0.54) based on an espoused central composite experimental design. The experimental results confirmed that the average workability increased with increasing the acetate dose, particularly with CaA. The density and compressive strength of 28 days of water-cured mixtures increased with increasing acetate dose following the order: Ca > K > Ethyl acetate and decreased with increasing w/c ratio. The high rise in compressive strength and workability linked to control mixtures was 30.8% and 77.3% as well as 15.7% and 64.3% for the mixtures incorporated with 5.6 wt.% CaA and KA, respectively. While it was 14.2% and 58.3% for the mixtures incorporated with 3.5 wt.% EA. RSM was employed to optimize and model the design and hardened properties of concrete mixtures. ANOVA results predicted the same trend, which was obtained from the experimental results. The mathematical models were valued with high-regression coefficients. The highest compressive strength of 42.68 MPa has been achieved for a concrete mixture of 0.48 w/c ratio by the incorporation of 5.1 wt.% CaA through a model with R2 96.97%. The relatively low-cost acetate admixtures, particularly CaA, seemed promising for the fabrication of concrete with outstanding properties.

The possibility of improving the strength properties of concrete materials based on ash/slag waste from thermal power plants of Almaty (Kazakhstan) by adjusting their chemical composition is considered. An X-ray phase analysis, scanning electron microscopic (SEM) analysis, infrared analysis (IR), and elemental determination analysis (EDAX) of ash and slag wastes were carried out, and additives to correct their chemical composition were selected. The analysis of the conducted studies shows that the addition of polypropylene fiber leads to an increase in the compressive crack resistance compared to the composition of the mixture in which ash is present. The highest compressive strength in which cenospheres increase in strength characteristics is observed on samples modified with 7% cenospheres. It was found that the strength of the concrete with the addition of cenospheres increased by more than two times in comparison with a sample without additives.

Without the restriction of formwork, 3D–printed concrete (3DPC) shows great advantages in construction; for the same reason, it presents stability problems, which greatly affect its buildability. In the present paper, a fluid–solid integrated peridynamic (PD) model is proposed for the modeling of 3DPC buildability. The considerations of fluid- and solid-like behaviors of 3DPC and the transition between them during the printing process are incorporated in by bond-based correspondence PD. Under the correspondence framework, the affinity hydration model is employed to combine the liquid bridge model and concrete damage model to capture the age-dependent material performance. In addition to the mechanical behavior, the simulation of the layer-by-layer printing process is also considered, including the new layer activation and time-dependent parameters. These constitute a complete scheme for 3DPC buildability modeling, which is then verified by two case studies with experimental results. The experimental and computational results exhibit plastic flow and/or elastic buckling. The case studies indicate that the proposed model can satisfactorily reproduce both the deformation shape and failure mode of 3DPC, thus providing guidance for the design of 3D concrete printing processes. Financial supports from the Spanish Ministry of Economy and Competitiveness, through the Severo Ochoa Programme for Centres of Excellence in R&D (Grant No. CEX2018-000797-S), the National Natural Science Foundation of China (Grant No. 52078361) and the Innovation Program of Shanghai Municipal Education Commission, China (Grant No. 2017-01-07-00-07-E00006) are greatly appreciated.

The use of construction and demolition (C&D) waste as aggregate in concrete results in a reduction in strength due to its porosity. To compensate, mix designs often require higher cement contents, which increase the material’s environmental impact. This study presents an experimental and numerical analysis of the effect of steel fibres on the mechanical properties of the concrete produced with recycled C&D aggregates with varying densities. The variation in fibre content did not present any influence on the compressive strength of concrete, which is significantly affected by the lower density of the recycled C&D aggregate. The fibres collaborate to mitigate the loss of flexural strength of the steel fibre reinforcement in recycled coarse aggregate concrete (SFRRCAC) provoked by lower density of recycled aggregates when the water-to-cement ratio is lower. When the water-to-cement ratio is above 0.65, there is a great reduction of the matrix strengths due to the paste porosity and the influence of aggregate density and fibre content was insignificant.

Assessing concrete quality as construction goes on provides early warnings of potential flaws and leads to timely corrections in mix proportioning and placement techniques. Compressive strength and maturity modeling are among the most common parameters used by the concrete industry. Past studies indicated that non-destructive methods, NDTs, relate well to maturity and concrete strength predictions. In this study, the hydration temperature–time history of concrete was explored in defining “master curves” for concrete maturity for the first time. Well-accepted NDTs, such as ultrasonic pulse velocity and resonant frequency, were used in this effort. The study findings indicated that the novel approach of “master curves” for the maturity of concrete can be defined and follow a generalized logarithmic form. The best fit models relating NDT response and the maturity temperature–time product provided a high coefficient of determination (i.e., in almost all cases above 0.9 and p < 0.05), thus resulting in a very good fit. The shift factors for each mixture’s maturity function in relation to the master curve were related to concrete properties. The shifted maturity functions from the concrete mixtures included in the study had a perfect transition to the master curve (i.e., all the shifted data overlap the master curve trend line with an R2 = 1). The NDTs’ ability to capture the hydration temperature-time history was assessed with impeded sensors into the concrete mixtures. This approach has provided strength prediction models with a high accuracy (i.e., good agreement between observed and predicted strength values with R2 = 0.93). The proposed NDT-based maturity modeling through “master curve” development provides significant benefits in relation to traditional maturity modeling since it offers the opportunity to: (i) predict strength without having to repeat maturity testing each time a producer adjusts mixture proportioning to fine tune mix design; (ii) save testing time and cost due to reduced maturity evaluation from the use of master curves; and (iii) be able to quickly predict without further testing what the strength gain will be due to variations in mixture proportioning. The ability to monitor concrete maturity, and thus strength, with NDTs in reinforced concrete is of particular interest since using cores is problematic due to the presence of reinforcement.

The object of the study was concrete floors in a poultry house with different types of litter. The paper addressed the problem of reducing microorganism contamination of concrete floors in poultry houses to prevent biological corrosion. Corrosion of the surface of the concrete floor in the form of the formation of calcium oxalate monohydrate crystals was established by scanning electron microscopy; microscopic fungi: A. pullulans, F. sporotrichioides, and A. niger were detected. The TPD MS method established that concrete samples obtained in a room with straw lose moisture by 51.52 % more, with granules – by 342.42 % (р≤0.05), with shavings by 6.06 %, compared to control. CO from concrete samples is released less with sawdust litter by 86.40 %, with straw – by 83.49 %, with shavings – by 76.69 %, with granules – by 69.90 % (р≤0.05). The CO2 content in concrete samples from the room with sawdust was lower by 86.88 % (р≤0.05), with straw – by 55.73 %, with shavings – by 38.52 %, with granules – by 23.77 %, compared to control without litter. Microbiological studies have established that 48 hours after disinfection, the total number of colonies of microorganisms on a concrete floor with a sawdust litter likely decreased by an average of 90.19 %, straw – by 91.62 %, shavings – by 79.76 %, granules – by 82.88 % (р≤0.05), in the control – by 83.73 %. It can be argued that the disinfectant destroys microorganisms on the concrete surface regardless of the type of substrate. The peculiarity of the experiment was the use of scanning electron microscopy and TPD MS methods to study structural changes in concrete. The research is distinguished by the use of a powdered disinfectant to reduce microbial damage to a concrete floor with different types of litter. The results of the experiment could be used in the aggressive environment of poultry houses to reduce the impact on concrete structures, Об’єктом дослідження були бетонні підлоги у пташнику з різними типами підстилки. В дослідженні вирішувалась проблема зменшення контамінації мікроорганізмами бетонних підлоги у птахівничих приміщеннях для попередження біологічної корозії. Встановлено методом скануючої електронної мікроскопії корозію поверхні бетонної підлоги у вигляді утворення кристалів моногідрату оксалату кальцію та виявлені мікроскопічні гриби: A.pullulans, F.sporotrichioides та A.niger. Методлом TPD MS встановлено, що зразки бетону отримані у приміщенні з соломою втрачають вологу на 51,52% більше, з гранулою – на 342,42% (р≤0,05), зі стружкою на 6,06%, порівняно з контролем. СО зі зразків бетону виділяється менше з підстилкою тирса на 86,40%, з соломою – на 83,49%, зі стружкою – на 76,69%, з гранулою – на 69,90% (р≤0,05). Вміст СО2 у зразках бетону з приміщення з тирсою був менший на 86,88% (р≤0,05), з соломою – на 55,73%, зі стружкою – на 38,52%, з гранулою – на 23,77%, порівняно з контролем без підстилки. Мікробіологічними дослідженнями встановлено, що через 48 годин після проведення дезінфекції загальна кількість колоній мікроорганізмів на бетонній підлозі з підстилкою тирса вірогідно зменшилась в середньому на 90,19%, солома – на 91,62%, стружка – на 79,76%, гранула – на 82,88% (р≤0,05), в контролі – на 83,73%. Можна стверджувати, що дезінфектант знищує мікроорганізми на поверхні бетону не залежно від виду підстилки. Особливістю експерименту є застосуванням методів скануючої електронної мікроскопії та TPD MS для дослідження структурних змін в бетоні. Проведене дослідження відрізняється застосуванням порошкоподібного дезінфектанту для зменшення мікробного ураження бетонної підлоги з різними типами підстилок. Результати експерименту можна застосовувати в умовах агресивного середовища птахівничих приміщень для зменшення впливу на бетонні конструкції

The predictive ability of statistical methods such as Scheffe’s and Osadebe’s models is apodictic as they are often adopted for optimization of concrete properties. But attention is drawn to their limitations. In this paper, Ibearugbulem’s optimization model was applied to predict the compressive strength of nanostructured cassava peel ash (NCPA)-cement composites. Three hundred and six concrete cubes were prepared in the laboratory with varying water-cement ratios and mix ratios with 1.5 % NCPA replacement interval. The 28 days’ compressive strength was varied with that of 56 days’ strength. The experimental results were modelled using Ibearugbulem’s approach. The optimum experimental and modelled outcome of the concrete strength was 24.20 N/mm2 and 30.10 N/mm2, 22.61 N/mm2 and 28.54 N/mm2 at 28 days and 56 days curing age respectively. These values were obtained at 16.5% and 19.5% NCPA replacement intervals at water-cement ratios of 0.72 and 0.75 for the model and experiment respectively with their mix ratios being 0.835:0.165:1.5:3 and 0.805:0.195:1.5:3. The percentage difference of 7.03 % and 5.47 % being less than 10 % at 28 days and 56 days for the optimum values reveals the adequacy of the model. Fisher’s statistical tool was used in the analysis and the calculated value of fisher of 1.11 and 1.08 were lower than the fisher value of 1.94 derived from the statistical f-distribution table. This implies that there was no significant difference between the laboratory-strength values and the modelled-strength values at 95 % confidence level. The formulated model is therefore reliable, safe and recommended for production of cement-composites.

This poster received the outstanding poster award from the RILEM Week Kyoto 2022.

Concrete industry poses a great threat to the environment not only by its consumption of natural resources, but also in its role on the global emission of carbon dioxide in the atmosphere from cement industries which in turn results into global warming. In light of these scenarios, serious interventions have to be incorporated in designs to promote sustainable construction and prevent environmental pollution and degradation. In order to minimize the use of cement, a study has been done by developing simple soil arch elements which can be used to support the topping concrete slab of around 30 mm thick. The technique utilizes the semi-prefab technology and therefore eliminates the use of shuttering for slab panel construction. Through this study, it has been shown that the consumption of cement is reduced to 49.32% while the timber formwork is reduced to 60.00%. The technique is recommended for application in upper floor slab casting as it reduces the cost of construction and is environmentally friendly.

Among the most important properties of a concrete are its workability, strength and durability. These properties ordinarily are achieved by varying the grading of aggregates and proportions of the basic concrete components. Today, admixtures have taken over because they are easier to apply and are also more effective. However, the technology and availability of admixture is not easily assured, especially in developing countries. This work is concerned with the use of a combination of fly ash and a generic sulfonated naphthalene-formaldehyde (SNF) condensate superplasticizer to show the water reducing, workability and strength enhancement potentials of their combination. A grade 20 concrete of nominal mix proportion of 1:2:4 and an initial water-cement ratio (w/c) of 0.6 was used; and a constant consistency of 50 mm slump maintained throughout the experiment. The variation of the strength of the concrete and the water-cement ratio (w/c) was studied as the various combined quantities of superplasticizer and fly ash was added. It was observed that the 28-days strength of the concrete increased with increase in either fly ash or superplasticizer in the combination. The strength obtained was much higher than that of the control mix. The water-cement ratio also reduced in the same order, showing more reduction than using fly ash or SNF superplasticizer alone. This showed that there is a great advantage in the combined use of both admixtures.

Growing environmental awareness and scarcity of natural resources are forcing the world to migrate from linear to circular economies. The possibility of partially replacing cement with ceramic-based waste from construction and demolition waste (C&DW) is a government and industry focus. The present study analyzes the effects of including finely ground complete walls of ceramic blocks (including masonry mortars) as supplementary cementing materials (SCM) on the physical, mechanical, and transport properties (water absorption and permeability) of concrete. The replacement ratio employed was 25% by weight of cement. Studies of the hydration evolution of cement pastes support the described properties of concretes. The findings reveal that the ground ceramic-based waste from C&DW stimulates hydration at all ages. Initially, this stimulation is predominantly physical (filler effect), but in later stages, it becomes chemical (pozzolanic reaction). Based on the results obtained in this study, it is possible to produce concrete with mechanical properties comparable to those of conventional concrete at 28 days.

Concrete naturally contains a large number of circular-like stochastic pores which weaken the tensile strength of concrete and change the crack propagation path. This study investigates the influences of the size distribution and the spatial distribution of stochastic pores on the fracture behavior of concrete based on the splitting tensile test. The mesoscale model of concrete containing coarse aggregate, mortar, interface transition zone (ITZ), and circular pores is established to simulate the crack initiation, propagation, and coalescence of concrete. Concrete samples with a single hole are prepared to verify the effectiveness of the numerical simulation method. Numerical tests are conducted on numerous mesoscale concrete samples with various porosities, pore size distributions, and pore spatial distributions. The numerical simulation results indicate that the tensile strength decreases with the increase of pore size at the same porosity. Based on multifractal theory, a quantitative indicator to describe the spatial distribution uniformity of concrete stochastic pores is proposed. There is a positive correlation between the spatial distribution uniformity of stochastic pores and the tensile strength. The stochastic circular pores can have a profound effect on the concrete’s fracture pattern, which results in three typical macro-crack patterns in the numerical simulation of the splitting tensile test. The presented results deepen the understanding of the influence of stochastic circular pores on the tensile mechanical properties of concrete and provide a reference for the design of concrete structures.

El informe está estructurado de la siguiente manera: una descripción del perfil de la empresa, que incluye información sobre su estructura organizacional, su portafolio de productos y servicios, su infraestructura y sus recursos técnicos y tecnológicos utilizados. Se presenta también un marco normativo que contiene leyes, decretos, resoluciones, normas y reglamentos relacionados con las actividades de la pasantía. Se expone el cronograma de actividades, junto con su descripción y evidencia fotográfica, y se incluye un análisis DOFA que evalúa la empresa y el desempeño personal durante la pasantía. También se detallan los principales aportes e impactos logrados durante la pasantía a la empresa y se presentan lecciones aprendidas y recomendaciones. Finalmente, se hace una síntesis de los aspectos más importantes de la pasantía en una forma clara y sencilla. The report is structured as follows: a description of the company's profile, which includes information on its organizational structure, its portfolio of products and services, its infrastructure, and its technical and technological resources used. A regulatory framework is also presented that contains laws, decrees, resolutions, norms and regulations related to the internship activities. The schedule of activities is exposed, along with its description and photographic evidence, and a SWOT analysis is included that evaluates the company and personal performance during the internship. The main contributions and impacts achieved during the internship to the company are also detailed, and lessons learned and recommendations are presented. Finally, a synthesis of the most important aspects of the internship is made in a clear and simple way. Ingeniero Civil http://www.ustavillavicencio.edu.co/home/index.php/unidades/extension-y-proyeccion/investigacion Pregrado

The use of by-products and recyclable materials in the production of concrete has become an interesting alternative to mitigate environmental impacts, especially those generated by the construction industry, as long as their mechanical and durability properties do not early compromise the service life of the structures. The resistance of concrete to the penetration of harmful agents, such as chloride ions, is an important property since it directly correlates with the performance, integrity, and durability of reinforced concrete structures. This study evaluate four concrete mixes were cast for aggressiveness class III of NBR 6118 [1] produced with 8% of partial replacement of Portland cement with silica fume, resulting of metallurgical production, and with 30% partial replacement of natural fine aggregates by recycled fine aggregate from fresh concrete waste, obtained from the concrete production process in concrete mixer trucks. At 28 days of age, the specimen was submitted to capillarity, mechanical resistance and chloride migration tests, according to the NT BUILD 492 standard [2]. In general, the results indicated that the proposed replacements improved mechanical properties and chloride ion penetration resistance, mainly with the incorporation of silica fume. Resumo A utilização de subprodutos e materiais recicláveis na produção de concreto tornou-se uma alternativa interessante para mitigar os impactos ambientais, principalmente os gerados pela construção civil, desde que suas propriedades mecânicas e de durabilidade não comprometam precocemente a vida útil das estruturas. A resistência do concreto à penetração de agentes nocivos, tais como íons cloreto, é uma propriedade importante, pois se correlaciona diretamente com o desempenho, integridade e durabilidade das estruturas de concreto armado. Este estudo avaliou o desempenho de quatro misturas de concreto moldadas para classe de agressividade III da NBR 6118 [1] produzidas com 8% de substituição parcial de cimento Portland por sílica ativa, resíduo de produção metalúrgica, e com 30% de substituição parcial de agregados miúdos naturais por agregado miúdo reciclado de resíduo de concreto fresco, obtido do processo de produção de concreto em caminhões betoneira. Aos 28 dias de idade, as amostras foram submetidas aos testes capilaridade, resistência mecânica e de migração de cloretos, este, conforme preconiza a norma NT BUILD 492 [2]. De maneira geral, os resultados indicaram que as substituições propostas melhoraram as propriedades mecânicas e a resistência à penetração do íon cloreto, principalmente quando se utilizou a incorporação de sílica ativa.

Basalt fibers are a type of reinforcing fiber that can be added to concrete to improve its strength, durability, resistance to cracking, and overall performance. The addition of basalt fibers with high tensile strength has a particularly favorable impact on the splitting tensile strength of concrete. The current study presents a data set of experimental results of splitting tests curated from the literature. Some of the best-performing ensemble learning techniques such as Extreme Gradient Boosting (XGBoost), Light Gradient Boosting Machine (LightGBM), Random Forest, and Categorical Boosting (CatBoost) have been applied to the prediction of the splitting tensile strength of concrete reinforced with basalt fibers. State-of-the-art performance metrics such as the root mean squared error, mean absolute error and the coefficient of determination have been used for measuring the accuracy of the prediction. The impact of each input feature on the model prediction has been visualized using the Shapley Additive Explanations (SHAP) algorithm and individual conditional expectation (ICE) plots. A coefficient of determination greater than 0.9 could be achieved by the XGBoost algorithm in the prediction of the splitting tensile strength.

RESUMO A construção civil exerce função importante no consumo de energia em todo o mundo e influência, de forma significativa, o consumo total de recursos naturais e as emissões de CO2. A utilização de materiais renováveis está intrinsecamente relacionada à pesquisa e à inovação. A reutilização, a reciclagem, bem como o desenvolvimento de novos materiais e a descoberta de novas aplicações para materiais renováveis já conhecidos, podem contribuir de maneira expressiva para o desenvolvimento sustentável. A quitosana (CS) é um biopolímero com uma estrutura química e características únicas aliadas à sua farta disponibilidade como derivado da quitina, fazem com que suas possibilidades de aplicação nos mais diferentes campos tecnológicos, tenha se expandido consideravelmente. No presente trabalho, a utilização da quitosana para produção de concretos por meio de teores ótimos é investigada. Os valores de quitosana incorporados na dosagem foram 0,1%; 0,3% e 0,4%, com relação à massa de cimento. Os diferentes concretos obtidos foram submetidos a ensaios de propriedades mecânicas e microestrutural. Os resultados mostraram que a microestrutura foi favorecida com a utilização da quitosana. Bem como, apresentaram resultados favoráveis à incorporação dos teores utilizados de quitosana (se desatacando as amostras com 0,1% de substituição), sendo positivos quanto às propriedades mecânicas para a maioria das técnicas utilizadas, o que indica fortemente que a quitosana pode ser considerada como material promissor a ser incorporado na produção de concreto. ABSTRACT Civil construction plays an important role in energy consumption worldwide and significantly influences the total consumption of natural resources and CO2 emissions. The use of renewable materials is intrinsically related to research and innovation. Reuse and recycling, as well as the development of new materials and the discovery of new applications for already known renewable materials, can significantly contribute to sustainable development. Chitosan is a biopolymer with unique characteristics and chemical structure which, combined with its wide availability as a chitin derivative, have considerably expanded its application possibilities in the most different technological fields. In the present work, the use of chitosan for the production of concrete through optimal levels is investigated. The chitosan values incorporated in the dosage were 0.1%; 0.3% and 0.4%, in relation to the cement mass. The different concretes obtained were submitted to tests of mechanical and microstructural properties. The results showed that the microstructure was favored with the use of chitosan. In addition, they presented favorable results for the incorporation of the chitosan levels used (especially considering the samples with 0.1% of substitution), also being positive regarding the mechanical properties for most of the techniques used. This strongly indicates that chitosan can be considered as a promising material to be incorporated in the production of concrete.

Concrete developed from light expanded clay aggregate (LECA) and glass fiber has good performance, durability, and sustainability. Towards this, the experimental investigation was designed to study cubes, cylinders, and simply supported beams. Four mixtures had LECA volume of 0%, 75%, 85%, and 95% as coarse aggregate replacement and glass fiber content volume of 2% (N, L75, L85, and L95), and the other two mixtures had 75% LECA and glass fiber content of 1% and 1.5% (L75-F1 and L75-F1.5). Results compared to normal concrete showed the weight reduction of samples while adding more glass fiber caused slump reduction in contrast to LECA. Increasing glass fiber volume in the mixture had a negative influence on tensile strength while causing compressive strength enhancement. Moment resistance and energy absorption capacity of L85 were enhanced by 7.5% and 10.3%, respectively. For L75-F1 specimens, the beam stiffness and ductility were enhanced by 14.8% and 14.3%, respectively. &nbsp

Ricardo Barredo de Valenzuela was a leading figure in the technological development of construction in Spain in the first half of the 20th century. Guided by Eduardo Torroja, he developed a method of post-tensioning concrete structures, patented under his name, which competed on an international level with the most advanced of the time (Freyssinet, CCL,...). Barredo participated in the construction of the most recognized architectural and civil engineering works of the time, collaborating with such prestigious engineers as Eduardo Torroja or Fernández Casado. Miguel Fisac recognized its essential role in the development of roof structures made up of post-tensioned concrete voussoirs, known as “bone-beams”. This article reviews his extensive professional career, highlighting his work and expressing the well-deserved recognition of his legacy., Ricardo Barredo de Valenzuela fue una figura clave en el desarrollo tecnológico de la construcción en España en la primera mitad del siglo XX. Dirigido por Eduardo Torroja, desarrolló un método de postesado de estructuras de hormigón, patentado con su nombre, que compitió a escala internacional con los más avanzados de la época (Freyssinet, CCL,…). Participó en la construcción de las obras arquitectónicas y de la ingeniería civil más reconocidas de la época, colaborando con ingenieros de tanto prestigio como Eduardo Torroja o Fernández Casado. Miguel Fisac reconoció su esencial papel en el desarrollo de las estructuras para cubiertas formadas por dovelas de hormigón postesado, conocidas como “vigas-hueso”. El presente artículo recorre su amplia trayectoria profesional, poniendo en valor su obra y manifestando el merecido reconocimiento de su legado.

Knowing and promoting the strength development of concrete at an earlier age is essential for accelerating formwork circulation of the on-site construction and precast product manufacture. The strength development rate at earlier ages of less than the initial 24 h was investigated. The effect of measures of adding silica fume, calcium sulfoaluminate cement, and early strength agent on the strength development of earlier concrete at ambient temperatures of 10, 15, 20, 25, and 30 °C was studied. The microstructure and long-term properties were further tested. It is shown that the strength increases exponentially first and then logarithmically, different from what is commonly recognized. Increasing cement content exhibited a certain effect only above 25 °C. When the cement content increased from 420 to 460 kg/m3, the strength only increased from 6.2 to 6.7 MPa after 12 h at 25 °C. The early strength agent could increase the strength significantly, the strength could be increased from 6.4 to 10.8 MPa after 20 h at 10 °C and from 7.2 to 20.6 MPa after 14 h at 20 °C. All measures for promoting earlier strength did not have an evident negative effect. The results could be potentially referred for the formwork removal at a suitable moment.

Concrete structures under wind and earthquake loads will experience tensile and compressive stress reversals. It is very important to accurately reproduce the hysteretic behavior and energy dissipation of concrete materials under cyclic tension–compression for the safety evaluation of concrete structures. A hysteretic model for concrete under cyclic tension–compression is proposed in the framework of smeared crack theory. Based on the crack surface opening–closing mechanism, the relationship between crack surface stress and cracking strain is constructed in a local coordinate system. Linear loading–unloading paths are used and the partial unloading–reloading condition is considered. The hysteretic curves in the model are controlled by two parameters: the initial closing stress and the complete closing stress, which can be determined by the test results. Comparison with several experimental results shows that the model is capable of simulating the cracking process and hysteretic behavior of concrete. In addition, the model is proven to be able to reproduce the damage evolution, energy dissipation, and stiffness recovery caused by crack closure during the cyclic tension–compression. The proposed model can be applied to the nonlinear analysis of real concrete structures under complex cyclic loads.

In this thesis, the carbonation of functionally graded concrete is investigated through a combination of experimental and analytical approaches. The properties of functionally graded concrete vary throughout the cross-section to satisfy performance requirements in a resource-efficient manner. In this research, functional grading of concrete elements is achieved by casting discrete layers of concretes possessing different properties. Layers are cast in the fresh state to prevent formation of a cold joint and associated interface weakness. Carbonation is the process of environmental CO2 diffusing into and reacting with concrete, thereby changing its chemical composition. It is a durability concern for concrete structures, since carbonated concrete does not provide adequate corrosion protection to embedded reinforcement. Increased resistance to carbonation has traditionally been achieved by increasing the cement content in concrete elements, which increases embodied carbon. Carbonation presents as a surface phenomenon. As such, the concrete mix adopted at the outside face is of most concern when designing carbonation-durable elements. Given the ability to relate properties to performance, functional grading presents a promising approach to providing carbonation durability with reduced cement content. In such an element, a high-cement carbonation durability layer could be placed in exposed areas, but retaining low-cement concrete as the material in the bulk remainder. This would have theoretically equivalent durability to a single-mix element cast from the high-cement mix, but significantly lower cement content. The presented research seeks to answer the question “Is layered functional grading a viable method of reducing cement contents in concrete elements without sacrificing carbonation durability?''. This is achieved by first understanding the carbonation behaviour of single-mix concrete specimens, thus establishing baseline processes for accelerated carbonation testing and the influence of material parameters on carbonation performance of different concrete mixes. Next, machine learning is applied to predict properties of concretes from mix composition, such as carbonation performance. Following this, the carbonation of layered functionally graded specimens is experimentally investigated, and the results are used to validate a derived model for the carbonation depth in layers. Finally, it is acknowledged that structural cracking could provide a route for CO2 penetration beyond the depth of a carbonation durability layer. Therefore, a further experimental series investigates the cracking behaviour of layered prisms under loading and their carbonation performance when subjected to simultaneous cracking and carbonation. Digital image processing methods are implemented in multiple areas to improve the detection and analysis of carbonation fronts from phenolphthalein indication tests. Overall, the results demonstrate that layered functionally graded concrete elements offer a viable route to cement reduction, without loss of carbonation durability. Therefore, it is recommended that practitioners consider this approach to design durable structures with reduced cement consumption.

One of the most promising ways to solve the problem of reducing the rate of depletion of natural non-renewable components of concrete is their complete or partial replacement with renewable plant counterparts that are industrial and agricultural waste. The research significance of this article lies in the determination at the micro- and macro-levels of the principles of the relationship between the composition, the process of structure formation and the formation of properties of concrete based on coconut shells (CSs), as well as the substantiation at the micro- and macro-levels of the effectiveness of such a solution from the point of view of fundamental and applied materials science. The aim of this study was to solve the problem of substantiating the feasibility of concrete consisting of a mineral cement–sand matrix and aggregate in the form of crushed CS, as well as finding a rational combination of components and studying the structure and characteristics of concrete. Test samples were manufactured with a partial substitution of natural coarse aggregate with CS in an amount from 0% to 30% in increments of 5% by volume. The following main characteristics have been studied: density, compressive strength, bending strength and prism strength. The study used regulatory testing and scanning electron microscopy. The density of concrete decreased to 9.1% with increasing the CS content to 30%. The highest values for the strength characteristics and coefficient of construction quality (CCQ) were recorded for concretes containing 5% CS: compressive strength—38.0 MPa, prism strength—28.9 MPa, bending strength—6.1 MPa and CCQ—0.01731 MPa × m3/kg. The increase in compressive strength was 4.1%, prismatic strength—4.0%, bending strength—3.4% and CCQ—6.1% compared with concrete without CS. Increasing the CS content from 10% to 30% inevitably led to a significant drop in the strength characteristics (up to 42%) compared with concrete without CS. Analysis of the microstructure of concrete containing CS instead of part of the natural coarse aggregate revealed that the cement paste penetrates into the pores of the CS, thereby creating good adhesion of this aggregate to the cement–sand matrix.

Concrete contributes 8% of all global carbon emissions, making the need to find substitutes critical for environmental sustainability. Research has indicated the potential for recycled plastics to be used as concrete substitutes. This study extends existing research by investigating the use of polycarbonate (PC) in plastic sand bricks as a mechanical equivalent to concrete. PC has high compressive strength, durability, impact strength, thermal resistivity, clarity, fatigue resistance, and UV resistance. This work provides a method and mold to produce a matrix of sand–plastic sample compositions with dimensions adhering to the ASTM D695 standard for compressive properties of rigid plastic. Compositions of 0% (control), 20%, 30%, 40%, and 50% sand by weight were tested. Samples were tested for compressive strength until yield and stress–strain behaviors were plotted. The results for 100% PC demonstrated an average and maximum compressive strength of 71 MPa and 72 MPa, respectively. The 50% PC and 50% sand composition yielded an average and maximum compressive strength of 71 MPa and 73 MPa, respectively, with an increase in compressive stiffness and transition to shear failure resembling concrete. With a composite density of 1.86 g/cm3 compared to concrete’s average of 2.4 g/cm3, and a compressive strength exceeding commercial concrete demands of 23.3 MPa to 30.2 MPa, this lightweight alternative meets the strength demands of concrete, reduces the need for new construction materials, and provides an additional recycling opportunity for nonbiodegradable waste plastic.

Hydraulic structures are typically subjected to long-term hydraulic loading, and concrete—the main material of structures—may suffer from cracking damage and seepage failure, which can threaten the safety of hydraulic structures. In order to assess the safety of hydraulic concrete structures and realize the accurate analysis of the whole failure process of hydraulic concrete structures under the coupling effect of seepage and stress, it is vital to comprehend the variation law of concrete permeability coefficients under complex stress states. In this paper, several concrete samples were prepared, designed for loading conditions of confining pressures and seepage pressures in the first stage, and axial pressures in the later stage, to carry out the permeability experiment of concrete materials under multi-axial loading, followed by the relationships between the permeability coefficients and axial strain, and the confining and seepage pressures were revealed accordingly. In addition, during the application of axial pressure, the whole process of seepage–stress coupling was divided into four stages, describing the permeability variation law of each stage and analyzing the causes of its formation. The exponential relationship between the permeability coefficient and volume strain was established, which can serve as a scientific basis for the determination of permeability coefficients in the analysis of the whole failure process of concrete seepage–stress coupling. Finally, this relationship formula was applied to numerical simulation to verify the applicability of the above experimental results in the numerical simulation analysis of concrete seepage–stress coupling.

In construction, brick and concrete are the most widely used materials, occupying an important part of the building budget. Its great versatility in construction, contrasts with the fragility of these elements. This solution is suitable for low-rise buildings, but it is not so clear for medium and high-rise buildings, due to its low ductility and its weight. The proper location of these walls in buildings could improve their resistant and ductile behavior. In this research, the optimal solution is found for the placement of infill walls with bricks in 4- and 8-story frames, considering ductility and resistance., En la construcción, el ladrillo y el hormigón son los materiales más utilizados, ocupando una parte importante del presupuesto de edificación. Su gran versatilidad en la construcción contrasta con la fragilidad de estos elementos. Esta solución es adecuada para edificios de baja altura, pero no está tan clara para edificios de altura media y alta, debido a su baja ductilidad y su peso. La correcta ubicación de estos muros en los edificios podría mejorar su comportamiento resistente y dúctil. En esta investigación se encontrará la solución óptima para la colocación de muros de relleno con ladrillos en pórticos de 4 y 8 pisos, considerando ductilidad y resistencia.