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Durability is a major concern in concrete (particularly recycled concrete) structures exposed to carbonation-induced corrosion, given the social, economic, environmental and safety implications involved. This article explores carbonation performance in concrete with 25% or 50% mixed recycled construction and demolition waste aggregate, alone or in conjunction with cement containing 25% fired clay construction and demolition waste. Irrespective of cement type, the mean carbonation depth was slightly greater in materials with 25% or 50% recycled aggregate than in concretes with 100% natural aggregate, although the difference was not statistically significant for the 25% replacement ratio. In all the concretes studied, the carbonation coefficient was below the 4 mm/yr0.5 indicative of good quality. Based on the prediction model proposed in Spain’s concrete code, reinforcement passivity was guaranteed in all these types of concrete when exposed to class XC1 to XC4 carbonation environments for substantially longer than their 100 year design service life., This study was funded under research projects BIA 2013-48876-C3-1-R, BIA2013-48876-C3-2-R and BIA2016-76643-C3-1-R awarded by the Ministry of Science and Innovation and grant GR 18122 awarded to the MATERIA Research Group by the Regional Government of Extremadura and the European Regional Development Fund, ERDF. In 2016 University of Extremadura teaching and research personnel benefitted from a mobility grant (MOV15A029) awarded by the Regional Government of Extremadura and in 2018 from a José Castillejo (CAS17/00313) scholarship granted by the Spanish Ministry of Education, Culture and Sport. Philip Van den Heede is since October 2017 a postdoctoral fellow of the Research Foundation—Flanders (FWO) (project number 3E013917) and acknowledges its support.

In the recent era, built-up columns have been continuously used by the engineers in the design and analysis of tall buildings and bridges. Vibration analysis of these types of columns is essential to understand the failure modes of such columns. In that aspect, this study aims to analyze a concrete-encased built-up column made by configuring cold-formed steel angle sections connected by means of battens encased by normal weight and lightweight concrete with and without the inclusion of basalt fibre. Eight columns with battens were simulated, and it is encased with four different types of concrete and subjected to axial cyclic loading. The experimental results were correlated with the numerical investigation performed using FEA. The results indicated that the type of concrete dramatically influences the behaviour of columns. Higher ultimate strength and ductility was observed for all specimens, which is due to lower shear capacity of the battens. It was observed that the intensity of the axial cyclic load has a significant effect on the ultimate strength and deflection of columns, but it is less influential on the yield strength. It was concluded the results of experimental and FEA shows good compatibility between each other and depicts an error of 7.48%.

Lightweight aggregate concretes (LWAC) are versatile and interesting materials for projects that require greater structural efficiency. Due to the difference that exists between the densities of the materials used in these types of concrete, during transport and mainly compaction, their aggregates tend to separate from the mortar matrix, floating towards the surface, a phenomenon called segregation. Segregation in LWAC can affect its durability properties, its density, and directly affect its structural efficiency. In this work, different concrete densities (1700 kg/m3 and 1900 kg/m3) manufactured with different dosages (two different lightweight aggregates) and compaction methods (one or two layers) were analyzed to verify the impact of segregation on its structural efficiency. For this purpose, the segregation index of the LWAC was obtained by means of the image analysis technique. In addition, to obtain their structural efficiency, the density and compressive strength were obtained at different heights of the tested specimens. The results show the vibration of the samples in two layers leads to a more efficient elimination of trapped air, a reduction in the risk of segregation, and better structural efficiency. This research was funded by the University of Alicante ((GRE13‐03) and (VIGROB‐256)).

An earthquake causes a huge loss of life and property. After an earthquake, many buildings are seriously damaged or collapsed. On the one hand, it is necessary to make full use of nanomaterials technology to improve seismic strength during reconstruction; on the other hand, scientific planning is needed to reduce pollution, carbon emissions, and energy consumption. This paper mainly studies the application of nanomaterial technology in disaster prevention and reconstruction. Through a series of planning safeguard measures, the overall seismic performance of the city is improved in order to provide theoretical guidance and technical support for disaster prevention and reconstruction. This paper mainly introduces the stress analysis of frame joints after earthquake and the planning of urban disaster prevention and reconstruction. In addition to the different types of concrete materials (ordinary concrete, nano silica fiber concrete, PVA fiber concrete), the fixed amount of water, superplasticizer, reinforcement, sand, and gravel, the concrete strength grade is C30. Then, three kinds of concrete frame joints are tested under low cycle cyclic loading to compare the seismic performance of the three kinds of concrete. The experimental results show that the fuzzy evaluation of urban disaster prevention and reconstruction planning has been carried out for 6 communities in this city. Among them, 4 communities are qualified and 2 communities are unqualified. Therefore, it is necessary to focus on seismic reinforcement or carry out urban planning research again. Compared with ordinary concrete, the bearing capacity and ductility coefficient of nano silica fiber concrete and PVA fiber concrete are increased by 37.8% and 15.6%, respectively. It is proved that the seismic performance of nano silica fiber reinforced concrete is far better than that of ordinary concrete.

Over the last 20 years, remarkable advances have taken place in the research on reactive powder concrete (RPC). However, because of the high contents of cement and silica fume (SF) usually used in those types of concrete, the cost and environmental impact of RPC is considerably higher than conventional concrete. Hence, the use of supplementary cementitious materials as partial substitution of cement and SF has been an object of great interest by the scientific community. However, the replacement of cement and SF can result in the deterioration of certain properties of RPC, such as the early strength; however, RPC usually needs great amounts of cement and SF. This work presents a study to analyze the effect of metakaolin (MK) as a partial substitute of cement in a previously optimized mixture of RPC using statistical tools such central composite design, main effect plot analysis, and response surface methodology. In addition to MK, supplementary cementitious materials such as SF, limestone powder and recycled glass powder, and fine Type III cement were used. Based on the laboratory experiments results and statistical analysis, it was concluded than MK develops a high activity in the hydration process of RPC, helping it reach high strength at early ages, such as 1 and 7 days, which may be of interest for applications such as the connection of prefabricated elements or accelerated bridge construction. However, the effect of the partial substitution of Type III cement by MK on 28-day compressive strength was nonsignificant. Moreover, the MK inclusion in RPC provides a significant decrease in workability as the amount of MK increases., En los últimos 20 años se han producido notables avances en la investigación sobre el hormigón reactivo en polvo (RPC). Sin embargo, debido a los elevados contenidos de cemento y humo de sílice (SF) que suelen emplearse en esos tipos de hormigón, el coste y el impacto medioambiental del RPC son considerablemente superiores a los del hormigón convencional. De ahí que el uso de materiales cementantes suplementarios como sustitución parcial del cemento y el SF haya sido objeto de gran interés por parte de la comunidad científica. Sin embargo, la sustitución del cemento y el SF puede provocar el deterioro de ciertas propiedades del RPC, como la resistencia temprana; además, el RPC suele necesitar grandes cantidades de cemento y SF. Este trabajo presenta un estudio para analizar el efecto del metacaolín (MK) como sustituto parcial del cemento en una mezcla previamente optimizada de RPC utilizando herramientas estadísticas como el diseño compuesto central, el análisis de parcelas de efectos principales y la metodología de superficie de respuesta. Además del MK, se utilizaron materiales cementantes suplementarios como SF, polvo de caliza y polvo de vidrio reciclado, y cemento fino de tipo III. Basándose en los resultados de los experimentos de laboratorio y el análisis estadístico, se concluyó que el MK desarrolla una alta actividad en el proceso de hidratación del RPC, ayudando a que alcance una alta resistencia a edades tempranas, como 1 y 7 días, lo que puede ser de interés para aplicaciones como la conexión de elementos prefabricados o la construcción acelerada de puentes. Sin embargo, el efecto de la sustitución parcial del cemento Tipo III por MK sobre la resistencia a compresión a 28 días no fue significativo. Además, la inclusión de MK en el EPR proporciona una disminución significativa de la trabajabilidad a medida que aumenta la cantidad de MK.

In recent years, the application of electrically conductive concretes has been proposed as an anti-icing method on airport runways. In this work, it was aimed to evaluate usability of the nano carbon black obtained by the pyrolysis method from the waste tires and also the waste wire erosion obtained from the cutting processes for using in the electrically conductive concrete with application in airport runway anti-icing. In this regard, 36 different mixtures of the electrical conductive concretes were first investigated in the laboratory to find out general mechanical and electrical conductivity properties of the test concrete. After obtaining the result of their general characteristics, 10 different types of concrete slabs were produced. Electrothermal tests of conductive concrete slabs were carried out in a cooling chamber at -10 degrees C. A heat power within a range of 180-1315 W/m(2) has been provided for heating electrically conductive concrete slabs obtained from different mixtures and consequently an optimization method was utilized and obtained results were compared on figures and diagrams. Numerical simulation of the problem has been also carried out to find out heat flux and temperature distribution of test concretes. (C) 2020 Elsevier Ltd. All rights reserved.

Methods of designing underground structures with monolithic spans comprised of different types of concrete with monolithic bonding of the layers and possible nonuniform settlements are examined. A method of calculating spans using finite-element software systems is presented.

Plastic, it is known to be the most widely used product in the world today. Although its existence is common nowadays, the rises of environmental threat caused by current plastic waste amount have reached its alarming heights. The consumed plastic is integrated into concrete to diverge it from being a waste into a beneficial product in the construction industry. This paper’s main purpose is to explore the development of plastic incorporated concrete as a sustainable building material. In addition, reuse and recycling of plastic waste specifically Polyethylene Terephthalate (PET) is implemented to reduce energy consumption in the construction sector, as well as improving waste management in resulting in an eco-friendly environment. Methods include laboratory experimental analysis by measuring engineering parameters including density tests, compressive strength and thermal properties test using four types of concrete mixes including 0% PET, 5% PET, 15% PET and 25% PET in concrete block. Finally, a sustainable approach to these new concrete materials, the outcomes acquired feature their improvements in thermal properties test, but with a low resistance to compression compared to traditional concrete mixes with the same test type. Through this implementation, optimisation of sustainable building materials towards efficient thermal performance could be achieved in building construction.

Concrete is an important building material which has been in human life for more than a century and is used continuously. Despite its age, many properties are still not known. There are different types of concrete according to the materials in the mixture. One of these types of concrete, called special concrete, is steel fiber reinforced self-compacting concrete (SFRSCC). There are different criteria for measuring the performance of concrete. Since the properties are not known exactly, different experiments are carried out in order to provide the characteristics of the requested concrete. In this study, the model was designed by using regression tree method to predict the performance of T50 of SFRSCC. In the designed model using regression tree algorithm, R-squared value was calculated as 0.7341, root mean square error (RMSE) value was calculated as 1.2636, mean absolute error (MAE) value was calculated as 0.8617.

Two years ago, Resolution 472 of February 28, 2017 urging the use of recycled materials in civil works and concrete structures in all over the city of Bogota, to counteract the use of aggregates from natural sources and encourage practices that promote the environment conservation. The main goal of this study is to encourage the use of explosives in demolitions by studying the granulometries through the optimization of explosive load factor to be competitive in the cost structure of the crushing of concrete and demolition waste (CDW). Starts with a little research of the market structure of natural sources aggregates in the city and its comparison with the use of is currently considered. Then, by means of 2 types of concrete samples of 4000 psi of resistance that simulate beam and column structures respectively, are detonated with 4 different doses of indugel. The mechanism to predict the theoretical granulometry, the type of explosive and the dosage of each of the samples is done through the Kuz-Ram fragmentation model, which is compared with the granulometries obtained from 8 detonations in total. Finally, by conservative decisions with peak particle velocity, technically efficient with the use of indugel and consistent with the desired size for the economic efficiency crushing required, a load factor of 1kg / m3 is obtained for beams and 1.2 kg / m3 for columns.

In pursuit of economic and social development objectives, governments of Pacific Island Countries (PICs) desire to upgrade unpaved low-volume roads (LVRs) for the improvement in connectivity and quality of life associated with all weather-access. Whilst the benefits are clear, the capital cost of conventional pavement technology and the recurrent cost of maintenance make it hard to justify the required investment in upgrading LVRs. Typical LVRs are surfaced with a bituminous chip seal or a thin asphalt concrete (AC) layer on processed aggregate base and subbase courses. Constructing such pavements in PICs is expensive, given the scarcity of aggregate of requisite quality, relatively limited domestic road construction capacity, and scale diseconomies in the use of equipment, plant and materials. Moreover, vulnerability to natural disasters and climate change necessitates consideration of more resilient paving alternatives. The findings of the study suggest that there is substantial promise for concrete pavements to be used for low-volume (

Consistent quality in concrete production is an essential requirement in the ready-mix concrete industry. Insuring batch-to-batch uniformity is, in fact, an ever-present challenge. Moreover, modern concretes mixture designs often have complex behaviors in their fresh states, and yet the focus is on the slump (related to the yield stress) only, presenting an incomplete picture when one wants to assess the properties of various types of concrete. A second parameter known to be highly informative in this situation is the plastic viscosity of the fresh concrete. Few authors have assessed the potential of rheology measurements with a ready-mix truck. After a short introduction on sustainability, the aim of the first part of this conference paper is to offer a review of the different methodologies and results available on rheology measurements in/with a ready-mix truck. The second part is focused on the description of the in-drum sensor system used in this project. Finally, methodology and results about the slump evaluation with the in-drum sensor system are presented.

Research on early stages of corrosion of steel bars caused by chloride penetration is relevant in improving the durability of reinforced concrete structures. Similarly, the formation and development of cracks induced in the surrounding concrete is also of great importance. This paper uses integration of the analytical models examined in the published literature, combined with experimental research in corrosion induced at the concrete/steel interface, in estimating the time-to-crack initiation of reinforced concrete subjected to corrosion. This work studies the influence of the porous network and electric current density on the cracking process at early ages. The experimental program was performed by using an accelerated corrosion test. Two types of concrete were performed: A conventional concrete (CC) and a concrete with silica fume (SFC). A current density of 50 &mu, A/cm2 and 100 &mu, A/cm2 was applied to specimens of both concretes. Examination performed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) provided both qualitative and quantitative information on the penetration of the rust layer in the surrounding concrete porous network. Strain gauges were used to measure corrosion-induced deformations between steel and concrete matrices, as well as the formation of corrosion-induced cracks. A good correlation between the rate of penetration of the rust products in the surrounding pores and the delay of the cracking pressure in concrete was observed from the experimental results. This phenomenon is incorporated into the analytical model by using a reduction factor, which mainly depends on the pore size of the concrete. The crack width obtained exhibited a significant dependency on electric current density at the beginning of the test, depending mainly on the pore size of the concrete later.

An estimate shows that approximately 50% of global annual construction activities account for the repair and retrofitting of structures and constructed facilities. Therefore, structural rehabilitation and repair are becoming hot topics among researchers, in order to find innovative and comprehensive solutions. Ultra-high-performance concrete (UHPC) is designed to achieve high strength and long-term durability. Such types of concrete offer a solution for complicated repair and retrofitting jobs. Although many benefits of using UHPC have been derived, many concerns have also been identified with the use of UHPC&mdash, sustainability is considered a critical concern due to the requirement of large proportions of cement, which results in an increase in cost and environmental impacts. This paper presents a recipe for UHPC that contains a small ratio of cement and a large proportion of fly ash, i.e., up to 50%, as a cement replacement material (CRM). In order to achieve long-term durability and increase bonding with old concrete or brickwork for repair and retrofitting purposes, ultra-fine calcium carbonate (UFCC) is also added. In selecting an appropriate material for structural repair, it is essential to acquire an understanding of the material behavior. Therefore, this research was focused on providing a comprehensive guide to the behavior and strength performance of UHPC. The experimental results have shown that the highest strength of UHPC with low cement content can be achieved using a binary combination of high-volume fly ash (HVFA) and ultra-fine CaCO3 (UFCC) as a substitution for cement by up to a ratio of 50% in the recipe. The UHPC with low cement content displayed excellent repair and retrofitting potential for structural strengthening in regions of high stress by developing a strong bond with the existing concrete substrate.

Self-Consolidating Lightweight Concrete (SCLC) is relatively a new concept and can be regarded as a revolutionary development in the field of concrete technology. It is a type of concrete that might not require vibration for placing it and could be produced by reducing the density of concrete. However, the density of normal Self Consolidating Concrete (SCC) is similar to normal concrete approximately 2400kg/m3. By using foaming agent, the density of concrete can be reduced up to 1800kg/m3. Due to the heavy density of concrete, it will give the initial higher supply cost over conventional concrete, has slowed down its application to general construction. It is also hard to handle for construction and transportation. Therefore, it is advantages to produce SCC with lower density to provide benefit and enhancement of its performance by a combination of two types of concrete technology that is SCC technology and Lightweight Foam Concrete technology. This paper was focused to identify the effect of foaming agent on the fresh properties and compressive strength of SCLC. The influence of foaming agent contained in the range from 0 second, 1 second, 2 second, 3 second and 4 second to the strength characteristic identified in the SCLC. The specimens were tested for compressive strength at 3, 7, 14 and 28 days. The result indicated that the compressive strength of SCLC is decreasing when foaming agent content was added. Meanwhile, the flowability of SCLC is increasing when foaming agent content added. Based on the finding, SCLC containing 3 second of foaming agent is achieving the density target, which is 1800kg/m3 and better compressive strength performance.

One of the major barriers to the use of UHPC (ultra-high performance concrete) in the precast industry is the high cost relative to conventional concrete. Often, the properties of UHPC are not fully utilized throughout a member. One solution is to create a hybrid member with UHPC in zones of high or unpredictable stresses while filling the rest of the section with a conventional concrete. Constructing such a member will require innovative techniques to achieve a successful bond between the two different materials. This paper is unique in that it investigates the bond behavior when both materials are in the fresh state. Several specimens of 2 × 2 × 17 inches (50x50x431 mm) were fabricated for direct tension tests. These specimens were fabricated with half UHPC and half SCC (self-consolidating concrete). The interface between the two types of concrete was perpendicular to the tensile force so that the bond was in direct tension. All materials were placed immediately after mixing and were separated by a removable barrier. Time dependency of the bond strength was controlled by removing the barrier at different times after placing. The quality of the bond strength between fresh UHPC and fresh SCC was compared to the tensile strength of the SCC. The results were used to determine a maximum allowable time by which both concretes can be combined while maintaining an acceptable bond strength.

Concrete deteriorates for a variety of reasons, but corrosion of steel reinforcement has been one of the most prevalent mechanisms of deterioration since concrete structures were introduced in the early 1900s. It affects many types of concrete elements, especially the substructures of coastal bridges. Steel reinforcement used in coastal bridge piles has exhibited corrosion damage within twenty years of construction. Therefore, it degrades the durability and reduces the service life of the bridges severely. As a result, it costs billions of dollars in rehabilitating or repairing the deficient components. The recent development of UHPC can mitigate these deficiencies because of its exceptional properties. However, the cost of UHPC is significantly higher than that of the conventional concrete. Therefore, it appears to be attractive to use UHPC jackets in coastal bridge piles, which allows to taking advantage of the superior properties of UHPC without using excessive amount of UHPC in the full section. This paper presents a study of the structural design of piles using UHPC jackets, including the working stress design and strength design. A numerical example of a square pile using a UHPC jacket is included to show how the flexural strength design can be handled.

Concrete cracking due to restrained drying shrinkage is a widespread problem that could happen to any structural element including bridge decks. One of the main causes of bridge deck cracking is the development of tensile stresses due to restrained drying shrinkage. Cracks allow harmful substances such as water and deicing salts to penetrate the deck and initiate corrosion. This research investigates the effects of using lightweight aggregate (LWA) on enhancing the performance of expansive Type-K cement. Four large-scale bridge decks of 2 m×3 m were built using four different types of concrete mixtures: (1) a mixture containing 100% Portland cement, (2) a mixture incorporating expansive Type-K cement, (3) a mixture containing internally cured fine lightweight aggregate (LWA), and (4) a combined mixture of Type-K cement and internally cured LWA. The combined mixture uses internal water from LWA to enhance the expansion of Type-K cement and produce compressive stress in the concrete; and eventually reduces the onset of cracking.

The increase in urban construction in China has been accompanied by increasing concrete output, which has reached 2250 million m3 in recent years, ranked as the highest in the world. Consequentially, its environmental burden is significant in terms of resource use and carbon emissions. An adaptive surrogate model based on an extended radial basis function and adaptive sampling method was used to optimize the design of a concrete mixture in order to reduce its CO2 emissions and cost. The adaptive sampling method based on the multi-island genetic algorithm was adopted in order to improve the adaptive capability and accuracy of the surrogate model by selecting the proper sample size and ensuring uniform distribution of the sample points in the designed space. Three types of concrete with different strength, that is, C70, C40 and C30, were optimized by controlling the amount of fly ash and phosphorous slag in the samples. The optimized results showed that fly ash and phosphorous slag have a significant influence on the CO2 emissions of concrete and optimized concrete&rsquo, s cost, while CO2 emissions were less than that of the reference samples. Therefore, the optimal mixture is with great significance to reduce the carbon emission of concrete, which also has implications for decreasing the environmental burden of concrete. In this way, we can optimize concrete of different strength to reduce carbon dioxide emission.

An equation to estimate the prestress loss in continuous unbonded prestressed concrete beams is proposed in this paper. The equation accounts for the creep and shrinkage of the concrete and the relaxation of the prestressing steel. In addition, a numerical model is developed based on the finite element method for the time-dependent analysis of these types of concrete beams. The approach also accounts for the presence of non-prestressed steel reinforcement and the friction between the tendons and their ducts. Furthermore, a well-justified integral-form equation is proposed to compute the strain at each section of the unbonded prestressing steel accounting for the friction between the tendons and their ducts. This equation is based on the equation for frictional loss accepted by different standards. The strain at each section of the unbonded prestressing is calculated from the strain in the concrete at the level of the prestressed tendon along the whole beam. Numerical and experimental results are compared to validate the proposed equation and the finite element approach and the good performance of both in modelling the behaviour of this type of prestressed concrete member over time is shown.

Track thermal buckling is one of the primary safety issues of continuously welded rail tracks. The lateral track resistance is the main resisting force against track buckling, which is mainly provided through the interaction of sleepers in the ballast material. In this sense, researchers have focused on determining the lateral resistance of various types of sleepers in ballast material through tie push tests; yet the implications of these results on track buckling temperature have not been fully addressed. The aim of this paper is to fulfill this gap by analyzing the performance of three types of concrete sleepers on track buckling temperature: B70, winged and frictional concrete sleepers. A finite element model of the track is developed and updated based on the results of single tie push tests performed on each type of sleeper. The model is then used to estimate the buckling temperature of tangent and curved sections of tracks. In addition, a sensitivity analysis of the parameters involved in track buckling is presented. It is concluded that for a tight curve of radius 100 m, only frictional concrete sleepers can resist track buckling, if a safe temperature of 40 °C is considered for the track. For the same safe temperature, conventional B70 sleepers can only be used in curves with a radius larger than 1200 m.

Infilling seawater sea-sand concrete (SWSSC) into stainless steel tubes may be a feasible means of overcoming the shortage of fresh water and river sand in remote coastal areas. Herein, cold-formed austenitic stainless steel (CFASS) circular tubular stub columns infilled with SWSSC were tested. The CFASS tubes had 5 different cross-sections and the concrete mixes were of strength levels 35 and 70 MPa. Axial compression tests were carried out to study their structural behaviour in terms of load–strain curve, strength, ductility and failure mode. The test results revealed that the use of SWSSC in place of conventional concrete in stainless steel tubes has little effect on the structural behaviour and thus should be feasible. The test results were also compared with predictions by existing design equations in the codes and literature. It was found that the existing design equations are either un-conservative or overly conservative. Based on the test results in this study and those in literature, a new and more accurate design equation for axially loaded concrete-filled stainless steel circular tubular stub columns that is applicable to different types of concrete infill, including conventional concrete and SWSSC, was proposed.

Ultrasonic measurements are used in civil engineering for structural health monitoring of concrete infrastructures. The late portion of the ultrasonic wavefield, the coda, is sensitive to small changes in the elastic moduli of the material. Coda Wave Interferometry (CWI) correlates these small changes in the coda with the wavefield recorded in intact, or unperturbed, concrete specimen to reveal the amount of velocity change that occurred. CWI has the potential to detect localized damages and global velocity reductions alike. In this study, the sensitivity of CWI to different types of concrete mesostructures and their damage levels is investigated numerically. Realistic numerical concrete models of concrete specimen are generated, and damage evolution is simulated using the discrete element method. In the virtual concrete lab, the simulated ultrasonic wavefield is propagated from one transducer using a realistic source signal and recorded at a second transducer. Different damage scenarios reveal a different slope in the decorrelation of waveforms with the observed reduction in velocities in the material. Finally, the impact and possible generalizations of the findings are discussed, and recommendations are given for a potential application of CWI in concrete at structural scale.

In this paper, twelve concrete beams with two different layers of concrete were evaluated as a simply supported beam under four-points loading. The beams assembled of two different types of concrete layers, one of which was normal-weight concrete (NWC) and the other was lightweight aggregate concrete (LWAC). The investigated parameters were the thickness of the lightweight concrete to the overall depth of beams (hLW/h), and the compressive strength of normal and lightweight concrete. Due to the weak lightweight aggregates used, lightweight aggregate concrete exhibits more brittleness and lower stiffness. Therefore, the viability of compensating for this degradation and providing a layer of normal concrete seems to be very interesting in such beams. The behavior of beams was evaluated based on cracking, failure mode, flexural strength, maximum deflection, stiffness, and toughness. The results showed slight variations on the majority of the above-mentioned performance aspects of two-layer beams compared to fully normal concrete beams. While there were great enhancements compared to fully LWAC beams. The variants were mainly attributable to the efficacy of using LWAC in providing lower stiffness and lower tensile strength. The experimental results have been compared to predicted values using the ACI 318-19, with some modifications for the equations to be matched with two-layer beams, the comparison was in terms of the deflection due to service load, moment capacity, and cracking moment.

Externally bonded fiber-reinforced polymer (FRP) is a promising tool to use for either preserving the integrity of new concrete infrastructure or mitigating the deteriorations of aged concrete infrastructure. This laboratory study evaluates the durability performance of carbon FRP-wrapped concrete with a 1.5 wt% montmorillonite nanoclay (NC) modified siloxane epoxy adhesive, under a simulated cold and chloride-laden environment. Five types of concrete samples were fabricated and tested, i.e., reference concrete, FRP-wrapped concrete, NC-modified FRP-wrapped concrete, FRP/pre-aged concrete, and NC-modified FRP/pre-aged concrete, respectively. Both before and after the salt scaling test in 3 wt% NaCl, the NC-modified FRP-wrapped concrete samples exhibited notably better mechanical properties (higher compression strength and elastic modulus) and significantly better transport properties at the interface (reduced water absorption and gas permeability), related to their unmodified FRP-wrapped counterparts. These benefits of nano-modification, along with better resistance to salt scaling, are attributable to the improved microstructure and reduced hydrophilicity of the adhesive, as revealed by microscopic investigations using a high-resolution optical microscope and a water contact angle tester. The Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis revealed that the admixed NC chemically reacted with the adhesive and increased its crosslinking density and thermal stability.

Applications of recycled concrete aggregate (RCA) in the production of new concrete can help in addressing the growing solid waste challenge and preserving natural aggregate resources from depletion. The behaviour of RCA concrete under different loading scenarios is a well-studied topic at both material and structural levels. However, little attention has been directed at studying the performance of concrete made with RCA at elevated temperatures. Most of the previous studies have focused on the residual mechanical response of coarse RCA concrete after exposure to elevated temperatures. This paper presents an experimental study on the behaviour of natural aggregate concrete (NAC) and recycled aggregate concrete (RAC) during and after exposure to elevated temperatures. The RAC in this study contained both coarse and fine recycled concrete aggregates (CRCA and FRCA) as partial replacements of natural aggregates. The compressive strength of the NAC and RAC were evaluated at ambient temperature (unheated), after exposure to three different temperatures of 150, 300, and 450 °C (residual), at an elevated temperature of 450 °C without preloading (steady state), and during heating while being preloaded with 40% and 70% of the ambient strength (transient). A rate of 2 °C/min was used in all these heating scenarios. The results indicated that concrete with aggregates partially replaced with CRCA and FRCA exhibited good performance at elevated temperatures, and it can be considered comparable to conventional concrete. The results also showed that the compressive strengths measured during elevated temperatures, with or without preloading, were relatively higher than the residual compressive strengths for both RAC and NAC. The total thermal strains were also investigated with Digital Image Correlation. Preloading had an impact on the evolution of the total thermal strains and the occurrence of spalling for the types of concrete that were tested.

Electronic waste (E-waste) is increasing constantly around the globe, affecting human health and the environment adversely. To cope with the alarming situation of E-waste production, it is essential to find its potential applications and limit its adverse environmental impacts. This study aims to examine the influence of E-waste as a partial replacement of natural coarse aggregates (NCA) on both the fresh and hardened concrete properties. Four types of concrete mix with manufactured plastic aggregate as a partial substitute for NCA prepared with substitution levels up to 20% (by weight of NCA). The mechanical performance of E-waste concrete was assessed based on the compressive and splitting tensile strength test results and the durability characteristics were evaluated via thermal exposure, sorptivity coefficient, ultrasonic pulse velocity (UPV), abrasion resistance, and alternate wetting and drying. The results revealed that the compressive and tensile strengths of E-waste concrete reduced in the range of 6.3%–17.1% and 23.5%–32.4%, respectively for replacement ratios of 10%–20%. However, the workability and durability properties improved with the E-waste aggregate incorporation. A substantial reduction in the sorptivity coefficient, UPV value, and abrasion loss was observed with an increasing amount of E-waste aggregates. Furthermore, concrete with E-waste aggregates showed better performance against alternate wetting and drying cycles compared to normal concrete and the increasing percentage of E-waste had no substantial effect on the drop in the compressive strength of E-waste concrete against thermal exposure.

Concrete hollow block masonry is widely used in North American and Australasian countries because it enables to accommodate grouting and reinforcement to resist higher axial and lateral actions, where it ultimately facilitates to construct high-rise masonry buildings. Subsequently only certain grades of mortars are recommended for the concrete block masonry in the standards mainly due to durability concerns. However, there is a lack of knowledge on the characteristics of concrete masonry with different grades of mortars and significant variations are found among the design standards. Therefore, in this research, an attempt has been made to investigate the compressive strength and deformation characteristics of concrete block masonry using different mortar grades, mortar bedding types and block types. In total, 40 concrete block masonry prisms were constructed and tested with three different types of mortars, two mortar bedding types and two types of concrete blocks. From the experimental results, the failure modes, compressive strength and stress-strain curves are derived and discussed. The experimental results revealed that the lower grade mortared prisms failed by mortar crushing and block splitting, whereas the other mortared prisms mainly failed by tensile splitting in the blocks. The compressive strength of concrete masonry was not significantly compromised for lower grade mortared prisms in comparison to other mortared prism combinations. The deformations and failure phenomenon of the mortar joints, blocks and prisms were investigated in detail using a non-contact digital image correlation (DIC) method. The experimental results were also verified through the finite element analyses and were compared with the predictions of four different masonry design standards. Discrepancies in the prediction of compressive strengths of concrete block masonry between the design standards were noted.

This paper evaluates two types of concrete with hemp fibres as natural aggregates prepared with inorganic binders, based on reactions (Si-Na) and (Si-Ca). It also was tested two states of conservation of the hemp: 1) fresh and 2) preserved in moist conditions for six months. The results indicate that the changes induced by wet preservation, above all the increase in the percentage of cellulose, improve the mechanical properties of the concretes and is equivalent to other pretreatments conducted to improve the conditions of the hemp fibres confirmed by performing compositional, mineralogical and physical studies of the raw materials and the concretes. The dosages used in this study provided high quality concretes in comparison with other studies with similar dosages.

The relationship of the diffusion coefficient and charge passed is developed employing the analysis of the traditional model and 244 groups of experimental data. The differences in the types of concrete were considered to determine the variation coefficient of the diffusion coefficient in the models. Results revealed that the different environmental conditions of the concrete chloride diffusion coefficient cannot be described solely by the existing maturity method. Reasonably good agreement is observed between the experimental and computational model of this paper, thus indicating that the proposed prediction model can be successfully used to estimate the chloride diffusion coefficient. An example of a durability assessment is performed to verify the applicability of the concrete durability assessment method. The concrete durability assessment method can control the durability quality and direction of the production of concrete.

Currently, concrete is the most widely used structural material in road infrastructure. Concrete is a sensitive material, cracks and micro-cracks may occur during operation. Although the cracking/micro-cracking of concrete does not implicitly cause structural damage, it creates a path for corrosive factors, which leads to decreased structural durability caused by material changes and reinforcement corrosion. The self-repairing ability of concrete refers to the process of closing cracks to prevent the entry of potentially aggressive agents. Concrete used in bridge construction is usually covered with a waterproof layer and a layer of asphalt mixture, which also acts as a wear layer, but which can prevent the entry of water containing corrosive ions, the natural aggressiveness of the environment or accelerated corrosion by the penetration of thawing substances etc. Road infrastructure repair works affected by degradation processes are costly, time consuming and lead to a reduction in traffic flow, by partially closing it during interventions. To overcome these shortcomings, over time, several types of concrete with self-repairing properties have been developed, based on several methods such as: pipe networks, superabsorbent polymer capsules and textile fibers, bacteria etc.

Environmental issues resulting from the sand over dredging have contributed to worldwide restrictions on its production, with a significant economic impact on concrete construction. The demolished building waste is not widely recycled globally. A suitable, environmentally friendly approach with an adequate alternative to sand is introduced in the present study. Four types of concrete, natural dune sand concrete (NDSC), recycled crushed sand concrete (RCSC), recycled crushed sand stone dust concrete (RCSSDC), and recycled crushed sand crumb rubber concrete (RCSCRC), have been introduced in the present study. In-situ compressive strength of demolished building concrete has been measured by the Non-destructive test (NDT) core testing. In the present research work, recycled crushed sand (RCS) was substituted by natural dune sand (NDS) in the ratio of 40%, 100%, and 80% in mixes 40NDSC, 100RCSC, 80RCSSDC, and 80RCSCRC, respectively. A detailed physical analysis was conducted to evaluate material properties such as specific gravity, water absorption, particle grading, and sand equivalent value. The chemical analysis pH, FTIR, and SEM-EDX have also been carried out on stone dust (SD) and crumb rubber (CR). The concrete specimens were tested at ambient and elevated temperatures 100, 200, 300, and 400 °C for four hours in an electric oven. Experimental studies show a slight increase in the compressive strength of 100RCSC (up to 300 °C) compared to 40NDSC. A sudden fall in the strength was observed at 400 °C for all concrete types 40NDSC, 100RCSC, 80RCSSDC, and 80RCSCRC. Replacement of RCS at 20% by SD and CR indicated a decreasing pattern in compressive strength. The compressive strength reduction rate was more in crumb rubber, which indicates that crumb rubber should not be used in higher percentages in concrete. The concrete samples 40NDSC and 100RCSC performed significantly better than the other concrete types.

The premature debonding of Fiber Reinforced Polymer (FRP) sheets has been well studied and understood for normal weight concrete. This type of failure mode can be averted by keeping the maximum FRP strain below the debonding strain of FRP as specified by ACI 440.2R-17. However, the debonding strain in lightweight concrete has not been addressed or evaluated yet. Accordingly, this paper investigates the debonding strain in lightweight concrete using full-scale reinforced concrete T beams strengthened with different layers of carbon fiber reinforced polymer (CFRP). These beams were prepared and strengthened in two series. The first series included three T beams that were cast with normal weight concrete. The second series consisted of another group of three T beams using lightweight concrete. Both series had identical geometry, reinforcement, and span lengths. Furthermore, they had almost identical concrete properties and the same FRP material to effectively examine the deboning strain difference in both types of concrete. The debonding strains of the lightweight and normal weight concrete are compared and the reduction factor is addressed in light of the current design equation in ACI 440.2R-17.

The structural behavior of the hybrid reinforced concrete beams of the trapezoidal section is investigated in this paper. This study aims mainly to investigate the interaction effect of hybrid concrete compressive strength for section has geometry variation upon beam strength characteristics. Throughout the considered experimental program, 10 simply supported reinforced concrete beams were prepared and tested using a four-point load setting. All specimens had equal cross-sectional area. These specimens were divided into two groups, each group contain 5 beams. The first group deals with flexural behavior and the second group concerned with shear behavior. In addition to hybrid compressive strength considerations, two types of concrete with different compressive strengths of (25 and 50 MPa) were used and three trapezoidal geometries with different alignment side angles (75, 80, and 85) are adopted. The experimental testing showed that the effectiveness of the hybrid trapezoidal force formation maintained the strength of the samples decreased more than the hybrid effect force. As for the flexural behavior, the ultimate strength decreased by (2.82%) and the deflection increased by (56.81%) with respect to rectangular specimens. For shear behavior, the ultimate load was close or identical to the control specimens with deflection increment ranging from (9% to 60%) with respect rectangular specimen. The effect of area distribution within section (section shape sides orientation) was clearly on the first crack load where the angle (80) recorded a highest value of crack load.

Nowadays concrete has become the most widely-employed construction material in civil engineering. But at present stage, not all internal factors’ effects on this material’s axial and transverse mechanical behaviors have been comprehensively understood, and highly-accurate formulas to predict its mechanical properties are still lack. This prevents designers and engineers to well construct structural components, and also separates people to better know the failure mechanism and strength rule of other types of concrete materials (such as the recycled aggregate concrete and the recycled lump concrete). Considering such situations, a series of discrete element simulations were conducted in this study. In current works, concrete was at mesoscopic level modeled as composed by coarse aggregates, mortar and interfacial transition zones (ITZs). The influences of each constituted phase’s attribution and content (including the shape, size, location, volume content and attribution of coarse aggregates, the mortar’s water-to-cement ratio as well as the property of the ITZs) on the concrete’s crack development process, failure pattern as well as longitudinal and lateral mechanical responses were analyzed carefully. The factors most important in determining concrete’s tensile and compressive strengths together with elastic modulus were identified, and accurate expressions for relating concrete’s uniaxial mechanical properties with the attributions of its components were also proposed. The present study showed that mesoscopic discrete element simulation is an ideal tool for expressing the concrete’s the development of internal damages/cracks and understanding its lateral deformation features under uniaxial loadings. The compressive strength of concrete is primarily governed by the mortar’s strength, the aggregate content and the bonding strength of aggregate-mortar ITZs, and its elastic modulus is notably affected by the mortar’s modulus and the aggregate content, while the tensile strength is greatly influenced by the strengths of mortar and ITZs. Expressions are proposed which usefully predict concrete’s properties based on its constituents, and they may be further extended to investigate the mechanical properties of other types of concrete.

The application of surface treatments in concrete has been widely investigated over the past decades. Surface treatment technology has become more important in concrete structures especially in preventing deterioration and damage when exposed to extremely aggressive environments, and in further extending service life. This paper presents comprehensive details of four types of concrete treatments, including surface coating, hydrophobic impregnation, pore blocking surface treatment and multifunctional surface treatment. Additionally, the knowledge of their interaction mechanisms with cementitious substrate is presented and discussed. The advantages and drawbacks of each treatment as well as the influencing factors on the protective effects of surface treatments on concrete, such as air permeability, bonding strength and cracking resistance, are also discussed. Despite decades of study, the mechanisms of many newly developed surface treatments remain poorly understood. A deeper understanding of the chemical and physical reaction mechanisms is therefore essential, especially at micro-scale levels.

This study focused on modeling the behavior of the compressive stress using the average strain and ultrasonic test results in concrete. Feed-forward backpropagation artificial neural network (ANN) models were used to compare four types of concrete mixtures with varying water cement ratio (WC), ordinary concrete (ORC) and concrete with short steel fiber-reinforcement (FRC). Sixteen (16) 150 mmx150 mmx150 mm concrete cubes were used; each contained eighteen (18) data sets. Ultrasonic test with pitch-catch configuration was conducted at each loading state to record linear and nonlinear test response with multiple step loads. Statistical Spearman\'s rank correlation was used to reduce the input parameters. Different types of concrete produced similar top five input parameters that had high correlation to compressive stress: average strain, fundamental harmonic amplitude (A1), 2nd harmonic amplitude (A2), 3rd harmonic amplitude (A3), and peak to peak amplitude (PPA). Twenty-eight ANN models were trained, validated and tested. A model was chosen for each WC with the highest Pearson correlation coefficient (R) in testing, and the soundness of the behavior for the input parameters in relation to the compressive stress. The ANN model showed increasing WC produced delayed response to stress at initial stages, abruptly responding after 40%. This was due to the presence of more voids for high water cement ratio that activated Contact Acoustic Nonlinearity (CAN) at the latter stage of the loading path. FRC showed slow response to stress than ORC, indicating the resistance of short steel fiber that delayed stress increase against the loading path.

An innovative steel and concrete composite bridge deck slab using bent bars and epoxy as shear connectors was proposed. Four slab specimens with different types of concrete were fabricated and tested to study the load capacities of positive and negative moment regions of the slabs. The cracking and ultimate loads of the specimens were recorded and compared with the results calculated through the reinforced concrete theory and with the design load of the bridge deck slab. It was found that reinforced concrete theory can generally be applied for the proposed slab as well. The effectiveness of the shear connector design of the proposed slab was validated. Meanwhile, the unfavourable effect of the haunch on the shear capacities of the positive moment region of steel and concrete composite bridge deck slab was observed.

The use of wastes in building materials is an interesting and necessary domain of research. In concrete different types of wastes can be used as aggregates, as replacement of cement or as filler. The paper presents the results of experimental researches made on eco-concretes that included scrap or powder of waste tires. Several variables were investigated including two types of concrete with cement or with polymer, prepared with different dosage of tire wastes: in the case of cement concrete, the tire scrap was added in dosages of 25%, 30%, 40% and 50%. In the case of polymer concrete the tire powder was added in dosages of 6.4%, 12.4%, 17%, 20% and 23%. The compressive strength on cubes, the tensile strength by bending and the split tensile strength were determined. The tire waste addition decreased the values of mechanical strengths. In the case of cement concrete the best results were obtained for the concrete with admixture and a content of scrap tires of 25%. In the case of polymer concrete the mix with 23% epoxy resin and 17% tires powder had shown the best results for compressive strength. In the case of tensile strengths the mixes with a reduced dosage of epoxy resin and tire powder had shown higher values.

Water tightness of concrete is usually specified by how much water penetrates or infiltrates into concrete. This indication is applied to detect the possibility of corrosion attack due to aggressive ions such as chloride into reinforced concrete. Since the corrosion occurs on the steel bar of concrete, corrosion level is another methods to express impermeability of concrete. Unfortunately, corrosion process due to chloride attack in the real environment needs several decades. One of the methods which is used to measure corrosion process rapidly is an accelerated corrosion test. This study investigates water tightness and corrosion resistance due to chloride ion in the concrete with calcium stearate by using absorption and electrolytic corrosion test. Two types of concrete mixture i.e. CS-0 and CS-1 are considered in the experiment. Each type of concrete mixture comprises three groups of testing, which are compressive strength, absorption, and electrolytic corrosion test. The dimension of the specimen for compressive strength is 100 mm of diameter and 200 mm in height, and for absorption is 75 mm of diameter and 150 mm in height. Meanwhile, dimension of the electrolytic corrosion specimen is a cube with a size of 100 cm x 100 cm x 200 mm. The result shows that concrete with calcium stearate 1 kg per cubic meter of concrete has a better water tightness property than concrete without calcium stearate. Furthermore, the tendency is also being supported by corrosion resistance result. It can be observed that concrete with calcium stearate is also more resistant to corrosion attack.

The present paper discusses bond strength between reinforcing steel and three types of concretes. The first type of concrete was concrete based on Portland cement. Two concretes were prepared - the first with a low content of cement and the second with a relatively high content of cement. The second type of concrete was alkali activated concrete, containing slag, and it was activated with a mixture of sodium water glass and potassium hydroxide. Similar concretes were prepared - the first with a low content of binder and the second with a high content of binder. Finally, the third type of concrete was designed using hybrid cement, containing slag and Portland cement, and it was activated with sodium carbonate. Similar concretes were prepared as in the previous cases. Bond strength was measured using the pull-out test. Usually, alkali activated concrete is considered to have a better bond with steel in comparison with Portland cement based concrete. The bond between hybrid cement based concrete and steel is very hard to evaluate. The results are important not only for the evaluation of bond between steel and concrete, but also for the development of alkali-activated or hybrid cement based steel-fibre concretes.

The influence of crumb-rubber on the mechanical properties of Portland cement concrete (PCC) is studied by experimental tests and numerical simulations. The main hypothesis of the study is that replacing part of the stone aggregate with crumb-rubber in the mix modifies the energy dissipation during the cracking process and affects the concrete behaviour under monotonically increasing loads. The experimental research program characterizes the mechanical properties of PCC for three different types of concrete with a variable content of crumb-rubber. The experimental results showed that fracture energy and other properties are directly related to the rubber fineness used in the mixture. The material properties derived for these laboratory tests are used to study, by numerical models, its response through its damage evolution. The numerical model used to simulate the damage evolution of the concrete is the Embedded Discontinuity Method (EDM). One characteristic of the EDM is that it does not need to modify the mesh topology to propagate the damage through the continuum solid. For this study, the Disk-Shaped Compact Tension specimen geometry, normed by the D7313-13 of the ASTM, is used. Results showed that the numerical methods provide good approximation of the experimental curve in the elastic and softening branches.

Concrete strength in compression is the common characteristic used in the design of concrete structures. However, in general, there are two different types of concrete specimens specified for the determination of concrete strength in compression. They are the standard 150mm diameter by 300mm length cylinders and the standard 150mm cubes. In the case where the maximum size of coarse aggregate is less than 40mm (1½ in.), 100mm diameter by 200mm length cylinders and 100mm cubes may be adopted. Cylinder specimens with aspect ratio (length/diameter) of 2 are likely to be closer to the uniaxial compressive strength as end friction effects at the platens tend to induced a more complex state of stress compared to that of a cubical specimen with aspect ratio of unity. Hence, the two types of test specimens do not provide the same measured strength for the same concrete. For the purpose of conformity testing, the consistency of test results is of greater interest than the magnitude of the measured strength of the concrete specimens. This paper reviews the issues concerning the two types of specimens, (cylinder or cube) and the size of the specimen in relation to maximum size of coarse aggregate used. Some experimental data for compressive strength at 3 strength classes for which slightly over 100 batches produced over several consecutive calendar months were tested. Three types of specimens, 150mm diameter by 300mm cylinders, 150mm cubes and 100mm cubes were adopted for testing at the age of 28- days. Maximum size aggregate of 20mm and CEM I cement were used for strength classes of C32/40, C50/60 and C65/80 achieved with added silica fume. The findings of these test regimes are summarised with recommendations for conformity testing based on EN 206 and its complementary British Standard BS 8500.

We observed the γ-ray shielding characteristics and compressive strength of five types of concrete using general aggregates and high-weight aggregates. The aggregates were classified into fine aggregate and coarse aggregate according to the average size. The experimental results obtained an attenuation coefficient of 0.371 cm-1 from a concrete with the oxidizing slag sand (OSS) and oxidizing slag gravel (OSG) for a γ-ray of 137Cs, which is improved by 2% compared with a concrete with typical aggregates of sand and gravel. In the unit weight measurement, a concrete prepared by iron ore sand (IOS) and OSG had the highest value of 3,175 kg·m-3. Although the unit weight of the concrete with OSS and OSG was 3,052 kg·m-3, which was lower than the maximum unit weight condition by 123 kg·m-3, its attenuation coefficient was improved by 0.012 cm-1. The results of chemical analysis of aggregates revealed that the magnesium content in oxidizing slag was lower than that in iron ore, while the calcium content was higher. The concrete with oxidizing slag aggregates demonstrated enhanced γ-ray shielding performance due to a relatively high calcium content compared with the concrete with OSS and OSG in spite of a low unit weight. All sample concretes mixed with high-weight aggregates had higher compressive strength than the concrete with typical sand and gravel. When OSS and IOS were used, the highest compressive strength was 50.2 MPa, which was an improvement by 45% over general concrete, which was achieved after four weeks of curing.

The amount of Plastics consumed annually has been growing increasingly in Bangladesh. Consequently, waste plastic recycling has become one of the major challenges in recent times. The present study has selected waste PET, a polymer compound of Polyethylene Terephthalate, to investigate its possible use as plastic aggregate in concrete application. The shredded waste plastic was used in concrete with partial replacement of 5%, 10% and 20% by volume of conventional coarse aggregate. Four types of concrete specimens including one without plastic aggregate, for comparison purpose, were prepared. All the concrete specimens were tested for its different mechanical properties after a curing period of 7, 21 and 28 days. Various physical properties of all aggregates and fresh concrete properties were also tested in the laboratory. The specific gravity of waste plastic aggregate was found 1.4 and the maximum density of concrete containing plastic aggregate was 115 lb/ft3. The density of concrete specimens containing plastic aggregate decreased with the addition of more amount of plastic aggregate. It was found that the concrete specimen containing waste PET at 10% volume showed higher compressive strength and higher modulus of elasticity than other specimens. The splitting tensile strength was about 8-11% of compressive strength. The flexural strength of concrete specimens containing plastic aggregate was lower than that of concrete without plastic aggregate. It was found that the strength of concrete containing PET aggregate falls in the category of lightweight concrete in terms of their strength, specific gravity and density. Thus, the waste PET aggregate could be effectively used to reduce the unit weight of concrete which results in a reduction in the dead weight of a structural concrete. Furthermore, it is concluded that the use of waste PET in concrete provides some advantages such as reduction in the use of conventional aggregate, disposal of wastes, prevention of environmental pollution, and energy saving.Progressive Agriculture 27 (3): 383-391, 2016

The fatigue behaviour of concrete is gaining new relevance against the backdrop of continuous development in concrete construction. Modern types of concrete achieving ever higher strengths; hence concrete constructions are becoming increasingly attractive for new fields of application such as onshore and offshore wind turbines. The fatigue of concrete has a special relevance for these cyclic-loaded constructions. Knowledge of the number of cycles to failure is no longer sufficient for the design of these kinds of constructions. There are further questions concerning strain and stiffness development and the combination of fatigue loading and maritime environmental conditions which have been investigated with new testing methods at Leibniz Universitat Hannover within the research project “ProBeton”. The first results of this research project, which is supported by the Federal Ministry for Economic Affairs and Energy, are presented here.

The aim of this paper is to quantify mechanical fracture and length change parameters of the two types of concrete with alkali activated binder. The six beam specimens (75 × 75 × 295 mm) were made from each mixture. After demolding specimens were placed in air storage for 28 days. During this period length change (shrinkage) were recorded in accordance with ASTM C490 (2011). After that the three-point bending test was performed on these specimens with initial stress concentrator at the age of 28 days to obtain the mechanical fracture parameters. Records of fracture tests in form load versus deflection (F–d) diagrams were evaluated using effective crack model and work of fracture method.

Using classical explicit nonlinear dynamic analysis software of ANSYS/LS-DYNA, this paper analyzes the process of perforating jet penetrating on four types of concrete target with unconfined compressive strength of 30 MPa, 50 MPa, 30 MPa & 50 MPa and 50 MPa & 30 MPa. The result shows that penetration of shaped charge will decrease if cross-formation perforation occurs and in order to guarantee the penetration performance during perforating, perforating should be parallel to the direction of oil formation and be avoided from working on high-strength tight formation and up-and-down cap-rock.