Proceedings of the 3rd RILEM Spring Convention and Conference (RSCC2020)

The present work describes an integrated approach that leads to the development of a new model capable of describing the tensile behavior (mode I) of fiber reinforced concrete (FRC), considering the orientation of the fibers, the fibers segregation along the cross-section of the FRC members and the pullout constitutive model of each fiber bridging the two faces of a crack. The possibility of the numerical model to capture the flexural behavior of non-metallic fiber reinforced concrete members is explored by simulating the response of polypropylene fiber reinforced concrete notched beams submitted to 3-point bending tests.

In this paper, a new approach is proposed for predicting reaction force in simply supported steel fiber reinforced concrete (SFRC) beams under impact loading (drop weight test) considering the energy conservation approach. If SFRC beams completely fail under impact load, it can be found that the total reaction force is equal to force capacity of SFRC beams. The force-deflection relationship can show the peak force that the SFRC beam can carry under impact load. Since concrete is a material sensitive to loading rates, the strain rate of loading and also the volume fraction of steel fiber will influence the beam’s response. The force-deflection relationship of the SFRC beam under impact loading is obtained using the proposed model. This model considers the effect of volume fraction of steel fiber and also the strain rate on the concrete properties. The model is then verified with the results collected from the literature that include 189 SFRC beams tested under drop-weight impacts and included in a database. The results obtained show that this method can estimate the maximum impact force with acceptable accuracy.

According to the Intergovernmental Panel on Climate Change (IPCC), global climate change induced temperature rise should remain below 1.5 °C by 2100 to guarantee the livability of our planet. This can only be achieved by immediate action by all sectors, including the cement and concrete industry. Carbonation of cementitious materials in presence of atmospheric CO₂ can on the one hand hamper the durability when used in steel-reinforced applications prone to corrosion. On the other hand, the binding of CO₂ through carbonation in non-steel reinforced applications could actually be of interest. When considering the worldwide application of cement-bound materials in construction along with their CO₂ sequestration potential, CO₂ emissions inherent to Portland cement production can partly be compensated for. Obviously, for such CO₂ uptake estimations to be reliable, a thorough understanding of the carbonation behavior is imperative. In this paper, this was studied for high-volume fly ash (HVFA) binder systems with a low production related carbon footprint. HVFA mortar was subjected to accelerated carbonation experiments at 1% and 10% CO₂. Carbonation-induced changes in microstructure were assessed using mercury intrusion porosimetry (MIP) while the changes in proportioning of CH and C–S–H carbonation reaction products were measured with thermogravimetric analysis (TGA). A carbonation-induced coarsening of the pore structure was observed which is more pronounced at 10% CO₂ levels and attributable to more dominant C–S–H carbonation. Also the calcium carbonate content in the carbonated zone tends to significantly increase with the applied CO₂%.

The low-level waste generated from boiling water reactor (BWR) power plant consists of very high concentration of sodium sulphate, higher than 25 mass% of Na₂SO₄. These liquid wastes are solidified with cementitious materials at elevated temperature. A critical concern of highly concentrated sodium sulphate nuclear waste with co-hydrating of cementitious materials is the degradation of the materials by chemical interaction of sulphate with cement hydrates and crystallisation of sodium sulphate as well as the deterioration due to external sulphate attack. Sulphate ions cause a serious chemical deterioration to cement matrix through either forming expansive products of ettringite and gypsum or sodium sulphate crystallization. In addition, a very high concentration of sodium sulphate solution could induce to form U-phase [(CaO)₄(Al₂O₃)_0.9(SO₃)_1.1(Na₂O)_0.5:16H₂O] and this may cause deterioration to cement matrix. A potential variation of the physicochemical properties of the materials because of internal and external sulphate interaction is the important factor to maintain the performance over the time scale required. The purpose of this study is to investigate the degradation of hydrated Portland cement and slag-blended cementitious materials, where the cement is replaced by 42% hydrated with 13% of Na₂SO₄ by weight, in sodium and magnesium sulphate solutions. The hydrated samples having diameter between 2.38 and 4.75 mm were immersed in 1300 mmol/L Na₂SO₄ and MgSO₄ for 28 days and phase changes as a result of sulphate interaction were investigated. In addition, the hydrated samples exposed to water and 1300 mmol/L of Na₂SO₄ and MgSO₄ for 6 months and spatial mineralogical distribution due to sulphate ingress from the external source or from the pore solution was determined. The results of shows a significant formation of ettringite due to sulphate ingress and U-phase instability. The type of exposure solution and the replacement of slag influence the dissolution of U-phase and consequent formation of ettringite causes severe degradation.

Concrete structures are sometimes believed to be less sustainable and difficult to disassemble properly compared to structures of other materials. However, when a holistic design approach and novel technology is applied in the design of concrete structures, they can be more sustainable than other solutions and designed for disassembly. A novel concrete technique, developed at the Technical University of Denmark, the Super-Light Deck, is one example of this new green generation of concrete. Pre-stressed deck elements of Super-Light concrete consist of a combination of light aggregate concrete and normal concrete. The flat decks can be used individually in buildings as horizontal divisions, or several decks can be joined together by post-tensioning in an arch shape for use in bridges or in vaulted roofs (the pearl-chain method). The technology makes it possible to create beamless structures by having blade joints between deck and support in buildings. Furthermore, an arch shaped structure consisting of several Super-Light Decks can be joined to the supporting structure by a designed “end-element” with a behaviour comparable to a concrete hinge. Both of these solutions are presented in the paper. They are novel designs, where the disassembly process is taken into account, and it will be possible to dismantle and reuse the Super-Light Deck elements, at the end of the lifetime of the structure.

The electromagnetic response of concrete can be used to the non-destructive testing of structures and to follow early-age property development. Fundamental understanding of the physical origins of the electromagnetic response of cement-based materials is critical to reduce the empirism in the interpretation of electromagnetic-based techniques. The pore solution is the main contribution to the electrical conductivity and dielectric response of porous geomaterials. Specific ion effects are known to impact the dynamics of ions in aqueous salt solutions. In this context, molecular dynamics (MD) simulation is a well-suited technique to compute and understand how the ionic composition of the pore solution affects the electromagnetic properties of concrete. Here, we discuss recent results of MD simulation on bulk solution mimicking concrete pore solution. Then, we upscale the information from the molecular scale up to the concrete scale in order to provide a multiscale model of the electrical conductivity and frequency-dependent dielectric response of cement-based materials.

Polymers are widely used for concrete coating applications such as surface coating materials for buildings, preventing penetration of water or air, aesthetic purpose like glazing finish, conservation materials for mural paintings and many more. In the field, the common practice is to coat concrete after it has set completely (28 days), but it is not well understood if this will maximize the interfacial strength. Hence there is a need to determine at what time after the addition of water, the coating should be applied and also how surface characteristics influence interfacial strength. The reason for better interfacial performance at the interface between coating polymers and cement paste is due to the physical and chemical interactions between the cement hydration products and the different functional groups in coating polymer. In the present work, the physical interaction and molecular mechanisms between functional groups of two different coating polymer (Epoxy and poly(methyl methacrylate) (PMMA)) and cement hydration products during early stages of cement hydration is studied using molecular dynamics simulation. The mechanical response and the physical interaction of functional groups of two different coating polymer Epoxy and PMMA are significantly influenced by (a) pore solution calcium (b) C–S–H substrate calcium and (c) adsorbed water layer.

Sustainable service life design of reinforced concrete structures relies on accurate input values. However, in the field of carbonation induced corrosion some input parameters and statistical distributions still need to be validated for worldwide climate conditions. Furthermore, many well-published literature data is not considered due to different storage conditions. At the suggestion of CEN/TC 104/SC1/WG1 the database “CarboDB” was created providing open access to extensive information on concrete carbonation under different storage conditions. The natural carbonation coefficient as well as the minimum concrete cover can be calculated for chosen situations. CarboDB provides reliable data on concrete carbonation in order to increase existing knowledge on concrete carbonation. The database is available online at http://​carbodb.​bgu.​tum.​de/​#/​. By registration further contribution is possible and appreciated. New insights can be gained by merging several sources. For natural carbonation, testing only up to 140 days underestimates the carbonation progress of concretes with limestone fillers and high amount of ground granulated blast furnace slag.

The Russian culture has a rich history and strong traditions, especially when it comes to ancient white-stone architecture. Usually the term “white stone” stands for light carboniferous limestone. White stone was one of the basic building materials in Old Russia and was of great historic importance in the 11th–15th cc. Unfortunately, natural white stone resources are gradually being depleted. Modern concrete technology is able to imitate and replace to the full the natural stones by artificial composites that are not inferior to them in their properties. One of the most promising areas of high-performance concrete (HPC) concept implementation is manufacture of architectural concrete with improved decorative properties based on mechanically activated composite binders and effective admixtures. Architectural concrete frost resistance reaches 300–600 freezing–thawing cycles and more; the open integral porosity does not exceed 2–4% vol. The values of the prism strength factor and the initial tangent modulus of elasticity of modified concretes meet or exceed regulatory requirements. Durability of architectural concrete may be additionally improved by impregnation with special organic silicate compounds. Thereby an optimum combination of construction and technical characteristics of concretes and decorative properties of products is achieved that should considerably expand the field of architectural concrete application, solve the problems of historical heritage preservation, and on the whole facilitate the growth of its social significance and attractiveness. Some of the most valuable of the white-stone architecture objects reconstructed in Russia with use of architectural concrete in the last decade are presented.

Indoor air quality is important for comfort and health of buildings inhabitants. The use of environmentally friendly building materials is also very important for sustainable and green buildings. In the present study, mechanical characteristics of five mortars were comparably analyzed: two unstabilized earth mortars, one earth-air lime mortar, one cement mortar and other gypsum mortar. The earthen plasters are nowadays commonly applied unpainted. The gypsum plaster system is composed by the base mortar and a finishing layer; it can be applied unpainted or painted. The cement plaster is generally finished with a paint system. Therefore, the adsorption and desorption capacities were assessed for all the plasters and the influence of the paint system was evaluated for the cement and gypsum plasters. Results show that the earth mortar stabilized with air lime presents lower mechanical strength, in comparison to all other mortars, and lower adsorption capacity, similar to the gypsum system. The unstabilized earth plasters present high adsorption capacity, in comparison to the cement and gypsum plasters. The paint system does not have significant influence on the adsorption capacity of the gypsum plaster but reduced that capacity on the cement plaster. These results demonstrate the important contribution that unstabilized earth plasters may provide as passive indoor hygrothermal buffers, in comparison to other plasters, thus to comfort and occupants health.

Cement and concrete construction inevitably impact on societies. By exploiting resources, modifying the landscape and facilitating the mobility of people and movement of goods and services, concrete construction activities are directly linked to climatic effects, local economies, and the socio-economic well-being of urban dwellers. Today’s rapidly accelerated urbanisation inevitably coins global societies all over the world, particularly in Africa, where the expected movement from rural to urban environments along with a significant population increase will reach unprecedented megacity dimensions. Megacities are already under massive socio-economic, cultural and infrastructural pressure today, and the future predictions indicate that complex challenges will need to be tackled. However, the future developments present both challenges and opportunities at the same time, since due to lacking existing solutions unprecedented environmentally and socio-culturally responsive solutions have to be developed using readily available local resources. The paper discusses challenges related to rapid urbanisation and highlights African distinct differences. Opportunities and potential material and structural solutions are also discussed, along with the associated architectural and socio-economic implications.

The resilience of a community to come across the natural hazard events is gaining popularity in planning and decision-making strategies. To utmost importance in seismic zones, is the safety and operability of structurally vulnerable existing structures, representing a high portion of the built stock. Manifested low resilience has shown many flaws in planning, managing, retrofitting the damaged structures, which in many cases takes years being completed. The scope of the research is to exploit numerical simulation strategies towards a resiliency enhancement by means of optimized retrofitting solutions. At present, the seismic design is based on elastic analysis. A simplified two-step procedure for the seismic retrofitting design is here proposed, by utilizing the capabilities of FE codes to perform advanced nonlinear analyses. In the first step, it is estimated the structural performance of the structure, whilst the vulnerable elements to be strengthened are indicated. A Retrofitting strategy is selected and implemented into the model, and in the second step, the structure is reanalyzed with the same strategy. Based on the obtained responses, each strengthening element is designed adequately to the required limit state. This strategy is computationally burdening; however, the progress in the numerical analyses makes possible its implementation, and the achieved accuracy is nonpareil. The proposed method is illustrated with a masonry church, severely damaged by the Emilia Romagna (Italy) Earthquake in 2012. The retrofitting strategies adopted for strengthening options, are the surface mounted: (a) FRP sheets; (b) GFRP bars and TRCM. Throughout the investigated case study, it is demonstrated that the vulnerable structures exhibit very low resilient features and the best strategy to enhance their resilience is by means of anterior measures.

Buildings are among the major contributors to environmental impacts, in terms of non-renewable resource depletion, energy and material consumption, and greenhouse gas (GHG) emissions. For this reason, modern societies are pushing towards the refurbishment of existing buildings aiming at the reduction of their operational energy consumption and at a major use of renewable energy and low-carbon materials. At the same time, buildings are expected to provide population with safe living and working conditions, even when hit by different kinds of hazards during their service life, such as earthquakes. Until recently, life cycle assessment (LCA) procedures tended not to include the effects of natural hazards. However, if considered in a building LCA, earthquake-induced environmental impacts would constitute a very informative performance metric to decision-makers, in addition to the more customarily used monetary losses or downtime indicators. Within this context, therefore, a comprehensive review of the existing literature is presented, with comparisons between available methodologies being carried out in terms of their employed seismic loss estimation method, environmental impact assessment procedure, damage-to-impact conversion, impact-to-cost conversion, and selected decision variable. Further, an illustrative case-study application is also included.

Through this research it is intended to catalogue different environmental scenarios taking into account extreme climatic actions and what is their mechanical, chemical and physical impact on the main materials used in construction (reinforced concrete, bricks, lime repair mortars, etc.). For this, a qualification of these material deterioration processes will be carried out after having done the data collection, the analysis of the different scenarios and a structural study. To move towards sustainability, where building is better described as a process than a product, a new integrated-design approach that accounts for durability is deemed to be essential. This approach will allow building assessment in a multi-performance perspective. The Sustainable Structural Design (SSD) methodology is presented based on environmental and structural performance parameters in a life-cycle approach. The concept of reuse is a sustainable perspective for extremely durable structures (ESD), new structures and existing structures. In this work we will focused in different building materials characteristics and their potential degradation under extreme events conditions. This work is framed in a research project of the National Plan of Spain, whose purpose is the development of a decision support system based on intelligent management tools for the maintenance of existing buildings and the design of new buildings, in order to extend its working life to cope with climate change and extreme events.

This work reports the results of an extensive experimental campaign aimed at investigating the Thermal Energy Storage (TES) behavior of PCM Recycled Brick Aggregate (RBA) mortars. Test specimens for TES measurements were produced following a new spherical-shaped technique, patented as “DKK test” by the Institute of Construction and Building Materials of TU-Darmstadt. DKK was used for characterizing the various test samples made of plain cement paste plus porous RBAs, these latter filled with paraffinic PCM waxes. Dynamic DSC tests and conductivity measurements were also done for thermally investigating both components and composites. Moreover, the study proposes a novel numerical approach for determining the energy storage capacity of the investigated systems, setting the experimental benchmarks for validation. Particularly, the experimental results have been finally employed for calibrating an enthalpy-based model, at both macro- and meso-scale level, to evaluate the temperature-based thermal parameters like specific heat, conductivity, or more in a general sense, the energy storage capacity of these systems under transient heat conduction conditions. The results show very promising possibilities for using RBAs as carriers in green concrete applications.

Thermal-Energy Storage (TES) properties of organic phase change materials have been experimentally investigated and reported in this paper. Three paraffin-based PCMs and one bio-based one are considered with melting temperatures of 24 °C, 25 °C and 26 °C. Sensible heat storage capacities, melting characteristics and latent heat enthalpies are investigated through DSC measurements. Two alternative methods, namely the classical dynamic and the step-wise approach, are performed and compared with the aim to eliminate and/or overcome possible measurement DSC errors. The latters are due to the size of the samples and their representativity, heating/cooling rate effects and the low conductivity of the PCMs, which may affect the results and possibly cause a loss of objectivity of the measurements. Based on results achieved from this study, clear informations can be figured out on how to conduct and characterize paraffin and bio-based PCMs, and possible how to apply them in TES calculations for building applications and/or simulations.

Hemp concrete has been widely recommended as bio-based material to limit carbon emissions and energy consumption of buildings. This material presents interesting hygrothermal and acoustic performances. It is produced of hemp particles embedded in a natural cement that forms a very heterogeneous and porous component. Few works have studied the evolution of the properties of hemp and flax concrete, over time. This research aims to study the evolution of the compressive strength, the microstructure and porosity of hemp concrete over the time. Thus, three accelerated aging protocols were conducted on the formulated hemp concrete before undertaken properties tracking experimentations. Results shows that compressive strength increases up to 58 days for hemp concrete. The hemp shiv deformation depending on the accelerated aging in hemp concrete is calculated by 2D image analysis. Optical investigation was used for this experimentation. Microscopic results confirm the high degradation of such heterogeneous materials which is confirmed by the porosity results.

In the framework of studies for the disposal of radioactive waste, ONDRAF/NIRAS, the Belgian National Agency for Radioactive Waste and enriched Fissile Materials investigates the option of a geological repository. In a geological repository, the waste is sidelined within a deep and stable geological layer, named host rock, behind a whole series of artificial barriers. Together, natural and artificial barriers ensure the isolation of waste, their confinement and the delay and spread of release of radioactive substances. The interaction of the host rock and the concrete support of disposal galleries is investigated to analyse the long-term sustainability of the structure. The host rock considered in this study is a poorly indurated clay present in the northern part of the Belgium, the Boom Clay. The behaviour of the interface between the Boom Clay and the concrete of the galleries is studied experimentally from both mechanical and gas transfer perspectives. Samples have been prepared consisting of two half cylinders, one made of concrete and the other one of Boom Clay to obtain an interface. A dedicated device has been designed using an HOEK type cell, which allow applying confining pressure to simulate lithostatic loading, injecting gas to measure transfer properties and generating relative displacement of both sides of the interface. Mechanical behaviour of the interface under short loading has first been studied. One originality of this study consists in using gas injection and Poiseuille’s law to monitor and quantify the opening and closure of the interface during mechanical loading. A partial irreversible closure of the interface and effects of long term loading have been observed. By increasing the confinement, the opening of the interface (clay-concrete) gradually decreases (initially 38 μm for 1.2 MPa of confining pressure) until it reaches 5 μm for 4.5 MPa. There is moderate expected irreversibility during unloading (19 μm at 1.7 MPa). The objective is to identify the main parameters allowing predicting the properties of the interface, such as initial roughness of the interface, water content, applied stress and time. The second part of the work consists in studying transfer properties at the interface. The aim is to identify paths available for gas produced during waste storage.

Many reinforced concrete (RC) piers have cut-offs where the number of rebars in the longitudinal direction are reduced according to the cross-sectional force. When such piers, the cover concrete in the intermediate section of RC piers can fall off in large earthquakes. Usually RC piers receive damage at their bases when large earthquakes lateral force act. Thus, for RC piers set in a river or those with deep-set bases, it can be that recovery work after earthquakes would require huge temporary construction facilities and result in large expenses and work time (Fig. 1). If damage can be made occur above the water surface and the ground level where recovery work can be easily done, more reasonable aseismic design of RC pier structure including recoverability can be achieved. In this research, we carried out cyclic loading tests using 3 specimens having cut-offs. We studied which position of piers will yield and failure occurred based on the cyclic loading tests. We set a flexural performance ratio (ratio of bending moment to flexural yield strength) at the rebar cut-off point. This ratio is the quantitative value that controls damage in the intermediate section of the frame. As a result, the difference in yield position and bending fracture due to difference in a flexural performance ratio, and difference in position of between yield and flexural fracture due to reinforce the inner spiral rebar of the cut-off point were clarified.

The experience of the 2016 earthquake in central Italy shows that the approach to the post-seismic phase is still based on an emergency approach, while the prevention and the reduction of seismic risk are proving difficult. In the particular context of rural and mountainous area, the seismic shock produced the depopulation of several minor historical centres and the scattering of urban communities. This kind of damage had dramatic impacts on the possibility of both preservation and restoration of traditional architectures, due to the specificity of the peculiar material used and construction techniques. In order to reverse the trend, the goal of future interventions must be to provide a reconstruction strategy, with the aim of defining the problems to be solved as a priority in the post-seismic phase and, at the same time, to provide risk prevention measures also within ordinary planning. The starting point of the current research is the impact of the earthquake on the historical centre of Caldarola to evaluate the damage state through three types of analyses: at the urban scale to identify the performance deficits that caused the loss of functionality of the whole urban system; at the building scale, through an expeditious assessment method to identify the vulnerability of the building façade in relation to the usability of the emergency routes; in addition, the vulnerability of the building aggregates have been examined to verify the correspondence between the real damage occurred post-earthquake. The analysis results highlight a strong link between the development of an empirical vulnerability assessment and the more effective strategies of damage mitigation.

The authors have recently proposed a new concept of crack analysis based on the assumed reinforcement strain profile between the adjacent cracks. Mean crack spacing is obtained from the equality of mean strains of the tensile reinforcement assessed from the strain profile and the mean value calculated by EC2. The current study considers mean crack spacing for both tensile and bending RC members. For bending members, mean spacing is established separately for primary and secondary cracks. The current paper quantifies constitutive parameters of the model for the cases mentioned above. The model is validated against independent test data. A comparative analysis has demonstrated that the predictions of mean crack distance by the proposed model agree well with the tests of RC elements.

Various infrastructure information is gathered nowadays in databases, which have become rather large after years of development and data collection. For thorough search and broad exploitation of the available information, even beyond its original scope, advanced data analysis approaches need to be employed. The present work is concerned with the exploitation of the data in the US National Bridge Inventory (NBI) maintained by the Federal Highway Administration (FHWA), which includes information for over 500,000 bridges. The information provided in NBI was analyzed in combination with additional data from other sources (for climatic conditions, earthquake hazard, etc.). Where needed, data were converted to correspond to bridge locations using spatial interpolation techniques. Then, Exploratory Data Analysis (EDA), Analysis of Variance (ANOVA) and regression analysis methods were utilized to study the causes of bridge deterioration. These statistical methods yield quantitative results and allow the identification, ranking and measurement of intensity of factors contributing to the decrease of the structural condition of bridges with time.

The aim of this paper is to provide an original, systematic and critical review of existing mix design methods for recycled aggregate concrete (RAC), with identification of research gaps. These design methods were compared to the design methods used for natural aggregate concrete (NAC). Also a short literature survey showing the effect of the design methods on the properties of RAC and NAC was conducted. Special emphasis was placed on the critical analysis of literature results to show the existing relations between the individual mechanical properties of RAC. Also, a critical comparison was made with existing relations for NAC that can be found in the literature. Based on the analysed research results, hypotheses related to the possible behaviour of RAC at early ages were formulated towards the understanding the role of the mix design method in the mechanical behaviour of RAC at early ages.

Analyses of end-block and beam-end specimens have been undertaken based on the finite element models. The purpose of the analyses is to investigate the effects of concrete early age properties on the response behaviour of the anchorage zone. Time dependent strains and stresses in the anchorage zone are evaluated. The mechanical concentrated load represents the anchorage in post-tensioning of slab or beam during construction where the load is transferred typically at 1 and 4-days ages. The analyses incorporate thermal, creep and shrinkage effects. The double power law (DPL) is adopted to represent the creep effects. The ACI 209 and the CEB-FIP shrinkage models in FE TNO DIANA were also adopted to account for shrinkage. The models are validated based on experiments. Results indicate that early ages concrete effects need to be considered for design of sensitive elements in particular such as anchorage zones of post-tensioned elements.

The superb performance of carbon fiber reinforced polymer (CFRP) composites as near surface mounted (NSM) reinforcement in strengthening solutions for structures is already well recognized. Due to their deficiencies in fire conditions, cement-based adhesives as an alternative to polymeric matrices are recently suggested as a solution in these systems. However, the interface between the CFRP laminate and cement-based adhesives should have good stress transferring capacity. Thus, it is of great importance the research on improving this interface to increase the bonding capacity of CFRP/cement-based adhesive system. For that purpose, pull-out tests were conducted to examine the interfacial debonding process of two types of CFRP laminates: conventional smooth surface laminates and sand surface treated laminates. Digital image correlation (DIC) technique was used to verify the potentiality of the proposed sand treating approach. Therefore, the interlocking mechanism of sand treated laminates with the developed cement-based adhesive is assessed and the results are compared to those with non-treated smooth surface laminates. Furthermore, the bond-slip behaviour from pull-out tests is compared to obtained data through the DIC technique. The results verified the effectiveness of sand treatment approach applied to NSM CFRP reinforcements. Moreover, the DIC technique has revealed capable of providing qualitative and quantitative information in this regard.

The 3D concrete printing has been developed as one of the digitized technologies for the construction industry aiming to cope with some drawbacks of conventional construction methods. One of the main particularities of 3D printed cement based materials is its anisotropic/orthotropic behaviour, which is related to the layer wised approach of these addictive manufacturing processes. In this work, a cement based composition reinforced with polyvinyl alcohol fibre was used to evaluate the post-cracking behaviour of printed specimens in two different loading directions related to the layers’ orientation. Three-point bending tests were used to indirectly obtain the tensile behaviour (i.e. stress–crack width relationship) through an inverse analysis procedure. The results of inverse analysis showed that tri-linear relationship was able to accurately model the post-cracking behaviour of PVA-FRC specimens. No significant differences were observed on the tensile behaviour of 3D printed and mould cast specimens.

The main objective of this work is to investigate the properties of a Fibre Reinforced Concrete (FRC) at fresh and hardened states, obtained by a partial substitution of coarse and fine natural aggregates with Electric Arc Furnace Slag (EAFS) and Fly Ash (FA). Recycled Tyre Steel Fibres (RTSF) were incorporated in the developed concrete in order to maximize and reuse wastes that were not biodegradable. The design of the FRC mixture with EAFS was based on a reference concrete by using the modified Andreasen and Andersen particle-packing model. The composition was optimized to achieve maximum packing density. Workability, compressive and tensile splitting strength, modulus of elasticity and post-cracking behaviour were evaluated for the different concrete mixtures developed and compared to the ones of the reference mixture. The selected concrete composition, with an EAFS and FA maximum content of 70% and 10%, respectively, has shown good workability and suitable elasticity modulus according to the specified requirements. The latter mixture revealed a lower compressive and tensile splitting strength, comparatively with the reference mixture (w/o fibres), which was compensated by the improved ductility and energy absorption capacity under compressive loading.