Aggregate interlocking and dowel bar systems are the two primary mechanisms in a jointed plain concrete pavement for transferring the wheel loads from the loaded slab to the adjacent unloaded slab, avoiding critical stresses and excessive deformations across the joint. Aggregate interlocking is suitable for small joint openings, while the dowel bar provides effective load transmission for both smaller and wider joint openings. In this study, a three-dimensional finite element model was developed to investigate the structural performance of dowelled jointed plain concrete pavements. The developed model was compared with an analytical solution, i.e., Westergaard’s method. The current study investigated the effectiveness of the dowel bars in jointed plain concrete pavements considering the modulus of elasticity and the thickness of the base layer, as well as dowel bar diameter and length. Furthermore, the load transfer efficiency (LTE) of a rounded dowel bar was compared with that of plate dowel bars (i.e., rectangular and diamond-shaped dowel bars) of a similar cross-sectional area and length. This study showed that the LTE was enhanced by 4% when the base layer’s modulus of elasticity increased from 450 MPa to 6000 MPa, while the increase in stress was 23%. A 1.2% improvement in the LTE and a 2.1% reduction in flexural stress were observed as the base layer’s thickness increased from 100 to 250 mm. Moreover, increasing the dowel bar’s diameter from 20 mm to 38 mm enhanced the LTE by 4.3% and 3.8% for base layer moduli of 450 MPa and 4000 MPa, respectively. The corresponding rise in stresses was 10% and 5%. The diamond-shaped dowel bar of a 50 × 32 mm size showed a 0.48% increase in the LTE, while sizes of 100 × 16 mm and 200 × 8 mm reduced the stress 6.7% and 23.1%, respectively, compared to that in the rounded dowel bar. With rectangular dowel bars, a 4% rise in the stress was noted compared to that with the rounded dowel bar. Increasing the length of the diamond-shaped dowel bar slightly improved the LTE but had no impact on the stress in the concrete slab. The findings from this study can help highway engineers improve pavements’ durability, make cost-effective decisions, contribute to resource savings in large-scale concrete pavement projects, and enhance the overall quality of infrastructure.

Concrete is the most used construction material, accounting for 8% of global CO₂ emissions. Various strategies aim to reduce concrete's embodied carbon, such as using supplementary cementitious materials, utilizing cleaner energy, and carbonation. However, a large potential lies in reusing concrete for new buildings in a Circular Economy, thereby closing material loops and avoiding CO₂ emissions.

This study focuses on the reuse of precast concrete elements. We present a digital workflow for assessing reuse by predicting the remaining service life, estimating CO₂ uptake by natural carbonation, and calculating the embodied carbon savings of concrete reuse. Both carbonation rates from EN 16757 and our investigation were applied to a case study building.

While EN 16757 rates suggest that most precast elements have reached the end of their service life, our assessment shows that these elements have a sufficient lifespan for reuse. Plaster and coverings significantly delay carbonation and extend service life. During the first service life following EN 16757, carbonation was 19,2 kg CO₂/m³, whereas our prediction was 5,4 kg CO₂/m³. Moreover, CO₂ uptake during service life, including reuse, was less than 6% of the embodied carbon. The climate benefits of reuse greatly exceeded those of carbonation.

Furthermore, carbonation did not have a decisive influence when applying Cut-Off, Distributed, and End-of-Life allocations for assessing embodied carbon of re-used elements in subsequent life cycles. The digital workflow is useful in quickly assessing lifespan, carbonation, and embodied carbon of concrete. It can be leveraged as a decision-making tool when designing for reuse.

Transverse joints are introduced in jointed plain concrete pavement systems to mitigate the risk of cracks that can develop due to shrinkage and temperature variations. However, the structural behaviour of jointed plain concrete pavement (JPCP) is significantly affected by the transverse joint, as it creates a discontinuity between adjacent slabs. The performance of JPCP at the transverse joints is enhanced by providing steel dowel bars in the traffic direction. The dowel bar provides reliable transfer of traffic loads from the loaded side of the joint to the unloaded side, known as load transfer efficiency (LTE) or joint efficiency (JE). Furthermore, dowel bars contribute to the slab’s alignment in the JPCP. Joints are the critical component of concrete pavements that can lead to various distresses, necessitating rehabilitation. The Swedish Transport Administration (Trafikverket) is concerned with the repair of concrete pavement. Precast concrete slabs are efficient for repairing concrete pavement, but their performance relies on well-functioning dowel bars. In this study, a three-dimensional finite element model (3D-FEM) was developed using the ABAQUS software to evaluate the structural response of JPCP and analyse the flexural stress concentration in the concrete slab by considering the dowel bar at three different locations (i.e., at the concrete slabs’ top, bottom, and mid-height). Furthermore, the structural response of JPCP was also investigated for several important parameters, such as the joint opening between adjacent slabs, mispositioning of dowel bars (horizontal, vertical, and longitudinal translations), size (diameter) of the dowel bar, and bond between the slab and the dowel bar. The study found that the maximum LTE occurred when the dowel bar was positioned at the mid-depth of the concrete slab. An increase in the dowel bar diameter yielded a 3% increase in LTE. Conversely, the increase in the joint opening between slabs led to a 2.1% decrease in LTE. Additionally, the mispositioning of dowel bars in the horizontal and longitudinal directions showed a 2.1% difference in the LTE. However, a 0.5% reduction in the LTE was observed for a vertical translation. Moreover, an approximately 0.5% increase in LTE was observed when there was improved bonding between the concrete slab and dowel bar. These findings can be valuable in designing and evaluating dowel-jointed plain concrete pavements.

Self-compacting concrete (SCC) and 3D printed concrete (3DPC) are two exciting technologies with potential to increase both the productivity and the working environment in the concrete industry. Permanent 3DPC formwork filled with SCC constitutes an interesting alternative for columns. The goal is to create a composite column with complete bond between the form and the core. Laboratory studies on composite columns of this type have been conducted at KTH investigating form pressure, load-carrying capacity, and durability. This paper is focusing on the form pressure that has been an issue ever since SCC was developed in Japan in the early 1990s because of the flowing nature of this concrete type. Two tests series have been performed. In the first one, two 2.4 m high composite columns with radius R = 0.25 m were tested. The casting rate was 2.6 m/h and resulted in a form pressure approaching full hydrostatic pressure but no form failures or any leakage arose. In the second test series, four composite columns with height h = 3.0 m and R = 0.15 m were cast at a casting rate r = 1 m/h. The form pressure was close to the one calculated with Gardner's model. No failures, cracks or leakage occurred. The results are promising but tests on columns with larger dimensions would be of even larger interest.

Extrusion-based 3D concrete printing (3DCP) is a promising technique for fabricating complex concrete elements without formwork, offering advantages like cost reduction and enhanced design flexibility by decoupling manufacturing costs from part complexity. However, this extended formal freedom is still constrained by the fabrication process and material properties. This paper presents a novel method for applying topology optimisation internally i.e. preserving the external boundaries of the concrete element while reducing material use and weight. This method adapts the extrusion thickness along the part according to the expected stresses, reducing the material use while enhancing structural performance. To validate this method, three different unreinforced 3DCP beams are tested in three-point bending. Results show that beams with optimised material distributions presented a higher strength-to-weight ratio, averaging 47% and 63% compared with the conventional 3D printed beam. This paper demonstrates the potential of internal topology optimisation for improving the efficiency and sustainability of 3DCP.

In recent decades, new techniques have been developed to produce concrete. Such a technology is self-compacting concrete (SCC) and another is 3D-printed concrete. In both cases, compaction through vibration, which is a labour-intensive moment, is omitted. In the present research project, both techniques have been combined. Traditionally, concrete columns are produced by pouring concrete into a column mould or form that is either made of wood or steel. The steel mould can be used many times while the wooden mould can at best be used maybe two or three times. Building and then dismantling the formwork takes time and costs money. It also leads to increased material use and increased transport. An alternative is columns with a lost form. Steel pipe columns filled with concrete is a proven technique, but it is rarely used. The steel must be protected from corrosion and in buildings also fire protected. A new alternative – which is being studied in the present project – is a lost 3D-printed concrete form in which a core of SCC is cast.

The project included load tests on four composite and two homogeneous concrete columns. The columns were 3 m high and had a circular cross-section with a diameter of 300 mm. The composite columns consisted of a 40 mm thick, 3D-printed concrete form that was filled with SCC. The homogeneous columns were cast with the same SCC. All columns were reinforced with four vertical F8 mm bars and ten stirrups F5 mm. In the load tests, the compressive strength was 56 and 44 MPa for the concrete for the 3D-printed forms, respectively. the self-compacting concrete.

The composite columns achieved failure loads as high as the corresponding homogeneous columns. However, there was a difference between columns whose entire cross section was loaded (Group A) and columns where only an inner part (corresponding to the size of the SCC core) of the cross section was loaded (Group B). The failure load for Group B was only 60% of the failure load for Group B. A possible reason for the difference is that the eccentricity was greater in the cases where only a smaller part of the cross section was loaded.

Concrete for 3D printing today has a small maximum aggregate size, which leads to more cement paste. Normally, the water-cement ratio (w/c) is also low. It gives high cement contents but, on the other hand, the possibility of a dense concrete. Dense concrete generally provides good durability. In the project, the conditions for using the 3D-printed concrete form as concrete cover were investigated. It was done by frost testing and testing resistance to carbonation and chloride migration. The frost test showed "good frost resistance" on the border of "very good frost resistance". The resistance to carbonation was comparable to the resistance of other concretes of the same w/c. The measured resistance to chloride migration, on the other hand, was worse. This is probably because the thickness of the printed form varies (thickest in the middle of a layer and thinnest between two layers). The tightness of the joint between two layers is possibly also lower than the tightness of a layer.

The general conclusion is that the technology of columns with lost 3D-printed concrete forms filled with SCC is promising. The report concludes with half a dozen suggestions for further research.

Despite the Paris Agreement and numerous actions, climate change seems to be inevitable. Events and phenomena as forest fires, hurricanes, floods, and melting glaciers can hardly be explained solely by natural changes in the weather. We need to do our very best to limit the climate change, but also a thermal increase below 1.5 ℃ affects our planet. Up to now, most research has been devoted to mitigation, how can we reduce and preferably prevent the climate change. This is particularly valid for the concrete research that in recent years has been dominated by making the concrete material more environmentally friendly or greener by replacing parts of the Portland cement with industrial by-products, e.g., fly ash, ground-granulated blast-furnace slag and silica fume. However, in order to protect our built environment for higher sea levels, greater floods, forest fires close to urban areas, and possible increased wind loads, measures to protect our built environment, not least our infrastructure are urgent. The years 2030, 2040 and 2045, which frequently are mentioned in the environmental agreements, are coming closer. Concrete has a large role to play both in protecting structures such as barriers around cities close to the sea or rivers and for strengthened existing or new structures that can withstand increased loads and attacks from water, moisture, wind, and fire. The paper describes and discusses research needs focusing on Scandinavian conditions identified in an ongoing pilot study.

Despite the Paris Agreement and numerous actions, climate changeseems to be inevitable. Events and phenomena as forest fires, hurricanes,floods, and melting glaciers can hardly be explained solely by natural changesin the weather. We need to do our very best to limit the climate change, but alsoa thermal increase below 1.5°C affects our planet. Up to now, most research hasbeen devoted to mitigation, how can we reduce and preferably prevent the climatechange. This is particularly valid for the concrete research that in recentyears has been dominated by making the concrete material more environmentallyfriendly or greener by replacing parts of the Portland cement with industrialby-products, e.g., fly ash, ground-granulated blast-furnace slag and silica fume.However, in order to protect our built environment for higher sea levels, greaterfloods, forest fires close to urban areas, and possible increased wind loads,measures to protect our built environment, not least our infrastructure are urgent.The years 2030, 2040 and 2045, which frequently are mentioned in theenvironmental agreements, are coming closer. Concrete has a large role to playboth in protecting structures such as barriers around cities close to the sea orrivers and for strengthened existing or new structures that can withstand increasedloads and attacks from water, moisture, wind, and fire. The paper describesand discusses research needs focusing on Scandinavian conditions identifiedin an ongoing pilot study.