Concrete structures are the most common structures. However, the carbon emissions during the entire life of concrete structures have reached a non-negligible level. Developing the carbon emission reduction technologies (CERT) for concrete structures is essential to promote green development of construction industries. In terms of structural life-cycle, the service is divided into three stages,namely before the service (material preparation and construction), during the service (operation and maintenance), and after the service (destruction and recycling). The total carbon emissions and the annual carbon emissions are proposed to describe the concept of carbon emission reduction. The research progress of CERT in each stage is presented, including applying novel low carbon cementitious materials，increasing the durability of concrete structures, and recycling the demolish waste. The design theory of life-cycle carbon emission reduction for concrete structures is also introduced, and a balanced design considering reliability, economy and carbon emission by multi-objective analysis is recommended. The future research and implementation of life-cycle carbon emission reduction for concrete structure is proposed.

3D concrete printing (3DCP) is an emerging and highly automated building technology that holds great potential in promoting evolution of low-carbon constructions industry. In this study, advantages and challenges of 3D concrete printing in terms of low-carbon construction are systematically elaborated. Compared to traditional construction techniques, the benefits of 3DCP with respect to labor-saving and formwork-free cause revolutions in labor structure and building process, which can largely mitigate carbon emissions and wastes from traditional on-site construction. Moreover, the high flexibility of 3DCP technique in construction to complex structures provides possibilities for achieving new types of low-carbon structural designs. Innovative designs like topological structural optimization, energy integration and rebuildable design can contribute to material saving, energy conservation and resources recycling. Low carbon material design has been one of the critical issues for low carbon 3DCP. From this aspect, the utilization of solid wastes, lightweight concrete, geopolymer concrete and fiber-reinforced concrete for 3D printing can provide effective solutions. Based on the collaborative development of technique optimization, structural design and material research, 3DCP technology will definitely promote the transformation of traditional construction industry towards automation and green low carbon in the future.

Existing studies on the charring properties of engineered bamboo generally suffer from deficiencies such as short duration of fire exposure and untimely extinguishing of fire. As an attempt to solve this problem, this study conducted comparative experimental tests on the charring properties of eight engineered bamboo columns exposed to four-side fire. The studied parameters included the material type, section size, fire direction, processing technology and fire exposure time. The results show that the section of engineered bamboo after charring can be basically divided into three areas, namely, charring layer, pyrolysis layer and normal temperature layer. The corner area of the engineered bamboo in the four-side fire changes from corner to arc due to heating from two directions. The charring rate of engineered bamboo decreases slightly with the increase of fire exposure time, and the charring rate of the specimen with larger section size is slightly lower. Under the same condition, the charring rate of bamboo scrimber is significantly lower than that of laminated bamboo. The charring rate of the transverse grain is slightly higher than that of the tangential grain, and the difference is not obvious when the fire time is longer. The charring performance of the bamboo scrimber compressed once is slightly better than that of the bamboo scrimber compressed twice. A numerical model was also proposed to predict for the charring properties of engineered bamboo. The numerical model can quickly simulate the charring performance of engineered bamboo, and the error of simulated charring rate is within 10.2%, which meets the engineering accuracy requirements. The proposed calculation model can accurately predict the charring depth of engineered bamboo. Based on the fire test and numerical simulation results, it is suggested that the nominal linear charring rate of laminated bamboo and bamboo scrimber for 1.00 h in fire design can be taken according to the standard T/CECS 1101—2022 ‘Standard for design of engineered bamboo structures’, namely 54 mm/h and 30 mm/h respectively for laminated bamboo and bamboo scrimber members.

In order to address issues such as poor durability of bamboo tubes leading to a short lifespan of traditional bamboo construction, weak performance of traditional bamboo culm structural joints, and high construction costs of modern bamboo culm spatial structures, a new approach was proposed. This approach involves a frame-unit prefabricated bamboo culm lattice structure system, composed of affordable standard fasteners connected straight bamboo culms. One key feature is that all joints require only two bamboo culms to connect, providing ample reinforcement space in the joint area. The fabrication process for planar polygonal frame units is straightforward, and the use of bolted connections makes the assembly process of the structure quick and convenient. Construction positioning is greatly simplified, as it only requires control of the vertical coordinates at the corner of the frame unit, reducing the complexity of construction for complex curved structures. The lifespan of structure can be extended by replacing deteriorated frame units in situ. This system has been proven feasible and reasonable through the construction of cylindrical, spherical, and hyperbolic paraboloid form buildings. Two enhanced structural forms, stacked and truss lattice structures, were proposed, and their effectiveness in improving structural load-bearing capacity and stiffness has been demonstrated through component loading tests. It is emphasized that in the development of new structural systems, increasing the level of industrialization in the production process and reducing costs in all construction phases are crucial for widespread application. Additionally, it is noted that the establishment of bamboo culm structural analysis and design theories will face critical challenges related to material nonlinearity, geometric nonlinearity, and interface contact.

Extending the service life of concrete structures is an effective way to reduce the average annual carbon emission during the life-cycle of structures. An analysis method of durability control strategy considering the service life and carbon emission of concrete structures was proposed. Based on the reliability theory,  three stages of deterioration process of concrete structure durability were considered, the influence of different durability control strategies on the reliability of concrete structures was studied, and the life calculation model and carbon emission calculation model of the durability control strategy of concrete structures were established. The quantitative index describing the effect of structural carbon reduction was put forward. By comparing the life-prolonging effect and carbon emission composition of different durability maintenance and repair methods, the service life and average annual carbon emission under different durability control strategies were calculated by considering the construction state and existing state of the structure respectively, and the life-prolonging and carbon reduction effects of different strategies were compared. The results show that the durability control strategy can extend the service life of the case structure by about 22 years and achieve 8.76% carbon reduction rate. In engineering practice, durability control strategies should be adopted for concrete structures as soon as possible in order to achieve better life-prolonging and carbon reduction effect.

To explore the impact of the inherent combustibility of cross laminated timber (CLT) on the fire temperature field within CLT compartments, a comprehensive approach combining numerical simulations and theoretical analysis was employed in this study. Firstly, a refined solid modeling of CLT components and the moveable fuel load (wood cribs) was carried out using a complex pyrolysis model in the FDS (fire dynamics simulator) software, establishing a CLT compartment fire test model. The results indicated that the complex pyrolysis model could reasonably reflect the pre-decay temperature development trends in the CLT compartment fires. It accurately predicted critical parameters such as the ignition temperature, peak temperature, and fully developed fire duration, with errors falling within the range of -3.4% to -27.8%, -1.1% to -12.5%, and 0.3% to 34.0%, respectively, when compared to existing experimental data. Secondly, as a progression from the preceding research, the moveable fuel load was simplified to a custom heat release rate burner based on the iBMB parameterized fire curve. This simplified modeling approach in FDS enhanced computational efficiency and generated temperature-time curves that closely aligned with experimental results during the fire growth and fully developed stages. However, it tended to overestimate the fully developed fire duration, extending it by 15 to 20 minutes. Finally, by considering the combustibility of wood, adjustments were made to the iBMB parameterized fire curve, involving modifications to fire load density and peak heat release rate. This led to the development of a hand-calculation model suitable for modeling the temperature-time curve in ventilated control-type CLT compartment fires. The calculated results closely matched experimental values, with errors in peak temperature remaining within 10%. In comparison to parameterized fire curves by other researchers considering wood combustibility, the modified iBMB parameterized fire curve hand-calculation model demonstrated superior accuracy in predicting fire growth time and temperature development during the fire decay phase.

To investigate the fire endurance of CLT-concrete composite slabs in fire, four CLT-concrete composite slab specimens and two CLT slab control specimens were designed and tested at normal temperature and in fire, respectively. Numerical simulation of the specimens was also conducted. The test results indicate that the failure modes of the CLT slab specimen at normal temperature basically include tensile failure along the grain of the bottom dimension lumbers, transverse grain splitting failure between the two adjacent layers of dimension lumbers, and rolling shear failure of the middle dimension lumbers. The failure modes of CLT-concrete composite slab specimen at normal temperature include shear failure at the interface between the cast-in-place concrete layer and the CLT panel, and tensile fracture failure of the bottom dimension lumbers along the grain. The initial stiffness and bending capacity of the CLT-concrete composite slab specimen at normal temperature are 237.8% and 60.1% higher than those of the CLT slab specimen. After being exposed to fire, there are obvious charring layers in the CLT panels, and the composite slab specimens have obvious bending deformations. Under the same load ratio, the fire endurance of the CLT-concrete composite slab specimen is 335.3% higher than that of the CLT slab specimen. With the load ratio increasing from 0.20 to 0.50, the fire endurance decreases from 74.1min to 30.6 min. The finite element model provides good prediction accuracy for the fire endurance of the CLT-concrete composite slab specimens, and the modelling errors are within 14.1%, which can satisfy the engineering accuracy requirements.