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Polyurethane concrete has a high strength-to-weight ratio in the short term, and the strength-to-weight ratio stage during the maintenance period is critical. Freeze-thaw cycles have a noticeable damaging effect on the durability of polyurethane concrete. The engineering specification of polyurethane concrete with incomplete hydration reaction must be studied, as well as the development of internal structure during curing. In this paper, the polyurethane concrete tests were set up under eight distinct maintenance settings based on the climate features of the northern area and the service environment. The test results were evaluated to determine the effect of the number of early freeze-thaw cycles and the time node of early freeze-thaw cycles on the mechanical characteristics of polyurethane concrete, which revealed that the time node of freeze-thaw damage impacted the freeze-thaw resistance of polyurethane concrete susceptible to early freeze-thaw damage.

The early-age freeze-thaw damage polyurethane concrete was experimentally studied by controlling the time node of the freeze-thaw cycle and the curing environment. The test considered the time node, frequency of freeze-thaw damage of polyurethane concrete and the influence of subsequent curing environment and observed the mass change, relative dynamic elastic modulus, relative durability index, compressive strength and apparent damage of polyurethane concrete. The early mechanical properties of polyurethane concrete were studied by analyzing the change of numerical value. The microscopic mechanism of strength formation of polyurethane concrete was analyzed by XRD, FTIR and SEM image.

The closer the time of freeze-thaw damage was to the specimen hardening, the worse the mechanical properties and structure were, according to SEM photographs. For specimens with serial number of 12-groups, its compressive strength is only 82.39% of that of the standard group, even if the curing process continues after 20 times thawing, which increased early environment exacerbate strength loss in polyurethane concrete and also reduced freeze-thaw resistance. The findings of the tests reveal that curing can restore the freeze-thaw resistance of damaged polyurethane concrete. Curing in water has a better recovery impact than curing in air; the mechanical properties can be restored by sufficient re-curing time and good re-curing conditions.

By studying the freeze-thaw cycle test and test results of polyurethane concrete in different curing time nodes, the relationship between the mechanical properties of polyurethane concrete and the time node, number of freeze-thaw cycles, and subsequent maintenance environment was explored. Considering the special mechanism of strength formation of polyurethane concrete, the polyurethane concrete damaged by freeze-thaw has the ability to continue to form strength under subsequent maintenance. This experimental study can provide an analytical basis for the strength formation and reconditioning of polyurethane concrete structures subjected to freeze-thaw environments during the curing time under extreme natural conditions in fall and winter in actual projects.

This study investigates the impact and economic viability of energy-efficient building envelope and orientation for contributing net zero energy building (NZEB) and suggests optimum thermal insulation thickness, optimum wall thickness, appropriate orientation and glazing types of window in the contexts of unique Bangladeshi subtropical monsoon climate.

The whole study was conducted through energy simulation perspective of an existing office building using building information modeling (BIM) and building energy modeling (BEM) tools which are Autodesk Revit 2017, Autodesk Green Building Studio (GBS) and eQUEST. Numerous simulation patterns were created for energy simulation considering building envelope parameters and orientations. A comprehensive data analysis of simulation results was conducted to sort out efficient passive design strategies.

The optimum thermal mass and thermal insulation thickness are 6.5 and 0.5 inches, respectively, considering energy performance and economic viability. This study highly recommends that a building should be designed with a small window-to-wall ratio in the south and west face. The window should be constructed with double glazing Low-E materials to reduce solar heat gain. The studied building saves 9.14% annual energy consumption by incorporating the suggested passive design strategies of this study.

The output of this work can add some new energy-efficient design strategies to Bangladesh National Building Code (BNBC) because BNBC has not suggested any codes or regulations regarding energy-efficient passive design strategies. It will also be useful to designers of Bangladesh and other countries with similar subtropical climatic contexts which are located in Southeast Asia and Northern Hemisphere of Earth.

Irregularly shaped architectural designs with surfaces curved in multiple directions, known as free-form designs, have gained significant public interest in recent decades. However, it is challenging to convert complex designs into real structures. This paper aims to realize free-form construction by developing a novel workflow in which additively manufactured thermoplastic polyurethane (TPU) molds are used.

The workflow is developed through mechanical tests on additively manufactured TPU specimens, determination of TPU mold design criteria and exploration of mold preparation methods. Two concrete elements with free-form geometries are fabricated using the proposed workflow.

TPU is a thermoplastic elastomer that is strong and inexpensive, making it an ideal mold material for casting complex concrete structures. An innovative workflow is developed in which TPU molds are used, appropriate release agents are selected for different concrete casting conditions and a mold subdivision method is proposed to facilitate the demolding process. Furthermore, the integrity of TPU molds can be maintained by following the proposed workflow, enabling repetitive use of molds. The fabrication of the two free-form structures shows that complex concrete members with high dimensional accuracy and excellent surface quality can be manufactured using the proposed method.

To the best of the authors’ knowledge, this is the first systematic study on using additively manufactured TPU molds for concrete casting of complex structures. The new techniques developed in this research can be applied to large-scale architectural, engineering and construction projects.

As the service time of bridges increases, the degradation of bending capacity, the lack of safety reserves and the decrease in bridge reliability are common in early built bridges. Due to the defective lateral hinge joints, hollow slab bridges are prone to cracking of hinge joint between plates, transverse connection failure and stress of single plates under the action of long-term overload and repeated load. These phenomena seriously affect the bending capacity of the hollow slab bridge. This paper aims to describe a new method of simply supported hollow slab bridge reinforcement called polyurethane–cement (PUC) composite flexural reinforcement.

This paper first studies the preparation and tensile and compressive properties of PUC composite materials. Then, relying on the actual bridge strengthening project, the 5 × 20 m prestressed concrete simply supported hollow slab was reinforced with PUC composites with a thickness of 3 cm within 18 m of the beam bottom. Finally, the load test was used to compare the performance of the bridge before and after the strengthening.

Results showed that PUC has high compressive and tensile strengths of 72 and 46 MPa. The static test revealed that the measured values and verification coefficients of the measured points were reduced compared with those before strengthening, the deflection and strain were reduced by more than 15%, the measured section stiffness was improved by approximately 20%. After the strengthening, the lateral connection of the bridge, the strength and rigidity of the structure and the structural integrity and safety reserves were all significantly improved. The application of PUC to the flexural strengthening of the bridge structure has a significant effect.

As a new type of material, PUC composite is light, remarkable and has good performance. When used in the bending strengthening of bridge structures, this material can improve the strength, rigidity, safety reserve and bending capacity of bridges, thus demonstrating its good engineering application prospect.

Polyurethane concrete (PUC), as a new type of steel bridge deck paving material, the bond-slip pattern at the interface with the steel plate is not yet clear. In this study, the mechanical properties of the PUC and steel plate interface under the coupled action of temperature, normal force and tangential force were explored through shear tests and numerical simulations. An analytical model for bond-slip at the PUC/steel plate interface and a predictive model for the shear strength of the PUC/steel plate interface were developed.

The new shear test device designed in this paper overcomes the defect that the traditional oblique shear test cannot test the interface shear performance under the condition of fixed normal force. The universal testing machine (UTM) test machine was used to adjust the test temperature conditions. Combined with the results of the bond-slip test, the finite element simulation of the interface is completed by using the COHENSIVE unit to analyze the local stress distribution characteristics of the interface. The use of variance-based uncertainty analysis guaranteed the validity of the simulation.

The shear strength (τ_f) at the PUC-plate interface was negatively correlated with temperature while it was positively correlated with normal stress. The effect of temperature on the shear properties was more significant than that of normal stress. The slip corresponding to the maximum shear (D₁) positively correlates with both temperature and normal stress. The interfacial shear ductility improves with increasing temperature.

Based on the PUC bond-slip measured curves, the relationship between bond stress and slip at different stages was analyzed, and the bond-slip analytical model at different stages was established; the model was defined by key parameters such as elastic ultimate shear stress τ₀, peak stress τ_f and interface fracture energy G_f.

Research deals with aspects of systemic thinking that explain environmental innovation in organizations, especially in the construction sector. The paper aims to address the issues.

The research for this paper is based on the collection and analysis of quantitative and qualitative data, dialectal systems theory (DST), environmental management systems (EMS), life cycle analysis (LCA) and recycling.

The research results show that systemic thinking (and environmental innovations) are still a novelty; it can be regarded as an engine for novel changes in social, economic and political arrangements in companies and other organizations as well as for society as a whole. Research is aimed at finding an answer to the question: what dialectal system approach can bring in the long‐run sustainable development?

Research was limited to management of construction.

Environmental innovation efficiency and processes in organizations with a systemic thinking can be innovated more easily.

This paper breaks new ground in using systemic thinking to explain environmental innovation. In research, a model is proposed for recycling isolating materials, made of hard polyurethane and lightweight concrete with aggregates containing expanded glass, based on DST, EMS, LCA and recycling. This is the first attempt, to the best of one's knowledge, to make a new synergy of the dialectal systems theory, environmental management system and innovations supporting sustainable development, decision making and action.

The purpose of the study is to present a simplified model to replace the complicated foaming simulations for investigating the liquid polyurethane behavior just before solidification.

This model is inspired from the traveling heater method of crystallization because of the low injection velocity. Besides, the heat generated during the reaction is considered as a heat source function in the energy equation.

Various distributions of the heat generation function inside the geometry have been studied to choose the most realistic one. Effect of parameters such as the soil material and porosity on the temperature distribution and flow field are examined for different values of heat flux on the boundaries. Results show an almost linear dependency of pressure drop to the velocity, a uniform velocity profile and an expected temperature distribution compared to literature, which approves the suggested model.

A new model is presented in this study for foaming which replaces a heat generation function (exponential) in the source term of the energy equation instead of the heat produced at the exit boundary (the solid–liquid interface), and the traveling method is used instead of moving the geometry; besides, the growth ratio has been neglected; therefore, this model has been validated by a foaming simulation to confirm the suggested simplified idea.