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All concrete structures contain reinforcement spacers, and deep sections can be affected by bleeding and segregation without displaying visible indications during casting. However, their effects on mass transport and long-term durability are not well studied. In this paper, reinforced concrete columns were prepared with plastic and cementitious spacers to achieve 50 mm cover, and compacted at different vibration frequencies and durations. 28d cured samples were extracted along the height, conditioned to equilibrium (21 °C, 75% RH or 50 °C, 7% RH), and then subjected to water absorption, electrical conduction, epoxy impregnation and fluorescence imaging. Samples from the top of the column consistently gave higher accessible porosity and mass transport compared to samples from the bottom. Presence of spacers caused additional increases in mass transport because of preferential flow through the spacer-concrete interface which is more porous and microcracked compared to bulk concrete farther away. Image analysis on cross-sections showed that the columns experienced some aggregate segregation despite care taken to avoid over-compaction. The resistance of concrete to ingress of aggressive agents decreases with increasing height due to the combined negative effects of reinforcement spacers and segregation.

Plastic waste greatly contributes to environmental pollution; therefore, using plastic waste in various applications, such as in concrete, is an important waste reduction strategy which could be contributed by the construction industry. This study presents the development of a concrete stress and strain model under compression for confined concrete specimens using polypropylene plastic as a substitution for coarse aggregate. Various short-column specimens were analyzed for stress and strain characteristics, effect of steel confinement, and compressive performance. Steel confinement increased the compressive strength and ductility of the section. The parametric identification of a stress-strain model defined for normal concrete was used in the experimental results to obtain new parameter values for the confinement coefficients k1 that are suitable for cylindrical and square lightweight concrete sections. The stress-strain diagrams for lightweight concrete of experimental cylinder and square column specimens, compared with the stress-strain modeled by the modified coefficients, indicate a fairly close agreement.

Stakeholder management has an important role in the success of the project because the strategies, plans, methods, and processes for stakeholders greatly determine the success of sustainable construction implementation. Lean construction is one of the principles in implementing sustainable construction by maximizing value and minimizing waste to increase productivity. This study aims to analyze the stakeholder engagement assessment matrix in lean construction, analyze the drivers and barriers in lean construction, and develop stakeholder engagement strategies to improve the implementation of sustainable lean construction. For this study, a questionnaire survey with 61 respondents was used. The data analysis method uses the Certainty Index, RII, Fuzzy AHP, and Fuzzy-TOPSIS. The findings of this research show that there are engagement gaps among stakeholders such as owners, contractors, consultants, subcontractors, architects, the government, local governments, and NGOs. There is no engagement gap between project suppliers and investors. The highest barrier to implementing sustainable lean construction is a lack of knowledge and skills in using lean tools and principles, while the highest driver to implement sustainable lean construction is improved time efficiency and process standardization. The best strategy for increasing stakeholder engagement is by having governments develop regulations and standardize green and sustainable materials.