Performance of Concrete Mixes Containing TBM Muck as Partial Coarse Aggregate Replacements

This study investigated the potential utilization of the TBM muck obtained from the Gold Line of the Doha Metro Project as a partial replacement of coarse aggregates in concrete mixes. First, the TBM muck particles were screened to coarse aggregate standard sizes. Then, concrete mixes were prepared using 0%, 25%, 50%, and 75% TBM muck replacement of coarse aggregates. The compressive and flexural strengths were determined for all mixes at 28 and 56 days. Moreover, the results obtained were validated using EDX analysis and SEM images. A t-statistical analysis did not show a significant impact of TBM muck usage on the compressive strength results of the concrete mixes. However, another t-statistical analysis showed that TBM muck replacement of coarse aggregates had adversely affected the flexural strength results. The EDX analysis indicated the presence of Na+ ions, which can replace the Ca2+ ions in the C-S-H gel, cause discontinuities of it, and hence reduce the strength at later ages. Finally, the SEM images showed that the ettringite and carbon hydroxide (C-H) contents in the mixes with TBM muck were higher than that of the control mix, while the C-S-H gel was less in such mixes.

Factor Analysis of Construction Waste in Riyadh Metro Project, KSA

Development of the infrastructure is favorable for the growth and economy for any country; however, the issues to manage construction waste due originating from development exercises is a noteworthy reason for concern. The waste from construction contributes to negative repercussions on time, cost, productivity, and environment. Therefore, to reduce these negative and undesirable effects, a detailed review of waste generation and management must be provided. The significant construction waste causes were identified and grouped into seven clusters: construction management, design, construction material procurement, construction material handling, construction site condition, and external factor. A total of 150 questionnaire survey forms were distributed to professionals working on the Riyadh metro project, and only 118 questionnaire forms were received. The collected data from the questionnaire is analyzed using the average index and factor analysis. Analysis identified that ‘Design errors; ‘Accidents; ‘Damage during handling’; ‘Communication problems; ‘Frequent variation orders’ ; ‘Congestion of the site’ and ‘Damage caused by workers’; are highest significant causes in each category respectively. Furthermore, factor analysis was conducted through Exploratory Factor Analysis (EFA) technique to the top fifteen (15) factors and found five factors responsible for the construction waste was identified such as management, workers issues, material related issues, improper handling, and design. The findings from this study are useful for policymakers to develop or/and enhance recommendations on construction waste generation to prevent problems in construction industries. The government or building industry should establish or strengthen regulations that regulates how construction materials should be disposed of.

PPP for Metro Project: A Case Study of Hyderabad Metro

The new metro rail policy was enacted by the government of India in the year 2017. Under this policy, under section xiv, the Government of India (GOI) made it compulsory to seek Public-Private Partnership (PPP) for metro projects which are intending to seek financial assistance from the central government. Hyderabad Metro is by far the largest metro project to be executed under PPP, but is it successful? This paper investigates various factors that affected the timeline of the Hyderabad metro. It evaluates various aspects in the preconstruction, construction, and post-construction phase of the Hyderabad metro. Finally, suggestions are made in the form of conclusions that would increase the likelihood of a successful PPP in the metro.

Performance of Flowable Concrete in Underground Structures

Flowable concrete gives special combinations of uniformity, performance and consistency requirements that cannot be possible by traditional normal slump concrete. It is more superior concrete than the traditional concrete with high workability without segregation, bleeding, and is also suitable for use on structures with long distance pumping i.e., more than 120-meter length, for example, in NATM tunnels and cross-passages, and the concrete structure of the station box. Flowable concrete can flow itself without vibration or little bit vibration like surface tamping outer surface of the formwork for achieving a smooth surface finish after de-shuttering. The proportion of the mix is to be used in concrete, it must ensure a balance between deformability and stability. The behavior of concrete can be influenced by the properties of the selected item in the concrete, and the aspect ratio of the mixture. There is a need for the development of a methodology for the design of the flowable concrete mix. The paper presents an experimental procedure for the mix design of flowable concrete for grade M40 and implementation of the same mix at the cast in situ Base slab, Roof slab Rcc walls for underground metro stations, NATM tunnel & cross passages in Mumbai Metro Project, package -UGC-07. The test results for acceptance characteristics of M40 grade flowable concrete such as Slump flow test, compressive strength at the ages of 7, 28, and 56 days determined, and results are included here. Successful production of temperature control flowable concrete from batching plant, transportation, placement procedures, and proper planning of handling and execution of flowable concrete at the site are presented in this article.