Public defence in Building Technology, M. Sc. Hassan Ahmed

Title of the thesis: Evaluating Concrete Compaction: A Multi-modal Approach

Doctoral student: Hassan Ahmed
Opponent: Prof. Andrzej Cwirzen, Luleå University of Technology, Sweden
Custos: Prof. Jouni Punkki, Aalto University School of Engineering, Department of Civil Engineering

This study assesses the quality of concrete compaction by examining both segregation and entrapped air pores. The aim was to develop and refine methods for evaluating concrete compaction, focusing on monitoring segregation during compaction, evaluating segregation in hardened concrete, analysing surface bubble emergence, and characterizing entrapped pores. The thesis is relevant to ongoing research in concrete durability and construction practices, proposing the use of advanced techniques like AC Impedance Spectroscopy (ACIS), X-ray computed tomography (XCT), and Digital Image Analysis (DIA), which offer more accurate assessments of concrete quality than traditional methods. Key findings include the development of an ACIS measurement system correlated with aggregate distribution for real-time segregation detection, the proposal of three indices to evaluate segregation in hardened concrete, and insights that bubble emergence is an unreliable indicator of compaction quality. XCT analysis further revealed how concrete workability and compaction time influence entrapped pores characteristics, highlighting the complex relationship between compaction parameters and pore distribution. The study concludes that improving concrete compaction quality control requires considering both the extent of segregation and the content of entrapped air, emphasizing the inadequacy of traditional indicators like surface bubble emergence. The proposed segregation indices and analysis methods provide valuable tools for enhancing concrete durability and performance in construction practice.

Key words: Concrete compaction, concrete segregation, entrapped pores, compaction quality, electrical impedance spectroscopy, x-ray computed tomography, digital image analysis

Thesis available for public display 10 days prior to the defence at: https://aaltodoc.aalto.fi/doc_public/eonly/riiputus/

Contact information: Hassan Ahmed, [email protected], tel.: +358 45 257 7811

Doctoral theses of the School of Engineering: https://aaltodoc.aalto.fi/handle/123456789/49