In-Situ Appraisal and Classification of Concrete Structures Prior Demolition: Chemical Composition Analysis Using Handheld X-ray Fluorescence Analyzer with Cement Type-Driven Separation

Abstract

Recycled concrete aggregates (RCA) have been recognized as a sustainable solution to satisfy the demand and address the environmental impacts of the concrete industry. However, construction engineers and contractors still have reservations about RCA due to their heterogeneous origin and lower quality compared to natural aggregates. It is essential to know the properties of the parent concrete, in particular its chemical composition, before demolishing concrete structures in order to identify the source of the raw materials. Despite its importance, this has never been done before. This thesis aims to analyze in-situ chemical composition of concrete and to identify the type of cement used in concrete structures by applying the non-destructive characterization technique of a handheld X-ray Fluorescence (hXRF) analyzer. To achieve this, laboratory experiments were performed to assess important factors in measuring cement paste and concrete surface chemical composition using the hXRF. These examined the impact of different water-to-cement (w/c) ratios, curing age, relative humidity, and carbonation on the chemical composition analysis with hXRF, and to gain valuable insights regarding the oxide concentrations of concrete and the most influential factors in hXRF measurements. The results indicated no impact on the chemical composition measurements with the hXRF despite the w/c ratios, the curing age, and carbonation. It was identified that higher relative humidity conditions than 75% affect the measurements with hXRF. Subsequently, three case studies were considered for the in-situ assessment of chemical composition. Conducting tests with hXRF demonstrated the device’s potential for analyzing concrete characteristic oxides (MgO, Al2O3, SiO2, SO3, CaO, Fe2O3). As a result, it facilitated cement-type recognition and provided valuable information regarding its opportunities and challenges. Drawing on insights from the literature review, laboratory experiments, and in-situ measurements, a guideline for in-situ testing of concrete composition was developed.