Quantitative measurement of the influence of degree of saturation on ion penetration in cement paste by using X-ray imaging

Abstract

The external penetration of ions into concrete plays an important role in long-term durability of concrete structures. In addition, the degree of saturation (DoS) of the paste has a large impact on rate and mechanisms of fluid penetration into concrete. There is little knowledge of the dynamic process of fluid penetration into these materials because few experimental techniques are able to give quantitative spatial measurements of the fluid movement without damaging the sample. This paper uses laboratory transmission X-ray microscopy (TXM) to investigate the in-situ penetration of an iodide based tracer into cement paste with water-to-cement ratio of 0.40 conditioned at four different relative humidities (RH). This technique can non-destructively image the distribution of the dissolved ions at 8.8 m resolution in minutes. In addition, micro X-ray fluorescence (µXRF) imaging and conventional gravimetric measurements were used to compare I and Cl penetration rate and validate the results from TXM. Mathematical models have been proposed to account for ion penetration in partially-saturated samples. The results show that samples that were ponded for two days after being conditioned in 35% and 70% RHs (DoS of 40.8% (± 0.1%) and 68.8% (± 0.5%) respectively) show a 40x and 10x increase respectively in the penetration coefficient over the saturated sample. Furthermore, important insights about combined ion transport mechanisms have been observed from concentration profiles by TXM.

Performance Evaluation of Silane in Concrete Bridge Decks Using Transmission X-ray Microscopy

“…The iodide The diffusion test in this study used a potassium iodide (KI) tracer on top of the unwaxed surface of the samples. X-rays were used to take images before and after applying KI on top of the samples to study the one-directional mass transport into the samples for 28 days [3,5,47]. In this test, the gravity and moisture movement in the samples were in the same direction.…”

Enhanced recyclability of waste plastics for waterproof cementitious composites with polymer-nanosilica hybrids

“…neutron radiography [80]). Therefore, several studies have used different contrast agents to enhance the visualization of water in l-XCT images, such as, cesium (Cs) [33,77,78,[81][82][83] and iodide (I) [84][85][86][87] solutions. For instance, when a small amount of soluble cesium-based salt (e.g.…”

Estruturas De Concreto Armado Revestidas Com Argamassa: Um Método Para Avaliar O Grau De Saturação E O Coeficiente De Difusão Do Concreto E Argamassa No Mesmo Ambiente, Frente Ao Ataque De Cloretos

“…A influência do GS sobre a difusão de íons cloreto tem sido objeto de inúmeras pesquisas, sendo demonstrada a sua importância em modelos de análise de vida útil de estruturas de concreto armado e protendido. Entre vários desses estudos, pode-se citar: Guimarães e Helene (2000,2007), Climent et al (2002Climent et al ( , 2007, Souza (2005), Guimarães et al (2011), Bandeira et al (2015), Moradllo (2017), Savoye et al (2018) e Zhang et al (2020).…”