Use of Non-destructive X-ray Microscopic Techniques to Study Fluid Transport in Cement-based Materials

Most of the urban infrastructure is made of concrete with a design service life of over 50 years. Unfortunately, many concrete structures suffer from premature deterioration due to durability issues, most commonly caused by corrosion. The external penetration of ions into cementitious materials is the primary factor influencing the long-term durability of concrete structures. Current test methods to study ion transport in cement-based materials are typically destructive, time consuming, labor intensive, and have a poor spatial resolution to study complex transport phenomenon and capture the effect of complex geometries on fluid transport. In addition, there is little knowledge of the dynamic process of fluid penetration into cement-based materials because few experimental techniques are able to give quantitative spatial measurements of the fluid movement without damaging the sample. This study aims to develop a systematic approach to use micro X-ray fluorescence (�XRF) and Transmission X-ray microscopy (TXM) to study ion transport in different cementitious systems. Examples were shown where these powerful, non-destructive techniques can identify the influence of local abnormalities on ion transport with high spatial resolution and can image the early age combined ion transport mechanisms in real time. The current study uses these techniques to evaluate and compare the time-dependent resistance of different alternative cementitious materials (ACMs) to ion penetration. In addition, the effect of degree of saturation, which is a crucial factor in durability of cement-based materials, on ion penetration into partially-saturated samples were investigated by using the developed X-ray imaging techniques. Furthermore, the performance of silane treatments, which is a commonly used surface treatment to reduce fluid entry into concrete was evaluated by �XRF. Also, the effective lifespan of this treatment in concrete bridge decks was determined. The use of developed techniques and observed results from this study helps to expand our understanding of ion transport in cement-based materials and to greatly improve the current models of mass transport and service life predictions of the concrete. This can help a large amount of money to be saved in repair, maintenance, and management of concrete structuresCivil Engineerin

Expected life of silane water repellent treatments on bridge decks phase 2 / M. Tyler Ley, Mehdi Khanzadeh Moradllo.

This report outlines the investigation of the service life of silane sealers on Oklahoma bridge decks as well as laboratory investigation of a silane sealer and a two part sealer that uses both silane and epoxy. The performance of silanes on bridge decks was completed on 60 bridges that were in service between 5 to 20 years. Samples were taken from the travel lane and the shoulder. The work found that after 12 years that 100% of the silane applications were effective. By 15 years then only 68% were still effective and between 17 to 20 years then only 16% were still effective. The investigations suggest that abrasion was not a major deterioration mechanism; instead, deterioration from the high alkaline pore solution is suggested to be of importance. This work goes on to investigate a two part system of silane and epoxy sealer, a silane, and then a control sample and their resistance to chloride penetration. Both sealers show improved performance over the sample with just concrete. Additionally, a new experimental technique is presented that is capable of non-destructively imaging the penetration of external fluids into paste and mortar. This test is rapid, accurate, and can be used for in-situ testing. This test method again shows that the silane investigated was effective at reducing the ingress of ions.Final report, October 2013 _ September 2015N

Examining Curing Efficiency using Neutron Radiography

Many state highway agencies use prescriptive specifications for the curing of concrete bridge decks, pavements, flatwork, or structural elements. For example, concrete pavements are frequently specified to have a curing compound applied shortly after placement and bridge decks typically require seven days of wet curing. These specifications are often based on historical practices that have developed over the last century as opposed to quantitative measurements of performance. New approaches to curing are being introduced which include advanced curing compound formulations or internal curing, for example. However, clear information is not always available as to how this may affect curing requirements. This paper demonstrates the potential to use neutron radiography to quantify the degree of hydration at various distances from the finished surface. It describes how different curing approaches affect cement hydration in terms of both time and distance from the surface. The results show that in a sample exposed to drying after one day the top 12.5 mm (1/2 in) of the mortar was dramatically affected by evaporation, and the degree of hydration in this region was 32% lower than in a 14-day moist-cured sample. Also, the use of superabsorbent polymers increased degree of hydration by about 3.7–7.8% for sealed samples and samples exposed to drying. While these results are preliminary, it is believed by the authors that neutron radiography provides a powerful approach that could be used to determine equivalent curing requirements for new materials. </jats:p

Data for Novel Alternative Cement Binders for Highway Structures and Pavements

The contents of data file include raw data for all the data plots included in the final report titled Novel Alternative Cement Binders for Highway Structures and Pavements. The excel spreadsheets were named based on chapter numbers in the final report.The ubiquity and the necessity of concrete infrastructure prompts innovation in addressing the global challenge of meeting societal needs in the most sustainable and economical ways possible. Increasing the use of non-portland cements or “alternative cementitious materials” (ACMs) is increasingly of interest due to their special properties and to their potential to reduce the environmental footprint of concrete. The special properties of ACMs may vary by material but include rapid setting, rapid strength development, higher ultimate strength, improved dimensional stability and increased durability in aggressive environments. The increased strength and increased durability further contribute to enhanced service life which can help offset initially higher materials costs, and also to enhanced sustainability. In the past, most ACMs have primarily been used in specialty limited applications and some of them have been shown in lab-scale studies to be feasible for the partial or full replacement of traditional portland cements used in concrete. However, there is limited understanding of the scalability of construction with these material systems, their long-term performance and durability in a range of environments, and their structural response when subjected to transportation-relevant loading conditions. This data presents the results from the comprehensive investigation of the applications of these commercially available ACMs in durable and sustainable transportation infrastructure, which include the early-age and long-term material properties as well as complete multi-scale durability investigations.Office of Infrastructure Research & Development, Federal Highway Administration, 6300 Georgetown Pike, McLean, VA 22101-2296. Grant number: DRFH61-14-H-000