Ultra-high performance concrete (UHPC) is a class of concrete materials that has received significant attention from the infrastructure community due to its favorable mechanical and durability performance. As the use of UHPC in infrastructure projects is becoming more common, there is an increasing interest in identifying appropriate testing techniques to assess the durability properties of UHPC-class materials. The dense microstructure of UHPC-class materials and the presence of a high concentration of fiber reinforcement have made it difficult to rely on existing standard testing approaches for concrete durability assessment. This study explores the application of various conventional-concrete durability test methods to UHPC, including electrical resistivity (American Association of State Highway and Transportation Officials (AASHTO) TP 119-22), freeze–thaw (ASTM C666), water absorption (ASTM C1585), and rapid chloride migration test (NT BUILD 492). The selected tests are meant to qualify and quantify the microstructural penetrability of UHPC to ions and fluids, a surrogate property commonly used as an indicator of durability. The findings from this study indicate that electrical resistivity can be used as a durability indicator for UHPC-class materials. Moreover, strong correlation between electrical resistivity and the chloride migration coefficient is identified, a potential benefit given that chloride migration can be used to estimate service lives of UHPC-class materials. Other tests, including freeze–thaw and water absorption, although identifying the favorable performance of UHPC relative to conventional concrete, were unable to provide insightful information through which the performance of individual UHPCs could be differentiated.

The setting behavior of ultra-high performance concrete (UHPC) is demonstrably different from that of conventional concrete; thus, tools and guidance extending beyond common test methods such as Vicat and penetration are needed. While UHPC is known for its enhanced mechanical and durability properties, due to the low water and high cementitious contents, UHPC-class materials are prone to early-age autogenous shrinkage. Recognizing that UHPCs are commonly supplied to construction sites as prebagged, proprietary mixes with unknown constituents, and that accurate determination of setting time is crucial in determining the early-age autogenous shrinkage of UHPC-class materials as well as for scheduling construction operations and quality control actions, this study explores alternate test methods such as isothermal calorimetry (ASTM C1679), semi-adiabatic calorimetry (ASTM C1753), autogenous shrinkage (ASTM C1698), chemical shrinkage (ASTM C1608), and dual ring test (American Association of State Highway and Transportation Officials (AASHTO T 363) to evaluate the setting behavior of UHPCs. Setting times obtained using the alternate test methods aligned well with each other and were found to be different than the setting times indicated through standard test methods. Discussion and guidance on the applicability and the use of alternate test methods to determine the setting time of UHPCs for various laboratory and field applications are provided.

Concrete pavement durability in the United States is an important characteristic that owners are considering in new construction and rehabilitation projects, and many are including durability tests in the next generation of their specifications. Specifically, focus has fallen on electrically based testing owing to its rapid testing time and economical testing equipment. Results from electrically based tests have also been shown to be good inputs to service life models and can correlate with a wide range of other material properties used to understand how ions and fluid are transported through concrete. This study aimed to correlate the two most common electrically based test results (resistivity and formation factor) with more established and involved tests of transport properties, such as rapid chloride migration and water absorption. The major difference between these two tests resides in the conditioning solution, which is typically limewater for resistivity and an alkali-concentrated solution for the formation factor. Based on the results, both electrical resistivity and formation factor were deemed acceptable tools for mixture approval and acceptance, though formation factor demonstrated higher correlations with the other transport properties and, therefore, was preferrable for performance modeling. Overall, concrete resistivity and formation factor measurements at ages beyond 28 days could be used to indicate the durability of a concrete material during its lifespan. During the investigation, the authors observed that compressive strength measurements were independent of the type and volume of the conditioning solution.

Due to the declining availability of coal fly ash, there is a need to identify alternative sources of supplementary cementitious materials (SCMs). This article presents an investigation on the reactivity of ground and sieved bio ash that can be used as alternative sources of SCM. The oxide contents of bio ash are similar to Class-C coal fly ash. Accordingly, bio ash was found to have both hydraulic and pozzolanic reactivity. Ground bio ash showed higher heat of hydration and similar compressive strength compared to coal fly ash at the early stage (i.e., up to 7 days) of cement hydration due to the hydraulic reactivity. Grinding the bio ash improved its pozzolanic reactivity by 25% as per the modified Chapelle test. Using bio ash as SCM was also found to increase the ettringite formation in cement matrix. Nevertheless, the potential of excessive expansion of the paste samples due to the ettringite formation was found to be negligible.

Proprietary, prepackaged materials such as some cementitious grouts and ultra-high performance concretes (UHPC) are commonly used in the bridge construction industry due to their convenience and desirable properties. However, due to particularities of their mixture designs, grouts and UHPC are prone to exhibit shrinkage, thus resulting in potential durability issues. This paper describes a step-by-step methodology for including internal curing (IC) in these types of materials, with the main goal of addressing some of their shrinkage and durability issues. A brief analysis of the relative cost implications is also provided, along with a compilation of experimental results to show the effect that IC has on important material properties. The results from this study indicate that the inclusion of IC in cementitious grouts and UHPC has the potential to increase durability, leading to more sustainable bridge structures with longer service lives.