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Determining the in-place properties of mass concrete placements is elusive, and currently there are minimal to no test methods available that are both predictive and a direct measurement of mechanical properties. This paper presents a three-stage testing framework that uses common laboratory equipment and laboratory-scale specimens to quantify thermal and mechanical properties of mass high-strength concrete placements. To evaluate this framework, four mass placements of varying sizes and insulations were cast, and temperature histories were measured at several locations within each placement, where maximum temperatures of 107 to 119°C (225 to 246°F) were recorded. The laboratory curing protocols were then developed using this mass placement temperature data and the three-stage testing framework to cure laboratory specimens to represent each mass placement. Laboratory curing protocols developed for center and intermediate regions of the mass placements reasonably replicated thermal histories of the mass placements, while the first stage of the three-stage framework reasonably replicated temperatures near the edge of the mass placements. Additionally, there were statistically significant relationships detected between calibration variables used to develop laboratory curing protocols and measured compressive strength. Overall, the proposed three-stage testing framework is a measurable step toward creating a predictive laboratory curing protocol by accounting for the mixture characteristics of thermomechanical properties of high-strength concretes. [ABSTRACT FROM AUTHOR]

Over 450 cores were extracted from roadways throughout Mississippi to provide a realistic picture of mechanical properties in later-age chemically stabilized soil. Cores ranged from 10 to 54 years old and were stabilized with either lime-fly ash, cement, or lime. Indirect tensile strength (IDT), unconfined compressive strength (UCS), and elastic modulus (E) tests were used to quantify mechanical properties. Generally speaking, IDT, UCS, and E values tended not to exceed 250, 1500, and 1,500,000 psi (1724 kPa, 10,342 kPa, and 10,342 MPa), respectively, in pavements over 10 years old. Cores were also compared to mechanical property relationships found in the 1993 AASHTO design guide and the Mechanistic-Empirical Pavement Design Guide (MEPDG) and the literature to determine their applicability to later-age pavement properties. Relationships from the literature comparing IDT to UCS were generally good predictors of later-age property relationships; however, relationships between E and UCS were not good predictors of later-age strength as most equations did not account for the decrease in E development over time when compared to UCS. [ABSTRACT FROM AUTHOR]

This paper evaluated constituent proportions on mechanical and thermal properties of ultra-high-performance concrete. This paper assessed how fine aggregates and fibers at varying proportions enhance cement paste and can improve its mechanical properties to a desired compressive strength, elastic modulus, or tensile strength. Approximately 400 specimens were tested for mechanical properties within four curing regimes and 22 different mixtures. These experiments aimed to add to the body of knowledge found during literature review. Past efforts found in literature have drawn conclusions by varying one ingredient at a time, whereas the current effort systematically varied multiple ingredients. Results showed compressive strength to be due to synergistic relationships between cement paste, fine aggregates, and steel fibers where absence of any ingredient reduced strength. Tensile strength and elastic modulus were dominated by a single ingredient. [ABSTRACT FROM AUTHOR]

Aggressive use of supplementary cementitious materials (SCMs) in concrete is becoming more appealing due to potential for cost effectiveness, reduced environmental impact, enhanced durability, and increased sustainability. Constructability, though, is often less attractive as time of set and early strength development can be delayed. This paper investigated the merits of incorporating portland-limestone cement (PLC) to improve concrete sustainability and performance when rounded gravel aggregates (most sustainable for some markets) were used in conjunction with dual SCMs proportioned for 50 % to 70 % total cement replacement. The family of concrete mixtures evaluated have not been widely studied with PLC (in the US or elsewhere). Mixtures containing PLC designed for improved synergies in the US construction market were compared to similar variations containing ordinary portland cement (OPC). PLC was shown to be able to produce concrete mixtures of greater compressive strength and lower set times compared to OPC in some, but not all, conditions. Individual mixture performance varied based on SCM use, PLC properties, and aggregate properties. [ABSTRACT FROM AUTHOR]

Objective. To describe the utilisation and safety of air medical services (AMS), when being used for inter-facility transfers of paediatric patients in the Western Cape Province, South Africa. Methods. A retrospective descriptive analysis was conducted for the time period January 2010 to December 2011. Data were recorded from the Cape Town base of the AMS provider for the Western Cape Provincial Department of Health Emergency Medical Services. Patient demographics, flight and transfer details, interventions performed and adverse events encountered were documented for all patients <13 years of age transferred by either helicopter or fixed-wing aircraft. Results. A total of 485 patients was analysed. More patients were transported by helicopter (n=263, 54%), with neonates making up the largest category for both modes of transfer. Respiratory (29%), neurological (18%), cardiac (14%) and gastrointestinal disorders (14%) made up the majority of non-traumatic reasons for transfer. Overall, transfers by helicopter were quicker (median mission time 03:00; interquartile range 02:32 - 03:25) compared with fixed-wing transfer (05:24; 04:22 - 06:20). The overall incidence of adverse technical events was relatively high (20%). Physiological adverse events ranged between 2% and 16% overall depending on the variable measured. The incidence of cardiac/ respiratory arrest and endotracheal tube obstruction/dislocation was low (<2%). Emergency intubation and desaturation >10% from baseline were the most common critical adverse events encountered (6%). Conclusion. Current utilisation of the AMS for paediatric inter-facility transfer is relatively high, at ∼25%. Across both the helicopter and fixed-wing platforms, patients with a diverse range of pathologies of equally varying severities were transferred. The adverse events observed were found to be lower than those of trials examining non-specialised paediatric transfer, and were comparable to those seen with transfer by specialised paediatric retrieval teams. The AMS remain a safe and viable alternative to non-specialised paediatric transfer, and may serve as a potential alternative to specialised paediatric transfer in the Western Cape. [ABSTRACT FROM AUTHOR]

The measurement of geosynthetic strain is important to the development of numerical models that can predict the behavior of geosynthetic-reinforced flexible pavements. This paper outlines the key issues regarding foil strain gage selection, installation, and calibration on geosynthetics for dynamic strain measurement in roadway applications. The flexible nature of geosynthetics and the interaction of these materials with the adjacent layers of the pavement structure in a dynamic loading application limit the ability to use all types of strain gages and adhesives. While this paper does not cover every type of geosynthetic, it provides sufficient procedural details and illustrations of foil strain gage installations on a variety of geosynthetics (woven geotextiles and geogrids, nonwoven geotextiles and punch/drawn geogrids) and then outlines several alternative methods (wire extensometers, inductance coils and fiber optics) of dynamic strain measurement. While foil strain gages and closely spaced wire extensometers provide a localized value of displacement on a geosynthetic, wire extensometers and inductance coils provide a measure of global displacement (which includes slack in the geosynthetic) and redundancy in total strain measurements. Fiber optics is an emerging and very promising method of accurately measuring strain in geosynthetics, and at least one delivery system has been developed. [ABSTRACT FROM AUTHOR]