Compressive Strength of Concrete Cylinders by Different Preparation Methods: Sulphur, Neoprene Pads and Grinding

The purpose of this evaluation is to compare the effects of four types of cylinder preparation methods prior to compressive strength testing in accordance to ASTM C 39

We Mean Green Environmental Science Club

Lesson Plans for an Environmental Science Club. This club seeks to promote environmental awareness to elementary students through hands-on activities, videos, and discussion

Evaluation of Nebraska’s Aggregate Reactivity by the Miniature Concrete Prism Test Method – AASHTO T380

The evaluation of nine different aggregates shows the viability of the T380 test method as an alternative to the standard C1293 test method. The T380 assesses the Alkali-Silica Reaction potential of aggregates with the same reliability as C1293 and correlates well with the C1293 test method. Results are obtained within 56 days by T380 compared to 365 days required by C1293. The T380 method at 56 days appears to characterize the aggregate reactivity similarly to C1293 for all the aggregates evaluated in this study. Therefore, T380 will be part of the Department test method for approval of interground/blended cements along with the ASTM C1567-Standard Test Method for Determining the Potential Alkali-Silica Reactivity of Combinations of Cementitious Materials and Aggregate. The Department has changed the specification for approving IP or IT cements to allow the use of T380 after the Department has completed the test method C1567. Per the specification, the mortar bars shall not exceed 0.10% expansion at 28 days while performing C1567. If the expansion is greater than 0.10% at 28 days while performing C1567, then the interground/blended cements shall be tested in accordance with AASHTO T380 using fine aggregate from an approved Platte River Valley and/or Elkhorn River aggregate source with an expansion not greater than 0.02% at 56 days

Effect of Moisture Condition on Concrete Core Strengths

The main purpose of this study was to determine if there would be any major differences between curing methods of cores taken for acceptance testing from a highway slab on a project. The comparison provided data to determine the effect of the moisture gradients created by these different curing treatments on core strength and core permeability. The strengths were measured of moist cured cores and sealed plastic bag cured cores from the day cores were obtained (14, 21 and 26 days) until they reached 28 days. Permeability was also measured at 26, 28 and 32 days. According to ASTM C42, it is current practice to allow the cores to remain in a sealed condition with a plastic bag or non-absorbent containers for at least 5 days prior to testing unless otherwise specified by the engineer. Currently, Nebraska Department of Transportation (NDOT) follows the ASTM C42 with the exception that all cores obtained for compressive strength testing must be delivered to the PCC Lab in a sealed bag, un-bagged and stored immediately in a moist cure room until the required 28-day testing. The findings from this study show no significant difference in strength nor in permeability between curing concrete core samples in bags versus storing them in a moist room

Ambiguity aversion under maximum-likelihood updating

Maximum likelihood updating (MLU) is a well-known approach for extending static ambiguity sensitive preferences to dynamic set-ups. This paper develops an example in which MLU induces an ambiguity averse maxmin expected utility (MEU) decision-maker to (i) prefer a bet on an ambiguous over a risky urn and (ii) be more willing to bet on the ambiguous urn compared to an (ambiguity neutral) subjective expected utility (SEU) decision-maker. This is challenging since prior to observing (symmetric) draws from the urns, the MEU decision-maker (in line with the usual notion of ambiguity aversion) actually preferred the risky over the ambiguous bet and was less willing to bet on the ambiguous urn than the SEU decision-maker. The identified switch in betting preferences is not due to a violation of dynamic consistency or consequentialism. Rather, it results from MLU's selection of extreme priors, causing a violation of the stability of set-inclusion over the course of the updating process

Learning under Ambiguity - A Note on the Belief Dynamics of Epstein and Schneider (2007)

Epstein and Schneider (2007) develop a framework of learning under ambiguity, generalizing maxmin preferences of Gilboa and Schmeidler (1989) to intertemporal settings. The specific belief dynamics in Epstein and Schneider (2007) rely on the rejection of initial priors that have become implausible over the learning process. I demonstrate that this feature of ex-post rejection of theories gives rise to choices that are in sharp contradiction with ambiguity aversion. Concrete, the intertemporal maxmin decision-maker equipped with such belief dynamics prefers, under prevalent conditions, a bet in an ambiguous urn over the same bet in a risky urn. I offer two modifications of their framework, each of which is capable of avoiding this anomaly

Precision requirements in pesticide risk assessments: Contrasting value-of-information recommendations with the regulatory practice in the EU

Pesticides, while rendering immense agricultural benefits, potentially entail risks to human health and the environment. To limit these risks, market approval of a pesticide is typically conditional on an extensive risk assessment demonstrating its safety. The associated testing procedures, often involving significant numbers of animals, however are not only costly; as has become apparent from recent discussions about the active substance glyphosate, testing is often incapable of providing definitive answers on concerns like human carcinogenicity. An important regulatory task, whether explicitly acknowledged or not, is hence to decide what level of remaining uncertainty is deemed acceptable in making the final market approval decision. Economic principles suggest a value-of-information (VoI) approach for this informational task. After presenting the basics of the VoI framework, this paper analyzes the actual regulatory practice in the EU's pesticide approval process, pointing out the defaults and substance-specific procedures that shape the precision of the European Food Safety Authority's (EFSA) risk assessment and hence the level of knowledge under which the European Commission decides on the approval of substances. The comparison between theory and practice uncovers substantial deviations, providing valuable insights for restructuring the risk assessment guidelines