Drying shrinkage of ternary blends in mortar and concrete

The work presented in this thesis involves the study of drying shrinkage behavior of mortars and field concrete mixtures made with ternary cementitious blends. The thesis is composed of two papers resulting from the study: (1) Short-Term Drying Shrinkage of Ternary Blends and (2) Drying Shrinkage of Ternary Blends for Use in Transportation Structure. In the former, statistical response surface analysis was employed to develop shrinkage models to better understand the drying shrinkage behavior of mortar mixes made with ternary blends. In the latter, ternary blend concrete mixtures used for pavement and bridge deck structures in different states were selected. Factors affecting drying shrinkage behavior of these ternary blend concretes were also investigated. In Paper 1, shrinkage behavior of mortar mixes made with various ternary blends was studied. Ternary blends consisting of different combinations of portland or blended cement, slag cement, fly ash (Class C and F) and/or silica fume were considered: the amounts of slag cement, fly ash and silica fume ranged between 15-35%, 13-30%, and 3-10% by mass of cementitious, respectively. Mortar bars were made with the ternary blends and subjected to a drying condition (i.e., T = 73 y 3 yF and RH = 50y4%) after standard curing for 28 days. Free shrinkage of the mortar bars was measured up to 28 days. Based on the test results, a response surface analysis was done to examine the effects of blend proportions on shrinkage behavior of the mortars and a statistical model was developed for predicting the mortar shrinkage behavior. Furthermore, to validate the models, shrinkage strains of an independent group of mortar mixes were measured, and the measured values were compared with the predicted values. The results indicated that among the three supplementary cementitious materials in the ternary blends studied, slag cement showed a dominant effect on mortar shrinkage. The contribution of Class C fly ash to the mortar free shrinkage was slightly less than that of slag cement. Increasing silica fume content slightly increased free shrinkage, while an increase in Class F fly ash content slightly decreased free shrinkage of the mortar. There was a good correlation between the measured shrinkage strain and the strain predicted from the shrinkage model developed from the response surface analysis. The work discussed in Paper 2 investigated the drying shrinkage behavior of ternary blend concretes that were used in transportation structures. Factors affecting drying shrinkage behavior of ternary blend concretes were studied. Five concrete mixes, used for either pavement or bridge deck construction, were tested for both restrained and unrestrained shrinkages. The effects of blend materials and mix proportion on the concrete shrinkages were assessed. The results indicated that shrinkage strain rate linearly increased with clay content of fine aggregate, cementitious material content, paste-to-void ratio (by volume), and dosage of water reducer of the concrete mixes. The study demonstrates that the supplementary cementitious materials (SCMs) can be used to develop a statistical model in order to quantitatively predict drying shrinkage strain. The study gives a better understanding on how SCMs affect mortar and concrete drying shrinkage behavior. Both free and restrained shrinkage methodologies provide efficient analyses on interacted drying shrinkage influence factors. The cracking potential derived from restrained ring shrinkage test can be used to predict drying shrinkage cracking potential of ternary blend concrete mixtures

Concrete Pavement Mixture Design and Analysis (MDA): Factors Influencing Drying Shrinkage

This literature review focuses on factors influencing drying shrinkage of concrete. Although the factors are normally interrelated, they can be categorized into three groups: paste quantity, paste quality, and other factors

Concrete Pavement Mixture Design and Analysis (MDA): Evaluation of Foam Drainage Test to Measure Air Void Stability in Concrete

The stability of air bubbles in fresh concrete can have a profound influence of the potential durability of the system, because excessive losses during placement and consolidation can compromise the ability of the mixture to resist freezing and thawing. The stability of air void systems developed by some air entraining admixtures (AEAs) could be affected by the presence of some polycarboxylate-based water reducing admixtures (WRAs). The foam drainage test provides a means of measuring the potential stability of air bubbles in a paste. A barrier to acceptance of the test was that there was little investigation of the correlation with field performance. The work reported here was a limited exercise seeking to observe the stability of a range of currently available AEA/WRA combinations in the foam drainage test; then, to take the best and the worst and observe their stabilities on concrete mixtures in the lab. Based on the data collected, the foam drainage test appears to identify stable combinations of AEA and WRA

Concrete Pavement Mixture Design and Analysis (MDA): Development and Evaluation of Vibrating Kelly Ball Test (VKelly Test) for the Workability of Concrete

Due to the low workability of slipform concrete mixtures, the science of rheology is not strictly applicable for such concrete. However, the concept of rheological behavior may still be considered useful. A novel workability test method (Vibrating Kelly Ball or VKelly test) that would quantitatively assess the responsiveness of a dry concrete mixture to vibration, as is desired of a mixture suitable for slipform paving, was developed and evaluated. The objectives of this test method are for it to be cost-effective, portable, and repeatable while reporting the suitability of a mixture for use in slipform paving. The work to evaluate and refine the test was conducted in three phases: 1. Assess whether the VKelly test can signal variations in laboratory mixtures with a range of materials and proportions 2. Run the VKelly test in the field at a number of construction sites 3. Validate the VKelly test results using the Box Test developed at Oklahoma State University for slipform paving concrete The data collected to date indicate that the VKelly test appears to be suitable for assessing a mixture’s response to vibration (workability) with a low multiple operator variability. A unique parameter, VKelly Index, is introduced and defined that seems to indicate that a mixture is suitable for slipform paving when it falls in the range of 0.8 to 1.2 in./√s

Comparison of Setting Time Measured Using Ultrasonic Wave Propagation with Saw-Cutting Times on Pavements

At present, there is little fundamental guidance available to assist contractors in choosing when to schedule saw cuts on joints. To conduct pavement finishing and sawing activities effectively, however, contractors need to know when a concrete mixture is going to reach initial set, or when the sawing window will open. Previous research investigated the use of the ultrasonic pulse velocity (UPV) method to predict the saw-cutting window for early entry sawing. The results indicated that the method has the potential to provide effective guidance to contractors as to when to conduct early entry sawing. The aim of this project was to conduct similar work to observe the correlation between initial setting and conventional sawing time. Sixteen construction sites were visited in Minnesota and Missouri over a two-year period. At each site, initial set was determined using a p-wave propagation technique with a commercial device. Calorimetric data were collected using a commercial semi-adiabatic device at a majority of the sites. Concrete samples were collected in front of the paver and tested using both methods with equipment that was set up next to the pavement during paving. The data collected revealed that the UPV method looks promising for early entry and conventional sawing in the field, both early entry and conventional sawing times can be predicted for the range of mixtures tested

Concrete Pavement Mixture Design and Analysis (MDA): An Innovative Approach To Proportioning Concrete Mixtures

Mixture proportioning is routinely a matter of using a recipe based on a previously produced concrete, rather than adjusting the proportions based on the needs of the mixture and the locally available materials. As budgets grow tighter and increasing attention is being paid to sustainability metrics, greater attention is beginning to be focused on making mixtures that are more efficient in their usage of materials yet do not compromise engineering performance. Therefore, a performance-based mixture proportioning method is needed to provide the desired concrete properties for a given project specification. The proposed method should be user friendly, easy to apply in practice, and flexible in terms of allowing a wide range of material selection. The objective of this study is to further develop an innovative performance-based mixture proportioning method by analyzing the relationships between the selected mix characteristics and their corresponding effects on tested properties. The proposed method will provide step-by-step instructions to guide the selection of required aggregate and paste systems based on the performance requirements. Although the provided guidance in this report is primarily for concrete pavements, the same approach can be applied to other concrete applications as well

Quantifying Repeatability Reproducibility Sources of Error and Capacity of a Measurement: Demonstrated Using Laboratory Soil Plasticity Tests

The repeatability, reproducibility, and sources of error inherent in a given measurement are important considerations for potential users. To quantify errors arising from a single operator or multiple laboratories, most testing standards uses a one-way analysis of variance- (ANOVA-) based method, which utilizes a simple standard deviation across all measurements. However, this method does not allow users to quantify the sources of error and capacity (i.e., the precision to tolerance ratio). In this study, an innovative two-way ANOVA-based analysis method is selected to quantify the relative contributions of different sources of error and determine whether a measurement can be used to check conformance of a measured characteristic to engineering specifications. In this study, the standardized Atterberg limits tests, fall-cone device Atterberg limits tests, and bar linear shrinkage tests widely used for determining the soil plasticity were selected for evaluation and demonstration. Comparisons between results of the various testing methods are presented, and the error sources contributing to the overall variations between tests are discussed. Based on the findings of this study, the authors suggest use of two-way ANOVA-based R&R analysis to quantify the sources of measurement error and capacity and also recommend using the fall cone device and ASTM standardized thread rolling device for determining liquid and plastic limits of soils, respectively

Loss of ATF3 exacerbates liver damage through the activation of mTOR/p70S6K/ HIF-1α signaling pathway in liver inflammatory injury.

Activating transcription factor 3 (ATF3) is a stress-induced transcription factor that plays important roles in regulating immune and metabolic homeostasis. Activation of the mechanistic target of rapamycin (mTOR) and hypoxia-inducible factor (HIF) transcription factors are crucial for the regulation of immune cell function. Here, we investigated the mechanism by which the ATF3/mTOR/HIF-1 axis regulates immune responses in a liver ischemia/reperfusion injury (IRI) model. Deletion of ATF3 exacerbated liver damage, as evidenced by increased levels of serum ALT, intrahepatic macrophage/neutrophil trafficking, hepatocellular apoptosis, and the upregulation of pro-inflammatory mediators. ATF3 deficiency promoted mTOR and p70S6K phosphorylation, activated high mobility group box 1 (HMGB1) and TLR4, inhibited prolyl-hydroxylase 1 (PHD1), and increased HIF-1α activity, leading to Foxp3 downregulation and RORγt and IL-17A upregulation in IRI livers. Blocking mTOR or p70S6K in ATF3 knockout (KO) mice or bone marrow-derived macrophages (BMMs) downregulated HMGB1, TLR4, and HIF-1α and upregulated PHD1, increasing Foxp3 and decreasing IL-17A levels in vitro. Silencing of HIF-1α in ATF3 KO mice ameliorated IRI-induced liver damage in parallel with the downregulation of IL-17A in ATF3-deficient mice. These findings demonstrated that ATF3 deficiency activated mTOR/p70S6K/HIF-1α signaling, which was crucial for the modulation of TLR4-driven inflammatory responses and T cell development. The present study provides potential therapeutic targets for the treatment of liver IRI followed by liver transplantation

RGAT: A Deeper Look into Syntactic Dependency Information for Coreference Resolution

Although syntactic information is beneficial for many NLP tasks, combining it with contextual information between words to solve the coreference resolution problem needs to be further explored. In this paper, we propose an end-to-end parser that combines pre-trained BERT with a Syntactic Relation Graph Attention Network (RGAT) to take a deeper look into the role of syntactic dependency information for the coreference resolution task. In particular, the RGAT model is first proposed, then used to understand the syntactic dependency graph and learn better task-specific syntactic embeddings. An integrated architecture incorporating BERT embeddings and syntactic embeddings is constructed to generate blending representations for the downstream task. Our experiments on a public Gendered Ambiguous Pronouns (GAP) dataset show that with the supervision learning of the syntactic dependency graph and without fine-tuning the entire BERT, we increased the F1-score of the previous best model (RGCN-with-BERT) from 80.3% to 82.5%, compared to the F1-score by single BERT embeddings from 78.5% to 82.5%. Experimental results on another public dataset - OntoNotes 5.0 demonstrate that the performance of the model is also improved by incorporating syntactic dependency information learned from RGAT.Comment: 8 pages, 5 figure