In-situ assessment of concrete bridge decks and pavements using stress-wave based methods

Concrete infrastructure of United States is aging and deteriorating. Accurate assessment the condition of concrete infrastructure is critical for its maintenance and rehabilitation. Stress-wave based methods, including ultrasonic surface wave (USW) and impact echo (IE), are becoming popular for characterizing defects and mechanical properties of concrete infrastructures. In this dissertation, a comprehensive literature review of seismic wave theory and common types of defects identified in concrete infrastructures, as well as stress-wave based methods used for concrete infrastructure monitoring and characterizing on a selected concrete bridge deck and two concrete pavement segments are present. The utility and reliability of both methods were carefully evaluated and validated based on the comparison analysis with other destructive or non-destructive testing (NDT) methods carried out in the field or laboratory for the same bridge decks and pavement segments, such as the concrete hydro-demolition, drilling, static modulus of elasticity of concrete specimens in compression and ground penetrating radar (GPR). Detailed investigation of the sensitivity and limitation of stress-wave based methods for different types of defects identified in concrete bridge decks and pavements has been performed and presented. The outcome of this study is to expand the knowledge of stress-wave based methods, to better understand their strengths and limitations, to evaluate the reliability and utility of both the USW and IE test results in characterizing and monitoring defects and mechanical properties of concrete infrastructures. The result of this study is most beneficial for transportation agencies and researchers to use stress-wave based methods properly and effectively for further feasibility studies or monitoring of concrete infrastructures --Abstract, page iv

Adding Value to Lignocellulosic Biorefinery: Efficient Process Development of Lignocellulosic Biomass Conversion into Polyhydroxybutyrate

Polyhydroxybutyrate (PHB) is bacteria synthesized polymer that has comparable mechanical properties as petroleum-based plastics and high biocompatibility. Current commercial PHB production process is not cost effective. Raw materials make up about 50% of the production cost. Lignocellulosic biomass are cheap, abundant feedstocks that can be converted into PHB to add profit and sustainability to lignocellulosic biorefinery. Lignocellulosic biorefinery upstream process produces polymeric sugar rich stream and lignin-enriched stream. Polymeric sugars are then hydrolyzed into a sugar stream with glucose, xyloseand arabinose mainly present. To the best of the author’s knowledge, limited studies have been done on sugar mixture conversion into PHB. For lignin, previous research achieved a PHB production ranging from 0.13 to 1 g/L, which is too low to be economical. The primary objectives of this research were twofold: (1) process development of polymeric sugars conversion into PHB, with a focus on sugar mixture conversion into PHB by Burkholderia sacchari DSM 17165, and (2) process development of lignin into PHB by Cupriavidus necator DSM 545, with a focus on enhancing PHB production using various types of supplements. For sugar mixture conversion into PHB, first, shake flask (250 mL) scale statistical experimental design and modeling were performed to optimize sugar mixture ratio and process variables for maximal PHB production; second, bioreactor scale (3L) fed-batch cultivation was conducted to produce PHB from simulated corn fiber sugar mixture. The highest PHB production reached 67 g/L for 4:2:1 (glucose:xylose:arabinose) mixture at 41 h corresponding to an accumulation of 77% of cell dry weight. Corresponding sugar conversion efficiency and productivity were 0.33 g PHB/g sugar consumed and 1.6 g/L/h, respectively, which are comparable to or higher than most previous studies. For lignin conversion into PHB, first, shake scale (250 mL) study achieved 10-fold increase (0.2 to 2.1 g/L) in PHB production by optimizing supplement formulations with Plackett-Burman and central composite designs. Second, fed-batch cultivation at bioreactor scale (1.7 L) were conducted to enhance PHB production to 4.5 g/L. This is the highest PHB production from lignin that the author has been aware of in the literature. Advisor: Mark R. Wilkin

Adding Value to Lignocellulosic Biorefinery: Efficient Process Development of Lignocellulosic Biomass Conversion into Polyhydroxybutyrate

Polyhydroxybutyrate (PHB) is bacteria synthesized polymer that has comparable mechanical properties as petroleum-based plastics and high biocompatibility. Current commercial PHB production process is not cost effective. Raw materials make up about 50% of the production cost. Lignocellulosic biomass are cheap, abundant feedstocks that can be converted into PHB to add profit and sustainability to lignocellulosic biorefinery. Lignocellulosic biorefinery upstream process produces polymeric sugar rich stream and lignin-enriched stream. Polymeric sugars are then hydrolyzed into a sugar stream with glucose, xyloseand arabinose mainly present. To the best of the author’s knowledge, limited studies have been done on sugar mixture conversion into PHB. For lignin, previous research achieved a PHB production ranging from 0.13 to 1 g/L, which is too low to be economical. The primary objectives of this research were twofold: (1) process development of polymeric sugars conversion into PHB, with a focus on sugar mixture conversion into PHB by Burkholderia sacchari DSM 17165, and (2) process development of lignin into PHB by Cupriavidus necator DSM 545, with a focus on enhancing PHB production using various types of supplements. For sugar mixture conversion into PHB, first, shake flask (250 mL) scale statistical experimental design and modeling were performed to optimize sugar mixture ratio and process variables for maximal PHB production; second, bioreactor scale (3L) fed-batch cultivation was conducted to produce PHB from simulated corn fiber sugar mixture. The highest PHB production reached 67 g/L for 4:2:1 (glucose:xylose:arabinose) mixture at 41 h corresponding to an accumulation of 77% of cell dry weight. Corresponding sugar conversion efficiency and productivity were 0.33 g PHB/g sugar consumed and 1.6 g/L/h, respectively, which are comparable to or higher than most previous studies. For lignin conversion into PHB, first, shake scale (250 mL) study achieved 10-fold increase (0.2 to 2.1 g/L) in PHB production by optimizing supplement formulations with Plackett-Burman and central composite designs. Second, fed-batch cultivation at bioreactor scale (1.7 L) were conducted to enhance PHB production to 4.5 g/L. This is the highest PHB production from lignin that the author has been aware of in the literature. Advisor: Mark R. Wilkin

White Rot Fungi Pleurotus Ostreatus Pretreatment on Switchgrass to Enhance Enzymatic Hydrolysis and Ethanol Production

Biofuels and high value chemicals derived from cellulosic biomass are good substitutes for petroleum energy and are more environmentally beneficial than corn or soybean based biofuels. The high cost of biomass conversion to biofuels is the main impediment for large scale biofuel production, in which pretreatment is one of the most expensive processing steps. White rot fungal pretreatment shows good potential to efficiently degrade lignin and enhance enzymatic hydrolysis and fermentation under mild environmental conditions. In this thesis biological pretreatment was applied to switchgrass with an emphasis on white rot fungi-associated pretreatment. Two specific studies were conducted: Pleurotus ostreatus pretreatment on large switchgrass bales (either square or round bales) in a natural environment and lab scale P. ostreatus pretreatment in a controlled environment. For the study in a natural environment, P. ostreatus was applied to large switchgrass bales and stored for 9 months. Sampling was done at three months, five months, seven months and nine months after fungus applied. Fungal treated samples were subjected to composition analysis, hydrothermolysis pretreatment and enzymatic hydrolysis. Fungal treated square bales had a lignin fraction ranging from 1.8% to 3.2% higher than untreated bales. There were no clear trends for composition of hydrothermolysis pretreated samples or glucose yield from enzymatic hydrolysis. Fungus did not grow in round bales and bale moisture contents varied between 6% and 11%, which was too low for fungal growth. Glucan and lignin contents of stored samples increased and xylan contents decreased from March to May and were constant from May to September. For enzymatic hydrolysis of hydrothermolysis (200 �C/10 min or 180 �C/20 min) treated samples, there were no significant differences among samples of unwashed and washed samples, which indicates washing is not necessary. For the lab study in a controlled environment, switchgrass was treated with varied initial inoculum loading and substrate moisture content. Results showed that no ethanol was produced during SSF of untreated switchgrass. For fungal treated samples, after 80 days fungal pretreatment, samples with 75% substrate moisture content and 5 ml initial inoculum loading had the highest lignin degradation, 52%, and the highest ethanol yield, 45%.Biosystems & Agricultural Engineerin

Switchgrass storage effects on the recovery of carbohydrates after liquid hot water pretreatment and enzymatic hydrolysis

Perennial grasses that would be used for bioenergy and bioproducts production will need to be stored for various periods of time to ensure a continual feedstock supply to a bioprocessing facility. The effects of storage practices on grass composition and the response of grasses to subsequent bioprocesses such as pretreatment and enzymatic hydrolysis needs to be understood to develop the most efficient storage protocols. This study examined the effect of outdoor storage of round switchgrass bales on composition before and after liquid hot water pretreatment (LHW) and enzymatic hydrolysis. This study also examined the effect of washing LHW pretreated biomass prior to enzymatic hydrolysis. It was determined that switchgrass composition after baling was stable. As expected, glucan and lignin contents increased after LHW due to decreases in xylan and galactan. Washing biomass prior to enzymatic hydrolysis reduced saccharification, especially in samples from the interior of the bale, by at least 5%

Application of Acoustic Emission and Machine Learning to Detect Codling Moth Infested Apples

Incidence of codling moth (CM) (Cydia pomonella L.) infestation in apples has been a major concern in North America for decades. CM larvae bore deep into the fruit, making it unmarketable. An effective noninvasive method to detect larvae-infested apples is necessary to ensure that apples are CM-free in post-harvest processing. In this study, a novel approach using an acoustic emission (AE) system and subsequent machine learning methods was applied to classify larvae-infested apples from intact apples. \u27GoldRush‘ apples were infested with CM neonates and stored at the same conditions as intact apples. The AE system was used to collect the data emitted by 80 larvae-infested and intact apples in total. Eleven AE features that changed with signaling time were obtained with the AE system. For each feature, the area under the curve along the signaling time was calculated and used as an independent input variable for the machine learning algorithms, which included linear discriminant analysis (LDA) and ensemble method adaptive boosting. With signaling times ranging from 0.5 to 120 s, classification rates for infested versus intact apples ranged from 91% to 100% for the training set and from 83% to 100% for the test set. The quick signal collection and high classification accuracy obtained in this study show the potential of AE for detecting and classifying CM-infested apples