The goal of this research was to determine whether precast prestressed bridge elements with congested reinforcement could be cast using self-consolidating concrete (SCC) without vibration and yet comply with all parameters of strength, no honeycombing, and void-free surface finish. Eight wall panels and eight BT-72 13-ft long girder sections were fabricated in two precast plants. A qualitative and quantitative evaluation of the surface finish, and homogeneity of the concrete throughout the specimens was performed. Strength, creep, shrinkage and chloride permeability of the SCC field mixes were investigated. Good quality SCC mixes were produced for the walls and the BT-72 girder sections, which completely filled the specimens without the need of internal or external vibration, and resulted in a superior surface finish and a homogenous distribution of the aggregate throughout the section.

Over the last 50 years significant advancements have been made in the southern yellow pine (SYP) forests in the U.S. south. Due to silvicultural changes and large scale reforestation efforts the US south has seen significant increases in standing volume (more than 120% over the period). Landowners that grow SYP plantations largely manage for trees that are harvested to produce dimensional lumber. With the changes in growth patterns it is of interest if there have been any changes in structural properties of the lumber that is produced from timber grown today. Landowners desire confirmation that what they are doing in terms of management is maintaining the quality and strength of lumber that the market demands. This information is critical because timberland owners’ plant and manage trees that will ultimately be brought to market at lumber 25-40 years into the future. In an effort to provide clarity to this topic this dissertation investigates: 1) The extent to which the specific gravity (SG), bending strength (modulus of rupture, MOR), and bending stiffness (modulus of elasticity, MOE) of small clear specimens of SYP have changed, particularly with respect to reduction(s), during the interval from approximately 1965 to 2015. 2) The extent to which the compression parallel to grain and perpendicular to grain strength of small clear specimens of SYP have changed, particularly with respect to reduction(s), during the interval from approximately 1965 to 2015. Use statistical analysis of variance to investigate potential differences among data from a historical 1966 data set, a 2014 in-grade data set, and a 2018 staircase material data set. 3) The nature of the relationship between and among SG, MOE, and MOR of small clear specimens of SYP and how these relationships may have changed, during the interval from approximately 1965 to 2015. Use statistical regression analysis to explore changes to the interrelationships of SG, MOE, and MOR among the three samples, with particular interest toward how these may impact or influence non-destructive evaluation. This work consists of 3 independent chapters using varying appropriate statistical methods and is accompanied by an introduction and conclusion.

This investigation focuses on the production, strength properties, and marketability of a new ultra stiff wood composite. The basis of the examination is to compare strength properties such as, Modulus of Rupture, Modulus of Elasticity, Work to Max Load, and Density with currently available products. The final analysis of the ultra stiff product suggested that this product would compete favorably in today’s market due to the strength properties of the product. Although the current hot-pressing method is not economical for mass production, other ways of pressing can be utilized. It is noted in this research that the wood moisture content can influence MOE, MOR, and density properties. By manipulating and controlling the press cycle and the moisture content, a competitive product was produced.

The forest products industry is a significant contributor to the U.S. economy contributing six percent of the total U.S. manufacturing gross domestic product (GDP), placing it on par with the U.S. automotive and plastics industries. Sustaining business competitiveness by reducing costs and maintaining product quality will be essential in the long term for this industry. Improved production efficiency and business competitiveness is the primary rationale for this work. A challenge facing this industry is to develop better knowledge of the complex nature of process variables and their relationship with final product quality attributes. Quantifying better the relationships between process variables (e.g., press temperature) and final product quality attributes plus predicting the strength properties of final products are the goals of this study. Destructive lab tests are taken at one to two hour intervals to estimate internal bond (IB) tensile strength and modulus of rupture (MOR) strength properties. Significant amounts of production occur between destructive test samples. In the absence of a real-time model that predicts strength properties, operators may run higher than necessary feedstock input targets (e.g., weight, resin, etc.). Improved prediction of strength properties using boosted regression tree (BRT) models may reduce the costs associated with rework (i.e., remanufactured panels due to poor strength properties), reduce feedstocks costs (e.g., resin and wood), reduce energy usage, and improve wood utilization from the valuable forest resource. Real-time, temporal process data sets were obtained from a U.S. particleboard manufacturer. In this thesis, BRT models were developed to predict the continuous response variables MOR and IB from a pool of possible continuous predictor variables. BRT model comparisons were done using the root mean squared error for prediction (RMSEP) and the RMSEP relative to the mean of the response variable as a percent (RMSEP%) for the validation data set(s). Overall, for MOR, RMSEP values ranged from 0.99 to 1.443 MPa, and RMSEP% values ranged from 7.9% to 11.6%. Overall, for IB, RMSEP values ranged from 0.074 to 0.108 MPa, and RMSEP% values ranged from 12.7% to 18.6%.

Although it is common to model modulus of elasticity (MOE) and modulus of rupture (MOR) of graded lumber as normal, lognormal, or Weibull distributions, recent theories and empirical practices have cast doubt on these models. Mathematical proofs have been used to shown how the MOR distributions of graded lumber can be derived from the MOR distributions of mill-run populations. The MOR distribution of a graded lumber subpopulation is "pseudo- truncated" and does not exhibit the same theoretical form as the mill-run population from which it was drawn. Therefore, it is essential to explore the properties of mill-run lumber populations and properly characterize their MOE and MOR distributions. To investigate this topic, this dissertation has three objectives: 1) to determine if the within-mill means and standard deviations of MOE and MOR in mill-run southern pine (Pinus spp.) lumber differ over time, 2) to determine the correlations among hand-held grain angle meter readings, MOE, and MOR in mill- run southern pine lumber, and 3) to model statistical distributions of MOE and MOR in mill-run red pine (Pinus resinosa) and spruce (Picea spp.) lumber. This research features four main sections: 1) an introduction summarizing the conclusions of each chapter, 2) a chapter investigating if there are statistically significant differences between the means and variances of MOE and MOR in mill-run southern pine lumber populations at the same mill over time, 3) a chapter evaluating the bivariate correlations among handheld grain angle meter readings, MOR, and three measures of MOE in mill-run southern pine lumber, and 4) a chapter modeling the distributions of MOE and MOR in mill-run red pine and spruce lumber populations and comparing those to previous work on mill-run southern pine lumber populations.

Acetylation of wood is a modification technique that chemically alters the wood substance and enhances several properties of wood. The basic principle is to impregnate wood with acetic anhydride to react and replace OH-groups with acetyl groups in the wood cell wall. In this way, the hygroscopicity of the modified wood is significantly reduced resulting in increased dimensional stability and durability compared with unmodified wood.The objective of this work was to study finger-jointing of acetylated Scots pine (Pinus sylvestris L.) using a conventional melamine urea formaldehyde (MUF) adhesive. Two different types of acetylated pine specimens were investigated, acetylated pine sapwood (APS) and acetylated juvenile pine (AJP), the latter originating from young forest thinning trees (ca 20-30 years). The goal was to evaluate the bending strength, i.e. modulus of rupture (MOR), of such finger-jointed samples, in particular when the acetylated wood was combined with unmodified wood, in this case, Norway spruce (Picea Abies L. Karst) (US). The finger-jointing were performed at Moelven Töreboda by applying their existing industrial procedures. In total, five different of finger jointed sample groups were prepared combining the different specimens: APS-APS, AJP-AJP, US-US, APS-US, and AJP-US. Standardized procedures were used to determine the MOR of the finger-jointed samples, both unexposed at the factory condition state and after a water-soaking-drying cycle. In addition, the experiments also included determination of the moisture content (MC), density, and modulus of elasticity (MOE) (in bending along the grain) of the individual specimens.At the unexposed state, the APS-APS samples showed the highest MOR of 63,1 MPa, while those of the AJP-AJP showed the lowest value of 42,4 MPa. The corresponding values for the US-US, AJP-US and APS-US samples was 56,7, 47,5 and 46,9 MPa, respectively. In contrast to a typical wood failure for the US-US samples, a low amount of wood failure was observed in all cases involving the acetylated wood, indicating a low adhesive anchoring in the wood substrate at the finger-joint, although a surprisingly high strength was obtained for the APS-APS samples. A significantly lower MC content of 4,9 % and a remarkably low value of 1,7 %, was found for the APS and AJP, respectively, compared with 9,2% for the US. The significantly lower MC combined with an assumed increased hydrophobicity of the acetylated wood possible causes a less effective MUF-wood bonding, or adhesion, compared with that of the unmodified wood. Possible, so-called over penetration of the MUF resin in the acetylated wood could also be an explanation for the poor wood-adhesive anchoring. The MOE of the individual APS, AJP and US specimens was 12,6, 8,3 and 11,4 GPa, respectively, indicating a significantly lower mechanical performance of AJP, and hence also of finger-joints of AJP, despite its very low MC, possible due to a higher microfibril angle in the cell walls in juvenile wood compared with mature wood. No clear correlation was found between the MOR and density of the acetylated samples.For the samples exposed to a water-soak-drying cycle, the highest MOR, and lowest reduction of 14 % compared with the unexposed state, was obtained for the US-US samples, whereas all samples involving the acetylated wood showed a distinctly higher reduction. The MOR of the AJP-AJP and AJP-US samples were reduced with 47 % and 50 %, respectively, while the MOR of the APS-APS and APS-US samples were reduced with 43 % and 23 %, respectively. It should be emphasized, however, that after the standard drying-time, which was the same for all samples, the acetylated samples, compared with the untreated ones, did not dry out to the same level as for the dry unexposed state, i.e. the acetylated samples had a high MC of ca 30-40% in these MOR tests. This high MC level could be the main reason for the dramatic strength losses. Furthermore, a less efficient wood-MUF adhesion as well as the drying under acidic conditions may also be possible causes for the reduced bending strength of the finger-jointed samples with acetylated wood.

The primary aim of this research was to develop a method for determining the true uniaxial tensile strength of concrete by conducting a series of cylinder splitting, modulus of rupture (MOR) and cylinder/cube compression tests. The main objectives were: • Critically reviewing previous published research in order to identify gaps in current knowledge and understanding, including theoretical and methodological contributions to the true uniaxial tensile strength of concrete. In order to maintain consistency and increase the reliability of the proposed methods, it is essential to review the literature to provide additional data points in order to add additional depth, breathe and rigor to Senussi's investigation (2004). • The design of self compacting concrete (SCC), normal strength concrete (NSC) and high strength concrete (HSC) mixes and undertaking lab-based experimental works for mixing, casting, curing and testing of specimens in order to establish new empirical evidence and data. • Analysing the data, presenting the results, and investigating the application of validity methods as stated by Lin and Raoof (1999) and Senussi (2004). • To draw conclusions including comparison with previous research and literature, including the proposal of new correction factors and recommendations for future research. 29 batches of NSC, 137 batches of HSC, 44 batches of fly ash SCC and 47 batches of GGBS SCC were cast and their hardened and fresh properties were measured. Hardened properties measured included: cylinder splitting strength, MOR, cylinder compressive strength and cube compressive strength. A variety of rheological tests were also applied to characterise the fresh properties of the SCC mixes, including: slump flow, T50, L-box, V-funnel, J-ring and sieve stability. Cylinders were also visually checked after splitting for segregation. The tensile strength of concrete has traditionally been expressed in terms of its compressive strength (e.g. ft = c x c f ). Based on this premise, extensive laboratory testing was conducted to evaluate the tensile strength of the concretes, including the direct tension test and the indirect cylinder splitting and MOR tests. These tests however, do not provide sufficiently accurate results for the true uniaxial tensile strength, due to the results being based upon different test methods. This shortcoming has been overcome by recently developed methods reported by Lin and Raoof (1999) and Senussi (2004) who proposed simple correction factors for the application to the cylinder splitting and MOR test results, with the final outcome providing practically reasonable estimates of the true uniaxial tensile strength of concrete, covering a wide range of concrete compressive strengths 12.57 ≤ fc ≤ 93.82 MPa, as well as a wide range of aggregate types. The current investigation has covered a wide range of ages at testing, from 3 to 91 days. Test data from other sources has also been applied for ages up to 365 days, with the test results reported relating to a variety of mix designs. NSC, SCC and HSC data from the current investigation has shown an encouraging correlation with the previously reported results, hence providing additional wider and deeper empirical evidence for the validity of the recommended correction factors. The results have also demonstrated that the type (size, texture and strength) of aggregate has a negligible effect on the recommended correction factors. The concrete age at testing was demonstrated to have a potentially significant effect on the recommended correction factors. Altering the cement type can also have a significant effect on the hardened properties measured and demonstrated practically noticeable variations on the recommended correction factors. The correction factors proved to be valid regarding the effects of incorporating various blended cements in the HSC and SCC. The NSC, HSC and SCC showed an encouraging correlation with previously reported results, providing additional support, depth, breadth and rigor for the validity of the correction factors recommended.

yes / The present paper reports the testing of 12 alkali-activated mortars and a control ordinary portland cement (OPC) mortar. The main aim is to develop cementless binder activated by sodium silicate powder. An alkali quality coefficient combining the amounts of main compositions of source materials and sodium oxide (Na2O) in sodium silicate is proposed to assess the properties of alkali activated mortars, based on the hydration mechanism of alkali-activated pastes. Fly ash (FA) and ground granulated blast-furnace slag (GGBS) were employed as source materials. The ratio of Na2O-to-source material by weight for different mortars ranged between 0.038 and 0.164; as a result, alkali quality coefficient was varied from 0.0025 to 0.0365. Flow loss of fresh mortar, and shrinkage strain, compressive strength and modulus of rupture of hardened mortars were measured. The compressive strength development of alkali activated mortar was also compared with the design equations for OPC concrete specified in ACI 209 and EC 2. Test results clearly showed that the flow loss and compressive strength development of alkali-activated mortar were significantly dependent on the proposed alkali quality coefficient. In particular, a higher rate of compressive strength development achieved at early age for GGBS-based alkali-activated mortar and at long-term age for FA-based alkali-activated mortar. In addition, shrinkage strain and modulus of rupture of alkali-activated mortar were comparable to those of OPC mortar.

The mechanical properties of boron carbide (B4C) with 10 and 20 vol% particulate inclusions of commercially available nano-sized alpha-phase silicon carbide (a-SiC) or micron-sized titanium diboride (TiB2) were investigated so as to produce a fine-grained material with high hardness, toughness, and overall strength in order to increase the effectiveness of B4C as a structural ceramic, whose use in the field has been limited because of the extreme brittle nature of the material. Full density sintering of the ceramics (≥99% theoretical) was completed using the novel Plasma Pressure Compaction (P²C®) technique, which limited grain growth due to a reduced processing temperature and a significantly reduced consolidation time. The reinforced ceramic composites had particulate grains homogeneously distributed within the B4C matrix. X-ray diffraction patterns confirmed that the constituents did not interdiffuse. The four-point flexure strength for the monolithic B4C ceramic was found to be significantly larger than any recorded value found in scientific literature, and was most likely attributed to the fine-grained microstructure resulting from the P²C® processing. The mechanical properties of the nano-sized a-SiC-B4C ceramics showed a slight increase in the Chevron-notched four-point bend fracture toughness due to the crack deflection toughening mechanism. A slight decrease in the Vickers microhardness and the static elastic modulus values were also observed. A significant increase in the fracture toughness as well as a slight increase in the microhardness and elastic modulus of the micron-sized TiB2-B4C materials was found. The toughening mechanism of this composite was attributed to the slight chemical bond between the B4C matrix and the ultra-small, ultra-tough TiB2 particulates, which forced a propagating crack to completely rip apart the TiB2 reinforcing particles. This cleaving nature resulted in significant amounts of energy being absorbed by the micron-sized particulates. It was concluded that the composite with 20 vol% TiB2 allowed for the largest gain in toughness because it possessed the largest number of ultra small, ultra tough particulate-cracktip interactions.

A model is presented to use normalized multi-linear tension and compression material characteristics of strain-hardening textile reinforced concrete and derive closed form expressions for predicting moment-curvature capacity. A set of design equations are derived and simplified for use in spreadsheet based applications. The model is applicable for both strain-softening and strainhardening materials. The predictability of the simplified model is checked by model calibration and development of design charts for moment capacity and stress developed throughout the cross section of a flexural member. Model is calibrated by predicting the results of Alkali Resistant Glass and Polyethylene fabrics. A case for the flexural design of Glass Fiber Reinforced Concrete (GFRC) specimen as a simply supported beam subjected to distributed load is used to demonstrate the design procedure.