Shear Strength and Microscopic Characterization of a Bamboo Bonding Interface with Phenol Formaldehyde Resins Modified with Larch Thanaka and Urea
The aim of this study was to understand the microscopic characteristics of the bamboo bonding interface with phenol formaldehyde resin modified with larch thanaka and urea (PTUF) and its effect on the shear strength of two-ply bamboo laminated lumber. Bleached and carbonized bamboo strips were used, and two assembly patterns (outer-to-outer and inner-to-inner) were adopted to make two-ply bamboo laminated lumber with PTUF. The microstructure of the bonding interface and the bond-line thickness were investigated using a scanning electron microscope. The average depth and effective depth of PTUF on bamboo surfaces were evaluated by fluorescent microscopy characterization. The shear strength of two-ply bamboo laminated lumber was also examined. The results revealed a shallow depth of penetration of PTUF into the bamboo surface that was distributed primarily in the broken cell cavities formed during preparation, as well as between the cell walls. When the assembly pattern was inner-to-inner, the depth of penetration and bond-line thickness were higher, but the shear strength was lower than that of the outer-to-outer pattern. The carbonized bamboo laminated lumber provided a greater resin penetration and bond-line thickness, but lower shear strength, than the bleached bamboo laminated lumber.
Alkali- and glutaraldehyde-modified pig blood as renewable adhesives for engineered bamboo products
Abstract Environmentally friendly fabrication of engineered bamboo lumber is enabled by the application of renewable, formaldehyde-free bio-adhesives. In this study, protein-based adhesives made from pig blood (PB) were developed for this purpose. PB was modified by alkali (NaOH) and glutaraldehyde into either alkali-modified pig blood adhesive (APB), glutaraldehyde-modified pig blood adhesive (GPB), or alkali-and-glutaraldehyde-modified pig blood adhesive (AGPB), which were expected to be more water-resistant. Two-ply laminated bamboo lumber samples were assembled, and their bonding strengths were measured. The thermal properties, presence of functional groups, and cross-sectional micro-morphologies of the modified adhesives and unmodified PB were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The thermal stabilities of all the modified adhesives were improved compared to that of the unmodified PB. FTIR confirmed that the NaOH treatment successfully induced the unfolding of the PB protein, exposing the hydrophobic groups in the APB and that glutaraldehyde became grafted onto primary amides in the AGPB. Compared with the PB and APB, the cross-sectional micro-morphologies of the GPB and AGPB were more homogeneous and compact. The wet shear strength of the laminated bamboo lumber (LBL) was clearly increased by the modified adhesives. The AGPB had a higher wet shear strength of 4.6 MPa. Thus, the GPB and AGPB can be considered as potential protein adhesives for use in a variety of engineered bamboo products.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.