Energy efficiency is an increasing requirement in the modern construction industry. The building envelope design plays an important role for increasing energy efficiency. The main objective of this study was to evaluate different roof and wall designs for energy efficiency in order to fulfil the future requirement for a sustainable building envelope. The comparative case studies were carried out by calculation and analysis of the different building parts. Of the roofs compared, the koljern-technique worked best. During the analysis of the wall constructs, an exterior wall with polyisocyanurate (PIR) insulation showed the best results. One of the conclusions was that better insulation is needed to meet future requirements for a sustainable building envelope. Another important finding was that the construction industry should be open to new technologies, such as the koljern-technique and PIR-insulation.

The optimization of the process conditions for fire retardant ultra-low density fiberboards (ULDFs) was investigated using response surface methodology (RSM). Three parameters, namely those of Borax-Zinc-Silicate-Aluminum (B-Zn-Si-Al), chlorinated paraffin (CP), and chloride-vinyl chloride emulsions (PVDC) were chosen as variables. The considerably high R² value (99.98%) indicated the statistical significance of the model. The optimal process conditions for the limiting oxygen index (LOI) were determined by analyzing the response surface's three-dimensional surface plot and contour plot, and by solving the regression model equation with Design Expert software. The Box-Behnken design (BBD) was used to optimize the process conditions, which showed that the most favorable dosages of B-Zn-Si-Al, CP, and PVDC were 800 mL, 46.47 mL, and 35.64 g, respectively. Under the optimized conditions, the maximum LOI was 48.4.

Response surface methodology was used to optimize the refining conditions of Pinus massoniana cellulose fiber and to improve the mechanical properties of ultra-low density plant fiber composite (ULD_PFC). The effects and interactions of the pulp consistency (X1), the number of passes (X2), and the beating gap (X3) on the internal bond strength of ULD_PFC were investigated. The results showed that the optimum internal bond strength (91.72 ± 2.28 kPa) was obtained under the conditions of 8.0% pulp consistency, two passes through the refiner, and a 30.0 μm beating gap. Analysis of the physical properties of the fibers and handsheets showed that the fibrillation of fibers with optimum refining conditions was improved. Also, the tear index of the optimal specimen was 13.9% and 24.5% higher than specimen-1 with a lowest beating degree of 24 oSR and specimen-6 with a highest beating degree of 73 oSR, respectively. Consequently, the optimal refining conditions of the fibers are valid for preparing ULD_PFCs.

timber-concrete composite structure (TCC) is economically and environmentally friendly. One of the key design points of this kind of structure is to ensure the reliability of the shear connectors. The objective of this paper is to study the mechanical property of stud-groove-type connectors and to provide shear capacity equations for stud-groove connectors in timber-concrete composite structures. Based on the Johansen Yield Theory (European Yield Model), some mechanical models and capacity equations for stud-groove-type connectors in timber-concrete structures were studied. Push-out specimens with different parameters (stud diameter, stud length, groove width, and groove depth) were tested to obtain the shear capacity and slip modulus. The experimental strengths were used to validate equations given in the paper. The shear capacity and slip modulus of stud-groove-type connectors was in direct proportion to the diameter of studs and the dimension of the groove. Comparison between the theoretical and the experimental shear strength results showed reasonable agreement. The highlight of this study on shear capacity equations could significantly reduce the push-out tests before investigating the other properties of TCC

To evaluate the quality of laminated particleboard, a typical type of laminate was used in laminating particleboard with operational parameters similar to industry operation. Pull-off tests using Elcometer 510 were conducted. In addition, panel vertical density profiles (VDP) and the pH of particleboard at different layers were tested. The results showed that the laminated panel bonded by polyvinyl acetate (PVA) glue had higher pull-off strength than that of the phenol formaldehyde (PF) glue within corresponding sanding thickness. Sanding off 0.0762 mm resulted in higher pull-off strength than sanding off 0.0254 mm. The laminates had the highest pull-off strength when the PB were sanded off 0.0762 mm and glued by PVA. This has provided a solution to improve lamination pull-of strength for industry. The test results have also shown that the laminated panels produced in the manufactures have the potential to be improved. It also indicates that Elcometer 510 is a good tool to evaluate the particleboard lamination quality.

Bending tests were conducted with cross laminated timber (CLT) panels made using an alternating layer arrangement. Boards of Norway spruce were used to manufacture five-layer panels on an industrial CLT production line. In total, 20 samples were tested, consisting of two CLT configurations with 10 samples of each type: transverse layers at 45° and the conventional 90° arrangement. Sample dimensions were 95 mm × 590 mm × 2000 mm. The CLT panels were tested by four point bending in the main load-carrying direction in a flatwise panel layup. The results indicated that bending strength increased by 35% for elements assembled with 45° layers in comparison with 90° layers. Improved mechanical load bearing panel properties could lead to a larger span length with less material.

Co-polymer systems of methylene diphenyl diisocyanate (MDI) and phenol-formaldehyde (PF) resins with different molecular weights were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The FTIR and TGA coupled with differential thermogravimetric (DTG) results showed that higher molecular weight of PF resins not only promoted the reaction of isocyanate and PF co-polymer system, but also resulted in a better thermal property of prepared co-polymers. The XRD results revealed that higher molecular weight led to a higher proportion of ordered or crosslinking structures in the hybrid resin system. The relationship between the thermal resistance, mechanical properties and the molecular weights of phenolic resins needs further study.

B-Zn-Si-Al compounds are modified Si-Al compounds made of sodium silicate, zinc sulfate, borax, and aluminum sulfate. They act as a fire retardant during the preparation of ultra-low density fiberboards (ULDFs). An orthogonal experiment was used to optimize the contents of the four compounds according to the limiting oxygen index. Fourier transform infrared spectroscopy was employed to preliminarily analyze the chemical structure of the compounds. Additionally, a cone calorimeter was used to assess the fire performance of the ULDFs. The results suggested that the optimized solution was made of 27.0 mL of sodium silicate solution, 27.0 mL of aluminum sulfate solution, 3.0 g of zinc sulfate, and 6.5 g of borax, resulting in an oxygen index of 29.5%. The bond Al-O-B was detected at 1397 and 796 cm-1. The Si-O-Zn bonds were detected at 867 cm-1. The heat release rate, total heat release, and total smoke release decreased and the mass residual ratio increased in the sample using the optimal conditions from the orthogonal array design. It was concluded that B-Zn- Si-Al compounds effectively protect fibers from fire.

This is the second part of a two-part study aimed at examining the effect of extreme adhesive pH on bond durability. The first part dealt with short-term exposure and this second part dealt with long-term exposure. This part also included an examination of wood degradation by adhesive pH.Nine structural wood adhesives [four high pH phenol formaldehyde (PF), one intermediate pH phenol-resorcinol formaldehyde (PRF), two low pH melamine formaldehyde (MF), and two low pH melamine-urea formaldehyde (MUF)] were studied in terms of their pH effect on wood-adhesive bond durability using Douglas-fir wood substrate with specimens tested in block shear. The block shear specimens were initially subjected to vacuum-pressure treatment under water, followed by exposure, while wet, at 50°C for 0, 4, 8, 12, and 17 months. At each exposure period, the specimens were dried to their original moisture content prior to testing for shear strength and evaluation of wood failure.Indications of the extent of degradation of the wood layer adjacent to the bond line due to adhesive pH during the long-term exposure were also examined by the 1% sodium hydroxide solubility test. There were indications that the wood layer closest to the bond line, which contained included glue, had higher solubility compared to those farther from the bond line. This suggests that wood degradation and/or adhesive decomposition occurred and was considered to be induced by the adhesive alkalinity or acidity under the long-term exposure conditions.The PF showed the best durability performance followed, in decreasing order, by PRF and MF/MUF. The latter adhesives degraded completely after an exposure period of 8 to 17 months.The four PF adhesives passed the shear strength and wood failure requirements of the well-known North American structural wood adhesive standards indicating that their high pH had no significant detrimental effect on the wood-adhesive bond durability after the 17-month exposure period despite their being subjected to multiple cyclic tests. This observation was not apparent for the PRF, and the pH effect was considered inconclusive for the MF/MUF since they degraded during the exposure period.The results of this study provide support to wood adhesive standards that do not impose restriction on the upper spectrum of the pH range, and would be useful to adhesive standard developers. These results also serve as background information for adhesive companies in their formulation of wood adhesives as well as for bonded wood product manufacturers in their use of adhesives and for builders in their use of bonded wood products.

The block shear strength of Norway spruce (Picea abies (L.) Karst.) glulam joints was tested under low temperatures. Glulam samples were glued with the three of the most common outdoor structural adhesives. The cold temperatures tested were 20, -20, -30, -40, -50, and -60 degrees C. Within the temperature test range, the block shear strength of the glulam joints was resistant to the effect of temperature. As the temperature decreased, the joints' block shear strength did not show any significant change. In most cases, phenol-resorcinol-formaldehyde (PRF) adhesive yielded the strongest block shear strength, while melamine-formaldehyde (MF) adhesive yielded the weakest block shear strength. Melamine-urea-formaldehyde (MUF) adhesive yielded similar results to those of MF adhesives for all temperatures tested. The block shear strengths of the glulam joints with PRF, MUF, and MF adhesives were not sensitive to temperature change. The results indicated that PRF, MUF, and MF adhesives are stable for outdoor structural engineered wood construction in cold climates. The results also suggest that the SS-EN 14080 (2013) standard for the block shear method may not be the proper standard for testing differences in shear strength at different temperatures. The EN 302-1 (2011) standard could be more suitable for this purpose.