Volume 10 Issue 2

The construction industry is one of the largest and most active growth sectors worldwide. It presents an important environmental impact, and one way to reduce the impact of the construction activity is to substitute pozzolanic materials for ordinary Portland cement. In this work, barley straw, barley straw ash, and other natural and artificial pozzolans from Mexico were characterized and compared. Also, the pozzolanic activity of barley straw ash was compared with the pozzolanic properties of some natural and artificial pozzolans from Mexico. Materials considered included recycled dust of fired clay brick, fly ash, volcanic ash, and wheat straw ash.

In this study, effects of adhesive and additive’s type and ratio on burning characteristics of particleboard (PB) added glass wool (GW) and rock wool (RW) were researched. PB’s furnish was derived from 50% Crimean pine, 30% Eastern Black Sea oak, 15% quaking aspen, and 5% residues of wood machining, and moisture content of furnish was 1.5 to 3%. Seventy PBs with 0.64 g/cm3 density, urea formaldehyde (UF)/melamine formaldehyde (MF) fixed amount, 14 mm thickness, 45×45 cm2 dimensions and 10%, 15%, 20% SW/GW additives were produced. The 150 ºC pressing temperature with 25 kg/cm2 compression pressure was constant. Burning tests for determination of ignition time, flaming combustion temperature, flaming combustion duration, smoldering combustion duration, and mass loss during burning were made according to DIN4102 standards. According to the results of the tests, adhesive type did not affect ignition time and mass loss. While flaming combustion temperature of PB with UF was 19% higher, flaming combustion duration and smoldering combustion duration was 32% and 29% lower than those of PB with MF, respectively. While ignition time of PB with GW was 50% higher than that of PB with RW, changes in burning properties were similar for both PBs. An increase in the content of GW and RW affected burning properties of PB positively and an increase of ignition time up to 196% were obtained.

An experimental study was conducted to investigate the effect of size on the strength properties of Chinese larch (Larix gmelinii) dimension lumber. 7546 pieces of dimension lumber were sampled in three sizes, 40 by 65 mm, 40 by 90 mm, and 40 by 140 mm. After visually-grading and grouping, mechanical properties of bending strength, tensile strength, and compression strength parallel to grain were measured in a full-size test. Using nonparametric estimates, the combined length and width size effect parameters of H and L were 0.21 and 0.23 for the bending strength. The width effect parameters were 0.29 in H and 0.33 in L for the ultimate tensile strength parallel to grain. The width effect parameters of H and L were 0.12 and 0.20 for the ultimate compression strength parallel to grain. These size effect factors between H and L could be used when using the lumber for practical purposes.

In this study, a mathematical model of tangential tensioning stress in the edge of a circular saw blade tensioned by multi-spot pressure was established by theoretical analysis for the quality control of circular saw blades. The multi-spot pressure tensioning process was assumed to include three mechanical processes: the one-spot pressure process; the process of elastic deformation of a disk with a through-hole subjected to uniform, radial compressive stress; and the stress superposition process. The tangential tensioning stress on the edge of the circular saw blade could be accurately predicted by the established mathematical model. The model for the tangential tensioning stress on the edge of the circular saw blade tensioned by multi-spot pressure was shown to be correct by measured values.