جستجوی مقالات مرتبط با کلیدواژه "persian gum" در نشریات گروه "عمران"

Evaluation of mechanical behavior of the soil-structure interface has been the focus of many researchers as an effective factor on the strength performance and deformation of the structure. Since the interaction of the structure and the soils around it will have a great impact on the soil bearing capacity, it is important to study the physical conditions. In this study, taking into account the curing time, effect of using Persian gum and the roughness of the steel on the behavior of the soil-structure interface using large-scale direct shear test have been investigated. The Persian gum was used in three amounts of 0.3, 0.6 and 0.9% on three smooth, rough and geotextile covered surfaces. Based on the results, by injecting Persian gum into the soil-candle interface, the adhesion between soil and contact surface increases by about 20 times and the internal friction angle increases by one degree. The rate of increase of strength parameters decreases with increasing curing time.

The constraints such as altering soil acidity and environmental concerns stemming from the use of traditional soil stabilizers like cement have justified the exploration of environmentally friendly, cost-effective materials with fewer secondary risks, such as biopolymers. This study focuses on examining the effect of adding Persian gum and calcium chloride to two types of soils, silicate sand from Firoozkooh and carbonate sand from Hormuz. For this purpose, initial parameters such as the weight percentage of Persian gum and the molarity of calcium chloride were evaluated through an unconfined compressive strength test, identifying optimal additive percentages. Then, the impact of factors such as curing time, curing place, and wetting-drying cycles on the compressive strength and durability of the optimized treated specimens was investigated. The results of this research indicate that the compressive strength of Persian gum-treated Firoozkooh and Hormuz sands increases up to 2.75 and 3 MPa, respectively, after a 28-day curing period at 40°C with the optimal Persian gum percentage (2.5% and 3%). Under dry conditions, Persian gum and calcium chloride-treated Firoozkooh and Hormuz sands at the optimal percentage (1.5% Persian gum and 3 molar calcium chloride for Firoozkooh sand and 2.5% Persian gum and 2 molar calcium chloride for Hormuz sand) achieve compressive strengths of 6.2 and 5.1 MPa, respectively, after 28 days, representing a 125% and 70% improvement compared to specimens treated with Persian gum. Persian gum exhibits acceptable durability against wetting and drying cycles, demonstrating initial dry and wet uniaxial compressive strengths (after immersion in water) for Firoozkooh and Hormuz sands treated with Persian gum, which were initially 2200 and 200, 2250 and 240 kPa, respectively. After undergoing 10 wetting and drying cycles, these strengths decreased to 750 and 110, 600 and 80 kPa, respectively, and will maintain this resistance in subsequent cycles.

Suitable tensile strength is one of the important parameters in soils subjected to tensile stress. In recent years, biopolymer materials have been widely used to control cracking and increase the tensile strength of soil. In this laboratory study, the tensile strength of sand treated with Persian gum was investigated. For this purpose, the effect of parameters of initial relative dry density of soil, materials mixing method, temperature and humidity of curing place and curing time on the tensile strength of treated samples was evaluated by indirect tensile test. After examining the results, it was found that adding a uniform gum-water solution (including 2% gum and 16% water related to the weight of dry soil) to the dry soil was the best mixing method and the initial relative density of 50% for the soil was the optimal density to obtain the highest tensile strength. Also, there is a direct relationship between the increase in temperature and the decrease in humidity with the increase in tensile strength, so that when the temperature increases from 25 degrees in the room to 50 degrees in an oven and the relative curing humidity environment decreases from seventy to fifteen and then to zero percent, the maximum tensile strength of treated samples increases from 154 to 270 and 442 kPa respectively.

Various improvement methods have been proposed to improve the mechanical and physical characteristics of soil for the construction and the other similar matters. One of the improvement methods is using of the environmentally-friendly elements such as Persian herbal gum as a renewable hydrocolloid biopolymer. Regarding this, in the present laboratory study, the effect of adding this gum to the Firouzkooh sand (No 161) was investigated. Persian gum-water mixture was added in different percentages relative to the weight of dry soil, and the created samples were subjected to unconfined compressive strength test to identify the optimal conditions of the composition. In spite of the variability of the weight percentages of water and gum added to the soil, the effect of the weight of the soil, curing temperature (room or oven temperature), and curing time (7 to 56 days) were investigated. To interpret the effect of Persian gum addition, several scanning electron microscope tests were performed on selected dry samples. The results clearly revealed an increase in the unconfined compressive strength of the samples improved with Persian gum up to 4 MPa due to the presence of many carboxyl and hydroxyl groups in the gum. Samples cured at room temperature with relative humidity of 15% displayed lower unconfined compressive strength than similar samples cured in an oven temperature due to the hydrophilic properties of herbal gum and increased flexibility of the created bonds.