Beyond 20% the homogenization of the mixture being more difficult, the fibers are not all linked to each other by the matrix; this discontinuity of the fibers and the non-homogeneity which leads to the agglomeration of fibers has been detected by the scanning electron microscopy in Fig. 8c, showing an area where the fibers were agglomerated when their content increases.The design standard of soil appeared in codes, construction manuals, regulations and so on, because of their wide variety of applications. The applications of soil depended on topographical area, climate condition and land use. In such applications, soil could be utilized in various forms, such as compacted earth, bricks, composite materials. Other than the applications, soil engineering properties have been studied in researches, such as soil strength in order to ensure its safety. This was important due to the fact that natural soil were poor in strength, which could be determined by mechanical tests, such as unconfined compressive strength tests, direct shear tests, triaxial tests, California Bearing Ratio tests, tensile and flexural tests. As a comparative example, the unconfined compressive strength of soil was obviously lower than cement admixed material. In order to improve the strength of soil, researchers used various kind of strengthening methods, i.e., mechanical, biological and chemical treatments. One of the applications of the soil strengthening methods is seen in ground improvement technology. Such kind of application is mostly developed by applying cement or chemical products to enhance the mechanical properties of soil. However, the usage of those products can possibly lead to two main issues. First, the in-situ ground improvement technique, dry rack cannabis which traditionally uses cement or chemical products, must disturb improved soil. Second, the production process of cement and chemical products can create harmful toxic, for example, in the process of cement production.
Therefore, an alternative technique is required.There was an alternative technique which used microbial biotechnology to produce a special material called biocement. This technique, many times called microbially induced calcite precipitation , can remedy the two aforementioned issues in ground improvement. First, this biocemented treatment can improve the strength of grounds without disturbing soil, because the microorganisms in the treatment can naturally reproduce and penetrate through the ground by themselves. Second, the biocementation process of MICP is non-pathogenic. On the other hand, microorganisms, which were used to induce calcite precipitation in biocementation solution or medium, contained urea and calcium ion. Therefore, there have been many increasing applications of biological or biocementation processes to improve the strength of soil, despite the requirement of interdisciplinary research fields including geotechnical engineering, geology, civil engineering, geochemistry and microbiology . In spite of the two aforementioned advantages of MICP, there are two important factors to be considered, i.e., environmental impacts and cost. Involving the environmental impacts of biocementation, Deng et al. used the life cycle assessment method to quantitatively analyze the energy consumption and carbon emissions of MICP technology, based on considering resource consumption and environmental impacts. They found that most of produced CO2 came from raw materials. In comparison, the MICP applied with cement consumed less non-renewable resources, but caused a greater environmental impact than lime and sintered brick. The major environmental impact produced by MICP consisted of smoke and ash, but the secondary impact was found in terms of global warming, photochemical ozone creation, acidification, and eutrophication. In applying to the production of five traditional materials,the carbon emissions and the energy consumption of MICP were found 3–7 times and 15–23 times, respectively, greater than those of traditional technologies. Furthermore, Rahman et al. reviews researches and developments over the past 25 years in using microbial-induced calcite precipitation as an environmentally sustainable and economic solution to engineering problems.
Using the sustainability analysis, they concluded that MICP treatment was possibly not environmentally sustainable nor economically viable technology, based on the current technology. However, they suggested that alternative sources of nutrients might lower the environmental footprint and cost, such as using a by-product from the milk industry “lactose mother liquor”, and waste products from the tofu industry. Related to cost consideration, Omoregie et al. investigated an inexpensive food-grade yeast medium for possible use as an alternative media for bacterial growth, urease activity and calcium carbonate precipitation. This was done in order to remedy the issue on high-cost bacterial cultivation as a consequence of the conventional use of laboratory-grade growth medium for MICP studies. For this, they compared low-cost food-grade media with eight laboratory-grade media . From comparison, it was found that the cost of bacterial cultivation by low-cost food-grade media was significantly reduced by 99.8%. Finally, they suggested that in terms of cost, the food-grade yeast extract had a potential for bacterial cultivation in MICP application. Currently, Jain et al. reviewed the study of Ivanov and Chu, and concluded that the cost for raw materials in chemical grouting was about $2–$72 per m3 of soil treatment, while that for MICP-based biogrouting is only $0.5–$9.0 per m3 . Moreover, the use of various wastes for microbial nutrient and cementation reagents made the MICP process both cost-effective and environmental friendly. Moreover, the biostimulation-based MICP made the reaction process more cost-effective then other augmentation-based MICP techniques. In spite of two aforementioned advantages of MICP, a further development is still needed. In other words, the process of MICP is quite time-consuming, because it requires days to weeks to induce the occurrence of natural biocementation process reaction. In order to accelerate its reaction, urease enzyme was proposed and used in researches.
As an example, Iamchaturapatr et al. used enzyme induced carbonate precipitation method due to its faster reactions. In the other words, the EICP process was done within a week, while the MICP process needed about 2 months. For other applications, Cui et al. proposed a high efficiency EICP method, which adopted a one-phase injection of low pH solution strategy. In their method, EICP solution consisting of a mixture of urease solution , urea and calcium chloride was injected into soil. Their results revealed that as compared to the conventional two-phase EICP method, the one-phase-low-pH method in their study could significantly improve the calcium conversion efficiency and the uniformity of calcium carbonate distribution in the sand samples. Furthermore, the unconfined compressive strength of sand treated using the one-phase-low-pH method was much improved, and the one-phase-low-pH method involved less number of injections. Although the EICP method has been found efficient, the strength of soil with EICP is still not satisfied in many occasions. Therefore, a novel material is further required. In many cases of soil stabilization, researchers made use of natural materials such as wool, straw bale, coconut fibers, rise husk, sugarcane, jute and sisal fibers.Hence, the composite materials that consisted of soil and natural fibers were being studied in many researches. As an example, Sharma et al. proposed to use natural vernacular fibers of Grewia Optivia and Pinus Roxburghii for improving the compressive strength, stabilization of Northern Indian sand clay. By varying the unconfined compression test periods, the results indicated that fiber reinforcement with Grewia Optivia and Pinus Roxburghii increased the compressive strength of soil by about 94–200% and 73–137%, respectively, depending on the proportion of fibers. In addition, the tensile strength of fibers of Grewia Optivia was found to be higher than that of Pinus Roxburghii. Son and Lee determined the changes in the compressive and tensile strength of soil cement reinforced by natural human hair fiber. In their tests, factors were considered, i.e., soil type, the amount of cement and fiber, fiber length, loading type, and curing age. Their results indicated that both the compressive and tensile strengths either increased or decreased depending on the conditions. Moreover, natural hair fibers could be effective and environmentally friendly to improve soil ground subjected to tensile loading, such as an embankment slope, roll bench, road subgrade, or landfill, thus reducing the cost for cement and waste treatment.
According to the aforementioned review, it can be seen that there is no research that uses hemp fibers with sandy soil under biocementation. In order to bridge this gap, this study aims to carry out a set of experiments which combine natural hemp fiber with EICP biocementation process to strengthen sandy soil. In the experiments, various tests are used, i.e., real-time bender element tests to estimate the shear wave velocity through sandy soil samples, the spectophotometer and pH meter to measure ammonification rate and solution pH, respectively, direct shear tests to determine both cohesion and internal friction angle, and XRD and SEM tests to confirm the binding effect of CaCO3. Humans have been utilizing the Cannabis sativa L. plant for millennia for both medicinal and recreational purposes. The C. sativa L. plant originates from Central Asia and has recently seen an increase in interest likely because of its many applications due to the large phytochemical content as well as being a rich source of both cellulosic and woody fibers. Two preparations of marijuana for recreational use are hashish and marijuana. Synthetic cannabinoids are emerging as psychoactive substances and have recreational use. Recreational use of marijuana, hashish synthetic cannabinoids are associated with ischemic and other types of strokes . The cannabinoids, which are oxygen containing aromatic hydrocarbon compounds, are one of the most researched groups of all the phytochemicals in C. sativa L. and include at least 70 compounds, of which delta-9-tetrahydrocannabinol and cannabidiol are some of the most well-known. THC and synthetic cannabinoids have affinity for the cannabinoid receptors. CBD does not have affinity for the cannabinoid 1 receptor and the cannabinoid 2 receptor and there is animal model evidence to show it modulates the adverse effects of ischemic stroke and likely acts on the sigma 1 receptor. Additionally, CBD, in laboratory animal models, has been shown to be a beneficial treatment in substance use disorder including protection of the liver from alcohol damage. The US government recently passed the Agriculture Improvement Act which included changes to the production and marketing of hemp and derivatives of cannabis with extremely low concentrations of delta-9-tetrahydrocannabinol . These changes removed hemp from the Controlled Substances Act, but preserved the US Food and Drug Administrations’ authority to regulate cannabis and cannabis-derived compounds. This study is investigating the toxicology of a proprietary CBD rich hemp extract. With the increasing interest in using products containing CBD in humans, it is essential to fully evaluate the safety of CBD consumption. While the published oral toxicological studies on CBD and hemp extracts are limited, the current available data suggests CBD is safe for human consumption, though additional studies need to be conducted. A review by Bergamaschi et al. described in vivo and in vitro reports of CBD administrations at a variety of dose levels.
The authors concluded that several studies support the conclusion that CBD is well tolerated and safe for humans at high doses and with chronic use, but there is evidence of potential drug metabolism interactions , cytotoxicity, and decreased receptor activity.Therefore, the authors also stated additional studies are needed to further evaluate the safety of CBD. A more recent review was conducted by Iffland and Grotenhermen to build on the Bergamaschi et al. review regarding CBD safety and any potential side effects. This review also concluded that numerous studies show that CBD is well tolerated and safe in humans at high doses and with chronic use. However, in order to further understand CBD and validate these findings, additional studies evaluating the safety of CBD are needed. The objective of the current studies was to assess the genotoxicity and preclinical safety of a proprietary hemp extract and to contribute significant safety data on CBD to the currently limited available data. Sprague-Dawley male and female rats were used in the 14-day and the 90- day studies. For both studies, the rats were 6 weeks of age at the start of the conditioning interval. The acclimation period was 6 days for the 14-day study and 12 days for the 90-day study. Criteria used for selecting animals for both studies were adequate body weight gain, absence of clinical signs of disease or injury, and a body weight within ± 20% of the mean within a sex. For the 14-day study, 40 rats were distributed to treatment groups according to stratification by body weight so that there was no statistically significant difference among group body weight means within a sex .