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Although cemented soil as a subgrade fill material can meet certain performance requirements, it is susceptible to capillary erosion caused by groundwater. In order to eliminate the hazards caused by capillary water rise and to summarize the relevant laws of water transport properties, graphene oxide (GO) was used to improve cemented soil. This paper conducted capillary water absorption tests, unconfined compressive strength (UCS) tests, softening coefficient tests, and scanning electron microscope (SEM) tests on cemented soil using various contents of GO. The results showed that the capillary water absorption capacity and capillary water absorption rate exhibited a decreasing and then increasing trend with increasing GO content, while the UCS demonstrated an increasing and then decreasing trend. The improvement effect is most obvious when the content is 0.09%. At this content, the capillary absorption and capillary water absorption rate were reduced by 25.8% and 33.9%, respectively, and the UCS at 7d, 14d, and 28d was increased by 70.32%, 57.94%, and 61.97%, respectively. SEM testing results demonstrated that GO reduces the apparent void ratio of cemented soil by stimulating cement hydration and promoting ion exchange, thereby optimizing the microstructure and improving water resistance and mechanical properties. This research serves as a foundation for further investigating water migration and the appropriate treatment of GO-modified cemented soil subgrade.

[Abstract:] Despite having been used for decades, the structural performance of emulsion-treated materials has still not been investigated as intensely as in the case of hot-mix asphalt (HMA). Proof of this is the lack of evolution of specific technical tests and standards. Due to this, many studies with cold asphalt mixtures (CAM) are carried out based on HMA specifications. Throughout the present paper, a new methodology is proposed in order to study different mechanical properties of CAM, such as unconfined compression strength (UCS), indirect tensile strength (ITS) and indirect tensile stiffness modulus (ITSM) not only in an independent way but also by giving a global approach. The consistency and applicability of the method is discussed and from its application to a practical case study with two very different CAM, new conclusions about their performance are laid down.

To evaluate the potential utility of a new biogrout based on calcium phosphate compounds (CPC) (CPC biogrout), we conducted unconfined compressive strength (UCS) tests and scanning electron microscope (SEM) observations of sand test pieces made from CPC biogrout. To produce CPC biogrout, we used soil extracts including microorganisms derived from two soils differing in pH, three amino acids, and urea as a pH increasing reactant. Temporal increase in pH was observed in slightly acidic soil by the addition of ammonia sources. On the other hand, there was no significant increase in pH in slightly alkaline soil except for urea. In most cases, the UCS of the test pieces made from CPC biogrout with soil extracts from acidic soil was higher than that without the addition of ammonia sources. Whisker-like crystals of CPC were identified SEM observation of test pieces with UCS of over 50 kPa. These results suggest that CPC biogrout has sufficient strength as a countermeasure for liquefaction and that amino acids can be made available as new pH-increasing reactants for CPC biogrout In addition, they suggest that either CPC biogrout or CPC chemical grout alone, or a combination of the two grouts, can be used depending on the various properties of grounds and soils.

To evaluate the potential utility of a new biogrout based on calcium phosphate compounds (CPC) (CPC biogrout), we conducted unconfined compressive strength (UCS) tests and scanning electron microscope (SEM) observations of sand test pieces made from CPC biogrout. To produce CPC biogrout, we used soil extracts including microorganisms derived from two soils differing in pH, three amino acids, and urea as a pH increasing reactant. Temporal increase in pH was observed in slightly acidic soil by the addition of ammonia sources. On the other hand, there was no significant increase in pH in slightly alkaline soil except for urea. In most cases, the UCS of the test pieces made from CPC biogrout with soil extracts from acidic soil was higher than that without the addition of ammonia sources. Whisker-like crystals of CPC were identified SEM observation of test pieces with UCS of over 50 kPa. These results suggest that CPC biogrout has sufficient strength as a countermeasure for liquefaction and that amino acids can be made available as new pH-increasing reactants for CPC biogrout In addition, they suggest that either CPC biogrout or CPC chemical grout alone, or a combination of the two grouts, can be used depending on the various properties of grounds and soils.

Tato práce se věnuje problematice vývoje a výroby geopolymerů. Zabývá se jejich základními fyzikálními vlastnostmi, které jsou důležité pro konstrukce, které by v budoucnu z toho materiálu mohly být vytvářeny. Věnuje se také optimalizaci a výrobě optimální směsi., This thesis is engaged in the progression and the production of the geopolymers. It puts mind to the physical properties of these materials. Their properties are of consequence for the gunnery which could be constructed from geopolymer materials. It pursues of the optimization and the production of the ideal mixtures for these tasks., Katedra dopravního stavitelství, Uchazeč prezentoval komisi hlavní výsledky a závěry své bakalářské práce. Po prezentaci bakalářské práce zodpověděl dotazy vedoucího a oponenta bakalářské práce. V diskusi o bakalářské práci podrobně zodpověděl všechny dotazy členů komise., Dokončená práce s úspěšnou obhajobou

LTRC Project No. 03-8GT, State Project No. 736-99-1213, Blended Calcium Sulfate (BCS) is fluorogypsum (FG), an industrial by-product, blended with lime or limestone. Approximately 90,000 metric tons (100,000 tons) of FG are generated annually in the United States, posing a serious problem for environmental disposal. The Louisiana Department of Transportation and Development (LA DOTD) has been using BCS in pavement construction over the last 15 years. While this material has performed satisfactorily after construction, its moisture sensitivity has concerned LA DOTD engineers because it has presented construction difficulty in wet environments., Therefore, there is a need to better understand the strength deterioration of BCS in a wet environment, and find ways to eliminate or reduce such deterioration by stabilizing BCS with various suitable cementitious agents. This study was divided into two major parts: laboratory and field tests. Laboratory tests were conducted to identify factors that significantly affect the strength development of raw BCS and to seek a suitable stabilization scheme for ameliorating water susceptibility of raw BCS. The effectiveness of each stabilization scheme was evaluated from the perspective of water resistance, strength, and volumetric expansion incurred by stabilization. Laboratory tests also investigated the resilient modulus and permanent deformation characteristics of stabilized BCS. Samples tested in the laboratory included ones both molded in the laboratory and cored at the test section of the Pavement Research Facility (PRF) test site at the Louisiana Transportation Research Center (LTRC)., The field test program included two parts: (1) building a full-scale test section at the PRF site according to proposed construction specifications; and (2) evaluating the performance of stabilized BCS base courses through in-situ tests, such as DCP, FWD, and DYNAFLECT to characterize their strength and structural properties., Ground granulated blast furnace slag (GGBFS) with a grade of 120 was used to stabilize BCS to improve its water resistance in this study. Portland cement, lime, and fly ash were also used as additives to GGBFS with different proportions to improve the properties of GGBFS-stabilized BCS., The results from this study indicate that moisture content controlled the strength of raw BCS, although other factors such as dry unit weight also influenced the result. Curing conditions affect the strength of raw BCS through the change of moisture content in the material. The loss and regaining of strength is generally a reversible process and the presence of free water among gypsum crystal particles is the reason for this phenomenon. BCS stabilized by 10 percent 120-grade GGBFS by volume can serve as a good pavement base. It achieved a fairly higher stiffness and a structural layer coefficient of 0.30 can be used for pavement design purpose. The tentative construction specifications used in the study proved to be adequate for the field construction. Therefore, it can be used with minor modification for future projects. Researchers recommend that the LA DOTD consider building several field test sections in different traffic and environmental conditions using the GGBFS-stabilized BCS as pavement base course.