This paper presents a detailed study focused on investigating the effects of fines content on the engineering properties of sand-fines mixtures. Specimens with a low-plastic fines content of 0, 15, 30 and 50% by weight were tested in static triaxial and consolidation tests to determine such parameters as compression index, internal friction angle and cohesion. The test procedures were performed on specimens of three cases: constant void ratio index, e = 0.582; same peak deviator stress of 290kPa; and constant relative density, Dr = 30%. The test results obtained for both the constant-void-ratio-index and constant-relative-density specimens showed that as fines content increased, the internal friction angle decreased, but cohesion increased. In testing of the same deviator stress specimens, both cohesion and internal friction angle were insignificantly altered with the increase in fines content. Furthermore, undrained behavior of sand-fines mixtures were recognized and discussed in three types of specimens

This paper presents the experimental results of the production of Nano-SiO₂ (NS) from rice husk ash (RHA) and the engineering properties of High Strength Concrete (HSC) containing various NS contents. Firstly, the mesoporous silica nanoparticles were effectively modulated from RHA using NaOH solution, and subsequently precipitated with HCl solution until the pH value reached 3. The optimum synthesis for the manufacture of SiO₂ nanoparticles in the weight ratio of RHA/NaOH was 1:2.4, and the product was calcined at 550 °C for 2 h. The EDX, XRD, SEM, TEM, FT-IR, and BET techniques were used to characterize the NS products. Results revealed that the characteristics of the obtained NS were satisfactory for civil engineering materials. Secondly, the HSC was manufactured with the aforementioned NS contents. NS particles were added to HSC at various replacements of 0, 0.5, 1.0, 1.5, 2.0, and 2.5% by the mass of the binder. The water-to-binder ratio was remained at 0.3 for all mixes. The specimens were cured for 3, 7, 28, 25 days under 25 ± 2 °C and a relative humidity of 95% before testing compressive and flexural strengths. Chloride ion permeability was investigated at 28 and 56 days. Results indicated that the addition of NS dramatically enhanced compressive strength, flexural strength, chloride ion resistance, and reduced chloride ion permeability compared to control concrete. The optimal NS content was found at 1.5%, which yielded the highest strength and lowest chloride ion permeability. Next, the development of flexural and compressive strengths with an age curing of 3–28 days can be analytically described by a logarithmic equation with R² ≥ 0.74. The ACI code was used, and the compressive strength at t-day was determined based on 28 days with R² ≥ 0.95. The study is expected to solve the redundancy of waste RHA in southern Vietnam by making RHA a helpful additive when producing high-strength concrete and contributing meaningfully to a sustainable environment.

This study presents an experimental study of engineering properties of soil stabilized with cement and fly ash for layers in roadway construction. The fly ash was used in this study satisfies the requirement according to ASTM C618. Five proportion mixes were used in this work with varying quantities of Ordinary Portland cement amounts of 8 %, 10%, and 8% cement combined with fly ash content of 2%, 4%, and 6%. Specified curing periods of 7, 14, 28 days were applied for all types of specimens. Some engineering tests were carried out, such as unconfined compressive strength, splitting tensile strength, stiffness of stabilized soil, SEM, and XRD techniques. SEM images, magnified 3000 times, showed that compacted soil structure was found as small and odd particles arranged without gel bound, while cement-fly ash stabilized soil was covered foam formation due to cement-fly ash crystal, and small particles cannot be observed. The peak intensity of Silicon Oxide was seen in the region 26-28° with an angle of 2. In addition, cement and fly ash significantly improved the mechanical properties of stabilized soils. Finally, the specimen containing 8% cement and 2% fly ash at 14-day curing has a splitting tensile strength greater than 0.45 MPa, satisfying the base layer of road construction requirement according to current Vietnamese standards. The obtained results provided a shred of evidence for capable of using fly ash for road construction in the context of an increase the fly ash in thermal plants.