การพัฒนากำลังอัดของดินเหนียวปนดินตะกอนผสมกากแคลเซียมคาร์ไบด์และเถ้าลอย

This paper investigates the possibility of using calcium carbide residue and fly ash to improve the strength of silty clay. Calcium carbide residue (CCR) is waste products remaining from acetylene gas. Fly ash is waste products remaining from power plants. This paper aims to determine the suitable mixing ratio and explain the strength development. The strength development is investigated by the unconfined compression test. The microstructural analysis is done via scanning electron microscope. It is found from this investigation that the mixing of CCR and fly ash in the silty clay leads to lower dry unit weight and higher optimum water content. The maximum strength of compacted CCR and fly ash stabilized silty clay is at the optimum water content. The 7% CCR content provides the highest strength and pozzolanic reaction plays a great role when CCR content is over 7%

Comparative Experimental Study of Sustainable Reinforced Portland Cement Concrete and Geopolymer Concrete Beams Using Rice Husk Ash

The ordinary Portland cement (PC) manufacturing process emits toxic carbon dioxide into the environment. Minimizing cement consumption in the construction industry is a major scholarly priority. This paper studies the comparison of reinforced Portland cement concrete and geopolymer concrete beams, in which rice husk ash (RHA) is used as a partial replacement for cement. The study aims to determine the optimum mix proportion of Portland cement concrete with RHA (PC-RHA) and geopolymer concrete with RHA (GC-RHA) for compressive strength that meets the requirements for normal strength concrete of 18, 25, and 32 MPa and compares to ones of the control PC without RHA. Then, the load behaviors and the failure modes of the reinforced PCC beam and reinforced GC beam using RHA as partially PC (PC-RHA beam and GC-RHA beam) were investigated. The obtained experimental load capabilities were also compared to ones predicted by the equation for designing reinforced concrete beams developed by ACI Committee 318. According to the test results, the compressive strength of the PC-RHA and GC-RHA decreased when there was a higher proportion of RHA replacement in the concrete. In terms of the structural behavior, all the PCC, PC-RHA, and GC-RHA beam curves are bilinear up to the first crack load and before the yield load, then become nonlinear after the yield load of the beam specimens. The maximum crack width of the GC-RHA beam was less than that of the PC-RHA beam. Furthermore, the GC-RHA beam was more ductile than the PC-RHA beam. Finally, the ACI equation provides reliable predictions with a margin of error of 4 to 7%. This concludes that the experimental load capabilities of the PC-RHA beam and GC-RHA beam were consistent with the ACI design equation

Comparative Experimental Study of Sustainable Reinforced Portland Cement Concrete and Geopolymer Concrete Beams Using Rice Husk Ash

The ordinary Portland cement (PC) manufacturing process emits toxic carbon dioxide into the environment. Minimizing cement consumption in the construction industry is a major scholarly priority. This paper studies the comparison of reinforced Portland cement concrete and geopolymer concrete beams, in which rice husk ash (RHA) is used as a partial replacement for cement. The study aims to determine the optimum mix proportion of Portland cement concrete with RHA (PC-RHA) and geopolymer concrete with RHA (GC-RHA) for compressive strength that meets the requirements for normal strength concrete of 18, 25, and 32 MPa and compares to ones of the control PC without RHA. Then, the load behaviors and the failure modes of the reinforced PCC beam and reinforced GC beam using RHA as partially PC (PC-RHA beam and GC-RHA beam) were investigated. The obtained experimental load capabilities were also compared to ones predicted by the equation for designing reinforced concrete beams developed by ACI Committee 318. According to the test results, the compressive strength of the PC-RHA and GC-RHA decreased when there was a higher proportion of RHA replacement in the concrete. In terms of the structural behavior, all the PCC, PC-RHA, and GC-RHA beam curves are bilinear up to the first crack load and before the yield load, then become nonlinear after the yield load of the beam specimens. The maximum crack width of the GC-RHA beam was less than that of the PC-RHA beam. Furthermore, the GC-RHA beam was more ductile than the PC-RHA beam. Finally, the ACI equation provides reliable predictions with a margin of error of 4 to 7%. This concludes that the experimental load capabilities of the PC-RHA beam and GC-RHA beam were consistent with the ACI design equation

Strength development in soft marine clay stabilized by fly ash and calcium carbide residue based geopolymer

This research investigates strength development and the carbon footprint of Calcium Carbide Residue (CCR) and Fly Ash (FA) based geopolymer stabilized marine clay. Coode Island Silt (CIS), a soft and highly compressible marine clay present in Melbourne, Australia was investigated for stabilization with the CCR and FA geopolymers. CCR is an industrial by-product obtained from acetylene gas production, high in Ca(OH)2 and was used as a green additive to improve strength of the FA based geopolymer binder. The liquid alkaline activator used was a mixture of sodium silicate solution (Na2SiO3) and sodium hydroxide (NaOH). The influential factors studied for the geopolymerization process were Na2SiO3/NaOH ratio, NaOH concentration, L/FA ratio, initial water content, FA content, CCR content, curing temperature and curing time. The strength of stabilized CIS was found to be strongly dependent upon FA content and NaOH concentration. The optimal ingredient providing the highest strength was found to be dependent on water content. Higher water contents were found to dilute the NaOH concentration, hence the optimal L/FA increases and the optimal Na2SiO3/NaOH decreases as the water content present in the clay increases. The maximum strength of the FA geopolymer (without CCR) stabilized CIS was found at Na2SiO3/NaOH = 70:30 ratio and L/FA = 1.0 for clay water content at liquid limit (LL). The role of CCR on the strength of FA geopolymer stabilized CIS can be classified into three zones: inactive, active and quasi-inert. The active zone where CCR content is between 7% and 12% is recommended in practice. The 12% CCR addition can improve up to 1.5 times the strength of the FA geopolymer. The carbon footprints of the geopolymer stabilized soils were approximately 22%, 23% and 43% lower than those of cement stabilized soil at the same strengths of 400 kPa, 600 kPa and 800 kPa. The reduction in carbon footprints at high strength indicates the effectiveness of FA geopolymer as an alternative and effective green soil stabilizer to traditional Portland cement

Temperature and duration impact on the strength development of geopolymerized granulated blast furnace slag for usage as a construction material

Through the process of extracting iron from iron ore, a by-product is generated known as granulated blast furnace slag (GBFS). Traditional stabilization methods such as cement stabilization are not entirely sustainable options. This research investigates the engineering properties of geopolymer-stabilized GBFS and their viability for usage as a construction material. A combination of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) was used as the liquid alkaline activator (L) along with low-carbon pozzolanic binders, namely, fly ash (FA) and slag (S). The L was prepared with a Na2SiO3:NaOH ratio of 70 30 and binders were added up to 30%. The effect of different curing regimes on the strength of geopolymerized GBFS was evaluated using scanning electron microscopy (SEM) and unconfined compressive strength (UCS) tests. The effect of both the temperature and duration of curing had a vital role in the strength development of the mixtures. The test results indicated that the combination of FA+S as a geopolymer binder could perform better than FA or S alone. With the lowest UCS value of 7.8 MPa and highest value of 43 MPa, all the geopolymer-stabilized GBFS were found to be suitable for a variety of civil and construction applications. © 2020 American Society of Civil Engineers

Strength and microstructure evaluation of recycled glass-fly ash geopolymer as low-carbon masonry units

The objective of this research was to evaluate the strength development of industrial by-products, namely Recycled Glass (RG) and Fly Ash (FA) in the manufacture of low carbon masonry units. A low carbon concept for manufacturing masonry units using RG-FA geopolymers was explored by applying low curing temperature of 50 °C and a low curing period of just 3–7 days. RG, being rich in silica was used as a filler material. FA, being a silica and alumina rich industrial by-product was used as a precursor in the RG-FA geopolymers. A liquid alkaline activator (L) comprising of a sodium hydroxide-sodium silicate solution was used for the alkali activation of 30% content of FA in the RG-FA blend. Factors found to affect strength development of the RG-FA geopolymers were: (1) the ratio of sodium hydroxide and sodium silicate in the liquid activator, (2) application of a low curing temperature of only 50 °C, (3) short curing periods of just 7 days and (4) the L/FA ratios. A geopolymer composed of a 70% Na2SiO3:30% NaOH ratio with a L/FA ratio of 0.625 was found to be the most efficient combination to provide the required unconfined compression strengths for manufacturing masonry. The usage of RG-FA geopolymers as low carbon masonry units was found to be viable using a low curing period of just 7 days and a curing temperature of just 50 °C. The RG-FA geopolymers had sufficient compressive strength be used as structural masonry units and needed only a low amount of heat treatment to achieve the minimum strength requirement. Optimally, 30% of FA was found to be sufficient for geopolymerization to occur for this novel low carbon RG-FA masonry units. Furthermore, the core materials needed to produce RG-FA masonry units were industrial by-products, the sustainable usage of which would contribute significantly to efficient waste management, through the production of aesthetically pleasing masonry units

Calcium carbide residue: Alkaline activator for clay-fly ash geopolymer

Calcium Carbide Residue (CCR) and Fly Ash (FA) are waste by-products from acetylene gas and power plant production, respectively. The liquid alkaline activator studied in this research is a mixture of sodium silicate solution (Na2SiO3), water and CCR. The primary aim of this research is to investigate the viability of using CCR, a cementitious waste material, as an alkaline activator and FA as a precursor to improve the engineering properties of a problematic silty clay to facilitate its usage as stabilized subgrade material. The influential factors studied are Na2SiO3/water ratio, FA replacement ratio, curing time, curing temperature and soaking condition for a fixed CCR content of 7%. Strength development is investigated via the unconfined compression test. Scanning Electron Microscopy (SEM) observation is used to explain the role and contribution of influential factors on strength development. CCR dissolves the silicon and aluminum in amorphous phase of FA and the Na2SiO3 acts as a binder. The maximum soaked strength of the clay-FA geopolymer is found at Na2SiO3/water ratio of 0.6 and FA replacement ratio of 15%. The optimal Na2SiO3/water ratio is approximated from index test, which is a very practical approach. The clay-FA geopolymers with 40 C curing exhibit higher strength than those with room temperature curing, indicating the possibility of using clay-FA geopolymer for pavement subgrade applications. The 7-day soaked strength at the optimal ingredient meets the strength requirement for subgrade materials specified by the local national road authority. CCR is found to be a sustainable alkaline activator for geopolymer stabilized subgrade materials, which will result in the diversion of significant quantities of this by-product from landfills

Performance of Asphalt Concrete Pavement Reinforced with High-Density Polyethylene Plastic Waste

This research investigates the possibility of using high-density polyethylene (HDPE) plastic waste to improve the properties of asphalt concrete pavement. HDPE plastic waste contents of 1, 3, 5, and 7% by aggregate weight were used. HDPE plastic waste=stabilized asphalt concrete pavement (HDPE-ACP) was evaluated by performance testing for stability, indirect tensile strength, resilient modulus (MR), and indirect tensile fatigue (ITF). In addition, microstructure, pavement age, and CO2 emissions savings analyses were conducted. The performance test results of the HDPE-ACP were better than those without HDPE plastic waste. The optimum HDPE plastic waste content was 5%, offering the maximum MR, ITF, and pavement age. Scanning electron microscope images showed that the excessive HDPE plastic waste content of 7% caused a surface rupture of the sample. Improvements in the pavement age of the HDPE-ACP samples were observed compared with the samples with no HDPE plastic waste. The highest pavement age of the HDPE-ACP sample was found at an HDPE plastic waste content of 5% by aggregate weight. The CO2 emissions savings of the sample was 67.85 kg CO2-e/m3 at the optimum HDPE plastic waste content

Spent coffee grounds-fly ash geopolymer used as an embankment structural fill material

The drinking of coffee forms a deep-rooted pastime in many communities worldwide. However, the culture of coffee drinking generates vast quantities of organic waste that ends up in landfills. Current research trends are inclined towards recycling of waste materials into alternative construction materials, hence the need to research sustainable uses for spent coffee grounds. Coffee grounds (CG) are highly organic with a very high percentage of biodegradable material. The objective of this research was to study the strength development of CG when used as a geopolymer stabilized embankment structural fill material aiming for a better understanding of geopolymer stabilization of highly organic material. Fly ash (FA), being a silica and alumina rich material, was used as a precursor. A liquid alkaline activator, L, being a sodium hydroxide-sodium silicate solution was used for alkali activation of FA in the CG-FA geopolymer. Factors found to affect strength development of the CG-FA geopolymer were: (1) the ratio of sodium hydroxide and sodium silicate in the activator liquid; (2) the curing time; (3) the replacement ratio of FA in the CG; (4) the alkalinity of the activator liquid used; and (5) the curing temperature. Optimally, FA can constitute up to 30% of the CG-FA mix for efficient geopolymerization to occur. The concentration of sodium hydroxide can be increased up to 12 mol before the strength development-to-alkalinity ratio decreases. The highest strength was found to occur when the curing temperature was 50°C. By introducing 30% of FA into CG, an efficient geopolymer can be synthesized with a L=FA ratio of 1.8 and a Na2SiO