Papers by Keyword: Fly Ash (FA)

Abstract: The use of supplementary cementitious materials (SCMs) has revolutionized the construction industry by significantly reducing the carbon footprint, minimizing waste, lowering labor costs, and enhancing both durability and precision in concrete structures. Accurately predicting compressive strength (CS), a critical mechanical property, is crucial for ensuring these structures' optimal performance and reliability. Given the nonlinear behavior of concrete mixtures incorporating fly ash and slag, machine learning (ML) techniques have become increasingly valuable for predictive modeling. This study assesses the performance of four ML models: Multilinear Regression (MLR), K-Nearest Neighbors (KNN), Random Forest (RF), and Random Forest integrated with Particle Swarm Optimization (RF-PSO). By addressing gaps related to compressive strength variability and comparing model performance, the study found that all four models achieved high accuracy in CS prediction, with RF-PSO consistently outperforming others based on multiple evaluation metrics. Visual analysis corroborates the models' effectiveness, highlighting potential advantages such as improved quality control, cost efficiency, enhanced safety, and environmental sustainability. Furthermore, an analysis of the importance of features was conducted to evaluate the contribution of individual variables in developing the RF-PSO model.

Abstract: This study looked into the economic production of self-compacting concrete (SCC) using affordable and locally available materials such as fly ash (FA), laterites (LA), and polyethylene terephthalate (PET) fibres. To achieve optimal properties of SCC, Response Surface Methodology (RSM) - Central Composite Design (CCD) was employed. Thus, twenty different SCC mixes were designed with varying input factor combinations (FA: 0–40%, LA: 0-50%, and PET fibre: 0–2%) and tested for six responses (rheological properties, namely slump flow, V-funnel time, and L-Box; and mechanical properties, namely compressive, split-tensile, and flexural strengths test). Mathematical models were created in response to the experimental results and assessed using analysis of variance (ANOVA) test. L-Box, V-funnel, and Slump flow test results showed that while fly ash may improve the flowability of SCC, inclusion of high volume of PET-fibres (above 1%) and laterite (above 25%), has high negative impact on SCC flowability. The results further revealed that inclusion of PET-fibres in SCC largely improves the flexural strength (FS) and split tensile strength (STS) by about 20%. However, high volume of laterite contributes negatively to the strength values. Although SCC’s compressive strength decreased with addition of each or a combination of the three different materials, a combination of 20% fly ash, 25% laterite and 1% PET-fibres can result in strength values that are comparative to that of the control mix. The RSM models developed showed relatively good predictive capabilities especially for the compressive strength, L-box and V-funnel models with adjusted R² values ranging between 0.8 – 0.9. Among all the combinations, it is recommended that 20% FA, 25% LA, and 1% PET fibres be adopted in production of sustainable and cost-effective self-compacting concrete, as it gave relatively stable characteristics compared to the control mix in terms of the strength and rheological properties.

Abstract: Metakaolin is in great demand worldwide as a highly active pozzolanic additive to Portland cement. The use of metakaolin helps to increase the density, water resistance, and mechanical strength of Portland cement, which makes it possible to reduce the consumption of clinker – the most energy-intensive and expensive component of cement/concrete. Usually, metakaolin is obtained by thermal processing of kaolin clays at a temperature of 600–850°C. Kaolin clay reserves in the world are strictly limited. Kaolin clays have not been identified in Georgia. However, there are kaolinized clays, which are distinguished by a lower Al₂O₃ content compared to kaolin clays. The purpose of this work is to study the possibility of obtaining a highly active pozzolanic additive – metakaolin based on kaolinized clays of Georgia and regulation of the parameters of their synthesis. It is proved that the addition of fly ash to kaolinized clay allows reducing the temperature of heat treatment and obtaining a highly effective pozzolanic additive to cement.

Abstract: Concrete is one of the most common building materials in the world, the production of which is associated with large energy costs, as well as greenhouse gas emissions, which negatively affect the planet’s ecosystem. Replacing OPC (ordinary Portland cement) with GPMs (geopolymer materials) makes it possible to reduce this impact significantly. Another advantage of GPMs compared to OPC is that during the production of geopolymers, various production wastes are mainly recycled. This work is devoted to the study of the possibility of regulating the properties of GPMs using FA (fly ash) – waste from the TPPs (thermal power plants) of Georgia. Various methods of ash activation have been developed, which makes it possible to optimize the properties of GPMs obtained on its basis. We intend is to optimize the properties of the GPMs using different FA activation approaches, which will make it possible to improve the physical-mechanical properties of the binder.

Abstract: This study investigates the substitution of river sand with respect to fly ash in self-compacting concrete (SCC) and its performance on workability, strength, and durability. Various mix designs were assessed through L-box, V-funnel and slump cone test to determine fresh concrete properties. The results indicated that higher fly ash content significantly improved the passing and filling abilities of SCC, as evidenced by increased L-box blocking ratios and larger slump flow measurements, albeit with a higher segregation tendency. The mix with 75% fly ash and 25% river sand (FA75-RS25) demonstrated the best overall performance, showing superior passing ability (L-box ratio of 0.87), excellent filling ability (slump flow of 700 mm), and acceptable segregation resistance. This mix also achieved the highest split tensile, flexural, and compressive strengths, outperforming the control mix (FA00-RS100). Flexural strength results for the FA75-RS25 mix showed significant improvements over time, with values of 7.67 MPa at 28 days, 10.33 MPa at 56 days, and 11.17 MPa at 90 days, compared to the control mix which achieved 5.83 MPa, 7.50 MPa, and 8.17 MPa, respectively. These findings underscore the potential of fly ash as a viable and sustainable substitute for river sand in SCC, enhancing performance and supporting sustainable construction practices. Further research is recommended to explore additional mechanical properties and long-term durability aspects of fly ash-incorporated SCC.

Abstract: This paper presents the results of an experimental investigation carried out on accelerated curing of Quaternary Blended Cement (QBC) Concrete with and without recycled aggregate. Cement is partially replaced with fly ash, micro silica and nanosilica to produce QBC Concrete. The variables of study include the grade of concrete, powder content and percentage of recycled aggregate. Two grades of concrete M-40 and M-60 were used in this investigation. Based on the earlier studies, fly ash and micro silica are kept constant as 20% and 10% respectively while nanosilica is varied as 2% and 3%. Three percentages of recycled aggregate as partial replacement of natural aggregate (0%, 50% and 75%) were used. Two methods of curing were employed; boiling water method and hot air curing. The test results are encouraging and it is observed that 90% of the design strength could be achieved in one day for both the grades of concrete by curing at 100°C for a period of 3 hours. Keywords: Quaternary Blended Cement Concrete (QBCC), Fly ash (FA), Micro silica (SF), nanosilica (NSF), Recycled Concrete Aggregate (RCA), Accelerated Curing.

Abstract: Geopolymers, which areinorganic polymers consisting largely of three-dimensional Al-Si-O networkformed by reactions between aluminosilicate solids and concentrated alkalisolutions, are gaining recognition as environmentally friendly engineeringmaterials. As a replacement for ordinary Portland cement (OPC), geopolymerconsumes much less energy to produce, and may be synthesized from various solidinorganic waste materials. This work describes the synthesis of geopolymerswhich combines two waste materials as aluminosilicate precursors: an ASTM ClassC coal fly ash from the Paiton powerplant, and Fe-rich metallurgical slag fromKratakau Steel. To study the effects of the reactant mixture composition, asimplex centroid experiment is undertaken with fly ash and slag as its majorcomponents, and level of addition of sodium silicate as the independentvariable. The highest slag to ash mass ratio is set at 50%. The solidaluminosilicates and sodium silicate are mixed with 10 M KOH solution at a massratio of 2.8. The mixture is processed in a planetary mixer to form a smoothpaste, which is then cast into specimens for the measurement of compressivestrength in a universal uniaxial load tester after a 1-week period of curing atroom temperature. The measured compressive strengths of all geopolymer pastesamples are lower than that of OPC, anddecreases with increasing slag proportion. Addition of Sodium silicateincreases the strength due to decreased porosity. Despite the highertheoretical reactivity of the slag compared to the Paiton fly ash, estimatedfrom their degrees of network depolymerization, the addition of slag reducesthe geopolymer mortar compressive strength. It is hypothesized that therelatively coarse size of the slag particles offsets its higher reactivity.

Abstract: In construction practice, we often encounter a situation where there is overloading of the existing columns and pillars, namely due to various adaptations and extensions. Masonry columns and pillars are usually loaded with vertical forces. Overloading these structural elements leads to the crushing of masonry. To prevent the destruction of columns and pillars it is often proposed to reinforce these elements.The paper deals with the possibilities of using new innovative materials in the reinforcement of masonry columns, namely a "green" fiber cementitious composite with the so-called "strain hardening", which uses industrial waste mainly from the Moravian-Silesian Region.

Abstract: For the production of quality autoclaved aerated concrete product is necessary to know the chemical composition of raw materials and with regard to that optimize the recipe. This paper deals with the verification of the influence raw materials mixture ́s chemical composition, the reactivity of the silica source and the molar ratio C/S on the shape and amount of tobermorite crystals in autoclaved aerated concrete.

Abstract: The paper discusses the creep cement pastes with addition of fly ash. The evolution of the creep was observed in age of one year, for length one month. The size of the creep is influenced by the amount the creep physically bound water. The material properties depend on the ratio of components from which the cement paste is composed. The paper presents the results of creep measurement for the ratio of cement and fly ash 70:30, 60:40 and 50:50. The basic creep and creep of the saturated cement paste were calculated from measurements.