Fly Ash Dosage Research Articles

Municipal Solid Waste Incineration (MSWI) Fly Ash as a Potential Adsorbent for Phosphate Removal

Phosphorus, in the form of phosphate, is an essential nutrient used in agriculture, but in excess, it becomes harmful to the environment by promoting the eutrophication of aquatic ecosystems, leading to oxygen depletion and phytoplankton overgrowth. This study aims to repurpose municipal solid waste incineration (MSWI) fly ash for phosphate removal by adsorption and develop sustainable, cost-effective MSWI fly ash-based mitigation strategies for phosphorus pollution. Batch experiments were conducted to examine the effects of contact time, phosphate concentration, MSWI fly ash dosage, and pH on phosphate removal efficiency. The results indicate that the phosphate removal efficiency significantly improved with a longer contact time, pH of 2, increased MSWI fly ash dosage, and higher initial phosphate concentrations. These findings highlight the potential of repurposing MSWI fly ash as an economical and sustainable adsorbent to mitigate the impacts of phosphate pollution on aquatic ecosystems, a strategy that promotes not only waste reduction and the circular economy but also environmental protection and conservation.

Predicting the Compressive Strength of Sustainable Portland Cement-Fly Ash Mortar Using Explainable Boosting Machine Learning Techniques.

Unconfined compressive strength (UCS) is a critical property for assessing the engineering performances of sustainable materials, such as cement-fly ash mortar (CFAM), in the design of construction engineering projects. The experimental determination of UCS is time-consuming and expensive. Therefore, the present study aims to model the UCS of CFAM with boosting machine learning methods. First, an extensive database consisting of 395 experimental data points derived from the literature was developed. Then, three typical boosting machine learning models were employed to model the UCS based on the database, including gradient boosting regressor (GBR), light gradient boosting machine (LGBM), and Ada-Boost regressor (ABR). Additionally, the importance of different input parameters was quantitatively analyzed using the SHapley Additive exPlanations (SHAP) approach. Finally, the best boosting machine learning model's prediction accuracy was compared to ten other commonly used machine learning models. The results indicate that the GBR model outperformed the LGBM and ABR models in predicting the UCS of the CFAM. The GBR model demonstrated significant accuracy, with no significant difference between the measured and predicted UCS values. The SHAP interpretations revealed that the curing time (T) was the most critical feature influencing the UCS values. At the same time, the chemical composition of the fly ash, particularly Al2O3, was more influential than the fly-ash dosage (FAD) or water-to-binder ratio (W/B) in determining the UCS values. Overall, this study demonstrates that SHAP boosting machine learning technology can be a useful tool for modeling and predicting UCS values of CFAM with good accuracy. It could also be helpful for CFAM design by saving time and costs on experimental tests.

Mechanical Properties, Durability Performance, and Microstructure of CaO-Fly Ash Solidified Sludge from Northeast, China.

In order to investigate the influence of the CaO and fly ash (FA) dosage and proportion on the mechanical properties, durability, and microstructure of solidified sludge, freeze-thaw (F-T) cycles and dry-wet (D-W) cycles are conducted to study the change in appearance and the strength attenuation of CaO-FA solidified sludge. Low-field nuclear magnetic resonance (LF-NMR) is used to analyze the microstructure of the solidified sludge with various dosages and ratios of CaO-FA. The results demonstrate that the unconfined compressive strength (UCS) and direct shear strength of solidified sludge increase with the prolongation of the curing age. Furthermore, the mechanical properties of solidified sludge are improved as the ratio of CaO-FA increases. As the curing age increases, the distribution of transverse relaxation time (T2) becomes narrow, the spectral area decreases, and the amplitude of the LF-NMR signal shows a downward and leftward tendency. Additionally, with the increase in the number of F-T cycles and D-W cycles, the UCS of solidified sludge declines and the degree of pore deterioration increased gradually. This study offers a theoretical foundation and empirical data for the dredging and treatment of sludge in cold regions.

Performance and microstructural characterization of fiber-reinforced cement-based grout incorporating waste tailing sand and fly ash

A fiber-reinforced cement and tailing sand-based grout (FRCTG) was proposed to improve the utilization of solid waste in construction. Different grout specimens were prepared using various proportions of ordinary Portland cement, iron tailing sand (ITS), fly ash (FA), basalt fibers (BFs), and water as raw materials. Used single-factor test, orthogonal test and artificial neural network model that provided a comparative analysis of the change in the rheological and mechanical properties of different grout mixes according to their component ratios. Furthermore, microscopic characterization techniques were used to reveal the intrinsic physicochemical mechanisms underlying the structural evolution of the considered grouting materials. The results indicate that ITS significantly increases the rheological properties of the grouting material. The maximum strength of the grouting material is achieved when the length of BF is 6 mm and the dosage is 0.2 %. An 8 % dosage of FA can effectively improve the rheological properties of the grouting material and enhance its flexural strength. Microscopic tests reveal that SiO2 in ITS exists in the form of quartz with low reactivity, thereby inhibiting the hydration reaction of the binder material. Different distribution patterns allow BF to serve both as reinforcement for the matrix and as a framework for hydration products, effectively enhancing the density between the BF and the surrounding matrix. The surface of FA is covered in layers by hydration products, forming a chain-like structure that improves bonding strength with the material. The results of this research offer a high-performance, low-cost, and environmentally friendly grouting material for construction grouting projects, which is of significant importance for promoting innovation in comprehensive utilization of solid waste.

PERTUMBUHAN DAN HASIL TANAMAN PADI GOGO (Oryza sativa L.) PADA TANAH PODSOLIK (ULTISOL) YANG DIAPLIKASIKAN ZEOLIT FLY ASH

The low productivity of upland rice on Podzolic (Ultisol) soil is caused by various constraints including low pH, the content of macronutrient N, P, K, Ca and Mg, BS and CEC were low, solubility and high Al saturation, high P fixation, delicate to erosion and water availability were low. Applied of zeolite synthesized from coal fly ash with high CEC is expected to overcome these constraints. The high negative charge on zeolite contributes to increasing soil absorption of nutrients provided or dissolved from soil minerals and decomposition of organic matter. The study was conducted experimentally using a completely randomized design, zeolite fly ash as the treatment consisting of 6 levels (0, 100, 150, 200, 250 and 300 kg ha-1) each repeated 3 times. The results showed that the application of zeolite fly ash dose 100-300 kg.ha-1 tends increased the plant height, filled grain number per panicle, the percentage of filled grain and 1000 grain weight compared without zeolite application and the highest increased showed in the number of maximum tillers and productive tillers and weight of milled dry grain per clump was obtained at a dose of 200 kg.ha-1 compared without zeolite is 45, 107 and 106% respectively.

The effect of pH and carbonation on the partially immersed mortar exposed to physical salt attack

In saline-alkali or salt-lake areas, the influence of pH value of underground aqueous solution and carbonation on the deterioration of cement-based materials remains an open question. This study utilizes various techniques to investigate the physical properties and degradation mechanism of partially immersed mortar incorporated with different dosages of fly ash exposed to combined action of salt solutions (10 wt% Na2SO4, 3.5 wt% NaCl + 10 wt% Na2SO4, and tap water) at different pH values (pH 5, 7, and 9) and carbonation (accelerated carbonation: 20 vol% CO2 and natural carbonation: 0.035 vol% CO2). The results indicate that the degree of deterioration of mortar increases with dosage of fly ash and pH value of salt solution, with the maximum mass loss exceeding 25 %. Physical sulfate attack (PSA) is responsible for the partially immersed mortar exposed to combined action of salt attack at various pH values and natural carbonation. However, when carbonation is accelerated, a more severe deterioration occurs, with the durability time of mortar reduced by nearly 60 %. PSA and decomposition of C-S-H are mainly responsible for the deterioration of mortar, while the formation of thaumasite and natrite is partially responsible for the deterioration of mortar. The presence of NaCl in mixed salt solution inhibits the precipitation of Na2SO4 crystals; the precipitation of NaCl clogs the pore network of mortar, which impedes the progressive penetration of CO2. The presence of NaCl in mixed salt solution is beneficial to salt resistance and carbonation resistance of mortar.

Modeling of effect of fly ash amount on microstructure and chloride diffusivity of blended fly ash-cement systems

Reasonable utilization of industrial fly-ash wastage in concrete engineering has been regarded as an effective way to reduce carbon emissions. By adding the reasonable dosage of fly ash to cement paste, the compactness and microstructure characteristics of the blended cement systems can be significantly improved, thereby effectively enhancing the durability of concrete structures. The vector hydration model of blended fly ash-cement systems with the interference effects of different hydration layers of fly ash and cement particles, the solubility equilibrium of solid phases and the electrical neutrality of the pore solution involved is established. By fully comparing with the experimental data of hydration degree, capillary porosity and CH content, the accuracy of the developed hydration model is verified. Based on the hydration model, the effect of fly ash content on the concentration of different ions and pH in the pore solution with curing time is discussed. Additionally, the evolution characteristic of hydration degree, capillary porosity and CH content with curing time at different fly ash content is also analyzed. Based on the reconstructed microstructure of blended systems, the rolling sweep (RS) technique is used to determine the pore size distribution of capillary pores. The effect of fly ash content on cumulative pore size distribution and differential pore size distribution at different curing time is quantitatively evaluated and discussed. By utilizing the first-passage cube, the dual-probability-Brownian motion method is constructed to predict the chloride diffusivity of blended cement systems. After diffusion model is verified by multi-group experimental data, the optimal dosage of fly ash at different water-binder ratio is calculated, which can provide theoretical guidance for practical applications in concrete engineering.

Study on the early volume stability of cement-based materials during CO2 curing

In this study, the impact of carbonation curing regime and fly ash dosage on the volume stability of concrete was investigated. The shrinkage of cement pastes specimens incorporating 0–30 % fly ash after 2–24 h pre-conditioning and 4–24 h carbonation curing was experimentally determined. Carbonation curing can lead to a maximum increase of 39.4 % on dry shrinkage of cement paste compared to the standard-cured ones. Prolonged carbonation curing can also enlarge the average and critical pore sizes by 123.4 % and 697.8 %, respectively. The water penetration of prolonged carbonation-cured cement mortar was increased by 56.1 %, consequently. However, appropriate carbonation curing increased compressive strength and sequestered CO2 effectively. The addition of an appropriate dosage of low-calcium fly ash can mitigate the adverse impact of carbonation curing on the volume stability of cement paste.

Preparation of carbon-negative artificial lightweight aggregates by carbonating sintered red mud (SRM): CO2 sequestration, microstructure and performance

This study investigated the possibility of employing CO2 curing for the production of cement-free artificial aggregates using low-value sintering red mud (SRM) and fly ash (FA). The effects of different curing methods (CO2 and air curing) and varying FA dosages on the properties of SRM artificial aggregates were analyzed. For SRM artificial aggregates subjected to CO2 curing, the calcium silicates depleted accompanied by precipitation of calcite and aragonite. The carbonated SRM artificial aggregates (CRAAs), exhibited a denser microstructure, with the pores of the SRM filled with carbonation products. For CRAAs with 100 wt% SRM, up to 9.67 wt% CO2 was sequestered and in turn produced calcium carbonate, which resulted in a 149.0% enhancement in crushing strength and a 29.5% reduction in water absorption compared to the similar aggregates under air curing. The introduction of FA led to an accelerated strength development in the CRAAs during subsequent air curing, which was attributed to the formation of carboaluminates as a result of the hydration between the carbonation products and aluminates derived from FA. From the perspective of environment, CRAAs was carbon-negative, with a potential reduction of up to 40.2 kg of CO2 per ton of CRAAs production, presenting a cleaner and sustainable alternative to natural aggregates. The results of the study provided a feasible solution for the effective treatment of SRM on a large scale and can be used as a reference for subsequent studies.

Predicting the impermeability and mechanical properties of manufactured sand polymer waterproof mortar using an optimised back-propagation neural network

Owing to its complex composition, accurately predicting the performance of polymer waterproof mortar (PWM) using ordinary equations is difficult. To quickly and accurately obtain the proportions of various components of high-performing PWM, in this study, we designed a back-propagation neural network (BPNN) model with a topology structure of 5–12–2 and optimised it using the particle swarm optimisation (PSO) algorithm, whale optimisation algorithm (WOA), and genetic algorithm (GA). The input layer of the model included cement (OPC), a waterproofing additive (WPA), dispersible polymer powder (DPP), tuff stone powder (SP), and fly ash (FA), whereas the output layer included the chloride-ion electric flux and compressive strength of PWM. The model dataset comprised 378 samples, of which 228 were used for model establishment and 150 were used for model validation. Correlation analysis was conducted to determine the relationship between the raw materials and the impermeability and mechanical properties of PWM; further, principal component analysis was performed on the PWM dataset. At 7 and 28 d, the dosages of WPA and DPP in the PWM were negatively correlated with the chloride-ion electric flux and positively correlated with the compressive strength. In addition, at 28 d, the OPC dosage was positively correlated with the chloride-ion electric flux and negatively correlated with the compressive strength; the SP and FA dosages were correlated negatively and positively with the chloride-ion electric flux and compressive strength, respectively. Group B4 performed the best in this study, and group E4 had the optimal ratio of mineral admixtures. The WOA-BPNN achieved the highest prediction accuracy for both the PWM chloride-ion electric flux and compressive strength, with prediction evaluation parameters of R2 = 0.98, MAE = 17.4, MAPE = 0.09, and RMSE = 21.2 and R2 = 0.98, MAE = 15.4, MAPE = 0.07, and RMSE = 21.0, respectively. Using the WOA-BPNN to predict the impermeability and mechanical properties of PWM is viable, and the WOA-BPNN can offer scientific guidance for the proportionate design of PWM.

Photosynthesis and stress response of coal fly ash on stem elongation in wheat.

Coal is one of the primary energy sources in China and is widely used for electricity generation. Crops growing in overlapped areas of farmland and coal resources (OAFCR) suffer from coal fly ash stress, especially during stem elongation, which is a key stage that impacts wheat yield and is sensitive to environmental stress. As a primary food crop of China, wheat is essential for food security. However, the characteristics of wheat under the combined stress of fly ash and various heavy metals have not been sufficiently investigated. In this study, we explored the response of stem elongation in wheat to different levels of coal fly ash stress and determined the content of heavy metals (HMs) in wheat leaves. We found that with an increase in fly ash content, the Cu content in the shoots increased, while that in the roots decreased. Coal fly ash exposure reduced the proportions of Pb and Zn in the cytoderm, and the proportion of Cu in the soluble constituents decreased from 58.3% to 45.7%. Total chlorophyll, chlorophyll a, and chlorophyll b levels decreased significantly, whereas peroxidase (POD) and catalase (CAT) activities generally increased with increasing fly ash dose. Meanwhile, chloroplasts, mitochondria, and their internal structures were damaged, and the cell structures of leaves, such as the internal membrane structure, were damaged.

Utilization of high fly ash dosage to reduce cement consumption in concrete formulations

The concrete production is responsible for high proportion of total carbon dioxide emission due to enormous consumption of Portland cement. This traditional binder system is due to high autogenous emission during calcination the main carrier of such negative environmental impact. The effective way to reduce the use of Portland cement is to replace that this binding material exhibiting lower energy demandingness. This paper deals with the utilization of fly ash as Portland cement replacement, which is frequently applied in concrete industry. The paper deals the highest replacement level in accordance with valid regulations. The experimental program was focused on the properties of fresh concrete mixture and basic physical and mechanical properties of hardened concrete. The attained results confirmed good potential of this approach, however the increase of plasticizer dosage was necessary to maintain a similar consistency of fresh mixture. That is why the fresh mixture exhibited lower level of air content.

Experimental Investigation on Ductility in Fly Ash Aggregate Concrete

Aggregate in concrete is structural filler, which occupies the most of the volume of the concrete The composition, shape and size of the aggregate have significant impact on the workability, durability, strength, weight and shrinkage of the concrete. In recent period some of the aggregates are chemically active and also that certain aggregates exhibit chemical bond at the interface of aggregate and paste. Aggregate occupy 60-80% of the volume of concrete is considerable. The utilization of fly ash in concrete as partial replacement of cement is gaining immense importance today, mainly on account of the improvement in the long term durability of concrete combined with ecological benefits. Three grades of ordinary Portland cement (OPC) are 33,43 and 53 as classified by Bureau of Indian Standard (BIS) are commonly used in construction industry. The main variable investigated in this study is variation of fly ash dosage in 10%, 20%, 30% and 40%. The compressive strength, durability and shrinkage of concrete were mainly studied. The fly ash is collected in Mettur Thermal Power Plant. Then the cement and fly ash proportions of 12.5:87.5, 15:85 and 17.5:82.5 will be adopted to get fly ash aggregates. The particle size distribution, specific gravity, bulk density, impact test on aggregate will be conducted. For the plain concrete and fly ash aggregate concrete of beams (Plain concrete and RCC beams), cubes and cylinders will be cast. All the specimens will be cured in a curing tank. The Ductility test and compressive strength test will be conducted on these plain and fly ash aggregate concrete specimens.

Stabilization of micaceous residual soil with industrial and agricultural byproducts: Perspectives from hydrophobicity, water stability, and durability enhancement

Micaceous residual soil is prevalent in the tropical regions of southern China. However, it is generally deemed unsuitable as a construction material in earthen structures due to its inferior engineering properties. Despite previous research into stabilizing micaceous soils, there remains an urgent demand for sustainable alternatives to traditional stabilizers to achieve circularity. Furthermore, uncertainties regarding the long-term performance of stabilized soils under hydraulic conditions complicated their use in flood-susceptible areas. To provide a sustainable and low-cost solution for creating stabilized soil for earthen structures in waterlogged regions, this study explores the impact of coir fiber and fly ash, agricultural and industrial byproducts, on the hydrophobicity, durability, and water stability of micaceous residual soil from Hainan, China. The study commenced with the preliminary mechanical tests to ascertain the optimal dosage of coir fiber and fly ash, which were determined to be 1% and 15%, respectively. Then, hydrophobicity, durability, and disintegration tests are conducted on fiber-reinforced fly-ash-treated soil under various stabilization conditions. The microstructural evolution of the soil fabric in response to the stabilization process was meticulously traced using scanning electron microscopy and energy-dispersive spectroscopy. Results indicated that the addition of fly ash could impart severe and persistent water repellency to the studied soil, with the contact angle improving from 16.7° to 102.9°, and the water drop penetration time significantly extending from 3.6 s to approximately 600 s. While incorporating coir fibers into the cemented soil presented negligible improvement on soil hydrophobicity, it markedly enhanced the soil’s durability, mitigated moisture-related deterioration and decelerated disintegration. Notably, the strength residual ratio of fiber-reinforced cemented sample maintained higher than 90% even after 20-day water immersion, and the disintegration rate decreased by 57% compared to unreinforced sample. Microstructural analysis revealed that bonding, friction, and interlocking among fibers, hydration products, and soil particles are the main contributors to the stable and robust matrix, ensuring improved mechanical behavior and longevity of micaceous residual soil. This study provides an innovative method for utilizing waste byproducts in stabilizing micaceous residual soil, as a viable option for earthworks in rain-soaked or flood-prone areas.

Mechanical properties and microstructural discrepancies of concrete with flotation-modified fly ash from circulating fluidized bed and pulverized coal furnaces

Fly ash (FA) is a by-product of coal-fired power generation in thermal power plants. Disparities in coal types and combustion furnaces result in varying levels of unburned carbon in FA, hindering its effective utilization. In this study, FA from a circulating fluidized bed furnace (CFBFA) and pulverized coal furnace (PCFFA) was modified using froth flotation technology, and the influence of the modified FA from the froth flotation process on the mechanical properties and microstructural discrepancy of concrete was analyzed through the preparation of mortar and cement paste specimens. The results indicated that the flotation process proved effective in reducing the unburned carbon content in FA, with modified PCFFA showing higher surface area and fluidity, opposite to CFBFA. Notably, the flotation process altered CFBFA's mineral content, reducing CaSO4·2 H2O from 26.6% to 7.5% and increasing CaSO4, enhancing hydration and strength in concrete applications. The optimal FA dosage was found to be 20%, with CFBFA specimens displaying superior compressive strength across all tests. Conversely, the modified PCFFA exhibited low activity, making it challenging to reach the desired strength after 28-d. This study serves as a theoretical foundation for the application of highly unburned carbon FA in construction engineering and promotes the circular development of FA resources.

Safety and Effect of Fly Ash Content on Mechanical Properties and Microstructure of Green Low-Carbon Concrete

Based on the promotion and application of green and low-carbon technology, this study aims to develop a high-safety performance cement concrete incorporating a large dosage of fly ash (FA). The safety and effect of FA content on the mechanical properties of FA composited cement were studied through compressive strength, flexural strength, and microscopic tests. The results show that when the FA replaced 20% cement, the properties of concrete were the best in this study. The flexural strengths and compressive strengths of the standard cured concrete for 28 days with 20% FA content are 0.82 MPa and 4.32 MPa larger than that of the pure cement concrete. The XRD and SEM analysis suggested that the mechanical properties of the composite cement FA system are improved significantly since the replacement of cement by FA promotes secondary hydration of calcium hydroxide in the concrete, leading to a more compact and safe interface between cement and FA.

Influence of Fly Ash on Soil Properties and Vegetation of Fresh Coniferous Forest during Long-Term Observation

Fly ashes produced in huge amounts during coal combustion requires proper management. The purpose of this study was to determine the impact of fly ash from burning hard coal used in large doses (250, 500, 1000 and 2000 t ha−1) on soil properties and vegetation of fresh mixed coniferous forest within 43 years from the ash application. The experiment was established in the Podzols in the forest habitat of Czułów, Katowice Forest district, Upper Silesia, Poland. Eight tree species were planted in ridges created by ploughing: Pinus sylvestris, P. nigra, Larix decidua, Betula pendula, Quercus robur, Q., Acer pseudoplatanus and Fagus sylvatica. The changes in soil morphology caused significant transformations in the physical and chemical properties of the soil such as soil texture, pH, macronutrients (P, K and Mg) content and C:N ratio. Increasing of ash doses changed the granulometric composition of the soil levels from loamy sand (250 t/ha−1) to silt loam (2000 t ha−1). Initially, the acidic Podzols were alkalized under the influence of the fly ash and then acidified, possibly due to the impact of accumulated litter layers, and the reaction of organic soil horizons changed from strongly acidic (250–1000 t ha−1) to alkalis (2000 t/ha−1). The macronutrients content increased in proportion to the fly ash dose, but the subsequent acidification resulted in a gradual decrease in the macronutrients share in the soil layers. The value of the C:N ratio grew after the ash application and then it gradually reduced, even by half. The transformations of soil horizons’ properties also increased the capacity of the soil sorption complex (CEC). All these processes led to a change in the trophic status of the habitat expressed by the soil habitat index (SIG) and the initial coniferous forest site can be classified as a mixed forest habitat even with the lowest ash dose used. The composition of plant communities developed forty years after the ash application was similar at the lower ash doses and the most frequent and abundant tree species were L. decidua, P. nigra and P. silvestris. B. pendula was previously co-dominant, but it was eliminated from the tree stands during the experiment. Planted trees characteristic of late stages of succession, such as Q. robur, Q. rubra, F. sylvatica and A. pseudoplatanus either did not survive or remained in very low quantities. The herb and moss layers developed in the process of spontaneous colonization, and together with the trees led to phytostabilisation of the bare substrates. After acidification of the topsoil horizons, the herb layers consisted mostly of coniferous, mixed, and deciduous forest species, and the most frequent or abundant were Lysimachia europea and Pteridium aquilinum. The moss layers were represented by coniferous forest flora. At the ash dose of 2000 t ha−1, Tilia cordata settled in one of the seral stages of spontaneous succession and this species dominated in the community and formed a dense tree stand. After the soil acidification, a shift from calcicole to calcifuge plant strategy took place among species of the herbaceous layer. The transformations of plant communities’ composition occurred in relation to changes in the soil properties.

Durability prediction of geopolymer mortar reinforced with nanoparticles and PVA fiber using particle swarm optimized BP neural network

Abstract In this study, polyvinyl alcohol (PVA) fibers and nanoparticles were incorporated to enhance the durability of geopolymer mortar (GM) with metakaolin (MK) and fly ash (FA). The dosage of nano-SiO2 (NS) was 0–2.5% and that of PVA fiber was 0–1.2%. The durability of GM includes resistance to chloride ion penetration, freeze–thaw cycles, and sulfate erosion. Compared with the single BP neural network (BPNN) model, a particle swarm optimized BPNN (PSO-BPNN) model was utilized to predict the resistance to chloride ion penetration, freeze–thaw cycles, and sulfate erosion of GMs with different dosages of nanoparticles and PVA fibers. In the model, the dosage of NS, PVA fiber, FA, and MK were used as input layers, and the durability parameters of electric flux, mass loss, and compressive strength loss of GMs were used as output layers. The result exhibits that the root mean square errors (RMSEs) of BPNN for resistance to chloride ion penetration, freeze–thaw cycles, and sulfate erosion of GM mixed with nanoparticles and PVA fibers are 145.39, 6.43, and 2.19, whereas RMSEs obtained from PSO-BPNN are 76.33, 2.87, and 1.03, respectively. The NN optimized by particle swarm algorithm has better prediction accuracy. The PSO-BPNN can be utilized for estimating durability of GM reinforced by NS and PVA fiber, which can provide a guide for the proportion design of GM with PVA fiber and NS as well as for the engineering practice in the future.

Machine Learning Method to Explore the Correlation between Fly Ash Content and Chloride Resistance.

Chloride ion corrosion has been considered to be one of the main reasons for durability deterioration of reinforced concrete structures in marine or chlorine-containing deicing salt environments. This paper studies the relationship between the amount of fly ash and the durability of concrete, especially the resistance to chloride ion erosion. The heat trend map of total chloride ion factor correlation displayed that the ranking of factor correlations was as follows: sampling depth > cement dosage > fly ash dosage. In order to verify the effect of fly ash dosage on chloride ion resistance, three different machine learning algorithms (RF, GBR, DT) are employed to predict the total chloride content of fly ash proportioned concrete with varying admixture ratios, which are evaluated based on R2, MSE, RMSE, and MAE. The results predicted by the RF model show that the threshold of fly ash admixture in chlorinated salt environments is 30-40%. Replacing part of cement with fly ash in the mixture of concrete below this threshold of fly ash, it could change the phase structure and pore structure, which could improve the permeability of fly ash concrete and reduce the content of free chloride ions in the system. Machine learning modeling using sample data can accurately predict concrete properties, which effectively reduce engineering tests. The development of machine learning models is essential for the decarbonization and intelligence of engineering.

Effect of mineral admixtures on the calcium leaching resistance of porous cement stabilized macadam

Porous cement stabilized macadam has a good drainage property, but the loss of strength due to calcium leaching can significantly reduce its road performance. The effect of the dosage of fly ash, silica fume, and slag powder on the calcium leaching resistance of porous cement stabilized macadam base material was investigated using the accelerated leaching method with 4 mol/L ammonium chloride. The results show that calcium leaching occurs simultaneously at multiple contact points between the internal cement paste and the leaching solution, and the leaching depth has exceeded the average thickness of the layered cemented paste within 3d. The dissolution of CH crystals and the decalcification of C-S-H gel increase the porosity of cement and reduce the strength of the base material. Volcanic ash reaction of silica fume and fly ash as well as slag powder by alkali excitation and sulfate excitation will consume CH and generate low alkalinity C-S-H gel with better dissolution resistance, which can reduce calcium leaching and delay the loss of strength. The optimum dosages of fly ash, silica fume, and slag powder are 20%, 15%, and 30%, respectively, and their optimum dosages can be estimated on the assumption that the mineral admixtures completely consume CH.