Ash Dosage Research Articles

Concretes meeting the requirements of sustainable construction

The article concerns the production of lightweight geopolymer concretes based on raw materials from alkali-activated waste, which is consistent with the doctrine of sustainable construction. Fly ash, which is the main component of these geopolymer composites, constitutes energy waste and causes lower emissions of greenhouse gases and other pollutants than traditional cement. The article presents the optimisation of the geopolymer concrete recipe with different dosages of fly ash (200, 300, 400, 500, 600 and 700 kg/m3) and two recipes, the first of which is based on the use of fly ash aggregate, the largest fraction of which was subjected to surface impregnation, and the second one is based on the use of aggregate without any impregnation. Both recipes use an alkaline solution for alkaline activation with a concentration of 6 mol/dm3. Compressive strength tests and apparent density were carried out on the samples. The adequacy of the use of surface impregnation has been demonstrated in the case of low fly ash content (<500 kg/m3), and the optimal recipe based on fly ash in the amount of 600 kg/m3 was indicated.

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.

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.

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.

Exploring sustainable solutions for soil stabilization through explainable Gaussian process-assisted multi-objective optimization

The adoption of sustainable solutions in soil stabilization has piqued the interest of the scientific community due to the potential reduction in carbon footprint. In this regard, the research community has started looking for the alternate sustainable solutions to limit the quantity of conventionally used ecologically unfriendly soil stabilizers like lime and cement by utilizing the agricultural and industrial by-products. The production of conventional soil stabilizers (lime and cement) is extremely energy-intensive and contributes tons of greenhouse gases to the atmosphere. In general, evaluating suitability of these additives requires in-lab investigation of soil samples with varying additive concentrations and curing periods, making this approach both resource and time-intensive. Hence, this article proposes a computational framework for accelerated characterization of soil-stabilization by using the coupled experimental-Gaussian process (GP) based machine learning (ML) model. The dataset utilized for constructing the GP models consists of input features such as the stabilizer content (lime and rice husk ash (RHA)), coir fiber content, and curing period (measured in days). The target responses are the strength measures of the stabilized soil, such as unconfined compressive strength (UCS), split tensile strength (STS), and California bearing ratio (CBR). The proposed computational framework is deployed to perform multi-objective genetic algorithm (MOGA)-based optimization to achieve maximum engineering performance from stabilized soil. The presented study demonstrated that with the optimal dosage of rice husk ash (agricultural by-product), and cashew nut shell liquid (CNSL) treated coir fiber, the requirement for lime dosage may be significantly reduced while maintaining the engineering performance of the soil. The presented computational framework can be extended to any construction practices for ensuring the strategic selection of the control variables for optimizing the desired performance.

Adsorption of Methylene Blue using Bottom Ash: Experimental Design, Isotherm Analysis, and Optimum Conditions

<p><span lang="EN-US" style="font-size:12.0pt"><span style="line-height:107%"><span style="font-family:"Times New Roman",serif"><span style="color:black">This study investigated the removal of methylene blue (MB) via adsorption using waste bottom ash.  The bottom ash, sourced from a waste storage site in the Çorlu district of Tekirdağ province, Thrace Region, was utilized as the adsorbent. The research examined the impact of several variables on MB removal, including bottom ash dosage, pH, contact time, and agitation speed. It was found that all parameters had a single-variable effect, while pH exhibited a quadratic effect on MB removal in a model-based analysis. The optimization of the model for maximum MB removal identified the optimal conditions as 0.978 g bottom ash dosage, pH 3, 15 minutes of adsorption time, and 50 rpm agitation speed. Under these conditions, the model predicted an MB removal efficiency of 71%, which was experimentally confirmed to be 72.5%. The adsorption process was found to fit with the Freundlich isotherm, indicating a multilayer adsorption mechanism on the heterogeneous surface of the adsorbent. This research not only highlights the feasibility of using bottom ash from coal combustion as an economical adsorbent for dye-contaminated wastewater but also underscores its potential to inform and inspire future studies on waste recycling and wastewater treatment. </span></span></span></span></p>

Evaluation of the Potential of Boiler Ash from Palm Oil Mill as an Alternative Material for the Improvement of Acid Coal Main Drainage

The study aimed to evaluate the potential of boiler ash from palm oil mills to improve the quality of acid mine drainage (AMD). The experiment was conducted using boiler ash with five doses of 0, 3, 6, 9, 12, and 15 mg. Quicklime was used as a comparison material with doses of 0, 0.02, 0.03, 0.05, 0.1, and 0.3 mg. Boiler ash and quicklime were added to each 500 mL AMD. The parameters of the AMD quality measured were pH, dissolved iron (Fe) and manganese (Mn), and the precipitates of Fe and Mn. The results showed that the addition of boiler ash and quicklime into AMD increased the pH and decreased the concentration of dissolved Fe and Mn and increased the precipitate of Fe and Mn. The pH value of AMD increased with increasing doses of boiler ash and quicklime. An increase in the pH value was followed by a decrease in the dissolved Fe and Mn and anincrease in the Fe and Mn precipitate. The highest pH values, Fe and Mn precipitates, and the lowest dissolved Fe and Mn were obtained by the treatment of 15 mg/L boiler ash and 0.3 mg/L quicklime. The boiler ash showed promising potential as an alternative neutralizing reagent to improve AMD even though the amount of boiler ash needed to repair AMD was more than quicklime.

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.

Optimizing mechanical and durability properties of recycled aggregate concrete using pozzolanic slurries and modified mixing approach

A sustainable and reliable methodology to strengthen the mortar adhered to recycled concrete aggregate (RCA) is crucial for optimizing its utilization in construction. This research proposes a mortar strengthening method by soaking RCA in different dosages (weight percentages) of pozzolanic slurries, i.e., fly ash and silica powder (F-S), fly ash and cement (F-C), cement and silica powder (C-S) for various durations. The influence of each slurry dosage and soaking duration on RCA's physical and mechanical properties and surface morphology were examined. Further, a modified two-stage mixing approach (M-TSMA) was employed to produce recycled aggregate concrete (RAC) incorporating 100% untreated and surface-treated RCA. The impact of M-TSMA and treated RCA on concrete was demonstrated regarding its mechanical and durability properties, such as compressive strength, ultrasonic pulse velocity, rebound hammer, sorptivity, and resistance to chloride ions. Results show that soaking RCA in 30% C-S slurry for 6 h enhances RCA's overall properties by increasing the calcium silicate hydrate (C-S-H) content. Moreover, employing M-TSMA and incorporating treated RCA improves the mechanical and durability properties of RAC by reducing microcracks and densifying the microstructure. Overall, the proposed surface treatment and M-TSMA can potentially enhance RAC performance with complete RCA utilization.

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.

Study on the Synthesis of LTA-Type Molecular Sieves from Coal Gangue and Aluminum Ash and Its Adsorption Properties towards Cu2+

Coal gangue and aluminum ash emerge as quintessential constituents within the ambit of coal-derived solid waste and industrial residue, respectively. Leveraging coal gangue as a primary substrate and aluminum ash as an adjunct aluminum source, molecular sieves can be synthesized through hydrothermal means. By modulating the dosage of aluminum ash, molecular sieves with varying crystalline structures can be obtained. The synthesized LTA-type molecular sieves manifest in two distinct morphologies: regular tetrahedral and stratified spherical stacking, evincing commendable Cu2+ adsorption efficacy. The Cu2+ adsorption phenomenon predominantly transpires via chemisorption, albeit with ancillary manifestations of physical adsorption. The valorization of coal gangue and aluminum ash towards the synthesis of molecular sieves not only underscores the elevation of industrial solid waste towards high-value utility, but also underscores the praxis of waste remediation through upcycling.

Soil Organic Matter and Microbial Biomass Under Cultivation of Urochloa Brizantha Fertilized with Wood Ash in the Cerrado of Mato Grosso

ABSTRACT The use of waste such as wood ash as an alternative fertilizer in agricultural production can result in an improvement in the chemical and biological characteristics of the soil. The objective of this research was to evaluate the effect of doses and management of wood ash application in the organic matter content and biological attributes of the soil in a Cerrado area cultivated with Urochloa brizantha cv BRS paiaguás. The experiment was performed in randomized blocks, in a 5 × 2 striped scheme, with five doses of wood ash (0, 8, 16, 24 and 32 t ha−1) and two application managements (with and without incorporation to the soil) with four repetitions. The variables analyzed were: soil organic matter content, microbial biomass carbon, basal respiration, qCO2 and β-glucosidase activity. During the evaluations it was observed a reduction of 0.36 g kg−1 of organic matter for each ton of ash applied to the soil, regardless of management. This reduction also occurred in microbial biomass carbon and β-glucosidase activity. initially the ash doses elevated the soil respiration and the metabolic quotient, evidencing a small stress in the soil microbiota, however, in the last evaluation the rates of these two variables remained stable. The application of wood ash, in doses ranging from 16 to 24 t ha−1, can be used as soil conditioner and fertilizer in pastures, because it results in better conditions for the soil.

Cowpea storage: Can small farmers use polyethylene terephthalate bottles and wood ash as an alternative to avoid damage caused by Callosobruchus maculatus?

The aim of this study was to investigate the effectiveness of the combination of Polyethylene terephthalate (PET) bottles and ash in controlling Csllosobruchus maculatus and maintaining the quality of grains of cowpea cultivars. The following storage structures were used: PET bottle in airtight conditions and glass jars in non-airtight condition (control). The wood ash used in this research came from the burning process of eucalyptus (Eucalyptus grandis) wood. The experiment was carried out in a 2 × 2 × 4 factorial scheme, with two cowpea cultivars (BRS Tumucumaque and BRS Guariba), two forms of storage (PET bottle – airtight and glass jars – non-airtight) and four doses of eucalyptus wood ash (0.0; 1.0; 2.0 and 4.0 kg t−1), in a completely randomized design with three replications. Each plot contained 500 g of cowpea. The effectiveness of treatments was measured by the instantaneous population growth rate (ri) of C. maculatus. In ri, 35 adult, non-sexed insects were used. Adult progenies were counted after 60 days of storage. For qualitative grain evaluation the following characteristics were analyzed: water content, germination, apparent specific mass and electrical conductivity. The results obtained in this study confirm for the first time that the combined use of PET and ash do not affect grain quality and it is efficient in the management of C. maculatus in cowpea cultivars. In the present study, a significant reduction in the emergence of C. maculatus was observed in the BRS Tumucumaque, making it possible that this cultivar has some potential for resistance to bruchid.

Research on using municipal solid waste incineration bottom ash for cement-stabilized macadam

Municipal solid waste incineration bottom ash (MSWIBA) is the waste generated by incineration power plants. Because of its low activity, it is an effective way to apply it to cement-stabilized macadam (CSM) in road construction. CSM was prepared using varying proportions of bottom ash (0%, 15%, 20%, 25%, 30%, and 35%) and different proportions of cement (3.5%, 4%, 4.5%, 5%, and 5.5%), respectively, to explore the effects of MSWIBA as fine aggregates on the characteristics of cement-stabilized MSWIBA macadam (CSBAM). MSWIBA was examined in terms of its microstructure, chemical makeup, and physical characteristics. Heavy metal leaching, water stability, splitting strength, unconfined compressive strength, and dry shrinkage were all investigated for CSBAM. The findings demonstrated that there was some cementitious and volcanic ash activity and that the bottom ash had a rough, porous surface. The strength of CSBAM decreased with the increase of MSWIBA dosage and increased with the increase of cement reference. Replacing fine aggregate with MSWIBA reduced the water stability of CSBAM. The water stability was better when the bottom ash dosage was more than 20%. Bottom ash reduced the dry shrinkage strain of cement-stabilized macadam, and CSBAM had better anti-dry shrinkage performance. CSBAM had a curing effect on heavy metals, and the leaching concentration of heavy metals was in accordance with the standard, which had less impact on the environment.

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.