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This research investigated the effect of Waste Marble Dust (WMD) and Corncob Ash (CCA) on expansive soil's engineering and microstructural properties. Various laboratory experiments were performed on the natural soil to ascertain its characteristics. The corncobs underwent pre-water treatment for fourteen days to remove excess potassium and increase their silica content, resulting in a rise in the silica level from 0% to 50%. At first, only WMD was added to the soil in increments of 5% to 30% using compaction and California bearing tests. The optimum dosage of 15% WMD addition yielded the best result. CCA was then incorporated by the weight of the soil from 2% to 10% in increments of 2% to the first optimum (15% WMD) to obtain the overall optimum for the study (15% WMD and 8% CCA). Stabilization of the natural soil using both materials led to the modification and solidification of the soil mass, evident by the rise in California bearing ratio values from 1.68% to 15.53% and unconfined compressive strength from 41.33 kN/m2 to 174.68 kN/m2. There was also a decrease in the soil's free swell from 120% to 15% as well as reductions in the liquid limits from 56.23% to 36.01% and in the plasticity index from 29.74% to 8.72%, respectively. The microstructural images showed the formation of cementitious compounds in the form of calcium silicate hydrate and calcium aluminate hydrate gels. The findings indicate that using WMD and CCA as a unit has great potential in enhancing engineering properties, like strength parameters and the swell potential of expansive soils. [ABSTRACT FROM AUTHOR]

The construction sector has been under growing public attention recently as one of the leading causes of climate change and its detrimental effects on local communities. In this regard, geopolymer concrete (GPC) has been proposed as a replacement for conventional concrete. Predicting the concrete’s strength before pouring is, therefore, quite useful. The mechanical strength of slag and corncob ash (SCA–GPC), a GPC made from slag and corncob ash, was predicted utilizing multi-expression programming (MEP). Modeling parameters’ relative importance was determined using sensitivity analysis. When estimating the compressive, flexural, and split tensile strengths of SCA–GPC with MEP, 0.95, 0.93, and 0.92 R 2-values were noted between the target and predicted results. The developed models were validated using statistical tests for error and efficiency. The sensitivity analysis revealed that within the mix proportions, the slag quantity (65%), curing age (25%), and fine aggregate (3.30%) quantity significantly influenced the mechanical strength of SCA–GPC. The MEP models result in distinct empirical equations for the strength characteristics of SCA–GPC, unlike Python-based models, which might aid industry and researchers worldwide in determining optimal mix design proportions, thus eliminating unneeded test repetitions in the laboratory.

The thermal performance (TP) of concrete structures is vital to the evaluation of the fire response. Thus, this study examined the thermal properties slag-based geopolymer concrete (GPC) incorporating corncob ash (CCA). Corncob was valorised and partially used as a substitution for slag under the ambient curing conditions. Sodium hydroxide (SH) solution and sodium silicate (SS) gel were used as alkaline activators at 12, 14, and 16 M concentrations. The TP of GPC was compared with that of Portland cement concrete (PCC). Thermal predictions were developed based on the thermal properties. Based on the findings, GPC exhibited lower thermal conductivity (TC) and thermal diffusivity (TD) with increasing specific heat capacity (SHC), indicating good thermal insulation properties (TIP) compared with PCC. The TIP increased with increasing CCA content in the mixture at all levels of alkaline activators. Thus, CCA improves the insulating capacity of the GPC. In addition, a good correlation exists between the GPC produced and thermal properties. These findings can be beneficial in the hot climate regions and utilised for structural insulating construction concrete. Finally, the proposed models can be used in the assessment of GPC structures incorporating supplementary cementitious materials (SCMs) to enhance the TIP of construction materials. [ABSTRACT FROM AUTHOR]

Highlights • Corncob has significant energy and is used as energy resource. • Generated ash is disposed to landfill sites or ash ponds locking the useful land. • Evaluated corncob ash as replacement of sand in concrete. • 22 MPa strength achieved with 10% CCA and can be used for structural application. • Addressed sustainability issues of ash disposal and natural resources depletion. Abstract The natural sand reservoirs are depleting globally due to nonstop consumption of aggregate in concrete. The detrimental effect of uncontrolled fine aggregate extraction from riverbeds is also a major concern. Moreover, the proper disposal of agricultural waste resulting from biomass burning is a major environmental challenge. Hence, in this research, we have proposed an eco-friendly solution by investigating the utilization of corncob ash with 0, 5, 10, 15 and 20% as fine aggregate in concrete. CCA was characterized to determine its suitability as fine aggregate by determining physical and chemical properties as well as investigating its morphology at micro and macro level. Thereafter, in fresh state, the CCA concrete was tested for slump, shrinkage and density while in hardened state; it was tested for compressive strength, water absorption, ultrasonic pulse velocity, and density at the age of 7, 28, 56, and 90 days. The thermal gravimetric analysis was also performed to evaluate the possible pozzolanic potential of CCA composite. Test results showed that CCA was well graded, amorphous, free from organic impurities, and having highly porous morphology due to the presence of micro pores, perforations, and tubules. The slump and shrinkage values increased while the fresh concrete density decreased with the increase in the percentage of CCA. The compressive strength, ultrasonic pulse velocity, and hardened concrete density decreased with the increase in the percentage of CCA while the values of these parameters increased with the age of testing. The values of water absorption were found to decrease with the age of testing. At 28 days, the compressive strength of concrete with 10% CCA as replacement of fine aggregate was found to be 22 MPa. For all mixes, the weight loss in sulfuric acid was more pronounced than hydrochloric acid due to more aggressive and destructive nature of sulfuric acid. Chemical composition of CCA and TGA results of CCA composite showed that CCA has pozzolanic potential when used in concrete as partial replacement of fine aggregate. The utilization of CCA provides eco-friendly solution of ash disposal problem. It also provides viable source of raw materials for construction industry and hence would help in conserving natural aggregate resources. Hence, the benefits of using CCA as fine aggregate in concrete were verified. [ABSTRACT FROM AUTHOR]

Harnessing energy from biomass is environmentally friendly because of the essentially zero net CO2 impact. As a common agricultural byproduct, corncobs are abundant in quantity. This study was carried out to examine the thermo-physical properties of corncobs and characterize the properties of corncob ash produced from gasification, in order to provide a basis for transforming it into value-added products. The results showed that the pyrolysis of corncobs followed a three-step, stepwise mechanism. Activation energies calculated by the Coats-Redfern method at heating rates of 5, 10, and 20 °C/min were 79.08, 76.73, and 75.78 kJ·mol-1, respectively, implying that the corncobs could be decomposed easily at high heating rates. The emissions of CO, CO2, CH4, H2, H2O, and O2 during pyrolysis corresponded well with thermal curves. Corncob ash could be a good fertilizer because of its high contents of K, P, and Ca. The high SiO2 content makes the corncob ash suitable for ceramics and blended cement concrete. Sylvite (KCl) and quartz (SiO2) were the two major crystal phases in the corncob ash. Relatively large particles of unburnt carbon residues in the ash indicated that low-cost adsorbent could be developed from these carbon residues.

As a by-product generated from the processing of corn, the production in China of corncob (CC) is abundant, with up to 3.87 million tons per year. The biomass gasification industries make use of the CC residue as feedstock, but large volumes of generated corncob ash (CCA) requires daily disposal. In this study, CCA was characterized by laser particle size analyzer (LPSA), X-ray fluorescence (XRF), X-ray diffraction (XRD), thermal gravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy, and energy dispersive X-ray (SEM-EDX). XRF results showed that the CCA was rich in K, Ca, and P, indicating its potential as a soil amendment. High content of SiO2 in CCA revealed its potential as a pozzolan in blended cement concrete. XRD showed the presence of crystal phases such as potassium carbonate, sylvite, arcanite, quartz, calcite, and nitrite. SEM images revealed the high agglomeration of CCA. EDX gave evidence of the external surface of agglomerated particles coated with KCl. TG-DTA analysis indicates that decomposition of CCA has stepwise mechanism. The CCA powders through a 0.154 mm sieve showed a high specific surface area of 162.32 m2/g, average pore size of 12.17 Å with pore volume of 0.116 cm3/g. The carbon residue separated from CCA has the potential to be used as activated carbon.

The high cost of conventional walling materials, increase in emission of CO2 due to cement production and improper disposal of corncob lead to persistent bottlenecks in low-cost and sustainable housing delivery, environmental pollution, and agricultural wastage respectively. This study investigates the use of corncob ash (CCA) as cement additive in producing lateritic interlocking blocks (LIB) and compares its physical characteristics and production cost with Sandcrete hollow block (SHB). Portland limestone cement (PLC) was replaced by CCA in varying percentages 5, 10 and 15%. The density, compressive strength and water absorption of the blocks were determined and compared with the Nigerian standard requirements and specifications. The experimental results showed optimal strength at 3% PLC and 10% CCA with a compressive strength of 4.13MPa, water absorption of 6.60% and density of 1869.47Kgm-3 at 28 days curing for LIB. For 450mm × 225mm × 225mm SHB, compressive strength, water absorption and density at 28 days curing were 3.86MPa, 4.69%, and 1849.95Kgm-3 respectively. All the blocks produced satisfied the recommendations of both the Nigerian Building and Road Research Institute and the Nigerian Industrial Standards. The cost per square meter of SHB and LIB was 4.62 USD and 2.35 USD respectively. The experimental results indicated that LIBs have better strength and are cheaper than SHBs. Recycling of CCA as a supplement material seems to be a feasible solution not only to the problem of adopting indigenous waste material in the production of LIB but also to the environmental problem. [ABSTRACT FROM AUTHOR]

Corncob, byproduct of maize crop, is one of the biomass from agricultural waste that is being used as energy source since it has significant energy content. After being burnt, the ash is disposed to landfill sites or ash ponds, locking the useful land. Moreover, corncob ash (CCA) is rich in silica and can be used as pozzolan but this characteristic is linked with temperature and grinding conditions. Hence, we aimed at evaluating the most favorable conditions of incineration and grinding to determine the pozzolanic activity of CCA. At first, the open burnt ash was sieved through #50 and #12 sieves (ashes retained on #12, #50 and pan were denoted as R12, R50 and R00 respectively) to find incineration requirement. It was found that R00 ash having smaller particle size could directly be used as pozzolan whereas R12 and R50 ashes having larger particle sizes needed further incineration. Thereafter, the research was divided into four phases to find optimum incineration (temperature and time) and grinding conditions. In Phase I, R12 ash was incinerated at 400 °C, 500 °C, 600 °C, 700 °C and 800 °C for 2 h to find the optimum incineration temperature. Best results for Chapelle activity (438 mg/g), CaO reduction in Frattini (82.8%) and Pozzolanic activity index (PAI) (97.3%) obtained at 500 °C signified it as optimum incineration temperature. In Phase II, R50 ash was incinerated at optimum temperature i.e. 500 °C for different time intervals (15, 30, 60 and 120 min) to find optimum incineration time and possibly reduce energy requirement. Test results showed that incineration time of 30 min was optimum and hence in comparison to larger particle size (R12 sample), ash having smaller particle size (R50 sample) require less time to achieve required pozzolanic activity. In Phase III, all three sieved ashes (R12, R00 and R50) incinerated at optimum conditions were mixed (to make use of entire corncob ash) and it was found to possess adequate PAI (80.3%). Based on above three phases, it can be concluded that R00 ash as obtained from sieving, R12 ash incinerated at 500 °C for 2 h and R50 ash incinerated at 500 °C for 30 min, provided good results mutually as well as independently. Finally, in Phase IV, the optimum grinding time was determined by grinding ash for 30, 60, 120 and 240 min. Test results showed that the surface area increased with the increase in grinding duration. However, keeping in mind that grinding is energy intensive process, 60 min of grinding showing specific surface area of 4220 cm 2 /gm, Chapelle activity of 511.05 mg/g and 28 days PAI of 77.6%, was selected as optimum. Thus, corncob ash after optimum conditions of incineration and grinding can successfully be used in cement based composites. Moreover, it would address sustainability issues of ash disposal and natural resources depletion by reducing the amount of cement production. [ABSTRACT FROM AUTHOR]

In the present study, fly ashes were obtained as a byproduct respectively from the processing of corncob in a gasification plant and from the combustion of corncob in a muffle furnace. The aim of this study is to characterize the basic properties of the fly ashes from gasification process and combustion process whilst comparing the results between these two types of solid residues to evaluate their potential applications. The results indicate that the CCA from gasification is more suitable to be used as a raw material for activated carbon owing to its larger specific surface area and higher carbon content compared with the CCA from combustion. With higher concentrations of K, Ca, and P, the CCA from gasification process is more bioavailable than CCA from combustion to be soil amendment. SEM images show that these CCA particles are agglomerated and irregular in shapes. The external surface of agglomerated particles is covered with potassium chloride. The influence of ashing temperature on ash morphology and agglomeration behavior is obvious, and the agglomeration tendency and melting degree are enhanced at high temperatures. Thermal analysis reveals the stepwise mechanism of decomposition for CCA. Specifically, the combustion CCA is more suitable for use as a pozzolan in blended cement concrete compared with the gasification CCA. Also, all ash samples with high silica content are suitable for ceramics. [ABSTRACT FROM AUTHOR]

The recycling and utilization of waste has attracted increasing attention due to the requirement of sustainable development. This study proposed a novel waste reuse technology using crop incineration waste (i.e., corncob ash) as an additive to enhance the methane production from anaerobic digestion of algae. Biochemical methane production tests demonstrated that corncob ash (0.6, 0.9 and 1.2 g/g TS (Total Solids)) enhanced methane production from algae, and the maximal methane production was 75.8 ± 1.2 ml CH 4 /g VS (Volatile Solids) achieved at 0.6–0.9 g/g TS of corncob ash addition, representing the relative increase of 35–37% compared to that without corncob ash. By monitoring the transformation of metabolic intermediates, corncob ash was confirmed to be beneficial to the solubilization, hydrolysis and methanogenesis processes during anaerobic algae digestion. This was supported by the microbial analysis results that corncob ash enriched the related key microorganisms, e.g., Longilinea sp. and Methanosaeta sp.. Moreover, mechanism studies revealed that corncob ash alleviated ammonia inhibition and improved the electron transfer efficiency for methane production, which was probably attributed to the porous structure and high redox characteristics of corncob ash. The anaerobic digestion residue with corncob ash rich in inorganic elements (e.g., potassium, calcium and magnesium) could also be used as a potential agricultural fertilizer for soil. The novel strategy proposed in this study might provide a new paradigm of an integrated waste-control by waste to bring significant economic and environmental benefits to waste disposal. [Display omitted] • Corncob ash enhanced methane production from anaerobic digestion of algae. • Corncob ash improved solubilization, hydrolysis and methonogenesis processes. • Corncob ash alleviated ammonia inhibition due to its inherent porous structure. • Corncob ash promoted electron transfer efficiency for methane production. [ABSTRACT FROM AUTHOR]