Shell Ash Research Articles

Cashew nut shell ash as a supplementary additive in lime stabilized expansive soil composites

In recent times, agro-industrial wastes have been valorized as supplementary additives in soil treatment and improvement of soft and poor soils. One such agro-industrial waste viz. Cashew Nut Shell Ash (CNSA) was evaluated to comprehend its performance as a supplementary additive to lime in treating expansive soils. The experimental programme investigated the performance of stabilized soil composites (SSC), stabilized using combinations of 3%, 5.5% and 7% lime modified with 0.25%, 0.5%, 1% and 2 % CNSA. The SSC were cast in to cylinders of dimensions 38 mm × 76 mm, air cured in sealed covers for seven days and tested for their uniaxial compressive strength. Comparison of the outcomes with the strengths developed by some other wastes like bagasse ash (BA), egg shell ash (ESA) and press mud (PM) available from literature was also done. It was revealed that CNSA as a supplementary additive to lime was able to boost the early strength of the lime SSC after seven days of curing but only when the lime dosage was 5.5%.

Experimental investigation on rice husk ash and coconut shell used in building materials

It is found that there are so many wastes which can be used in traditional concrete like E- wastes. Coconut shell and rice husk ash are also the main waste that can be used in traditional concrete. The coconut shells were taken on 10 % with replacement of coarse aggregate and rice husk ash were taken on 5 %, 10 %, 15 %, 20 % & 25 % with partial replacement of cement. It is found that compressive strength and tensile strength of concrete is increased. The volume of concrete also increased as replacement increased total cost of concrete is reduced by replacement coarse aggregate by coconut shells. Total cost of cement is reduced by replacing cement by rice husk ash. This coconut shell can be crushed and used as a coarse aggregate in production of concrete. Coconut shell concrete (CSC) could be used in rural areas and places where coconut is abundant and may also be used where the conventional aggregate is costly. The high cost of conventional construction material affects the economy of structure. It is becoming more difficult to find natural resources. Use of waste material not only helps in getting them utilized in cement, concrete and construction materials but also has numerous indirect benefits such as reduction in landfill cost savings in energy and protecting the environment from possible pollution effects. The characteristics properties of concrete such as compressive strength, split tensile strength and flexural strength using the mix made by replacing coarse aggregate with crushed coconut shell aggregate were reviewed in the present work. The compressive strength of the replacement concrete is 30.45 N/mm2. The compressive strength is increased by 9.3 % when compared to the conventional concrete. The Split Tensile Strength of the replacement concrete is 2.55 N/mm2. The Split Tensile strength is increased by 11.8 % when compared to the conventional concrete and the flexural strength of the replacement concrete is 8.45 N/mm2. The flexural strength strength is increased by 3 % when compared to the conventional concrete. Its utilization is cost effective and eco-friendly.

Tribo-mechanical behaviour of aluminium alloy (AlSi10Mg) reinforced with palmyra shell ash and silicon carbide particles

AlSi10Mg alloy is blended with palmyra shell ash (PSA) and silicon carbide (SiC) using stir casting route and its tribological properties on the reinforcement addition with the aluminium alloy (AlSi10Mg) hybrid composite are studied. Hybrid composites are fabricated by adding 3, 6 and 9 wt.% of silicon carbide and 9 wt.% palmyra shell ash particle into aluminium (AlSi10Mg) alloy. The dry sliding properties of the AlSi10Mg hybrid alloy composite were examined under different loading conditions against carbon steel disc using a pin-on-disc Tribometer. The results showed that the hybrid metal matrix composite reinforced with silicon carbide and palmyra shell had better tribological characteristics than the composite reinforced with single reinforcement (palmyra shell ash). Increase in wt.% of reinforcement increases the hardness as well as the tensile strength of the composites. Morphological analysis resulted that the abrasive wear mechanism was dominant and causes high wear evolution in dry sliding condition.

Durability performance of a lime stabilized expansive soil with egg shell ash as a subsidiary admixture

Stabilization is broadly classified as mechanical and chemical stabilization. Lime stabilization is the most commonly adopted method for stabilising expansive soils. In recent years, lime has been combined with other waste materials for improved performance in stabilization. One such waste is egg shell waste, generated by the poultry industry. Calcination of egg shell waste results in the formation of egg shell ash (ESA) which has a chemical composition very similar to that of quick lime. This investigation focuses on the potential of ESA as an auxiliary additive for lime in the stabilization of expansive soils. The initial consumption of lime of the expansive soil was determined using the Eades and Grim pH test. The lime content in the stabilization process was modified with ESA up to 0.5% in increments of 0.1%. Unconfined compression strength test samples of dimensions 38 mm x 76 mm were cast and cured for a period of 21 days and tested for their strength. The durability of the samples was also evaluated by subjecting the samples to 1, 4, 7, and 10 cycles of wetting and drying. The results of the investigation revealed that 0.2% ESA was the optimal dosage of additive to lime stabilization for improved performance.

Optimization and Tribological Properties of Hybridized Palm Kernel Shell Ash and Nano Boron Nitride Reinforced Aluminium Matrix Composites

The tribological properties of hybridized reinforced aluminium matrix composites were optimized using Taguchi and Grey Relational Analysis in conjunction with an L16 orthogonal array. The combination of palm kernel shell ash (PKSA) (0–5 wt. %) along with nano BN reinforcements was taken in interest. Loads and speeds (500, 750, 1000, and 1250 rpm) were employed as control parameters for the experiment. Using a Taber type abrasion machine, the wear samples were made, and the wear experiments were carried out. Speed and load were more important than the percentage of reinforcements in composites when it came to evaluating wear index and loss of volume. With respect to wear index and volume loss, Taguchi‐relational Grey’s analysis identified A3B1C1 (reinforcement = 5 wt. %; load = 500 g; speed = 500 rpm) as the optimal process parameter combination, with a reinforcement of 3 wt. %, load = 500 g, and speed = 500 rpm being the second‐best option. Validation tests have revealed that the anticipated and experiment values at the optimal situations are both within the acceptable range. Performance is influenced more by speed than by load, which is influenced more by the weight percentage of composites, as demonstrated by the application of the Taguchi and Grey Relational Analysis methods.

Utilization of coconut shell as a supplementary cementitious material in concrete

Cement is often used as a construction material in building development. Coconut shell, on the other hand is a waste material that is the byproduct from the agricultural industry. Coconut is vastly found and utilized in most tropical countries due to the versatility of its usage. Albeit coconut shells can be used in lots of different ways, it has yet been used fully by the people. This research focuses on determining the proper percentage of partial replacement of coconut shell ash for cement in concrete. Since cement is a non-renewable material, a potential and cheaper alternative is needed to future replace the use of cement once it depletes in supply or increases in size. The characteristics of coconut shell ash (CSA) and its fresh and hardened behavior in cement and concrete will also be focused on. Methodology adopted for this research includes tests such as slump test, compressive strength test, consistency test, and fineness test. All tests were conducted within a period of 45 days and from the results gathered, it was found that 5 % of coconut shell ash as a partial replacement of cement produce the best results. Results show that the strength of the concrete will decrease when more percentage of coconut shell ash is added into the concrete mix. Therefore, the partial replacement of 5 % of coconut shell ash in concrete is the most suitable.

Evaluating the effects of agricultural wastes on concrete and composite mechanical properties: a review

Wastes generation and emission of greenhouse gases are the major concerns of the contemporary world. Concrete’s cements companies in the globe are producing up to 2.8 billion tons of cements annually. This contributed to the emission of anthropogenic substances into the atmosphere which destroys the ozone layers. The incessant disposal of these agricultural wastes has detrimental effect on the environmental and human health. Thus, utilizing these wastes as secondary resources in concrete is a reasonable consideration in sustainable waste management in the circular economy. The use of agricultural wastes in concrete production has been gaining attraction in recent years, however, their effectiveness and performance in concrete need evaluation. This study presents an overview of the effects of some agricultural wastes: Bagasse, Coconut shell, Cotton, Oil palm and Hemp fibers on concrete and composite’s mechanical properties. As reviewed, Sugar-Cane Bagasse Ash (SCBA) and Coconut Shell Ash (CSA) are rich in cementitious (pozzolanic) properties (SiO2, Fe2O3 and Al2O3) for cement production up to 70%. Sugar-cane bagasse and oil palm-fiber ashes improved concrete workability. SCBA and CSA highly increased the concrete compressive strengths. The concrete tensile strengths were increased up to 97% with the inclusion of cotton and bagasse ashes. The SCBA, hemp-fiber and treated oil palm - fiber ash increased the concrete and composite’s flexural strengths up to 11.3%, 26.2% and 50.7% respectively. In conclusion, the output of this review will supply full data of the research gaps yet to cover on the use of agro-wastes in concrete for future investigations

Mechanical behaviour of stir cast aluminum matrix composites reinforced with silicon carbide and palm kernel shell ash

Microstructural analysis and mechanical behaviour of aluminum matrix composites (AMCs) reinforced with palm kernel shell ash (PKSA) and silicon carbide (SiC) were studied. The AMCs containing 6, 8, 10 and 12 wt.% reinforcements, with weight ratios of 0:1, 1:3, 1:1, 3:1 and 1:0 (PKSA: SiC) were produced using stir casting method. % Porosity, hardness, tensile strength (UTS), ductility and fracture toughness were determined following standard procedures, while Scanning electron microscopy (SEM-EDS) was used for structural characterization. The results show that the composites produced have improved hardness. The UTS improved with increase in PKSA attaining maximum value at reinforcement weight ratio 1:1 and then decreases, the 6 wt.% reinforcement being the only exception. The ductility of the composites was lower than the unreinforced aluminum alloy with the SiC single-reinforced having the lowest. Also Fracture toughness was observed to be less than the unreinforced aluminum alloy with the SiC single reinforced having the lowest value. The PSKA:SiC weight ratio 1:1 gave the best property combination with optimum properties in terms of UTS (175.48MPa), ductility (8.61) and fracture toughness [6.5MPa(m)1/2].

Assessment of Lime Stabilized Soils Modified with Egg Shell Ash for Road Construction

The need to have in-depth knowledge about the Engineering properties of soil and the sub-soil condition for road construction especially in the southwestern Nigeria brought about this study. Some strength properties (California Bearing Ratio (CBR), Compaction, Unconfined Compressive Strength (UCS), and direct Shear tests) of lime stabilized soils modified with Egg Shell Ash (ESA) were assessed. Soil samples were obtained from each state in the study area and transported to the laboratory, where they were stabilized with 6% lime and 0 to 10% ESA before the above-mentioned tests was conducted on them. The local additive was also subjected to a chemical analysis. Results showed that ESA additive has low SiO2 and high CaO compounds. Increase in ESA resulted in increase of all the strength properties (Maximum Dry Density (MDD), CBR, UCS, Cohesion (C), Shear strength (S) and Angle of Internal Friction (ϕ)) and reached peak at 8% ESA, thereafter decrease; albeit, Optimum Moisture Content (OMC) decreases. After the improvement process, almost all the unsuitable soil samples became suitable for use as pavement layer materials. Consequently, a blend of 6% lime and 8% ESA content is recommended for soil improvement, especially for road pavement layers in southwestern Nigeria.

Development of sustainable polymeric materials for ceiling tiles application and optimization by digital logic method using thermal insulation properties as the functional requirement

The swift rise in utilizing natural materials as additives in the manufacture of numerous composite systems has fueled the desire in many researchers and contemporary industries to create natural fiber composites that can be used as sustainable, low-cost substitute, as well as eco-friendly and eco-efficient materials for different applications. Although, previous studies have worked on the viability of fiber reinforced composite as a sustainable materials for ceiling tiles, the thermal properties of these composites however were not assessed. In this study, natural fibers such as sisal, jute, bagasse, cotton fibers, and coconut shell ash were incorporated into epoxy, high-density polyethylene (HDPE), polypropylene (PP), low-density polyethylene (LDPE), and polyvinyl chloride (PVC) respectively. The sisal fiber used was untreated while other fibers such as jute, bagasse, and cotton fibers were treated with sodium hydroxide (NaOH) and detergent. Composite samples were prepared using two production techniques. Epoxy-based samples were produced using the hand layup method while compression molding technique was employed in the preparation of HDPE, LDPE, PVC, and PP-based composites at a compression temperature that ranges between 125 and 160 °C. These samples were subjected to tests in order to measure their density and thermal properties. The results obtained from the tests for each material developed were used in the determination of the best material for ceiling application via the digital logic method. Polypropylene-reinforced with 20 wt.% bagasse fiber had the best performance index and figure of merit with values of 91.11 and 104.72 respectively. Hence, recommended for ceiling tiles production.

Comparative study of hazelnut-shell biomass ash and metakaolin to improve the performance of alkali-activated concrete: A sustainable greener alternative

Recently, the studies on the use of environmentally harmful wastes along with the building materials in the construction sector have come to the fore with its environmentalist aspect. In particular, the use of waste materials in cement contributes to the evaluation of waste and reduces the amount of cement usage. On the other hand, the production of sustainable environmentally friendly composite materials offers economic and ecological benefits. Moreover, cementless composite building materials give a promising solution to carbon footprints by allowing the re-evaluation of different waste materials. Accordingly, the potential of using hazelnut shell ash (HA), which is agricultural waste, as a mineral additive in the production of cementless concrete has been handled in the present research. The usability of HA in the mixture has been investigated by comparing it with metakaolin and blast furnace slag (BFS), which are frequently used in the production of concrete and alkali-activated composites. Alkali activated concrete (AAC) samples are cured for 3, 7, and 28 days in this study. In addition, the effect of curing type on AAC samples is deeply discussed in three different curing conditions. Physical and mechanical tests are performed on hardened AAC samples. As a result, it is noticed that the cure types have a remarkable effect on the physical and mechanical properties of AACs. In the conclusion, the present paper reports that HA materials can be effectively used in AAC mixtures and have a respectable potential to improve the abrasion resistance of the cementless concretes.

Analysis of soil characteristics on expansive clay stabilization using shell ash

Expansive clay is one of the problems in construction work. The soil has the characteristics of being easy to expand when exposed to water, causing a decrease in the strength value of the soil. The can be overcome by stabilizing the soil. The soil is formed from weathering and contains the mineral montmorillonite. The soil is very sensitive to moisture content, has a high shrinkage rate, thus interfering in construction work. Therefore, additional materials are needed to overcome the problem, one of which is soil stabilization. The study aimed to stabilize the expansive clay soil. This is done by analyzing the physical and mechanical properties of expansive clay with a shell ash mixture. Expansive clay is taken directly (undisturbed) or disturbed. Undisturbed soil is taken using a tube, so that the soil is not disturbed by outside air, while disturbed soil is taken using a shovel and then put into a sack container. Expansive clay stabilization method lies in adding the percentage of shell ash mixture (5 %, 10 %, 15 %, and 20 %). The soil, the initial moisture content (γd) of which has been determined, is mixed, then molded into a cylindrical shape. The mold was stored in a desiccator, then watered with 5 % water every day until the soil became saturated. Then, using a Proctor test, chemical tests (soil chemical test, soil mineral test), physical tests (soil moisture, Atterberg limit), and mechanical tests (unconfined compression test, compaction test, swelling test) were carried out. The results showed that the addition of an oyster shell ash stabilizing agent to expansive clay affected the physical and mechanical properties of the soil. The addition of shell ash can reduce soil moisture with various plasticity indexes. While the soil stress value decreased, the swelling of the soil increased significantly above the original soil.

Effect of Replacing Bone Ash with Fresh Water Snail (Pila Ampullacea) Shell Ash on Serum Biochemical Indices of Weaned Rabbits

Twenty five (25) mixed breed weaned rabbits were utilized in 84-days experiment to investigate the effect of replacing bone ash with fresh water snail (Pila ampullacea) shell ash on the serum biochemical composition of weaned rabbits. The experiment was conducted at the Teaching and Research Farm, University of Agriculture, Makurdi, Benue State, Nigeria for a period of 12 weeks. The rabbits were randomly assigned to the five dietary treatments and replicated five times giving a total of one rabbit per replicate in a completely randomized design (CRD). Rabbits were raised intensively in hutches of about 4ft × 4ft. Five experimental diets tagged T1 to T5 were formulated such that fresh water snail (Pila ampullacea) shell ash replaced bone ash at 0%, 25%, 50%, 75% and 100%. Feed and water were served ad libitum. Bio sanitary and bio security measures were strictly adhered to. At the end of the feeding trial, three rabbits per treatment were selected for the evaluation of serum biochemistry. The parameters assayed for were: total serum protein, serum globulin, serum albumin, cholesterol, serum calcium, and serum phosphorus. The study showed that the serum biochemical indices were not influenced (P˃0.05) by the dietary treatments except for calcium which was significantly (P<0.05) influenced, however, calcium values were within the normal reference values for rabbits. This study had shown that fresh water snail (Pila ampullacea) shell ash can serve as a substitute for bone ash in weaned rabbit diet up to 100% inclusion levels without adverse effect on the serum biochemical indices.

Effect of Replacing Bone Ash with Fresh Water Snail (Pila ampullacea) Shell Ash on the Performance of Weaned Rabbits

Twenty five weaned male rabbits of mixed breeds were used to investigate the effect of replacing bone ash with fresh water snail shell ash on the performance of weaned rabbits. The experiment was conducted at the Teaching and Research Farm, University of Agriculture, Makurdi, Benue State, Nigeria for a period of 12 weeks. The rabbits were randomly assigned to the five dietary treatments and replicated five times giving a total of one rabbit per replicate in a completely randomized design (CRD). Rabbits were raised intensively in hutches of about 4ft × 4ft. Five experimental diets tagged T1 to T5 were formulated such that fresh water snail shell ash replaced bone ash at 0%, 25%, 50%, 75% and 100%. Feed and water were served ad libitum. Bio sanitary and bio security measures were strictly adhered. The study showed that the growth parameters were not affected (P=.05) by the dietary treatments. This study had shown that fresh water snail shell ash can serve as a substitute for bone ash in weaned rabbits diet up to 100% without compromising their performances.

PHYSICO-TRIBOLOGICAL ANND WEAR MECHANISM CHARACTERISTICS OF HYBRID REINFFORCED Al6063 MATRIX COMPOSITES

The development of engineering materials is continuously attracting attention from scientists and engineers for numerous engineering applications. The physical properties and wear mechanism of aluminium (Al 6063) matrix reinforced with silicon carbide (SiC) and palm kernel shell ash (PKSA) particulates at different weight ratios ranging from 0 to 10 wt.% with 2 wt.% intervals were investigated. The liquid route of double stir casting was employed in synthesizing the composites. The wear experiment was conducted using the Taber-type wear abrasion machine. The worn surfaces were examined using scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDS), while the intermetallic phases were examined using the x-ray diffractometer (XRD). From the result, the increase in PKSA and SiC lowered and improved the density of the composites, respectively. The percentage porosity values (2 - 2.4%) obtained in this study were found to be within the acceptable limit of less than 4% for metal matrix composites castings. The mass loss and wear index increased owing to the rotating speed and applied load increase, resulting from the occurrence of mechanical mixing between the contacting surface of the sample disk and the machined disc. Adhesive and abrasive wear mechanisms were the major mechanisms observed in this study.

STUDY ON THE GEOTECHNICAL PROPERTIES OF LATERITIC SOIL STABILIZED WITH BENTONITE AND GROUNDNUT SHELL ASH AS ADMIXTURE FOR CLAY LINER IN WASTE CONTAINMENT

Waste management in Nigeria is characterized by poor landfilling practices in low-lying areas with improper planning of waste dumping. Whenever the soil on site is unfit for a barrier, it is blended with conventional stabilizers, but these additives are costly, hence the need to partially replace them with cheaper materials to achieve the desired results is essential. Consistency limit and engineering properties tests were conducted on the virgin and treated soil specimens. The Bentonite was added at a constant ratio of 6% whilst the groundnut shell ash was increased in the ratio of 0%, 2%, 4%, 6%, 8% and 10%. Samples were prepared at a moulding water content of (-2% ≥ OMC ≤ 4%), adopting BSL and BSH energy levels. Preliminary laboratory test on the natural soil indicated that the soil is A-4(3) and SM according to AASHTO and USCS classification systems, respectively. From the compaction test carried out, it was observed maximum dry density (MDD) increases and optimum moisture content (OMC) decreases upon stepped addition of Groundnut shell ash (GSA). Hydraulic conductivity, volumetric shrinkage strain and UCS values recorded at 6% bentonite/ 6% groundnut shell ash content gave satisfactory results that met the acceptable values of ≤ 1× 10-9 m/s, ≤ 4%, and ≥ 200 kN/m2 for BSL and BSH energy levels, respectively. The overall acceptable range for groundnut shell ash stabilized bentonite-lateritic soil was obtained at 6% bentonite/ 6% groundnut shell ash blend for samples prepared at moulding moisture content of 19.5 – 21.0% and 16.5 – 20.0% respectively. Investigation of leaching capability of groundnut ash into the environment using batch equilibrium test showed that the desorbed values of iron and pH for the optimally modified soil falls within the acceptable values endorsed by the Nigeria industrial standard (NIS) and world health organization (WHO).

MECHANICAL AND MICROSTRUCTURAL PROPERTIES OF BRASS REINFORCED WITH COCONUT SHELL ASH POWDER

Metal matrix composites (MMCs) are materials in which metals are reinforced with other materials preferably of lower cost to improve their properties. In this present study, Brass /Coconut Shell Ash powder (CSAp) composites having 0%, 5%, 10% and 15% weight CSAp were fabricated by stir-casting method. The tensile strength of the MMCs is in the order 15% > 10% >5% > 0% of CSAp. Hardness of the MMCs increases slightly with increase in the percentage body weight of CSAp, in the order 15% > 10% >5% > 0% of CSAp. The highest impact energy of 61 J was obtained for 5% CSAp. However, significant improvement in tensile strength and hardness values was noticeable at the 15%. Scanning Electron Microscopy (SEM) analysis of the MMCs shows dendritic structures formation, the reinforcing particles (CSAp) are visible and clearly delineated in the microstructure. Hence, this study has established that reinforcing brass matrix with coconut shell ash particles can result in the production of low cost brass composites with enhanced tensile strength, hardness and impact energy values.

Assessment of Corrosion Performance of Steel Rebar in Snail Shell Ash Blended Cements under Marine Environments.

An attempt has been made on a constructive approach to evaluate the performance of snail shell ash (SSA) for its corrosion performance under marine environments. Corrosion performance of steel rebar in chloride-contaminated SSA with (0% to 50%) replacement levels of cement extract medium was examined through electrochemical and weight loss techniques. Initially, snail shell powder (SSP) is made by pulverizing and subsequently SSA is by thermal decomposition methods. Both SSP and SSA were characterized by X-ray diffraction, Fourier transforms infrared spectroscopy, scanning electron microscopy, and energy dispersion X-ray spectroscopy. Concrete cubes with 0% to 50% replacement levels of cement by SSA were evaluated for their mechanical properties. A critical level of 20 to 30% SSA improved both corrosion resistance and strength of concrete. Extrapolation modeling for the strength and corrosion rate with respect to later age were made. SSA is a suitable replacement material for natural limestone in cement productions.

Application of walnut shell ash/ZnO/K2CO3 as a new composite catalyst for biodiesel generation from Moringa oleifera oil

A novel heterogeneous catalyst based on walnut shell ash (WSA)/ZnO/K2CO3 composite was synthesized and applied for the production of biodiesel via the transesterification process of Moringa oleifera non-edible oil. Chemical precipitation and calcination processes were used to produce the catalyst. The results showed that the specific active surface areas for free WSA, ZnO, and WSA/ZnO/K2CO3 composite samples were 8.1, 24.1, and 1.9 m2.g−1, respectively. XRD and FTIR tests were confirmed the occurrence of different functional groups or compounds in the structure of the synthesized catalyst and indicated the activity potential of the catalyst. A response surface method-central composite design (RSM-CCD) was used to investigate the effect of independent variables including the temperature and time of reaction, the methanol to oil ratio, and catalyst concentration on the process efficiency. A probability value (P-value) < 0.0001 and a Fisher value (F-value) of 192.16 were obtained indicating the high capability of the proposed model. The value of C.V.% of 1.10 showed that there is a little deviation between the experimental and the predicted data by the model, which shows the high accuracy of the model. In addition, R2 and Adj. R2 parameters confirmed the high ability and accuracy of the model. Based on RSM-CCD results, the maximum efficiency of 97.34 % was obtained using a reaction temperature of 65 °C, a reaction time of 4 h, a catalyst content of 4 wt%, and methanol to oil ratio of 18:1. Moreover, it was shown that that the synthesized catalyst can be re-cycled for multiple usages in the biodiesel generation process. The E factor showed that the produced fuel is biocompatible. The properties of the produced biodiesel showed that it has good compliance with ASTM-D6751 and EN-14214 and can replace diesel-derived fuels as a suitable fuel source.

Biomass ashes to produce an alternative alkaline activator for alkali-activated cements

In the last decade, herbaceous and agricultural biomass have been used as an alternative energy source. As consequence, large amounts of residual ashes containing potassium (potassium-rich ashes) have been generated. Olive biomass ash (OBA) and almond shell ash (ABA) have been successfully used as alkali source in the alkaline activation of ground granulated blast furnace slag (BFS). This study focuses on the production of new and alternative alkaline activators for BFS systems using nutshell ashes (NBA), mango seed-bark ashes (MBA) and hazelnut shell ashes (HBA). The chemical and mineralogical composition of these ashes were assessed and, the mechanical and microstructural properties of BFS pastes activated with NBA, MBA and HBA were evaluated. The results indicated that all assessed materials are potassium-rich ashes differing mainly on the amount of CaO and P2O5. The compressive strength of BFS pastes yielded about 26 MPa and, according to FESEM/EDS analysis, K2O (in the range 8.03–24.33%) replaces chemical bounded Ca+2, forming C-(K)-A-S-H gel.