Activated Fly Ash Research Articles

Phase Analysis of Alkali-Activated Slag Hybridized with Low-Calcium and High-Calcium Fly Ash

This paper investigates the hydrated phase assemblage, microstructure, and gel composition of sodium hydroxide (NaOH)-activated fly ash–slag blends with either low-calcium or high-calcium fly ash. The results show that the nature of precipitated calcium–aluminosilicate–hydrate (C-A-S-H) and alkali aluminosilicate-hydrate (N-A-S-H) depends on the fly ash composition and slag-to-fly ash ratio. However, regardless of fly ash composition and slag-to-fly ash ratio, a universal linear compositional relationship exists between Al/Ca ratio and Si/Ca ratio in precipitated gels. This indicates that there exists a structural limitation on the incorporation of Al3+ for Si4+ in the tetrahedral silicate of C-A-S-H, N-A-S-H, or metastable N-C-A-S-H gels. In a hybrid slag–fly ash system, the framework structure of precipitated gels is an assemblage of aluminosilicate units with heterogeneous Ca2+ and Na+ distribution. The amount and reactivity of calcium and alkalis seem to play a critical role in determining the structure and properties of precipitated gels in hybrid systems. The low cementitious capability in alkali-activated high-calcium fly ash may be attributed to the unstable N-C-A-S-H gel structure with concurrent high Na and Ca contents.

The Ratio Optimization and Strength Mechanism of Composite Cementitious Material with Low-Quality Fly Ash.

To resolve the limited large-scale methods of disposal of low calcium fly ash with poor activity, based on the double excitation principle, clinker and desulfurized gypsum are used as alkali/salt activators to activate fly ash and slag, avoiding the inconvenience of strong alkali activating fly ash in industry. Firstly, the strength test of a filling body with multiple ratio composite cementing material is carried out, and the weight coefficient of each material to strength is analyzed by grey correlation degree. The composition of the hydration products, microstructure, and pore structure of the filling body was analyzed by X-ray diffractometer, scanning electron microscope, thermogravimetric test, and mercury compression test. The strength mechanism of the cemented body was confirmed. The results show that cemented backfill prepared by composite cementitious material, which contained high content and low-quality fly ash, can meet the strength requirements of subsequent backfill in a mine. The degree of composite cementitious material influence on 7 d strength is slag > desulfurized gypsum > fly ash > clinker; the degree of influence on 28 d strength is: fly ash > slag > desulfurized gypsum > clinker. The main hydration products of the composite cementable material with high content low-quality fly ash are C–S–H gel and ettringite, and the unreacted fly ash particles can still be seen at 28 d. As the curing age grows, the difference in the number of hydration products under different proportioning conditions has a weaker effect on the strength, while the influence of raw materials and product morphology on the pore structure determines the development trend of the strength. Therefore, the threshold pore size can be used to characterize the strength advantages and disadvantages reasonably.

Characterization of mechanically activated fly ash-based lightweight geopolymer composite prepared with ultrahigh expanded perlite content

This study focused on the optimization of the production conditions of an ultrahigh expanded perlite lightweight aggregate-filled fly ash-based geopolymer composite and the determination of its product properties. The geopolymer matrix was synthetized using mechanically activated fly ash and an alkaline solution. In a systematic series of experiments, the effect of expanded perlite (EP) content, the compaction pressure and the compaction time on the mechanical properties of the lightweight composite were investigated. In the case of the optimal production conditions, the composites were characterized in terms of physico-mechanical properties, water absorption and microstructure. The composites produced under optimal conditions had an average uniaxial compressive strength of 246 kPa and density of 534 kg/m3 at 80% by volume EP content, and 264 kPa and 221 kg/m3 at 95% by volume EP content. Both the FT-IR spectroscopy and scanning electron microscopy results proved the formation of main geopolymerization reaction products in the matrix of the composite, as well its reaction with the lightweight aggregate.

Mechanical property and microstructure of cemented tailings backfill containing fly ash activated by calcium formate.

Cemented tailings backfill (CTB) is the most economical and environmental method to recycle tailings and fly ash (FA) for filling mining, but the high content of FA will weaken its strength property. This paper aims to use calcium formate (CF) as an activator to stimulate the activity of FA, thereby enhancing the mechanical property of CTB. The influence of FA and CF content on the stress-strain behavior, dilatancy deformation, and compressive strength of CTB was investigated using uniaxial compression test and scanning electron microscope. The coupling effect mechanism of FA and CF content on the compressive strength of CTB was revealed. The results show that increasing the content of FA and CF can enhance the bearing capacity of CTB during the dilatancy deformation stage, but the excessive content of FA and CF will lead to the attenuation of peak stress. The relations between FA content, CF content, and the compressive strength of CTB can be characterized by quadratic polynomial. Adding CF can stimulate the activity of insoluble FA, increasing the utilization of FA in CTB and producing rich hydration products to fill the internal defects of CTB. The microstructure of CTB is effectively improved by adding CF, including the size and distribution of microcracks and micropores, so that the strength property of CTB is optimized. However, too much CF will make the microstructure of CTB loose and porous, resulting in more microcracks and micropores. Microcracks propagate and connect with micropores to form defects, which deteriorate the microstructure of CTB, thus weakening the strength parameters of CTB. This study provides a method to increase the utilization of FA in CTB, which is of great significance for strengthening the mechanical properties of CTB and improving engineering economic benefits.

Influence of mechanical activation of fly ash on the properties of Portland cement mortars

Recently global warming, greenhouse gas and climate change have become a major and prominent topic of discussion in the general media. The cement industries are the most important producers of (CO2) after fossil fuels and land use change. The production of cement emits about 6–8% of the world's CO2 emissions into the atmosphere. The reduction of the amount of cement in the cementitious materials is a major challenge for researchers. The objective is to replace cement with eco-friendly materials such as fly ash (FA). The main objective of this research is to evaluate the effect of mechanical activation on the compressive strength of mortars containing FA. Two series of mortars are produced with FA from different sources in the weight proportions of 10%, 20%, 30% and 40% in replacement of cement and at a water-binder ratio (W/B) of 0.5. The results indicate that mechanical activation of FA improves particle fineness and increases silica and alumina content in the blended cement.

Influence of Chemical Composition on Compressive Strength of Soda Ash Activated Fly Ash and Copper Slag Pastes (Facsps)

Influence of Chemical Composition on Compressive Strength of Soda Ash Activated Fly Ash and Copper Slag Pastes (Facsps)

Comparison of alkali modified fly ash and alkali activated fly ash as Zn(II) ions adsorbent from aqueous solution

Fly ash which is solid waste can be used as an adsorbent for wastewater treatment. Alkali modification and alkali activation on fly ash can increase the adsorption capacity of fly ash. In this study, alkali modified fly ash and alkali activated fly ash were used as Zn(II) ions adsorbents. The effect of adsorption time and initial concentration of Zn(II) ions was studied, as well as the kinetics and isotherm adsorption. The results showed that the removal efficiency of Zn(II) ions by alkali activated fly ash is higher than that by alkali modified fly ash. The adsorptions of Zn(II) ions by alkali modified fly ash and by alkali activated fly ash have reached equilibrium after two hours. The increase of initial concentration of Zn(II) ions would decrease the removal efficiency with both alkali modified fly ash and alkali activated fly ash. Adsorptions of Zn(II) ions by both alkali modified fly ash and alkali activated fly ash tend to follow pseudo second order kinetics model and Langmuir isotherm model with maximum adsorption capacity of 62.696 mg/g and 66.667 mg/g, respectively.

Experimental analysis on alkali activated fly ash (AAFG) and GGBS based coarse aggregate in cement concrete

Many applications of fly ash have been studied and employed in various fields. Thermal power stations use pulverized coal as fuel. Thus produce large amounts of fly ash as a by-product of combustion. The present analyses investigates the manufacturing process of Alkali Activated Fly Ash (AAFG) and Ground Granulated Blast Furnace Slag (GGBS) Based Coarse Aggregate using an ordinary concrete mixer and its properties are analyzed. The flexural capacity of the Reinforce Concrete (RC) beam with AAFG increases by increasing the diameter of reinforcement and decreases in the replacement AAFG beam, and the crack width decreases as an increase in the replacement of the fly ash aggregate up to 50% in concrete. The durability property of concrete blended with AAFG shows similar results to conventional concrete. From the Rapid Chloride Permeability Test (RCPT) results, it shows that AAFG concrete and conventional concrete are both in the moderate zone only.

A study on the mechanical properties of alkali activated ground granulated blast furnace slag and fly ash concrete

Alkali activated concrete (AAC) is one concrete which is made without cement. As sustainable construction is gaining interest, this alkali activated concrete is a better option for conventional cement concrete. Concrete is the most used commodity second only to water with a global Carbon emission of 5%. The evaluation of strength under compression of alkali activated fly ash and ground granulated blast furnace slag concrete, was carried out in this study. The evaluation of compressive strength depending on the method of curing is also studied. In this study Ground Granulated Blast Furnace Slag (GGBFS) and fly ash are used as the pre-cursor materials. These two materials are used in varying proportions and are activated using sodium hydroxide and sodium silicate solutions of varying proportions, after which the strength properties of alkali activated concrete are studied under two methods of curing i.e., water curing and ambient temperature curing. When the results obtained for water curing and curing at ambient temperature were compared the later yields good results. So, the curing at ambient temperature can be preferred over water curing. When GGBFS alone was used as a pre-cursor material the results show higher compressive strength can be achieved in comparison to the specimens having both GGBFS and Fly ash as pre-cursor materials. With increasing proportions of fly ash and decreased GGBFS content, the decrease in compressive strength was witnessed. Also, the specimens kept under water curing and the specimens cured under ambient temperature are compared and found that the later yields higher compressive strength.

A methodological approach applied to elaborate alkali-activated binders for mine paste backfills

In cemented paste backfill (CPB), tailings are commonly bound with Portland cement (GU) blended with ground granulated blast furnace slag (GGBFS) and/or fly ash (FA). Instead of using GU, alkali activation of GGBFS and FA is possible; this alternative has been intensively investigated in the concrete field. However, the development of an alkali-activated binder (AAB) recipe suitable to CPBs is still challenging, especially due to the specificities of the mine tailings. This study presents a methodological approach to formulate suitable AAB for CPB at the laboratory scale. First, potentially reactive mine tailings were substituted with fine siliceous sand to investigate the mechanical properties related to the binders; the new CPB was called simulated cemented paste backfill (S-CPB). Secondly, mixtures and pure pastes were created to investigate reaction kinetics and microstructural properties of such binders by various techniques. This methodological approach allowed the optimization of the binder composition and mechanical properties independently of the mine tailing characteristics. Once satisfactory formulations were elaborated, they were applied to the CPB and were evaluated economically and environmentally in terms of CO2-eq. Results showed that 75GGBFS/25FA_F activated by NaOH within a [0.5 N; 1 N] concentration interval can be used as a binder in CPB instead of the traditional GU/GGBFS blended binder. These findings and methodology are promising and could help to promote new eco-friendly binders in CPBs. However, the cost of NaOH and the CO2-eq footprint are still significant, so further considerations and research are needed to apply AAB in CPB at an industrial scale.

Geopolymer hybrid fly ash concrete for construction and conservation in peat environment: A review

Fly ash is industrial residue from the coal combustion in electric and steam generating plants and recognized as an environmental pollutant. Fly ash contains a high concentration of silica and alumina and can be used as geopolymer concrete. Studies the use of fly ash as a geopolymer concrete mixture has been developing in recent decades. This review focuses on the characteristics of fly ash as hybrid geopolymer concrete, and its resistance is peat environment. The hybrid geopolymer is made by activating fly ash using an alkaline activator and Portland cement. The addition of fly ash geopolymer concrete with Portland cement forms N-A-S-H bond structure from fly ash, and C-S-H hydration bond from Portland cement forms C-A-S-H, which is more solid and stronger against aggressive environment such as peat. In addition, the geopolymer concrete is proven to be able to mobilize heavy metals in fly ash so the concrete has low leaching rate and not harmful to the peat ecosystem. This review proves that hybrid geopolymer concrete using fly ash is a potentially innovative and promising material in the future. The geopolymer hybrid not only has its resistance to peat and acts as conservative material in an environmentally friendly peat environment.

Alkali Aktive Edilmiş Uçucu Külün Sinterlenmesi, Karakterizasyonu ve Fiziksel Özelliklerinin İncelenmesi

Bu çalışmada, Sivas Kangal Termik Santrali’nden edinilmiş uçucu külden yapılan alkali aktivasyon yani jeopolimerleşmenin ardından, farklı sıcaklıklarda sinterlenmesi ile üretilen numunelerin mekanik özellikleri, toz özellikleri, termal özellikleri ve faz özellikleri tartışılmıştır. Mekanik özellikler için basma testi, termal özellikler için geçirgen plaka kaynağı ölçümü, yüzey ve toz özellikleri için taramalı elektron mikroskobu ve faz analizi için X-ışınları difraksiyonu kullanılmıştır. Yapılan çalışmalarda kolay bulunan ve silika kaynağı da olabilen bir alkali olan Na2SiO3 farklı molaritelerde kullanılmış ve özellikleri incelenmiştir. Uçucu külün hem jeopolimer olarak kullanılabilirliği, hem de sinterlenmiş malzemenin yüzey plakası olarak kullanılabilirliğinin olduğu sonucuna varılmıştır. Basma mukavemeti 10 MPa, termal iletkenliği 0.0006 W/m.K, belirlenen fazlar ise kalsiyum silikat, kalsiyum aluminate, amorf silika ve magnezyum alüminat ve sinterleme ürünü olan camsı kyanite yani aluminasilikat fazı görülmüştür.

The Latest Research in Mongolia on the Utilization of Coal Combustion By-Products

With a geological reserve of over 170 billion tons, coal is the most abundant energy source in Mongolia with six operating thermal power stations. Moreover, in Ulaanbaatar city over 210000 families live in the Ger district and use over 800000 tons of coal as a fuel. The three thermal power plants in Ulaanbaatar burn about 5 million tons of coal, resulting in more than 500000 tons of coal combustion by-products per year. Globally, the ashes produced by thermal power plants, boilers, and single ovens pose serious environmental problems. The utilization of various types of waste is one of the factors determining the sustainability of cities. Therefore, the processing of wastes for re-use or disposal is a critical topic in waste management and materials research. According to research, the Mongolian capital city's air and soil quality has reached a disastrous level. The main reasons for air pollution in Ulaanbaatar are reported as being coal-fired stoves of the Ger residential district, thermal power stations, small and medium-sized low-pressure furnaces, and motor vehicles. Previously, coal ashes have been used to prepare advanced materials such as glass-ceramics with the hardness of 6.35 GPa, geopolymer concrete with compressive strength of over 30 MPa and zeolite A with a Cr (III) removal capacity of 35.8 mg/g. Here we discuss our latest results on the utilization of fly ash for preparation of a cement stabilized base layer for paved roads, mechanically activated fly ash for use in concrete production, and coal ash from the Ger district for preparation of an adsorbent. An addition of 20% fly ash to 5-8% cement made from a mixture of road base gave a compressive strength of ~ 4MPa, which exceeds the standard. Using coal ashes from Ger district prepared a new type of adsorbent material capable of removing various organic pollutants from tannery water was developed. This ash also showed weak leaching characteristics in water and acidic environment, which opens up an excellent opportunity to utilize.

Synthesis and characterization of eco-friendly mortars made with RHA-NaOH activated fly ash as binder at room temperature

In this study, an ecofriendly binder was developed by using rice husk ash (RHA) and sodium hydroxide as the activator alongside fly ash (FA) as the aluminosilicate precursor at ambient conditions. The developed binder was used in the production of mortars with varying proportions of sand. A total of three mortar mixtures were developed with sand to binder ratios of 0.55, 0.83 and 1.11. The corresponding behaviour of the mortars and influence of the sand proportions was assessed in terms of the compressive strength, water absorption, density, porosity. Microstructural investigations such as scanning electron microscopy, energy dispersive x-ray spectroscopy, infrared spectrum analysis and mercury intrusion porosimetry were also used to validate the physical properties. The findings from this study demonstrated that RHA can be used successfully as an activator component in the production of mortars. In terms of the sand content, it was found out that increasing the sand to binder ratio has detrimental effects on the performance of the mortars due to the reduction in the binder content primarily. The microstructure analysis of the mortars made with sand to binder ratio of 0.55 showed a compact and strong structure justifying the higher compressive strength achieved. The MIP analysis confirmed that the formation of C-A-S-H gel at the advanced ages allowed the pores refinement with a significant decrease in the fraction of the capillary and macroscopic pores within the geopolymer mortars.

Composite application of naphthalene and melamine-based superplasticizers in alkali activated fly ash (AAFA)

Workability could be a serious drawback for fresh alkali activated fly ash (AAFA) due to its high viscosity caused by alkaline activators. However, the reported optimum superplasticizers (SPs) only produced a slight improvement of fluidity while brought ambivalent effect on the strength in final NaOH-activated AAFA products. To obtain AAFAs with high fluidity and strength, 8M NaOH-AAFAs with low w/b at 0.24 were synthesized, and the effect of composite SPs consisted of naphthalene and melamine on fluidity and strength was investigated. Compared with naphthalene and melamine used separately, the composite SPs gave a maximum reduction in plastic viscosity, corresponding to the largest mini-slump and the lowest fluidity collapse. The workability improvement caused by composite SP was provided from the synergism of melamine and naphthalene, as the significant improvement of melamine on initial fluidity and the excellent fluidity retention supplied by naphthalene. Moreover, the application of composite SPs at lower dosage (1%) could give a significant improvement on the compressive strength of AAFAs. Further, the stability and water reduction mechanism of composite SP were also assessed, and results revealed that the decomposition of sulfonate in naphthalene and triazine ring in melamine was delayed; indicating naphthalene and melamine could maintain their structural stability within 60 minutes when adopted together. In addition, the steric resistance effect cannot be ignored in the dispersion mechanism of composite SPs, while the electrostatic repulsion played a dominant role when naphthalene and melamine used separately. The outcome of this study will be supportive to the ongoing research related to the construction performance of AAFAs in the aim of promoting their in-situ applications

Geopolymers Based on Mechanically Activated Fly Ash Blended with Dolomite

This study reports the effect of natural dolomite addition to fly ash and the mechanical activation of this blend on the geopolymerization process. Dolomite was replaced with fly ash at 1, 3, 5, and 10 wt.%. Geopolymers were synthesized at ambient temperature using NaOH solution as an alkaline agent. The geopolymerization process, reactivity of the raw material, compressive strength, and microstructure were studied using X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetry, and scanning electron microscopy. It was shown that blending fly ash with dolomite and mechanical activation improved the geopolymer strength, especially during the early age of curing. For geopolymers prepared using a 90% fly ash + 10% dolomite blend cured for 7 d, the strengths were 8.2-, 2.3-, and 1.4-fold higher than those for geopolymers prepared using 100% FA for 30 s, 180 s, and 400 s milling times, respectively. A simple method for evaluating the increments of mechanical activation, carbonate additives, and the synergistic effect in the increase in the compressive strength of the composite geopolymer is proposed.

Enhanced autogenous self-healing of cement-based composites with mechanically activated fluidized-bed combustion fly ash

This study investigates the effect of the modification of cement-based composites with mechanically activated fly ash from lignite combustion in fluidized bed boilers (MAFBC fly ash) on self-healing. The subject of the research was mortar samples in which, after 28 days of maturing, cracks 0 to 750 µm wide were mechanically induced, followed by curing for 152 days. Via computer processing and analysis of high-resolution scanner (HRS) images, the maximum average crack width reduction was determined to be 43%. The analysis of samples via ultrasonic pulse velocity (UPV) measurements estimated the degree of crack filling with newly formed material during self-sealing to be as high as 58%. In terms of mechanical properties, a maximum flexural strength recovery of 54% was observed due to microstructural changes in the contact area between the cement matrix and polypropylene fibers. To examine self-healing at a microstructural level, optical and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) were applied to the surface of cracks and fragments cut out of the samples. The results showed that the use of MAFBC fly ash as a partial substitute for cement led to the modification of the products of self-healing. Hydrated calcium aluminates were observed in the cracks in addition to typical self-healing products. In the interior of the samples, the complete filling of cracks up to a width of 110 µm was observed.

Mechano-chemically activated fly-ash and sisal fiber reinforced PP hybrid composite with enhanced mechanical properties

This study explores the hybridizing effect of mechano-chemical activated fly-ash (FA) in polypropylene (PP) composites reinforced with sisal fibers. Activation and resistance against agglomeration of FA has been achieved by modifying it with 2, 4, and 6 wt.% of the cetyltrimethylammonium bromide (C-tab). FA activation with C-tab and particle size reduction to nano-level (< 1 µm) have been appropriately achieved with a planetary ball milling and the same has been confirmed from the dynamic light scattering technique. The hybrid composite containing 25 wt.% of sisal fiber and 5 wt.% of (6 wt.% C-tab) treated FA shows much improved tensile (40.12 MPa), flexural (53.27 MPa), and impact strengths (0.75 kJ/m2) than that of virgin PP and its 30 wt.% sisal fiber composites. This increase in tensile and flexural strength was 30.54% and 48% higher than neat PP. Maximum notched impact strength of 0.80 kJ/m2 have been reported by hybrid composite containing FA treated with 2 wt.% of the C-tab. Micromechanical modelling using a combination of rule of mixture and inverse rule of mixture separately with Halpin–Tsai predicted a value close to the experimental Young’s modulus. DSC studies showed an increment in the composite's crystallinity upon fiber addition. Morphological analysis of the hybrid composite revealed good wettability of reinforcing fiber and FA within the matrix, whereas TGA showed an improved thermal stability of the composites.

Mechanical properties, shrinkage, and heat evolution of alkali activated fly ash concrete

Use of high calcium fly ash as a binder to replace the ordinary Portland cement possibly cause a false set for alkali-activated concrete. Therefore, the appropriate mixed proportion of alkali-activated concrete must be considered for further applications. This research investigated the mechanical properties, shrinkage, and heat evolution of concrete using high-calcium fly ash as a binder with two alkali activators: sodium silicate (Na2SiO3) and sodium hydroxide (NaOH). Ratios of sodium silicate to sodium hydroxide (Na2SiO3/NaOH) of 0.3, 0.4, and 0.5 by weight, and NaOH concentrations of 2, 4, 6, and 8 Molar were used. The ratio of liquid to binder was 0.7, and the fly ash content was 400 kg/m3. The results indicated that increasing the Na2SiO3/NaOH ratio and NaOH concentration improved the compressive strength of the concrete. The maximum value for the compressive strength, 27.5 MPa, was observed for a Na2SiO3/NaOH ratio of 0.5 and NaOH concentrations of 2 Molar at 90 days. The modulus of elasticity of alkali-activated fly ash concrete was found to be similar to that of conventional concrete. Additionally, the shrinkage of concrete tended to decrease with increasing NaOH concentration, and increasing the Na2SiO3/NaOH ratio led to increased concrete shrinkage. Finally, the heat evolution of alkali-activated fly ash concrete was found to be two times lower than that of concrete made from Ordinary Portland cement at the same compressive strength. The increase of NaOH concentration and Na2SiO3/NaOH ratio resulted in higher temperature rise of alkali-activated fly ash concrete.

Pre-compression and capillarity effect of treated expansive subgrade subjected to compressive and tensile loadings

Pavement structures often are under tension and compression mobilised by the coupled effects of traffic loads and swelling stress. Seasonal moisture variations cause capillarity rise and volumetric movement within the subgrade. The objective of this investigation is to evaluate the pre-compression and capillarity effect of expansive subgrades stabilised with activated fly ash (α-FA), and sisal fibre, analysed for tensile (qt) and compressive qu strengths. Moulding moisture content corresponding to the optimum water content was used to prepare the subgrade soils by random inclusion of 0.25 %, 0.5 %, 0.75 %, and 1.0 % of sisal fibre by dry mass of the subgrade soils treated with 20 % and 30 % of α-FA. Confined pre-compression stresses equivalent to 10 kPa and 20 kPa after 12 h of preparation were applied followed by 14 days of air-curing condition. Subsequently, the prepared subgrades samples were subjected to capillary rise through soaking. The test results revealed that both tensile and compressive strengths of 10 kPa and 20 kPa precompressed specimens decreased from 1.48MPa to 0.98MPa on average due to the capillarity effect, compared to non-capillary specimens. Without capillarity effects, an equivalent strength increases of 12.21 % and 63 %.11 were recorded for 10 kPa and 20 kPa of pre-compressed specimens compared to un-precompressed specimens tested under tension. The results further revealed that the subgrade soils treated with the combination of fibre and α-FA exhibited significant strength resistance under tension. The strength indices (qt/qu) of 0.13 to 0.31 as the proportionality of tensile and compressive strengths is closely correlated for all the pre-compressed composites due to fibre deformability.