Implementation of Cement-based nano composite Energy Absorption Damper to improve the damping properties of concrete and monitoring applications

. The energy from the moving seismic waves through a building structure is dispersed by means of dampers. Dampers work by converting the kinetic energy into heat energy, dissipating it into the hydraulic fluid. Damper systems are designed and manufactured to protect structural integrity, reduce structural damage, and prevent injury to people by absorbing energy from earthquakes and minimizing structural deformations. The most effective way to achieve good vibration damping is by tailoring the construction materials such as cement with nanomaterials like Silica, Alumina, Graphene, CNTs, etc. This paper focuses on developing a vibration damper, prepared by cement nanocomposite containing MWCNTs and Carbon fibers. The tests, such as the Impact, Flexural, and Compressive strength tests, are conducted to investigate their energy-absorbing capacity, strength, and durability. The microstructural analysis SEM is performed to know the morphology of concrete mix with MWCNTs and Carbon fibers on damping mechanism. Impact test results indicate that the beams without MWCNTs and CFs exhibited an average energy absorption of 248 J, while those with MWCNTs and CFs absorbed an average energy of 262 J which shows almost 15% more energy absorption. Adding nanomaterials in a cement matrix improves concrete's frictional damping energy consumption ability and increases structures' energy-absorbing properties, flexural strength, and compressive strength.


Introduction
Typhoons and earthquakes are the main natural disasters that can destroy reinforced concrete structures, causing significant societal costs for adapting the structures.Although concrete is the most used structural material, its inadequate damping qualities cause catastrophic damage.For people's safety and comfort, better concrete damping characteristics are now necessary.To date, vibration control has been used in structures to increase their lifespan and save expenditures.Vibration control attempts to mitigate the harm that dynamic vibration responds to due to civil infrastructure.The three categories that best describe it are passive energy dissipation, smart control, active, and semiactive and vibration isolation of the substructure [1].To modify the structural material itself is the best way to apply these techniques to enhance vibration capacity such that endures high strength while contributing to ideal damping properties.The material which is exposed to cyclic stress undergoes damping.It will be more practicable to add the mixture to the cement matrix rather than outfit structures with damping devices to boost the damping property.To date, it has been standard practice to increase the damping qualities of cement matrix by adding admixtures, such as polymers, steel, and carbon fiber [2][3][4].The promising carbon material that has astonishing properties is the carbon nanotube (CNT).The compressive strength of road composites doped with multi-walled carbon nanotubes has dramatically risen, increasing by 46.8% MPa year over year, according to experimental data.The density of the composites is more or less going to rise as the particle size grows under the same carbon nano content.[5].One benefit of employing carbon nanotubes to enhance the qualities of concrete is the prevention of cracking, which has led to a substantial increase in their use in the sector.[6].A single CNT fiber has a tensile strength of 100 GPa, Young's modulus of 1 TPa, can sustain a 15% fracture strain, and has a specific surface area of up to 1000 m2/g.[7][8].Due to its bonding, bridging, and mesh-filling properties, CNT may be utilized as a reinforcing element in cement matrixes [9][10][11], which would stop microcracks propagation and improve damping qualities.CNT has been used in several studies to increase the ability of polymer composites to reduce vibration.For instance, according to Dai and Liao's [12] investigation into the damping properties of epoxy resin, adding CNT can improve the composite's damping characteristics without subjecting it to strain.Tehrani et al. [13] observed that as compared to the reference sample, the performance of the hybrid CNT-carbon fiber-reinforced epoxy composite had a better loss tangent of 56%.However, there haven't been many studies done on how to increase the cement matrix's damping capacity.Additionally, the effects of the CNT on the cement composite's damping capacity and its operational mechanism have not yet been described.
Numerous studies have identified the potential of carbon fiber-reinforced cement composites (CFRCCs) in terms of bending strength, impact strength, electrical conductivity, and behavior that senses strain [14][15][16].Due to the hydrophobic surface and low weight, it is difficult for carbon fibers to disperse uniformly in cement paste [17].And the higher flexural strength, conductivity, and toughness of the CFRCCs depend on the good dispersion of carbon fibers in the cement matrix [18][19][20].By comparing it was concluded that the pre-mixing method which involved the addition of 2-5 mm carbon fibers before the addition of cement achieved better dispersion than the post-mixing method.According to SEM findings, carbon fiber's capacity to prevent the development of microcracks and absorb energy by overcoming it pulling out is what accounts for the improved qualities of cement mortar filled with carbon fiber.[21].The interfacial modulation may greatly improve the damping ratio, loss factor, and energy dissipation ratio of UHPC, with the maximum damping ratio being provided by chemical modification of steel fibers.[22].
In the proposed work, we are developing a novel cement-based nano composite damper system to improve the damping properties and evaluate its efficiency, and mechanical and microstructural properties.Nanomaterials like MWCNTs and Carbon fibers have been incorporated into Cement to improve its energy-absorbing capacity by conducting various trial experiments like Impact Strength tests, Flexural strength tests, Compressive testing, etc. for the first time.The samples were cast as per the Mix design given in Table 3.The specifications of MWCNT's and Carbon fiber is presented in Tables 1 & 2. Three samples S1, S2, and S3 are the normal cement beams and are cast without any nanomaterials.D1, D2, and D3 are cast with the addition of nanomaterials viz MWCNTs which is taken as 0.5 wt% of the volume of cement, and Carbon fibers which is taken as 2 wt% of the total volume of cement as per the literature review as shown in Figure 1 properly in water and then put in an Ultra Sonicator for proper and uniform mixing.Then the required mold is properly cleaned and oiled and then the concrete mix is prepared by mixing the cement, sand, coarse aggregates, MWCNTs, Carbon Fibres, and water and then poured into the mold and kept for curing for 28 days in water in a tray at room temperature.One set of samples consists of the Dampers with nanomaterials and the other set is controlled specimens without nanomaterials.After 28 days of curing, the samples are tested for Damping and Energy Absorption Properties using the Impact, compression, and Flexural Beam Tests.The complete methodology and experimental procedure are shown in Fig 2.

Izod Impact Test
A conventional notched specimen's energy absorption while breaking under an impact force is measured by the Izod impact test.As demonstrated in Fig. 3, this test is still employed as a low-cost quality control procedure to evaluate the notch sensitivity and impact toughness of engineering materials such as metals, composites, ceramics, and polymers.
To strike a piece of material or sample with a notched edge, a pendulum with a hammer of known mass and length as shown in Fig 3 .is released from a certain height as part of the equipment.The energy absorbed is calculated by comparing the difference in the height of the hammer before and after the fracture

Compressive Strength Test
The concrete compressive strength gives an understanding of all the properties of concrete.By this test one can infer whether the concrete pouring was done correctly or not.Concrete compressive strength ranges from 15 MPa (2200 psi) to 30 MPa (4400 psi) for normal construction.The commercial and industrial structures having greater compressive strengths.For a compressive strength test either a cube or a cylinder is used as they are advised as the standard specimen for the test by several standard codes.Hence the compressive strength test was carried out to know the compressive strength of the samples.

Calculations of Compressive Strength
Size of the dampers =5 cm x 5 cm x 2.5 cm.The average compressive strength involves using the formula for stress, which is defined as the force applied divided by the cross-sectional area of the specimen

SEM Analysis (Scanning Electron Microscopy)
SEM analysis of the composite is necessary to evaluate the various properties of composites like bonding, fracture behavior, interfacial adhesion, and other properties.The SEM analysis of the samples was carried out at Karnataka University Dharwad, India.Figure 9 proves that the fiber pullout zones are hardly visible, as it is just a Cement composite without nanomaterials whereas fiber breakage is more visible in Fig 10.This is indicative that the composite has good fiber-matrix adhesion which leads to a higher interlaminar shear strength between the layers.And good adhesion and bonding lead to good damping and better Energy Absorption Capacities of the composite.FTIR spectroscopy is a controlling technique used to characterize the characteristics of vibrational bands/modes within the material and the presence of various functional groups associated with the bonds in the compound.Fourier Transform Infrared Spectroscopy (ASTMD5477-18, 2018) was carried out at KLE Pharmaceuticals Hubli and was adopted to determine the FTIR spectra of the cement-based nanocomposite damper doped with MWCNTs and Carbon Fibers.FTIR spectra, between 400 and 4500 cm -1 with a wavelength accuracy of 1 cm -1 , were gathered.FTIR spectra can be employed to quantify the constructive and destructive bonds to evaluate the strength.It is clear that the MWCNTs have their characteristic peaks band at 2171.51 cm−1 and 2021.54cm−1 corresponding to their octahedral and tetrahedral site vibrational modes as seen from Fig 12, it can also be stated

Fibres clattered due to improper mixing
Uniformly clustered fibres at some locations that IR spectra for oxygen display a strong and broad peak around 2981cm−1, which corresponds to the stretching mode of the O-H group.

Figure 8
Figure8shows a graph of the difference of compressive strengths test results of the specimens with and without nanomaterials.The compressive strength is highest for the specimens with Nanomaterials and it is 81.24N/mm 2 whereas the specimens without nanomaterials are having less compressive strength i.e., 77.18 N/mm 2 .The highest compressive strength is attributed due to the good bonding of Cement with MWCNTs and Carbon Fibers.

Figure 8 .
Figure 8. Compression test results of both the specimens with & without nanomaterials

Figure 7 .
Figure 7.The specimen under Compression Testing

Figure 9 .Figure 10 .
Figure 9. SEM analysis of the Cement Composite without nanomaterials

5 Conclusions
Experimental investigations provide more insight into the influence of MWCNT and Carbon fibres on the damping, flexural, and Compressive strength properties of the composite.The energy absorption capacity of the composite was observed to increase with the content of MWCNTs and CFs in the range of 0.5% & 1 to 2wt.% in all samples.Samples loaded with MWCNTs and CFs exhibit an increase in Energy absorption capacity in a range of 15% more than the normal Cement Composite.Experimental results also an increase in flexural strength.Samples supplemented with MWCNTs and CFs display an increase in compressive strength of up to 5%.The addition of nanomaterials in a cement matrix improves concrete's frictional damping energy consumption ability and increases structures' energy-absorbing properties, flexural strength, and compressive strength.mechanical and electrically conductive properties of cement-based materials", Construction and Building Materials Volume 125, 30 October 2016.22. Huinan Wei, Tiejun Liu, Ao Zhou, Dujian Zou, Ye Li.Toughening static and dynamic damping characteristics of ultra-high performance concrete via interfacial modulation approaches, Cement and Concrete Composites, Volume 136, February 2023, 10487

4. Multi-walled carbon Nanotubes (MWCNTs)-These are
2.1 Materials1.Cement-ULTRATECH brand, OPC 43 grade cement was used.Ordinary Portland cement confirming to IS8112-1989 has been used, it is used for all types of buildings.2. Aggregates-The coarse aggregate gives the completed product the volume, stability, wear, erosion resistance, and other necessary physical attributes.5mm aggregates are obtained from Sieve analysis and are mostly angular in shape.The fine aggregate used is a granular material composed of finely divided mineral particles.Sand has various compositions but is defined by its grain size.It was procured locally from Tungabhadra River Mundargi.3. Carbon Fibres-Carbon fibers are about 5 to 10 micrometers in diameter and are composed mostly of carbon atoms.Table 1 lists the characteristics of the carbon fibers.They were procured from Intelligent Materials Pvt Ltd, Village Sunderban, Derabassi-140507, Punjab India.a special type of carbon nanotubes in which the single-walled carbon nanotubes are layered one inside the other.The specifications of the MWCNTs are presented in Table 2.They were procured from Intelligent Materials Pvt Ltd, Village Suderban, Derabassi-140507, Punjab India.

Table 1 .
Specifications of Carbon Fibers.

Table 3 .
Mix design for Concrete Mix 2.2 Preparation of Samples-Experimental Procedure