Microstructure Properties Of Concrete Research Articles

Influence of replacing Portland cement with anionic asphalt emulsion on vibration damping, mechanical and microstructural properties of concrete

The effect of anionic asphalt emulsion (AE) as partial replacement of Portland cement to enhance the damping properties of concrete was examined. Five concrete mixtures were designed and prepared, increasing AE content from 0 to 40% in overall binder volume, in 10% increments. Loss factor, dynamic moduli, resonant frequencies, and compressive strength were obtained at the age of 7, 28, 90, and 180 days. Results show that the loss factor of concrete increased as the asphalt content increased, whereas the dynamic modulus and resonant frequency decreased. In addition to the viscous damping contributed by asphalt droplets, the more porous microstructure and weaker interfacial transition zones in AE modified concrete can also enhance the damping properties. However, an inverse correlation between concrete strength and damping can be observed with increasing AE content, where the substitution of AE results in a significant decrease in the compressive strength of concrete. Therefore, the anionic AE modified concrete seems to be more suitable for non-structural application where strength is not a key requirement.

Sustainable use of recycled fine aggregates in steel fiber-reinforced concrete: Fresh, flexural, mechanical and durability characteristics

Recycling construction waste is a viable tactic for advancing environmentally friendly building methods. With regard to concrete applications, the purpose of this research is to determine whether it is feasible to use recycled fine concrete aggregates (RFA) in lieu of natural fine aggregates (NFA) and to lessen the environmental impact of natural resource depletion and landfill space. A sustainable steel fiber-reinforced concrete was created by replacing NFA with RFA at the replacement ratio of 0 %, 50 %, and 100 %. Steel fibers (SF) were also included to mixes at three different contents of 0, 25 and 50 kg/m3 in order to further improve the qualities of the concretes. Thus, the aim of this paper is to appraise how the addition of FRA affects the mechanical, freeze-thaw, fresh, and non-destructive qualities of concrete. Nine concrete mixtures were cast, and tests were made to evaluate the following properties: flowability, fresh concrete unit weight, tensile and compressive strengths, elastic modulus, surface hardness, crack mouth opening displacement (CMOD), freeze and thaw performance, sulfate resistance and abrasion. Moreover, microstructure properties of concrete were also analyzed. The outcomes revealed that the mechanical, flexural, and durability performances of the concrete mixtures were enhanced by substituting RFA for NFA. The mixture with 50%RFA and 50 kg/m3 SF gained maximum compressive strength of 44.82 MPa which was 20.7 % greater than the reference mixture (RFA0F0). The mixture containing 100 % RFA and 25 kg/m3 SF had the highest elastic modulus and showed an approximately 33 % augmentation in elastic modulus as per the reference mixture. The mixture with 100%RFA and 50 kg/m3 SF exhibited the largest tensile strength indicating 60 % tensile strength enhancement as per the reference mixture. Combined use of RFA and 50 kg/m3 SF in concrete mixtures had the best abrasion and freeze-thaw resistance. SF incorporated concrete mixtures with RFA exhibited worse sulfate resistance. This study contributed significantly to global resource efficiency and environmental preservation by shedding light on the sustainable use of RFA and SF in the making of concrete. The results made important contributions to global research and promote environmentally friendly building methods all throughout the world.

Influence of Bacillus species on mechanical and microstructural properties of concrete

Influence of Bacillus species on mechanical and microstructural properties of concrete

Exploring the impact of red mud on the mechanical, durability, and microstructure properties of concrete

Purpose This study investigated the potential of partially replacing cement with red mud (RM) in concrete and examined its effects on its mechanical properties and microstructure. This study aims to explore sustainable alternatives to traditional cement and evaluate the performance of concrete mixtures with varying percentages (%) of RM as cement replacement. Design/methodology/approach This research aims to comprehensively understand the impact of RM on concrete, aiming for both environmental sustainability and improved construction materials. Subsequently, concrete mixtures were prepared with varying RM contents, ranging from 0% to 21% in increments of 3%, replacing cement. The workability of these mixtures was evaluated using the Slump Cone Test, whereas their mechanical properties (compressive strength, flexural strength and split tensile strength) were assessed through standardized tests. The durability was further investigated via water absorption, acid attack, rapid chloride permeability tests, open porosity test and Sorptivity test. To gain deeper insights into the internal structure of concrete, microstructure analysis was conducted using X-ray diffraction and scanning electron microscopy. Finally, the results were analyzed and quantified. Findings The finding demonstrates that substituting 12% of cement with RM not only boosts the mechanical characteristics of concrete but also mitigates waste disposal. The microstructural analysis identified a denser cement matrix and improved bonding between the cement paste and the aggregates, suggesting potential improvements in strength and durability. Originality/value These results suggest that RM can be efficiently used to produce sustainable concrete with potential applications in construction projects with environmental considerations.

Impact of new type of plastic as aggregate on fresh and hardened, microstructure properties of concrete

The goal of this work is to reuse plastic waste as a result of the production of valves on gas bottles into concrete. In this way, one can reduce and consume that waste and at the same time reuse it in concrete and study its effects on its properties to decide which best content. This kind of plastic waste was used in different quantities (5%, 7.5%, 10%, 12.5%, and 15%) to replace fine natural aggregate (sand) partially. The effects of these ratios on the fresh concrete's slump factor, the density of hardened concrete, compressive strength, absorption, microstructure, and ultrasonic pulse speed were studied and compared with a reference mixture free of plastic waste. The ANOVA analysis was used to analyze the results of the fresh and hardened tests, and it was concluded that 5% was the ideal percentage of the percentages used, as it had less negative influence on the properties of concrete. From laboratory work, it was concluded that increasing the percentage of plastic waste has a negative impact on the properties of concrete, such as reducing compressive strength, flexural strength, spitting tensile strength, and increasing absorption.

A Comprehensive Review on the Use of Wastewater in the Manufacturing of Concrete: Fostering Sustainability through Recycling

The primary aim of this review article is to find the influence of wastewater and its characteristics on recycling as an alternative to potable water for concrete preparation. On the other hand, scarcity, and the demand for freshwater for drinking are also increasing day by day around the globe. About a billion tons of freshwater is consumed daily for concrete preparation for various operations such as mixing and curing, to name a few. The rapid development of certain industries such as textile, casting, stone cutting, and concrete production has caused the water supply to be severely affected. Recycling wastewater in concrete offers various potential benefits like resource conservation, environmental protection, cost savings, and enhanced sustainability. This article reviews the effect of various types of wastewater on various physical and chemical properties of wastewater, rheological characteristics, strength, durability, and microstructure properties of concrete. It also explores the potential effects of decomposing agents on enhancing concrete properties. Currently, limited research is available on the use of various types of wastewater in concrete. Hence, there is a need to develop various methods and procedures to ensure that the utilization of wastewater and treated wastewater is carried out in the production of concrete in a sustainable manner. Although wastewater can reduce the workability of fresh concrete, it can also increase its strength and long-term performance of concrete. The use of various types of wastewater, such as reclaimed water and tertiary-treated wastewater, was found to be superior compared to those using industrial- or secondary-treated wastewater. Researchers around the globe agree that wastewater can cause various detrimental effects on the mechanical and physical properties of concrete, but the reductions were not significant. To overcome limited scientific contributions, this article reviews all the available methods of using various types of wastewater to make concrete economically and environmentally friendly. This research also addresses possible challenges with respect to the demand for freshwater and the water crisis.

Synergistic effect of nano silica and metakaolin on mechanical and microstructural properties of concrete: An approach of response surface methodology

Nano and micro materials are both effective individually in enhancing the mechanical and microstructural properties of concrete. The combination illustrates an iconic shift in material engineering to produce concrete with distinctive characteristics. In this work, the combined effect of Nano Silica (NS) and Metakaolin (MK) on the mechanical and microstructure properties were examined by conducting compressive strength, split tensile strength, and Field Emission Scanning Election Microscope (FE-SEM) with Energy-dispersive X-ray (EDX) analysis, X-ray Diffraction (XRD) spectroscopy, Fourier Transform Infra-Red (FTIR) spectroscopy, respectively. The concrete matrix was investigated by varying the concentration of NS and MK with different Water-Binder Ratio (WBR). Further, the Response Surface Methodology (RSM) technique was used to identify the complex interaction between NS (1–3 %) and MK (5–20 %) at different WBR (0.35, 0.40 and 0.45). The synergistic effect between NS and MK resulted in enhanced compressive and split tensile strengths of the concrete. The optimum mix proportion of the concrete was found to be 2 % NS and 12.5 % MK at a WBR of 0.4. The compressive strength enhancements for the optimum mix proportion were 35.75 %, 34.4 %, 33.1 %, and 32.5 %, while the split tensile strength enhancements were 26.56 %, 25.92 %, 20.95 %, and 17.8 %, respectively on the 7th, 28th, 56th, and 90th day. The RSM technique developed for all the mixes has been statistically validated to have less than 5 % of mean error. Moreover, the microstructural analysis revealed early hydration, formation of additional Calcium Silicate Hydrate (C-S-H) products, and presence of dense microstructure resulting in improved microstructural properties. The incorporation of NS and MK in the concrete changes the concrete’s configuration at the nano and micro levels, thus paving the way for the development of novel and sustainable construction materials.

Performance of coal gangue concrete with fly ash and ground-granulated blast slag: Rheology, mechanical properties and microstructure

This paper aims to examine the effect of coal gangue aggregate (CGA), fly ash (FA), and ground-granulated blast slag (GGBS) on the rheological, mechanical and microstructure properties of concrete. The rheological properties, compressive strength, splitting tensile strength, flexural strength, and uniaxial tensile behaviour of coal gangue concrete (CGC) were determined, and the microstructure of the concrete mixtures were investigated by use of XRD and SEM analyses. The results revealed the action mechanism of CGA and mineral admixtures on the microstructure and macroscopic properties of CGC. FA first increased and then decreased the yield stress and plastic viscosity, while GGBS considerably increased the yield stress and plastic viscosity. Furthermore, a constitutive model was established for CGC containing FA and GGBS under compression. The proposed stress–strain model for CGC is accurate and can be used for nonlinear analysis of structures made of this type of concrete. Moreover, the addition of FA and GGBS consumes calcium hydroxide, but increases products such as hydrated calcium silicate aluminate. These findings elucidate the understanding and optimisation of CGA use in concrete production, while contributing to lowering carbon emissions.

Experimental Investigation of Mechanical and Microstructural Properties of Concrete Containing Bentonite and Dolomite as a Partial Replacement of Cement

In this study, the effect of bentonite (BT) and dolomite (DT) on the mechanical and microstructural properties of concrete was evaluated on nine mixes. Cement was replaced with bentonite and dolomite by weight with varying mix ratios. The mixes are divided as M1 (Control mix), M2 (2.5% BT), M3 (2.5% DT), M4 (5% BT), M5 (5% DT), M6 (10% BT), M7 (10% DT), M8 (2.5% BT and 2.5% DT), and M9 (5% BT and 5% DT). Concrete specimens were subjected to mechanical and microstructural analysis tests. Mechanical test results show that the addition of bentonite (2.5%, 5%, and 10% ) leads to an increase in compressive strength (6.31%, 8.94%, and 13.15%) respectively. Similarly, the addition of 2.5% and 5% dolomite enhanced compressive strength by 10.52%, and 8.94% respectively, however, the addition of 10% dolomite reduced compressive strength by 6.8%. Replacement of cement with dolomite and bentonite individually also showed a small contribution to flexural and split tensile strength. Microstructural analysis shows that the addition of bentonite and dolomite filled the microstructure and refined the internal pores contributing to compressive strength. In addition, the replacement of cement with bentonite and dolomite enhanced the formation of CSH gel.

The Influence of Metakaolin and Polypropylene Fiber Concrete on Mechanics Properties and Microstructure Combined Action under Multi-Salt Soaking and Freeze-Thaw.

The wide distribution of alpine saline areas in China is faced with two major problems, which are salt intrusion and freeze-thaw. In total, 216 specimens were prepared with 6 kinds of concrete mix proportions in this paper. The effects of the single and compound incorporation of metakaolin (MK) and polypropylene fiber (PPF) of different amounts on the mechanical properties and microstructure properties of concrete were investigated under the dual action of multi-salt (NaCl, MgCl2, Na2SO4, and NaHCO3) soaking and freeze-thaw. Potable water and freeze-thaw concrete were adopted as the control group. Changes in the appearance morphology, mass loss, relative dynamic elastic modulus, and compressive strength of the concrete were tested, and the microstructure of the concrete was analyzed by scanning electron microscopy (SEM). The results showed that an admixture of both MK and PPF in the potable water and freeze-thaw cycle test can improve the mechanical properties and frost resistance of concrete. The admixture of PPF can effectively improve the mechanical properties and frost resistance of concrete. However, the admixture of MK failed to improve the mechanical properties and frost resistance of concrete during multi-salt soaking and freeze-thaw. The frost resistance of concrete under multi-salt soaking and freeze-thaw was optimally improved with 10% MK and 0.6 kg/m3 PPF. Its microstructure shows that PPF can effectively inhibit crack propagation and reduce the deterioration of concrete under multi-salt soaking and freeze-thaw.

Evaluating properties of high performance concrete containing metakaolin as cementitious material

Abstract High performance concrete is extensively used for construction works in recent era. For the preparation of high performance concrete (HPC) mineral and chemical admixtures are used. The addition of mineral admixtures minimizes the utilization of cement and makes concrete more sustainable. The addition of metakaolin as a substitute to cement enhances the properties of concrete. There is need to study the mechanical and micro-structural properties of concrete containing metakaolin as cementitious material. In this work an endeavour has been made to study the properties of HPC employing matakaolin as an alternative for cement. The cement has been replaced with metakaolin by 5%, 10%, 15%, 20%, and 25% respectively for 0.25, 0.3, and 0.35 w/c ratios. The strength and electrical resistivity tests are conducted for all concrete mixes on triplicate. Results confirm that the accumulation of metakaolin increases the properties of HPC. A maximum of 49% increase in compressive strength in concrete was observed by the accumulation of 15% of metakaolin in concrete as substitute to cement for 0.25 w/c ratio in comparison to standard concrete. The development of secondary calcium silicate hydrates and minimal Ca(OH)2 components was revealed by X-ray spectroscopy, indicating that the concrete was denser. The results of this study revealed that metakaolin has a considerable impact on high-performance concrete, particularly in terms of compressive and flexural strength.

Effect of pore structure and morphological characteristics of recycled fine aggregates from clay bricks on mechanical properties of concrete

To boost the recycling rate of demolished clay bricks, recycled fine aggregates from clay bricks (RFCBs) can be feasibly used as sand substitute for preparing green concrete. In this study, the influence of pore structure and morphology characteristics of RFCBs on the mechanical and microstructural properties of concrete was explored. The porous structure and morphological features of RFCBs were quantitively assessed by mercury intrusion porosimetry (MIP), atomic force microscopy (AFM) and digital image analyser. The RFCBs effects on concrete were investigated regarding compressive strength, splitting tensile strength, elastic modulus, MIP and scanning electron microscopy (SEM). The RFCBs possessed elongated shape, rough surface texture, microcracks, and porous internal structure and showed more complex surface morphology than the natural fine aggregates (NAFs). Incorporation of RFCBs without additional water and with partially additional water achieved similar or increased compressive strength, while RFCBs with wholly additional water reduced the compressive strength compared to NAFs concrete. Furthermore, the complex surface morphology of RFCBs helped in improving the splitting tensile strength, but RFCBs with additional water imposed a deteriorated effect on the elastic modulus. MIP results of RFCBs concrete showed that the porosity and total pore volume increased but with better pore refinement. Overall, incorporation of RFCBs in concrete displayed better mechanical interlocking of the ITZ and the compactness of reaction rim than NAFs concrete, and consequently, the soft core and stiff shell of RFCBs could be formed in concrete.

Study on Mechanical and Microstructural Properties of Concrete with Fly Ash Cenosphere as Fine Aggregate—A Sustainable Approach

The utilization of waste materials in concrete lowers its cost, and this method of dealing with the problem of trash disposal is viewed as the most environmentally friendly. Fly Ash Cenospheres (FAC) are one of the principal wastes produced by coal power stations. The huge volume of FAC produced worldwide has created a sustainability challenge, owing to the potential implications of inappropriate disposal. Using cenospheres in concrete materials would make effective and efficient use of these waste products while also supplementing what the present raw material, such as river sand, can supply for concrete material production. Though the application of FAC in concrete is currently carried out by the construction industry, there is still a lack of understanding about its performance in concrete with Manufactured Sand (M Sand) as fine aggregate. Therefore, in this paper, a comprehensive study explores the concept of adding FAC to M Sand concrete. The properties of fresh and hardened concrete, such as density, workability, compression, split tensile, flexure, and impact resistance after the addition of FAC in volume replacement (0–100% with a difference of 5% at thirteen different ratios) is represented, followed by microstructural analysis. From the results, it can be concluded that strength reduction takes place as FAC content increases from 0–100%, however, the strength is within the target limit of 31.2 N/mm2 of conventional concrete (CC) of grade M25 when the percentage replacement is below 35% of volume. Therefore, reducing the volume of fine aggregate does not negatively affect the strength properties, but also impacts the environmental concern positively with optimum recommendation of 35% of fine aggregate as FAC.

Experimental Research on the Effects of Waste Foundry Sand on the Strength and Micro-Structural Properties of Concrete

Now a days, a great distance has to be travelled to find good quality natural river sand. These supplies are also running out very quickly. So, a replacement for river sand is being sought after. Natural river sand is non-renewable and takes millions of years to be produced. By using manufactured sand, natural sand is completely replaced. Lack of research has led to the substitution of leftover waste foundry sand for manufactured sand in concrete. By adding used foundry sand to concrete, it is possible to enhance mechanical properties like compressive strength, fracture toughness, and flexibility. Using tests on cubes, cylinders, and unreinforced beams, the mechanical properties of concrete made with waste foundry sand and manufactured sand as fine aggregate were assessed. Tensile, splitting, and flexural strengths of the concrete were all determined after 7, 14, 28, 56, and 90 days of curing. SEM, EDS, and Thermo Gravimetric Analysis (TGA/DCs) were also used to perform micro structural analyses on the control mixture and mixtures containing 10, 20, 30, 40, and 50% waste foundry sand. The strength differences that occur when fine aggregates are replaced with waste foundry sand in different proportions are better understood, thanks to the micro structural experiments. In order to justify its use as a replacement for fine aggregate in terms of strength and microstructure studies, just the right amount of WFS was added to the concrete. Doi: 10.28991/CEJ-2022-08-10-010 Full Text: PDF

Investigation study of enhance the strength by using hybrid nano-composites on conventional cement concrete

Generally, incorporation of nano-particles with conventional concrete (CC) materials expands the bulk belongings of concrete by renovating molecular structures and permits the cement-based materials converted high-strength and durable products. The concentrated tensile possessions of the concrete confines its submissions where the flexural and tensile possessions of the concrete are major. In this steel and synthetic-fibres are expressively enhanced the tensile, toughness, impact resistance and energy-absorption capacity (EAC) of the concrete. Even yet the presence of fibre enhanced the tensile strength capacity (TSC) of the concrete, it hasn’t better the compressive strength capacity (CSC) of concrete suggestively. Therefore, it is very overbearing in growth of compressive strength of the concrete where the compressive tensile belongings to the concrete are major for its application. Investigation was carried to study the impact of nano-Al2O3, nano-Fe2O3, and their hybrid combinations on the setting time, microstructure, fresh, and strength properties of conventional cement concrete. Binding material of concrete mixtures was replaced by different nanoparticles, namely nano-Fe2O3 and nano-Al2O3, with four replacement rates (up to 4 %) that makes somewhat of change in building materials and gives energy to the building. The slump cone test was performed to assess the workability of concrete mixtures. Strength characteristics were evaluated, including the compressive, split tensile, and flexural strengths, for mixtures hardened after 7, 28, and 90 days. Moreover, the slump value of the mixture was decreased with an increase in the replacement rate of nanoparticles. However, slump values were within the acceptable workability and did not affect concrete compaction. However, the strength enhancement of the hybrid nano mixtures was relatively equal to that of the mixtures with only nano-Fe2O3 or nano-Al2O3. The test results revealed that nanoparticles can enhance the strength and microstructure properties of concrete.

Mechanical and microstructural performance of concrete containing high-volume of bagasse ash and silica fume

In this study, researchers examined the effect of replacing a high-volume of cement with sugarcane bagasse ash (BA) and silica fume (SF). In addition to the control, three binary and three ternary blends of concrete containing different percentages of cement/BA and cement/BA/SF were tested to determine the various mechanical and microstructural properties of concrete. For each mix, eighteen cylindrical concrete specimens were cast followed by standard curing (moist at 20 °C) to test the compressive and tensile strengths of three identical specimens at 7, 28, and 91 days. The test results indicated that the binary mix with 20% BA and ternary mix with 33% BA and 7% SF exhibited higher strengths than all the other mixes, including the control. The higher strengths of these mixes are also validated by their lower water absorption and apparent porosity than the other mixes. Following mechanical testing, the micro and pore structures of all mixes were investigated by performing scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM–EDS), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and nitrogen (N2) adsorption isotherm analysis. In SEM–EDS analysis, a dense and compact microstructure was observed for the BA20 and BA33SF7 mixtures due to the formation of high-density C–S–H and C–H phases. The formation of a large amount of C–S–H phases was observed through FTIR, where a prominent shift in peaks from 955 to 970 cm−1 was observed in the spectra of these mixes. Moreover, in N2 adsorption isotherm analysis, a decrease in the intruded pore volume and an increase in the BET surface area of the paste matrix indicate the densification of the pore structure of these mixes. As observed through TGA, a reduction in the amount of the portlandite phase in these mixes leads to the formation of their more densified micro and pore structures. The current findings indicate that BA (20%) and its blend with SF (40%) represents a potential revenue stream for the development of sustainable and high-performance concretes in the future.

Performance of sustainable concrete incorporating treated domestic wastewater, RCA, and fly ash

This study evaluates the impact of using treated wastewater (TWW), recycled concrete aggregates (RCA), and fly ash (FA) on the mechanical, durability, and microstructural properties of concrete. A total of eight concrete mixes were manufactured and tested. Fresh mixing water and natural gabbro aggregates were completely replaced with TWW and RCA, respectively, whereas 20% of cement was substituted by FA. Test results revealed that TWW slightly reduced concrete mechanical properties by 6% to 12%, while it drastically reduced the chloride permeability by 77% in comparison with freshwater concrete. In addition, RCA decreased concrete compressive and flexural strengths by 21% and 10%, respectively, compared to natural aggregate concrete. Moreover, TWW concrete mixes with RCA had 16% to 42% lower porosity and chloride permeability than their counterparts with gabbro aggregates. Furthermore, concrete mixes with TWW, RCA, and FA exhibited the lowest chloride permeability among the investigated mixes. It was also shown that the interfacial transition zones between RCA and cement matrix were improved by replacing FA for 20% of cement. Analytically, aggregate and concrete morphological images and chemical composition were investigated to support the experimental results.

Impact of elevated temperature on strength and micro-structural properties of concrete containing water-cooled ferrochrome slag as fine aggregate

A basic issue throughout the world is the disposal of waste substances. This study is performed to investigate the feasibility of utilizing water-cooled granulated ferrochrome slag (WCFS), a by-product of the ferrochrome plant as a partial substitution of river bed sand in concrete production and the effect of high temperature on its strength. Tests were conducted to determine the compressive strength and weight loss after exposure up to 1000 °C temperatures. The present work also involves the investigation of the thermal behavior of hydration products in concrete using thermogravimetry analysis (TGA) and differential scanning calorimeter (DSC). The outcomes of DSC and TGA were compared with X-ray diffraction (XRD) analysis. Scanning electron microscope (SEM) analysis was carried out for concrete samples subjected to temperatures of 500–800 °C. The test results obtained from the said analyses of concrete with WCFS were compared with the reference concrete and thereby ample utilization of WCFS for production concrete was substantiated. The outcomes revealed that the inclusion of WCFS up to 30% as a partial substitution of sand reduced the compressive strength by 10% only but its heat resistance performance measured in terms of residual compressive strength and mass is found better than normal concrete. There is reduction in voids and cracks of WCFS concrete in comparison to normal concrete after exposure to high temperature that observed in SEM investigation.

Performance Evaluation of Cementitious Composites Incorporating Nano Graphite Platelets as Additive Carbon Material.

Nano graphite platelets (NGPs) belong to the carbon family and have a huge impact on the construction industry. NGPs are used as multi-functional fillers and have the potential to develop reinforcing within cementitious composites. In this paper, NGPs were incorporated in cementitious composites to investigate the effects of NGPs on the fresh, mechanical, durability, and microstructural properties of concrete. Five mixes were prepared with intrusion of NGPs (0%, 0.5%, 1.5%, 3%, and 5% by weight of cement). The properties studied involved workability, air content, hardened density, compressive strength, tensile strength, flexural strength, sorptivity, ultrasonic pulse velocity (UPV), water absorption, and external sulfate attack. The workability and percent air content decrease by 22.5% and 33.8%, respectively, for concrete with 5% NGPs compared to the control mix. The specimens containing 5% of NGPs revealed the hardened density, compressive, tensile, and flexural strength to increase by 11.4%, 38.5%, 31.6%, and 44.34%, respectively, compared to the control mix. The results revealed that the incorporation of 5%NGPs in cementitious composites reduces the sorptivity and water absorption by 32.2% and 73.9%, respectively, whereas, it increases the UPV value by 7.5% compared to the control mix. Furthermore, the incorporation of NGPs provided better resistance against external sulfate attacks. SEM–EDX spectroscopy was carried out to investigate its microstructural analysis.

Impact of Addition of Banana Fibres at Varying Fibre Length and Content on Mechanical and Microstructural Properties of Concrete

This experimental study aimed at investigating the impact of addition of banana fibres on the mechanical (compression, splitting tension, and flexure) and microstructural (microscopic morphology and Energy Dispersive X-ray Spectroscopy) properties of concrete. Concrete mixes comprising of banana fibres of varying fibre lengths (40, 50, and 60 mm) and fibre contents (0.1, 0.2, 1.0, 1.5, and 2.5%) were assessed. Addition of banana fibres to concrete was observed to significantly impact on compressive strength only at lower fibre contents of up to 0.25% for all fibre lengths. Fibre length had no significant impact on compressive strength at lower fibre contents of up to 0.25%, but shorter fibres were observed to perform better than longer ones at higher dosages more than 0.25%. Increase in fibre content positively impacted on tensile strength of concrete at relatively lower fibre dosages of up to 1%. Similarly, fibre length impacted on tensile strength of concrete at lower fibre contents of up to 1% and, longer fibres were observed to be more effective than shorter ones. Addition of banana fibres generally did not greatly contribute to flexural strength of concrete but had a marginal impact only when shorter fibres were used at lower fibre dosages. Also, microstructure of concrete was improved through better bonding between the fibres and the matrix and reduction in porosity of the matrix, which resulted in improved mechanical properties of the composite. Banana fibres further contributed to changes in phases of the composite structure of Banana fibre-reinforced concrete (BFRC) through a reduction in its interplanar spacing and lattice structure. For optimal purposes, addition of banana fibres should be limited to a maximum of 1% fibre content preferably using shorter fibre lengths. Further research to improve flexural strength of BFRC to meet minimum technical requirements is required before it can be considered for structural applications.