Rapid Chloride Penetration Test Research Articles

The Use of Ground Coal Bottom Ash/Slag as a Cement Replacement for Sustainable Concrete Infrastructure.

Cement production requires considerable energy and natural resources, severely impacting the environment due to harmful gas emissions. Coal bottom ash (CBA) and coal boiler slag (CBS), byproducts of coal-fired powerplants having pozzolanic properties, can be mechanically ground and replace cement in concrete, which reduces waste in landfills, preserves natural resources, and reduces health hazards. This study was performed to determine the optimum cement replacement amount of ground CBA (GCBA) and ground CBS (GCBS) in concrete, which was 10% for GCBA and 5% for GCBS. GCBA-based concrete exhibited superior tensile strength, modulus of elasticity, and durability compared to the control. In the Rapid Chloride Penetration Test, 10% GCBA concrete resulted in 2026 coulombs at 56 days, compared to 3405 coulombs for the control, indicating more resistance to chloride penetration. Incorporating 2.5% nanoclay in GCBA-based concrete increased the optimum GCBA content by 5%, and the compressive strength of 15% GCBA concrete increased by 4 MPa. The mortar consisting of the finest GCBA(L1) having Blaine fineness of 3072 g/cm2 yielded the highest compressive strength (32.7 MPa). The study discovered that the compressive strength of GCBA and GCBS-based mortars increases with fineness, and meeting the recommended fineness limit in ASTM C618 enhances concrete or mortar properties.

Strength and Durability Properties of High-Volume Fly Ash (HVFA) Binders: A Systematic Review

South Africa is endowed with a wealth of coal-fired power stations that can produce extremely high volumes of fly ash per year exceeding 34 million tonnes. The use of high-volume fly ash (HVFA) binders in the construction sector has the capacity to significantly reduce greenhouse gas emissions associated with traditional cement production and offset the carbon footprint of Eskom. The excessive production of fly ash by Eskom warrants the need for developing ultra-high-volume fly ash binders (UHVFA, fly ash/binder > 60 wt%). Nonetheless, fly ash (FA) replacement of cement is still largely limited to 35% regardless of more ambitious research indicating the potential to surpass 60%. In view of the urgent need for South Africa to offset and reduce its carbon footprint, this work reviews and summarises the literature on the performance of HVFA binders with a focus on two specific areas: (i) strength and (ii) durability. On HVFA binder strength, the focus is drawn on work that analysed the compressive strength, flexural strength, and split tensile strength. This review focuses on the extant literature analysing the durability of HVFA binders using various tests, including sorptivity, resistivity, permeability, tortuosity, rapid chloride penetration tests, resistance to sulphate attack, and microstructural analysis. As the FA content increases towards optima, i.e., 50–80%, the most indicative composite characteristics of the strength and durability properties are UCS (30–90 MPa) and permeability (low). This review reveals the leading methodologies, instrumentation, findings, challenges, and contradictions.

Study of durability and mechanical properties for utilization of cupola slag as a coarse aggregate in M20 grade green concrete

Cupola slag is an industrial waste generated from cupola furnaces during cast iron production. The disposal of cupola slag is a matter of burden for the manufacturers of casting industry. This experimental study aims to reuse cupola furnace slag (CFS) in the construction industry, developing a novel way of solid waste management. In the M20 grade concrete, CFS is used as coarse aggregate (CA), partially replaced by 0–50 wt % in the step of 10 wt %. The mechanical and durability properties of the CFS-based concrete were examined after the required days of curing. The experimental result exposed that the dry density decreases with the increased weight percent of CFS in concrete. The cast samples with up to 40 wt% partial replacement of CFS effectively meet the requirements for the M20 grade of concrete in terms of compressive strength. A similar trend for the split tensile strength was observed, like the compressive strength. Durability test results reveal that water penetration depth increases with increased CFS weight percent in concrete. Moreover, in the case of rapid chloride penetration test, chloride ions penetration is decreased with the increase of CFS weight percent in concrete. FESEM, EDS and XRD were used to examine the microstructure, elemental mapping and phase analysis of the CFS-based concrete. According to the investigation, CFS is a sustainable material that works well as a partial replacement for natural CA in concrete.

Chemical durability evaluation of copper grit aggregate concrete against Alkali-Silica-Reaction, carbonation and chloride penetration

This study aims to explore the effects of varying proportions of copper grit (CG) as fine aggregate on the alkali-silica reaction (ASR), accelerated carbonation test (ACT), and rapid chloride penetration test (RCPT) of concrete. Other complementary experiments including the rate of water absorption and compressive strength of copper grit aggregate mortar (CGAM), as well as compressive strength, split tensile strength, and sorptivity test of copper grit aggregate concrete (CGAC), were conducted. The results indicate that a higher CG content, particularly at around 80% replacement in the concrete mix, enhances strength without inducing expansive ASR and mitigates carbonation and chlorination rates in concrete. Moreover, the compressive strength of CGAM increases up to a 60% replacement ratio. Water absorption decreases from 62.1 gm/cm2 for the control specimen to 47.9 gm/cm2 for mortar with 100% CG replacement. ASR test results show no significant expansion up to a 20% replacement ratio of CG, with further increases in replacement resulting in expansion below the threshold limit of 0.1%. A notable 27% increase in compressive strength is observed for 80% CG replacement at 28 days of CGAC. Additionally, carbonation depth decreases with an increase in CG quantity in CGAC mixes, with the lowest depth observed for 80% CG replacement. The carbonation coefficient remains below the threshold limit, indicating high-quality CGAC. Furthermore, the service life of CGAC was predicted and microstructural characteristics of both CGAM and CGAC were examined via Field Emissions Scanning Electron Microscopy (FESEM). The findings underscore the potential of utilizing CG as a substitute for conventional sand in mortar and concrete production, offering a promising ecological alternative for conserving natural resources and safeguarding the environment.

An Experimental Investigation on Self-Healing Concrete Made of Bacteria with Varying Doses

Abstract: The employment of carbonate-producing bacteria as a new approach to enhance the qualities of concrete has attracted a lot of interest since it is thought to be innocuous to theenvironment, natural, and maybe advantageous. This is a result of the favorable implications attached to these traits. The use of microbially induced carbonate precipitation as a remedy for several problems affecting concrete, such as fracture healing, reduction and change of porosity and permeability, and more, has been the subject of much investigation. Concrete crack healing is one of the topics that have been researched. Additionally, it has been shown that the procedure of bacterial carbonate precipitation, also known as bio deposition, contributes to the development of concrete's compressive strength. There has not yet been a thorough investigation of the research relating to the appropriate bacterial solution dose and its effect on concrete durability. This might occur as a result of the project not receiving enough time to complete it. As a result, it has been decided that an investigation will be conducted in order to determine the proper quantities of bacterial solution required for concrete. To do this, several concrete cube samples will be made using varying amounts of bacterial solution, such as 15 ml, 30 ml, 45 ml, 60 ml, and 75 ml, respectively. These quantities will be added to the appropriate moulds. This will allow you to determine the proper dosage of the bacterial solution to employ. In order to determine the optimal dosage that should be used, these various samples are also put through a battery of tests using a variety of laboratory techniques, such as the properties of materials, slump cone test, a compressive strength testing machine, an ultrasonic pulse velocity test, plate count cells, and scanning electron microscopes, Rapid Chloride Penetration Test (RCPT), Acid attack test.

Thermal and mechanical properties of a sustainable bio-flax fibre-based lightweight aggregate concrete

A novel lightweight aggregate concrete (LWAC) or lightweight concrete (LWC) is developed using expanded perlite powder and lightweight expanded clay aggregate as a replacement for conventional fine and coarse aggregates, respectively. Furthermore, the natural plant-based flax fibre in treated form was added to the LWC mix at three different volume fractions. The mechanical and thermal characterisation of LWC was carried out using the compressive strength test, split tensile test, modulus of rupture, thermal conductivity and thermal resistance test. Moreover, the microstructural and durability properties were obtained using scanning electron microscopy/energy dispersive X-ray spectrum analysis, rapid chloride penetration test, sorptivity test and water absorption test. Test results reveal that the addition of 2.0% flax fibre resulted in improved mechanical, thermal and durability properties when compared to LWC with no fibres. Moreover, the microstructural analysis using SEM revealed the formation of ettringite which is responsible for the strength development in the LWAC mix.

Influence of key parameters on the performance of RAP-inclusive geopolymer concrete pavements: An approach integrating sensitivity analysis

The current study investigates the integration of Reclaimed Asphalt pavement (RAP) aggregates into geopolymer concrete, thereby providing a promising avenue for reinforcing sustainability in rigid pavement systems. Fly Ash (FA) and Ground Granulated Blast Furnace Slag (GGBS) based geopolymer mixes were designed to accentuate the performance with regards to varying molarity of NaOH (10 M-16 M), aggregate replacement levels (0%−100%) and curing periods. The experimental findings revealed a significant decrease in 28 days of compressive and flexural strength within 14 M-100% RAP mixes (57.6% and 39.7%, respectively). Nevertheless, GPC mixes incorporating 50% coarse RAP successfully met the prescribed strength criteria, making them suitable for Pavement Quality Concrete (PQC) applications. Additionally, the assessment of porosity and Water Absorption (WA) revealed a noticeable decrease with an increase in molarity as well as RAP fractions in the mix. Long-term performance was further assessed through resistance to surface abrasion, showing a maximum abrasive depth of 0.302 mm for 10 M-100%RAP mixes, thus affirming the durability of the RAP-GPC system. Rapid Chloride Penetration Test (RCPT) additionally demonstrated that the presence of adhered asphalt in RAP aggregates reduces porosity and enhances resistance to chloride ingress. Subsequently, the microstructural analysis and the study of solid-state NMR aided in comprehending the matrix behaviour, potentially linked to the performance of the mixes. The experimentally obtained compressive strength results were further statistically analysed through the Sensitivity Analysis (SA) approach, thereby providing a comprehensive understanding of the interplay between various strength-affecting parameters.

Mechanical and durability assessment of phosphogypsum- bauxite residue - fly ash-based alkali-activated concrete

Phosphogypsum (PG), bauxite residue (BR), and fly ash (FA) are all by-products of different industries. This study presents the development of alkali-activated concrete (AAC) using industrial by-products like PG, BR, and FA. Therefore, the prime aim of this study is to analyze the mechanical and durability properties of the developed AAC. It is noteworthy to mention that the PG is replaced with FA at 10%, 20%, 30%, and 40% for a constant BR ratio. Subsequently, the results reveal that the optimum mix composition of the AAC is 20% BR, 20% FA and 60% PG (P6), resulting in a maximum compressive strength of 54.74 MPa. Additionally, water absorption, sorptivity tests, and the rapid chloride penetration test (RCPT) have been performed to assess the durability of the AAC, and P6 has exhibited the best resistance to the environment. Moreover, scanning electron microscope (SEM) and X-ray diffraction (XRD) test have been carried out to study the micro-characterization of the AAC. The fundamental parameters of the AAC are calcium alumino silicates hydrate gel (C-A-S-H) gel and sodium alumino silicates hydrate gel (N-A-S-H) gel, which play a crucial role in the development of the strength and durability of the AAC. Further, the leaching characteristics of the AAC show that all heavy metals are well solidified during the gel formation. Synergistically developed AAC can be used in construction applications such as foundations, pavements, and building materials as a substation of conventional cement concrete.

Rapid chloride penetration test: An evaluation of corrosion resistance in ultra-high performance concrete

Six Ultra-High Performance Concrete (UHPC) mixtures were tested to determine their chloride ion ingress potential using the rapid chloride penetration test (RCPT). The UHPC mixtures showed low to negligible chloride ion penetrability, depending on their water to cementitious materials (w/cm) ratio and curing regimen. Electrical resistivity and conductivity of the mixtures were determined based on the recorded electric current during the RCPT test. The electrical resistivity varied from 49 to 1419 Ω-meter, while conductivity ranged from 0.0007 to 0.0013 milli-Siemens/meter, indicating a moderate to very low expected corrosion rate for the mixtures. The chloride diffusion coefficient was calculated using the Nernst-Plank Equation, making corrections for Joule effect and temperature adjustment due to the temperature increase of the electrode solution during the RCPT test. The chloride ion diffusion coefficients of the UHPC mixtures ranged from 0.53–3.01 × 10−15 m2/s. These results suggest that UHPC mixtures with a w/cm ratio as high as 0.30 can exhibit excellent corrosion resistance.

Corrosion Studies on Ternary Blended High Performance Self-Compacting Concretes Containing Fly Ash and Graphene Oxide

Effective utilization of industrial byproducts as mineral admixtures and filler materials in cement concrete has been a practice to develop sustainable construction materials. The use of mineral admixtures like fly ash, silica fume, ground granulated blast furnace slag etc. as a partial replacement of cements have proved to improve the performance characteristics of concrete through reduced porosity and improved mechanical characteristics through pozzolanic effect and filler effect. Moreover, extensive research in the recent period has been mainly focused to study the effect of nano-additions in concrete. The present work was focused to assess the performance of ternary blended high performance self-compacting concretes with varied quantities of graphene oxide additions. Control concrete of M60 grade was designed in correspondence to IS-10262:2019 containing fly ash, and three other concretes mixes were formulated with 0.03%, 0.06% and 0.09% addition of Graphene Oxide (By weight of total cementitious material). The specimens were cast and tested at different ages to determine rheological, mechanical and durability characteristics by evaluating slump flow, Compressive Strength, Split Tensile Strength, Absorption- Desorption characteristics, Rapid Chloride Penetration Test values and resistance to accelerated corrosion cracking. Moreover, the specimens were assessed for corrosion resistance by conducting a cyclic wet – dry test, where parameters like UPV & depth of chloride penetration in concrete were measured. Results depict the fact that addition of Graphene Oxide improves the durability characteristics to a great extent. The optimum results for most of parameters were obtained at 0.06% of Graphene Oxide addition in comparison to remaining mix proportions.

Influence of graphene oxide on the long-term durability behaviour of high-strength rubberised concrete

Applying waste tire rubber as rubber aggregate (RA) in concrete is advantageous from the perspective of environmental sustainability. This study examines the action of graphene oxide (GO) on the durability properties of high-strength rubberised concrete (RC). The durability characteristics of concrete were assessed with the help of acid attack, water sorptivity, and rapid chloride penetration test (RCPT) on the hardened concrete specimens for the test periods of 7, 28, 56, and 90 days each. Acid attack tests (mass loss and compressive strength loss) were performed after immersing the concrete specimens in hydrochloric (HCl) and sulphuric (H2SO4) acids for the stipulated periods. The increased mass and compressive strength losses were observed with the incorporation of RA in concrete, which was finally mitigated by the action of GO in concrete. Water absorption was increased by RA alone but was reduced after the incorporation of GO in this RC. It was also observed that the chloride penetration was reduced after the incorporation of RA and GO in conventional concrete (CC). This study concludes that GO excellently strengthens the long-term durability properties of the RC.

Effect of low-calcium fly ash inclusion on long-term mechanical properties and durability of ground granulated blast furnace slag-based cement-free mortars

The present study focused on fabricating cement-free mortar based on ground granulated blast furnace slag incorporating low-calcium fly ash as precursors in an alkaline solution of sodium hydroxide and sodium silicate. The main purposes of the study were not only to find the optimum mixture proportions to confirm the fly ash role in contributing to the long-term mechanical properties and durability but also to expand the use of fly ash in cement-free binders based on ground granulated blast furnace slag. The ground granulated blast furnace slag was replaced with fly ash in the cement-free mortar at various levels of 30, 40, 50, 60, and 70% by mass. The cement-based sample as a control sample was prepared for comparison purposes. Results showed that the cement-free mortar samples with fly ash had the more superior long-term mechanical properties (i.e. flexural and compressive strengths and volumetric compaction via ultrasonic pulse velocity test) and durability (i.e. total charge passed via rapid chloride penetration test and sulfate resistance via length change of samples exposed to sulfate solution), lower water absorption and porosity, and denser microstructure than the control sample up to 120 days. The 40% replacement of ground granulated blast furnace slag by fly ash as an auxiliary source of alumina and silica was the optimum ratio in enhancing the long-term mechanical properties and durability of the cement-free mortar samples, which is in agreement with reducing the porosity and water absorption. The results of the environmental analysis indicate that using cement-free mortar samples has much lower environmental impacts. The cement-free mortar sample using 60% ground granulated blast furnace slag and 40% fly ash is found as an optimal mixture in terms of technical and environmental features.

Effect of zirconium oxide nanofiber on the strength and chloride ion penetration coefficient of concrete

In this study, zirconium oxide nanofiber with a mean diameter of 100 nm was added to concrete at various concentrations as a cement replacement. Various tests, including compressive strength, splitting tensile strength, flexural strength, and electrical resistance tests, as well as a rapid chloride penetration test, were performed on specimens containing zirconium oxide nanofibers for the concrete assessment, and the results were compared to those obtained from control specimens that did not contain nanofibers. The results showed that adding zirconium oxide nanofibers at 135 gr/m3 of concrete yielded a 28-day compressive strength equal to 44.62 MPa, which exhibits a 20.40% increase in strength with respect to the specimen that lacked nanofibers. The flexural strength and splitting tensile strength tests at 28 days of age and in the presence of 135 gr/m3 mentioned nanofibers were increased by 22.28 and 33.47%, respectively, in comparison to the control specimens. Moreover, revealed that at 28 days of age, in the specimens containing 270 gr/m3 zirconium oxide nanofibers, the migration coefficient of chloride ion was reduced by 29.86%, and its electrical resistance was increased by 68.33%. These findings highlight the potential of nanofibers as a promising solution for enhancing the strength and performance of concrete structures.

Production of waste carpet fiber-reinforced concrete as sustainable material

Waste materials evolve from various processes in industries that require efficient management for their disposal to ensure a cleaner environment. Disposing of solid waste, such as carpets, to sites has grown challenging since the development and management of sites are very costly. There is a dire need to manage such a vast amount of carpet waste efficiently. This study examines certain mechanical properties and durability characteristics of concrete incorporating discarded carpet threads and silica fume (SF). Initially, six different concrete mixes were produced, with 0.25%–1.0% waste carpet fibers by concrete volume and 10% SF by weight of cement. Then samples were tested for mechanical strength, i.e., compressive strength, tensile strength, and flexural strength. The durability characteristics, such as water absorption, rapid chloride penetration test, drying shrinkage, and freeze-thaw action, were also determined. The study shows that the abandoned carpet waste threads and SF (an industrial waste) in concrete significantly increase tensile and flexural strengths and various other durability characteristics. The further increase in fiber content resulted in a lowering of mechanical strengths and workability. Experimental results show the increase in tensile and flexural strengths of the concrete by waste carpet fibers (0.25%) and SF (10%) by 16.5% and 34%. SF and waste carpet fibers improve other durability characteristics, reducing freeze-thaw, drying shrinkage, and chloride ion permeability coefficient by up to 47%, 79%, and 50%. Additionally, using waste carpet fibers to ameliorate concrete properties instead of fresh fibers helps conserve natural resources. It leads to the conservation of resources, sustainability, recycling of wastes, and a circular economy.

Performance of slag based recycled coarse aggregate concrete with steel fibers

Designers may lessen the impact of concrete on the environment while yet ensuring enhanced performance and higher durability by using slag cement, which has proven long-term performance advantages. However, in actual practice, concrete constructions use slag to replace OPC up to 30 to 50 percent of the time, depending on the uses. By using M sand in place of river sand, this study shows differences in the strength and durability parameters of concrete manufactured using 100% with slag cement. Mechanical and durability study was made on replacement of natural coarse aggregates (NCA) with 30, 45 and 60% of recycled coarse aggregates (RCA); Based on the study optimum percentage of recycled aggregates for slag based concrete is 45%. Thus to study effect of fiber on concrete 45% of natural aggregates replaced by recycled aggregates with and without Nano silica.This reduces the consumption of natural resources and adds some additional benefits from a structural and financial standpoint. Steel fibers are added at a rate of between 0.5, 1 and 1.5 percent by volume of cement to give it strength. In order to obtain the optimum percentage of steel fibres using slag cement, concrete grades M20, M25, M30 and M35 were used. Testing techniques such as the compression test, flexural test, spill tensile test, Rapid Chloride penetration test used to assess properties recycled aggregate concrete and also performed the life cycle assessment. From the experimental study 1% Steel fibers was optimum for both with and without Nano silica.

MECHANICAL AND DURABILITY STUDY ON STEEL AND GLASS FIBERS BASED CEMENTITIOUS COMPOSITE

The study targets the utilization of steel and glass fibers in developing engineered cementitious composite. Compressive strength (CS) tests, split tensile strength (ST) tests, and static flexure tests were conducted to comment on the mechanical behavior of the composites. The durability properties of the designed mixes are commented on using rapid chloride penetration (RCPT) and sulfate tests. The CS of the conventional mix C-40 is compared with the S-ECC and G-ECC. The tested G-ECC specimens were more ductile than the S-ECC specimens and their respective variants. The S-ECC produced better results for both the CS and ST tests than the S-ECC and its variants. The conventional mixes of C-40 resulted in high penetration values than the composites prepared with steel and glass fiber inclusion. The destruction of the aluminosilicate skeleton, which leads to the liberation of silicic acid and sodium ions, is responsible for the deterioration caused during sulfate attack tests.

Durability assessment of concrete with natural and Linz Donawitz slag as coarse aggregates

Rapid growth of infrastructure has resulted in incessant consumption of natural aggregates in cement concrete leading to its depletion. Efforts have been made to utilize industrial by-products such as steel slag aggregates in concrete as partial replacement for natural aggregates. However, the utilization of Linz Donawitz (LD) slag aggregates in concrete is very limited compared to other slag aggregates. The limited utilization could be attributed to the expansive nature of LD slag aggregates, which may result in durability issues. In this study, the compressive strength and durability characteristics of concrete with 100% LD slag coarse aggregate are investigated considering three different cement types, including Ordinary Portland Cement (OPC), Portland Pozzolana Cement (PPC) and Portland Slag Cement (PSC) for all the mixtures. LD slag and control concrete were examined for durability by conducting water permeability, electrical resistivity, drying shrinkage, rapid chloride penetration (RCPT) and water absorption tests. X-Ray Diffraction (XRD) analysis along with the microstructural investigations using SEM-EDS was carried out to supplement durability results. The compressive strength results indicated that LD slag concrete depicted higher strength than control concrete and there was a steady increase in strength with curing duration. Interestingly, PSC concrete depicted higher rate of strength gain compared to other cements. Further, LD slag concrete depicted low permeability and water absorption compared to control concrete, where it can be anticipated lower freeze–thaw damage. RCPT results indicated lower penetration of chloride ions representing delayed corrosion of steel in LD slag concrete. Overall, LD slag concrete depicted enhanced durability than control concrete.

Sustainable development of recycled concrete aggregate through optimized acid-mechanical treatment: A simplified approach

Present research develops an optimized acid-mechanical treatment for recycled concrete aggregate (RCA). RCA prepared in the laboratory jaw crusher is further soaked for 24 h in a mild acetic acid solution. Acid-soaked recycled aggregates (SR) are mechanically treated at a series of charges and drum revolutions using Los Angeles machines. A performance-based quality identification approach is used to compare acid-mechanically treated recycled concrete aggregates (SRij). The VIKOR indices (QI) for each SRij is calculated by applying a multi-criteria decision-making approach. Based on performance, three SRij with the lowest QI are selected for an experimental study. The present research achieves 71.27 MPa compressive strength for concrete composed of a SRij with the lowest QI. This strength is around 16.06% higher than concrete composed of parent aggregate. Flexural strength, split tensile strength, fracture energy, ultrasonic pulse velocity (UPV) values, rapid-chloride penetration test (RCPT) values, water absorption, and abrasion resistance are in the range of what is expected for parent aggregate concrete. The scanning electron microscope (SEM) image analysis shows that the well compacted and uniform surface morphology of aggregate strengthens the newly developed interfacial transition zone (NITZ) and old interfacial transition zone (OITZ). Acid treatment reduces microcrack lengths and widths and mechanical treatment reduces microcracks and pores by reducing adherent mortar optimally. X-ray diffraction (XRD) analysis shows the lower calcium hydroxide (CH) content in the mortar attached to the SR. A reduced CH content lowers the porosity in the adhered mortar. Thus, improved quality of attached mortar and its reduced porosity strengthen the old interfacial transition zone (OITZ) and lowers the sorptivity of the concrete than reported and almost equal to that of parent aggregate concrete.

Utilizing Red Mud as a Partial Replacement for Cement in High- Performance Concrete: Assessing Mechanical and Durability Properties

Bauxite residue (Red mud) is one of the industrial caustic waste materials obtained from alumina production. Because of high annual production, it requires high costs and vast landfills to dispose it. In addition, due to high alkalinity, disposal of red mud (RM) may cause serious environmental problems. Considering use of concrete beside economic and environmental issues of cement production, replacing cement by industrial waste seems inevitable. In this study, RM has been used as high as 10% replacement of cement mass in order to study the performance of this waste material in high performance concrete (HPC) in terms of their mechanical properties, 5-10% of the cement in concrete was replaced with red mud, in increments of 2.5%. In addition, to enhance the pozzolanic reaction. A slump cone test was conducted to evaluate the workability. Compressive, flexural, and split tensile strength tests were conducted to observe the mechanical properties. A rapid chloride penetration test and water absorption tests were conducted to determine the durability properties of the concrete

Durability performance of low calcium Flyash-Based geopolymer concrete

This investigation aims to systematically evaluate the durability performance of 30 MPa grade of low calcium fly ash-based geopolymer concrete. The geopolymer concrete with fly ash as binder is manufactured using an alkaline activator solution (of 14 Molar and Na2Sio3/NaOH ratio of 2.5). The results were also compared with the Portland cement concrete of similar grade. The concrete samples were subjected to water absorption, water permeability, sorptivity, acid resistance, sulphate resistance, and rapid chloride penetration tests. Water absorption study findings revealed less water absorption by low calcium fly ash-based geopolymer concrete than Portland cement concrete. Also, the water permeability tests on geopolymer concrete indicated lower water penetration depth compared to Portland cement concrete. Sorptivity test results depict lower sorptivity by geopolymer concrete over ordinary Portland cement concrete. Geopolymer concrete shows better acid resistance and sulphate resistance performance than Portland cement concrete in terms of residual compressive strength. Rapid chloride penetration test results indicated moderate chloride penetrability of geopolymer concrete and low chloride penetrability by Portland cement concrete. In general, low calcium fly ash based geopolymer concrete outperformed Portland cement concrete in most durability indices, which led to the conclusion that low calcium fly ash based geopolymer concrete durability performance was superior to that of concrete of a similar grade made of Portland cement concrete.