Chloride Permeability Test Research Articles

Comparative analysis of chloride and acid resistance in one-part geopolymer and low-carbon concrete

This study presents a comparative analysis of the chloride and acid resistance of one-part geopolymer and low-carbon concretes, with a focus on their potential to replace traditional OPC-based systems in construction. The research evaluates the performance of geopolymer concretes against OPC concrete and OPC blended with supplementary cementitious materials (SCMs), particularly fly ash and slag, under aggressive environmental conditions. The findings reveal that while geopolymer concretes exhibit superior resistance to acid attack, their chloride resistance is highly dependent on the specific precursor materials used. The study also highlights the limitations of using rapid chloride permeability tests (RCPT) at standard voltages for geopolymer concretes, suggesting that lower voltage tests at 30V may offer a more accurate assessment. Overall, the results underscore the need for optimized precursor selection in geopolymer concretes to enhance durability and advocate for further research into testing methodologies tailored to these innovative materials.

Performance Evaluation of Drying Shrinkage and Durability in Pavement Quality Concrete with Recycled Aggregate, GGBS and I-Crete

<p style="line-height:200%;text-align:justify;"><span>The study examines replacement of natural aggregates (NA) with Recycled Aggregate (RA) in Pavement Quality Concrete (PQC) M40 grade (M1) with 25%, 50%, 75% and 100% RA replacing NA in M2, M3. , M4 and M5 mixes. The compressive strength decreases with higher RA, but all mixes reach the target strength at 28 and 90 days. M5 was tested by adding Ground Granulated Blast furnace Slag (GGBS) in increments of 5% to 15% in M6, M7 and M8 to reduce the cement content. The main performance parameters include compressive strength, drying shrinkage, water penetration, Rapid Chloride Permeability Test (RCPT) at 28 and 90 days and sorptivity at 28 days. M5 reduced compressive strength but increased drying shrinkage, sorptivity, penetration depth and RCPT charge passage. Increasing the GGBS by 10% in M7 improved the strength, while increasing the GGBS by 15% in M8 decreased the strength compared to M1 and M5.</span> <span>To address strength degradation, the study incorporated 2% I-Crete along with GGBS in 5% increments from 15% to 35% in M9 to M13 mixes. M11 mix (2% I-Crete, 25% GGBS) showed better strength, reduced shrinkage and lower RCPT charge, ensuring better durability for SEM and XRD pavement applications.</span></p>

Investigating the influence of various metakaolin combinations with different proportions of pond ash and Alccofine 1203 on ternary blended geopolymer concrete at ambient curing.

This paper explores the use of a ternary blended geopolymer concrete (TBGPC) incorporating metakaolin (MK), pond ash (PA), and Alccofine 1203 (AF). Three combinations of MK (25%, 50%, and 75%) with varying proportions of PA and AF were prepared, validating against M30 grade cement concrete (CC). TBGPC was prepared with an 8 molarity sodium hydroxide, sodium silicate to sodium hydroxide ratio of 2.0, liquid to binder ratio of 0.5, and an ambient curing mode. For CC, a water to cement ratio of 0.42 and water curing mode were adopted. The mechanical properties and durability behavior of TBGPC and CC specimens were evaluated through compressive strength, rapid chloride penetration test, permeability test, sorptivity test, and water absorption test. The M50P35A15 mix demonstrated remarkable compressive strength improvements, showing a 203% increase over the CC mix at 1day and 250% by 3days. This trend continued with a 155% increase at 7days, 68% at 28days, and 52% at 90days, consistently outperforming the CC mix. Additionally, microstructure characteristics of the M50P35A15 mix were analyzed through SEM studies, providing validation for the observed strength development. Notably, M50P35A15 mix demonstrated substantially higher early and later strength gain. This enhancement in strength was attributed to the gradual densification of the microstructure over time and the formation of additional NASH and CASH gel in M50P35A15 mix. At 28days, the M50P35A15 mix exhibited excellent durability characteristics, with a Coulomb value of 1008, permeability of 10mm, sorptivity of 0.45mm/√min × 10-4, and water absorption of 1.07%. This study demonstrates the potential of MK, PA, and AF as viable materials for sustainable geopolymer concrete, offering a low-carbon alternative to traditional cement concrete with superior strength and durability aspects.

A New Performance-Based Test for Assessing Chloride-Induced Reinforcement Corrosion Resistance of Geopolymer Mortars.

The widespread adoption of geopolymer concretes in the industry has been slow, mainly due to concerns over their long-term performance and durability. One of the main causes of concrete structures' deterioration is chloride-induced corrosion of the reinforcement. The reinforcement corrosion process in concrete is composed of two main stages: the initiation phase, which is the amount of time required for chloride ions to reach the reinforcement, and the propagation phase, which is the active phase of corrosion. The inherent complexities associated with the properties of precursors and type of activators, and with the multi-physics processes, in which different transfer mechanisms (moisture, chloride, oxygen, and charge transfer) are involved and interact with each other, have been a major obstacle to predicting the durability of reinforced alkali-activated concretes in chloride environments. Alternatively, the durability of alkali-activated concretes can be assessed through testing. However, the performance-based tests that are currently available, such as the rapid chloride permeability test, the migration test or the bulk diffusion test, are only focusing on the initiation phase of the corrosion process. As a result, existing testing protocols do not capture every aspect of the material performance, which could potentially lead to misleading conclusions, particularly when involving an electrical potential to reduce the testing time. In this paper, a new performance-based test is proposed for assessing the performance of alkali-activated concretes in chloride environments, accounting for both the initiation and propagation phases of the corrosion process. The test is designed to be simple and to be completed within a reasonable time without involving any electrical potential.

The role of low-quality calcined clay in enhancing the performance of cement mortar exposed to normal and aggressive media

This study focuses on the role of low-quality calcined Fanja (FNJ) clay in enhancing the behavior of cured cement mortar (CM) and its resistivity to chloride and sulfuric acid attack. Ordinary Portland cement was replaced with different quantities (10%, 25%, 35%, and 50% by weight) of FNJ, which was calcined at different temperatures (620 °C, 760 °C, and 900 °C). After 28 days of curing, all the hardened mortars were immersed in 5% sulfuric acid for up to 12 weeks. Additionally, a rapid chloride permeability test was conducted on the 91-day cured CM and CM-FNJ samples to evaluate the affinity of calcined FNJs to retard the chloride diffusion into CM. The results showed that all samples containing FNJ900 showed better physical and mechanical properties than the control sample, while CM with NFJ760 recorded nearly similar performance as CM-NFJ900. In contrast, the CM-FNJ620 mixtures showed lower properties than those of other mixtures. In addition to the pozzolanic reactivity of the calcined clay, the presence of hematite in the calcined clay strongly contributed to increasing the mechanical properties of the hardened mortar through forming calcium ferrosilicate hydrate binding phase, as confirmed by X-ray diffraction. Moreover, the existence of hematite increased the resistivity of CM against sulfuric acid attack as it acts as a buffer for an acidic medium. Compared with CM-FNJ900, the CM-FNJ760 is recommended for use as it exhibited a higher strength activity index and comparable resistance to accelerated chloride diffusion and sulfuric acid accompanied by lower energy demand and lower CO2 emission, achieving the concept of ‘sustainability’.

Workability, mechanical, durability, and microstructural investigation of sustainable concrete utilizing secondary treated wastewater, fly ash, and sodium nitrite

ABSTRACT This study explored the use of secondary treated wastewater (STW) from three secondary-level wastewater treatment plants, along with fly ash (FA) and sodium nitrite (SN), to produce sustainable concrete, comparing it to concrete made with tap water. Key properties examined included workability (slump cone), strength (compressive, split tensile, and flexural), and durability (rapid chloride permeability and efflorescence). Scanning electron microscopy (SEM) analysis was performed to investigate the concrete's microstructure. The results indicated that FA and SN content had a notable influence on the workability, mechanical strength, and durability of the concrete mixtures. However, the type of water (STW or tap water) used in the concrete preparation showed no significant impact. Durability tests revealed that the penetrability of the mixtures ranged from low to moderate, signifying good quality, and no efflorescence was observed. Ultimately, the study concluded that concrete made with STW, when supplemented with 10% FA and 2% SN, demonstrated comparable performance to that made with tap water across key properties, offering a viable option for sustainable concrete production.

Experimental investigation of using Ultra-High-Performance Concrete coating for anti-corrosion protection of reinforced concrete induced by chloride ions

The emergence of Ultra High-Performance Concrete (UHPC) is one of the latest developments in concrete technology. Repairing and rehabilitating damaged structures by applying a thin layer of several centimeters on conventional concrete (with or without reinforcement) has been one of the applications of UHPC. Due to its very small porosity and excellent permeability, UHPC has extremely high durability against the penetration of destructive substances such as water, chloride ions, oxygen, etc. In this work, we investigated the durable effect against external aggressive corrosive substances by coating a 2.5 cm thickness layer of UHPC on conventional concrete. The desired composite concrete consists of a conventional concrete core with a compressive strength of 40 MPa and a coating with a thickness of 2.5 cm of UHPC cover. Then, this concrete went through oxygen penetration, Rapid Chloride Permeability Test (RCPT), and electrical resistance tests. Finally, to verify the results of the durability tests, two sets of comparison reinforced concrete specimens with 5 cm as their covers were exposed to an accelerated corrosion test. It is found that the substitution of a 2.5 cm layer of UHPC instead of the conventional concrete resulted in a 30-times increase in resistance against water penetration, 41 times against chloride ion penetration, 307 times against oxygen penetration, and 8 times in its electrical resistance. Based on corrosion acceleration test results, after 30 days of applying a current with a voltage of 31 volts, the control specimens with a 5 cm cover started to corrode after one week. After 30 days, 47 % corrosion was observed. Even though after 365 days, no signs of corrosion were found in the UHPC-coated specimens.

Enhancing the self-healing properties of engineered cementitious composites by the application of super-sulfated cement

No research has been reported on the self-healing performance of engineered cementitious composites (ECCs) prepared with super-sulfated cement (SSC), despite its potential to reduce carbon dioxide emissions compared with ordinary Portland cement (OPC). This significant gap in the research literature was addressed by exploring the influence of SSC on the recoverability of pre-cracked ECC samples. In addition to mechanical characterisation of sound samples, an exhaustive investigation was undertaken to comprehensively assess the self-healing ability of pre-loaded SSC-based ECCs by means of flexural strength tests, deflection measurements, ultrasonic pulse velocity (UPV) tests and rapid chloride permeability tests. Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) was used to evaluate the microstructural changes and development of self-healing products within the microcracks of SSC mixtures prepared with various amounts of fly ash. The SSC-based ECCs, while maintaining comparable mechanical and ductility properties, exhibited significant improvements in recovery rates (more than 27%, 7% and 76% for flexural strength, UPV and chloride permeability, respectively, compared with the OPC-based control ECC). The SEM–EDS results confirmed the enhanced precipitation of ettringite as a new self-healing product related to the inclusion of SSC in ECCs, along with conventional calcium silicate hydrate/calcium aluminium silicate hydrate (C-S-H/C-A-S-H) gels.

Strength and Durability Studies on Concrete using Cashew Nut Shell Ash (CNSA) waste as Supplementary Materials

<p><span style="font-size:12pt"><span style="font-family:"Times New Roman","serif"">As the world population is expected to increase significantly, there is a greater need for housing and, as a result, building materials. Conventional manufacturing methods for materials such as concrete involve substantial energy usage and substantial release of carbon emissions, which contribute to environmental deterioration. This study investigates the incorporation of Cashew Nut Shell Ash (CNSA) as a partial replacement for Ordinary Portland Cement (OPC) as primary cement, while CNSA formed binary blends. The study examined various water-to-binder ratios (0.55, 0.50, and 0.45) and a total binder content of 310 kg/m³, with replacement levels at 0%, 10%, 20%, 30%, and 40%. Compressive strength tests were performed at 2, 7, 28, and 90 days, shows a consistent increase in strength over time. Optimal CNSA content (10-30%) enhanced long-term strength due to its pozzolanic activity. Additionally, the elastic modulus was tested, indicating improved stiffness in mixes containing CNSA in comparison with the conventional concrete systems. Durability tests such as Rapid Chloride Permeability Test and carbonation depth analysis showed that CNSA addition generally decreased chloride conductivity, thereby enhancing durability. However, replacement levels (beyond 40%) exhibited diminishing returns. The results suggest that CNSA is a viable partial replacement for cement, improving concrete's workability, density, and long-term strength while enhancing durability against chloride penetration and carbonation. These findings support CNSA's potential in creating sustainable and resilient concrete systems.</span></span></p>

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.

Answers to Your Resistivity Questions and Helpful Findings to Develop a Robust Resistivity Specification

Many states are currently in the process of evaluating the use of surface resistivity (SR) or bulk resistivity (BR) tests to assess permeability of concrete in lieu of the standard test method for electrical indication of concrete’s ability to resist chloride ion penetration (AASHTO T 277 and ASTM C1202) which is commonly referred to as the rapid chloride permeability test (RCPT). A few states, such as Louisiana and Maine, implemented resistivity testing in their specifications many years ago. As with any test method implementation, it is important to learn from data generated and experience gained to further refine the specifications in respect of both testing protocols and the specification limits. In this paper, the Federal Highway Administration’s Mobile Concrete Technology Center SR and BR data from 30 field projects in 25 states is analyzed to provide information that could be helpful to agencies as they specify or improve their specifications with respect to resistivity testing. This paper attempts to answer questions related to 1) change in resistivity testing results with age, 2) range and variability of resistivity data from mainline paving mixtures, 3) comparison of test results between SR and BR data, 4) comparison of resistivity data gathered with equipment from various vendors, and 5) use of 28 versus 56 day data.

Optimization and Characterization of Cementitious Composites Combining Maximum Amounts of Waste Glass Powder and Treated Glass Aggregates

This work investigates the combined use of waste glass aggregates (GA) and glass powder (GP) in cementitious mortars. For this reason, the optimized incorporation of GA by natural aggregates (NA) replacements was first studied after applying a surface roughening method with hydrofluoric acid. The compressive strength results were utilized to select the best mixture with GA. Then, different GP contents were added by cements substitutions to the optimized GA-based mortar. A control mortar without GA and GP amounts was also casted as a reference for comparison. The detailed mechanical, physical and durability properties of the resulted mixtures with combined GA and GP were assessed by considering the compressive and flexural strengths, ultra-sonic pulse velocity, alkali-silica reaction (ASR), rapid chloride permeability test (RCPT), magnesium sulphate attack and sulfuric acid resistance. The microstructure of different optimized (GA + GP)-combinations was characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS)in order to analyse the interfacial transition zone (ITZ) between glass materials and the surrounding matrix. The results showed that the optimized composition with 75% GA and 25% GP was shown with high compacity and durability characteristics due to the increased GA/matrix ITZ and the formation of C–(N,K)–S–H products with C–S–H.

Evaluation of the Durability of Concrete with the Use of Calcined Clays and Limestone in Salinas, Ecuador

This study aims at the evaluation of different formulations of concrete made with calcined clays and limestone (LC3 cement) exposed to aggressive environments. The study includes the evaluation of fresh and hardened properties and a comprehensive evaluation of durability over 24 months. The inclusion of calcined clays in cement increases the specific surface area of the cements, and thus the water demand. However, the high reactivity of calcined clays compared to any other pozzolan, and the synergy that occurs with limestones, enables the use of cements with very low clinker content that achieve strengths similar to those of Portland. Comparisons of LC3 formulations with Portland cement and with concrete containing silica fume prove the superiority of calcined clays in terms of strength and durability. The best results are obtained with LC3-50 cement with 50% clinker produced through co-grinding. Results of concrete made with a blend of 70% Portland cement with 30% LC2 (60% calcined clay, 35% limestone, 5% gypsum, separate ground) are also promising. All concretes made with LC3 show good durability in terms of the results of effective porosity, chloride permeability, and resistivity tests.

Post-fire curing and autogenous self-healing in alkali-activated slag: Microstructures and healing mechanisms

Among various ways to counter the effects of cracking and damage induced by exposure to elevated temperatures, self-healing appears to be a promising technique for maintaining construction materials' structural integrity and longevity. This research investigates the effectiveness and potential of autogenous self-healing for alkali-activated concrete performance recovery after exposure to elevated temperatures up to 800 °C. Two post-fire curing methods were examined: exposure to ambient air and immersion in sodium hydroxide (NaOH), to assess their effectiveness in promoting self-healing in AAS. To achieve better understanding of the mechanisms behind post-fire AAS's self-healing, a comprehensive evaluation of crack healing, microstructural changes, and the durability of the treated materials was conducted through a combination of visual inspection, ultrasonic pulse velocity, water sorptivity, rapid chloride permeability tests, scanning electron microscopy-energy dispersive X-ray, and X-ray diffraction. Findings reveal that NaOH immersion significantly enhances self-healing, evidenced by reduced crack widths and improved material properties. Changes in the amount of hydration products and various shapes of self-healing product crystals, such as trigonal, cubical, and rectangular, were detected. However, the dominant healing product was calcium carbonate (CaCO3), which precipitates through a combination of hydration reactions and carbonation processes, crucially contributing to the closure of microcracks and the restoration of the material's integrity. This process underscores the critical role of chemical reactions in AAS's self-healing mechanism, offering insights into its potential for enhancing the durability and resilience of construction materials. This emphasized the potential for leveraging AAS properties by self-healing and mitigating fire damage, thus extending the lifespan of structures and reducing maintenance costs.

A Study on Durability and Microstructural Analysis for Macro Synthetic Fiber Reinforced Concrete with Supplementary Cementitious Materials

Background: Thermal cracking, delayed ettringite production and low tensile strength are three significant problems for high-strength concrete. Objectives: The current experimental study aims to determine the durability characteristics of concrete for application in pavements. To test how well the M40 grade of concrete absorbed chloride and water, the amounts of Supplementary Cementitious Materials (SCM) like Granulated Blast-Furnace Slag (GBFS) and fixed amounts of Fly Ash (FA) and Macro Synthetic Fiber (MSF) were optimized. Methods: One sample (S1) was made entirely of Ordinary Portland Cement (OPC) and five samples (S2, S3, S4, S5, and S6) made simply of SCMs, in which OPC was substituted with 20% FA+20% GBFS+1.5% MSF, 20% FA+25% GBFS+1.5% MSF, 20% FA+30% GBFS+1.5% MSF, 20% FA+35% GBFS+1.5% MSF, and 20% FA+40% GBFS+1.5% MSF, respectively, were cast in standard blocks with a volume of one cubic meter for this purpose. Field Emission Scanning Electron Microscopy (FESEM), Fourier-Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) investigations are used to examine the number of hydration products created at 28 days, which differ for different percentages of SCMs. Findings: Furthermore, 501, 520, 535, 565, and 590 coulombs are the measured Rapid Chloride Permeability Test (RCPT) values for the S2 to S6 samples. Similarly, the S1 sample is projected to have more than 2600 coulombs, showing a better endurance of samples based on SCMs. The microstructural characterization findings (i.e., XRD, FTIR and FESEM) suggested that GBFS and FA are promising SCMs for enhancing the strength and durability properties of the mix. Novelty and applications: This study validates the viability of using GBFS, FA, and MSF in pavement applications, yielding noteworthy environmental advantages and lowering dependency on OPC. Keywords: Durability, Microstructural investigation, Macro synthetic fiber, Fly ash, Granulated blast furnace slag, Pavements

An experimental study on high strength self-compacting concrete inclusion of zeolite and silica fume as a potential alternative sustainable cementitious materials

One of the major sources of carbon dioxide and other greenhouse gases around the world is the cement industry. They make up 6–8 % of global warming. Therefore, by conducting this experiment, we may examine the possibility of replacing cement with different cementitious materials which include zeolite,silica fume and fly ash. These mineral additives will lessen the need for cement while enhancing the properties of the concrete that has just been hardened and also in fresh state. The objective of this experiment is to explore the impact of zeolite and silica fume on the physical and durability qualitiesof high strength, self-compacting concrete utilising nano silica that has been optimised. In the course of this study, various concrete mixtures were cast with zeolite and silica fume substituted for cement in varying amounts, and there was also a control mix for reference. These additives arereplacedcement in multiples of 5 up to 20 %. The preferred dosage as 2 % Nano silica is substituted as a regular mineral additive in all mixtures. Workability tests on the fresh qualities of concrete mixtures are conducted and the EFNARC stipulations are met by these experimental findings. All the concrete mixes' parameters, including strengths like splitting tensile and compressive were identified. Tests such as the Rapid chloride permeability test, the abrasion test, water absorption and desorption test were used to evaluate the concrete's durability.

Experimental Analysis on the Characteristics of Concrete by Incorporating Steel Slag as Partial Replacement of Sand

Abstract: Steel slag is a by-product obtained in the manufacture of pig iron in the blast furnace and is produced by the blend of constituents of iron ore with limestone flux. Presently in India, owing to restricted methods of use, massive amounts of iron and steel slag are deposited in the yards of every production facility, occupying significant agricultural land, and seriously polluting the entire ecosystem. Meanwhile, the application of ecological environment protection has limited the mining of gravel, leading to a shortage of natural aggregate. Numerous studies have sought to replace natural aggregate in concrete with steel slag aggregate due to its good engineering qualities. The current research work is to investigate the concrete’s characteristics for M40-grade concrete by substitution of sand with steel slag at 10%, 20% and 30% during various curing ages. Several experiments were conducted on the characteristics of the concrete, compressive strength, and durability properties (such as water absorption and rapid chloride permeability test) up to the age of 90 days

Effect of load on bonding properties and salt freeze-thaw resistance of bridge expansion joint concrete

In the seasonal frozen regions, the bridge expansion joint concrete (BEJC) is susceptible to damage during its service life, not only from vehicular loads but also from chloride salt erosion and the effects of freeze-thaw cycles. This study investigates the basic physical and mechanical properties of BEJC under different curing conditions. A rapid chloride permeability test was conducted to comparatively analyze the concrete's chloride ion penetration resistance. The microscopic crack width on the concrete bond surface is evaluated to assess the concrete bond performance under different loading durations. Additionally, the study explores the coupled effect of wheel loads and single-sided salt freeze-thaw cycles (WL-SFT) on the freeze-thaw resistance of BEJC, delving into factors such as spalling mass, water absorption rate, and pore structure characteristics (including air content, specific surface area, spacing coefficient) and connectivity. The results indicate that for specimens subjected to loading at 1–14 days and 3–14 days, the average crack widths on the bond surface are 14.36 µm and 10.09 µm, respectively, representing 5.27 times and 3.70 times those of unloaded specimens. The bond strength also decreases by 34.8% and 14.2%, respectively, compared to unloaded specimens. The increase in crack width leads to a reduction in bond strength, highlighting the importance of bond strength as a consideration for the actual opening time of roads in engineering projects. Furthermore, due to its smaller and more stable pore structure, the study suggests that WL-SFT almost does not damage standard curing (SC) concrete; however, it slightly disrupts the pore structure of natural curing (NC) concrete. In comparison, WL-SFT leads to the generation of more microcracks in both the surface and deeper layers of low-temperature curing (LC) concrete, resulting in the destruction of its pore structure and connectivity.

Mechanical and durability performance of ternary blended calcined clay and pulverized granite mortar composites

ABSTRACT Partially replacing cement with pozzolans, apart from the enormous technical benefits, has been reported as an effective approach to reducing greenhouse gases emanating from cement production. Calcined clay and pulverised granite, in recent years, have been experimented individually for their use as filler or pozzolan in concrete to improve workability and compressive strength. This research includes study of the synergistic characteristics of these two mineral admixtures and their influence on the mechanical and durability properties of mortar. Cement was partially substituted with 5–20% by weight of the composite material to form a ternary blended cement composite. The compressive strengths of the ternary blended cements were evaluated at 3, 7, 28 and 90 days. Durability properties such as alkali silica reactivity (ASR), rapid chloride permeability test (RCPT) and performance of the blended cements in aggressive media have been discussed. Test results indicated that, blended cements containing 5% and 10% of the pozzolan recorded similar compressive strengths at 28 days and outperformed it by 2.4% and 0.6% respectively at 90 days. Beyond 10% replacement, compressive strengths declined. The ternary blended cements were found to be highly reactive, potentially causing ASR in concrete than the reference cement.

Effect of Finely Ground Coal Bottom Ash as Replacement for Portland Cement on the Properties of Ordinary Concrete

This study investigates the use of finely ground coal bottom ash (FGCBA) as a substitute for Portland cement in concrete, comparing it with coal fly ash from the same power plant. The incorporation of this ash necessitates the addition of a superplasticizer to achieve the desired slump at the same replacement rate. The results demonstrate that at an optimal 20% replacement rate, as determined by 91-day compressive strength tests, the maximum strength achieved by FGCBA is 97.7% of the control group with pure cement, whereas coal fly ash reaches 114.0%. Drying shrinkage tests indicate for both materials have similar volume stability, while rapid chloride permeability tests show their effectiveness in reducing chloride ion permeability, with superior performance from FGCBA. Under optimal conditions, the result of the RCPT test was only 559 coulombs, which is significantly better compared to the 4108 coulombs when using fly ash from coal combustion. Our results demonstrate that utilizing low-cost bottom ash by finely grinding it to replace Portland cement in concrete is feasible, achieving both carbon reduction and economic viability.