The production of Ordinary Portland Cement (OPC) is highly resource-intensive, requiring significant energy and leading to the emission of large quantities of carbon dioxide. As a result, widespread research has been conducted to identify alternative binder materials that are both cost-effective and environmentally sustainable. One such promising alternative is Sugarcane Bagasse Ash (SBA), a byproduct of the expanding sugarcane industry. The large-scale generation of bagasse ash presents both disposal issues and environmental concerns due to the depletion of natural resources. Incorporating SBA into construction practices offers a sustainable solution by enabling its use as a partial replacement for cement. This study investigates the efficiency of manufactured sand (M-Sand) as a fine aggregate in mortar mixes comprising silica fume (SF) and SBA. To enhance workability and reduce the water requirement, a sulphonated naphthalene-based superplasticizer (SP) was added. Calcium chloride was also involved to boost early-age strength. Additionally, mineral admixtures were used to partially replace cement, aiming to improve mortar performance while curtailing carbon emissions. Mortar mixes were prepared using a volumetric water-to-binder ratio of 0.5, where the binder consists of cement, silica fume, and SBA. SBA was used to replace OPC at varying proportions: 10

Curved railway tracks are susceptible to lateral instability due to the combined effects of centrifugal forces, reduced ballast confinement, and thermally induced stresses in continuous welded rails. These factors increase the risk of track misalignment, rail-seat deterioration, and potential buckling, particularly under high-speed and high-temperature operating conditions. To address these challenges, this study proposes a novel steel-plated grooved section (SPGS) anchorage system, designed to improve lateral stability by enhancing the mechanical interlock between prestressed concrete sleepers and the surrounding ballast. The SPGS anchors are easily removable, compatible with standard maintenance practices, and suitable for retrofitting. Three SPGS anchors, varying in anchor lengths (10 cm, 13 cm, and 16 cm), were evaluated through a combination of experimental single-tie push tests and discrete element method (DEM) simulations. Additionally, the interaction between the SPGS-anchored sleeper and ballast particles was analyzed using DEM to examine the contact force chains and energy dissipation within the ballast particles. The results showed that SPGS-anchored sleepers increased lateral resistance by 195% to 256% compared to unanchored sleepers, with the 13 cm anchor length demonstrating the most effective length within the tested range, providing the most practical and efficient performance among the tested anchor lengths. DEM analysis revealed a deeper and more uniform distribution of contact force chains, along with increased energy dissipation, which contributed to reduced ballast displacement and enhanced structural stability. The proposed SPGS system significantly increases the lateral resistance capacity, allowing higher safe operating speeds on curved tracks, as validated through safety margin calculations and lateral force demand assessments. These findings suggest that the SPGS anchorage is a practical and scalable solution to enhance the lateral resistance of ballasted railway tracks, particularly in curved sections.

Prestressed concrete sleepers (PCS) are critical components of ballasted railway tracks, subjected to repeated cyclic loading from train passage and occasional high-intensity impact forces from wheel flats or rail irregularities. While the impact behavior and fatigue performance of PCS have been widely investigated separately, a clear comparative understanding of their combined implications for structural performance and durability remains limited, particularly for high-speed and semi-high-speed rail systems, where both loading scenarios are relevant. This study numerically investigates the impact resistance and fatigue life performance of two widely used sleeper designs, the Indian PCS and the Chinese Type III PCS (CT III), through full-scale finite element models developed in ANSYS. Impact response and fatigue life are assessed using separate finite element analyses based on standard impact assessment and S-N curve procedures, without explicit damage coupling between impact and fatigue, enabling consistent comparisons under service-representative conditions. The results show that the CT III sleeper exhibits approximately 40% higher impact energy absorption due to its rail-seat geometric configuration, whereas the Indian sleeper demonstrates a longer fatigue life, typically ranging from about 106–1010 cycles, depending on the load level, compared with approximately 105–109 cycles for the CT III sleeper. The study’s findings provide insight into the relative performance of the two designs under service-representative loading conditions, supporting comparative evaluation of sleeper designs used in modern ballasted railway systems.

Reinforced concrete (RC) structures exposed to aggressive environments will deteriorate quickly and shorten their service life. Many developed and developing countries face the great challenge of deteriorating construction infrastructure, with investments worth trillions of dollars. According to Federal Highway Administration (FHWA) regulations, billions of dollars are spent each year repairing bridge deck delamination in North America. The development of an efficient bridge deck rehabilitation system is vital for the efficient management of such infrastructures. LIFE-365 is a worldwide used service life prediction model proposed by NIST and ACI 2001. It was found and understood from the literature that the service life prediction model LIFE-365 uses a two-phase model (corrosion initiation period and propagation period) to assess the remaining service life of RC structures. It was also found that LIFE-365 software assumes a constant value of six years for bare steel bars and twenty years for epoxy-coated bars for determining the propagation period. The recent mathematical models use three-phase models (corrosion initiation period + free expansion period + propagation period), which consider porous zone thickness and rate of corrosion to predict service life. The present study focuses on the accurate prediction of service life of RC structures exposed to harsh environments using LIFE-365 and a mathematical model proposed by T El Maaddawy and K Soudki in 2007. It was observed that LIFE-365 accurately predicts the corrosion initiation period; however, the free expansion period was assumed to be six years without considering the rate of corrosion and steel–concrete interface (SCI) properties. The free expansion period was calculated using T El Maaddawy and K Soudki’s 2007 model, considering the properties of SCI and the actual corrosion rate. It is necessary to use both LIFE-365 and T El Maaddawy and K Soudki’s 2007 model to accurately predict the service life of corroding RC structures.

This study investigates the influence of water-repellent additives, specifically calcium stearate and zinc stearate, on the durability and corrosion resistance of cement mortar exposed to a 3.5 wt% NaCl environment for up to 173 days. Three mortar formulations incorporating a Ca-stearate to Zn-stearate ratio of 9:1 by weight were evaluated, W1 (control), W2 (1% dosage) and W3 (5% dosage). The addition of water-repellent additives reduced flow characteristics. However compressive strength of W2 reached 42.3 MPa at 28 days, higher than W1 (38.4 MPa) and W3 showed reduced performance due to excess dosage. Contact angle analysis indicated improved surface hydrophobicity with water-repellent addition. After 173 days of exposure to a 3.5 wt% NaCl solution, W2 exhibited strong corrosion protection compared to the control specimen W1. SEM-EDS analysis confirmed homogeneous distribution of water-repellent compounds in modified mortar samples, supported by elevated carbon and trace zinc levels. XRD patterns showed a reduction in the calcium hydroxide peak in W2 and W3, indicating interaction between stearate compounds and hydration products. Overall, W2 demonstrated a balanced performance across mechanical, electrochemical, and microstructural evaluations, making it a promising formulation for the least degradation of reinforcement in cementitious materials in chloride-rich environments.

The high carbon footprint associated with Ordinary Portland Cement (OPC) production necessitates the development of sustainable binder systems for structural concrete. Limestone calcined clay cement (LC3) offers a low-clinker alternative; however, achieving high-strength LC3 concrete remains challenging due to complex interactions among binder constituents, supplementary cementitious materials, and chemical admixtures. This study proposes an integrated multi-criteria optimization framework combining the Best–Worst Method (BWM) with the Taguchi experimental design to develop high-strength LC3 concrete while simultaneously satisfying strength and workability requirements. Three key mix-design parameters-binder proportion (OPC: LC2), ground granulated blast furnace slag (GGBS) content, and superplasticizer dosage were investigated using a Taguchi L9 orthogonal array, while BWM was employed to assign relative importance to selected performance criteria. The optimal mix (A3B2C1), corresponding to an OPC: LC2 ratio of 70:30, 20

Prestressed concrete sleepers (PCS) are an integral part of the railway track system which bears the loads exerted by the rails. To reduce the risk of damage during train derailments, and deterioration of sleepers caused by cracking under strong impact loads. To decrease the chances of these risks, the increase in demand for sustainable infrastructure has initiated research into eco-friendly alternatives in construction materials and methods. This study focuses on the development and evaluation of a sustainable PCS enhanced with steel fibers and silica fume. The experimental investigation involved the formulation of concrete mixture with ordinary Portland cement, silica fume as supplementary cementitious material, and steel fibers. The steel fibers were added to enhance the tensile strength and ductility properties of the sleeper. The specimens are subjected to impact and static bending tests. The results demonstrate the effectiveness of the sustainable PCS with steel fibers in resisting high impact loads, increasing energy absorption, and maintaining structural stability under static bending conditions. Compared to conventional sleepers, the sleeper with silica fume and steel fibers exhibited enhanced crack resistance and improved load-bearing capacity.

Railway sleepers play a crucial role in providing stability and support to railway tracks, ensuring the safe and efficient operation of the rail network. Sleepers distribute the load coming from the rails to the ballast. Prestressed concrete sleepers have advantages like high stability, strength, and durability compared to other types of sleepers. The rail seat region and the midspan region of the sleeper are the main critical zones in prestressed concrete sleepers (PCS), where damage typically occurs in each region due to high positive and negative bending moments, respectively. Throughout their lifespan, PCS may experience extreme loading conditions due to high-speed trains, high-magnitude wheel loads, and rail irregularities. Hence, selecting a suitable sleeper that performs better during harsh loading conditions becomes crucial. In the present study, two kinds of railway sleepers, namely, Indian sleepers, and B70 sleepers (German Rail Sleepers) are considered to assess the performance. Thus, the present work aims to experimentally investigate the behavior of two types of concrete sleepers under static and impact loading conditions. In this study Indian prestressed concrete sleepers outperformed B70 sleepers in both static bending and impact tests, demonstrating superior load carrying capacity, crack resistance, and energy absorption.

The present study attempts a detailed evaluation of the strength performance of Fiber reinforced Alkali Activated Concrete mixes containing fly ash and ground granulated blast furnace slag (GGBS) as a sole binder. Fly ash and GGBS, a by-product obtained from industries, is incorporated in the AASC mixes as a full replacement to ordinary Portland cement (OPC). Initially OPC and AASC mixes are designed to obtain M30 grade. This experiment investigates the effect of the addition of hooked end steel fiber and polypropylene fiber on the physical and mechanical properties of high ductile Alkali Activated Concrete. Geo-polymer is called one of the best substitutes for ordinary Portland cement (OPC) because of its benefits over OPC. Hooked end steel fiber of length 35 mm and diameter 0.5 mm with aspect ratio of 70, polypropylene fiber of 12 mm length is used in hybrid manner, with five different fiber volume fractions of 0.25 & 1.25%, 0.50 & 1%, 0.75 & 0.75%, 1 & 0.50% and 1.25 & 0.25% respectively. All mixes of fiber reinforced Alkali Activated Concrete includes 50% of GGBS and 50% of fly ash from total binder content. Alkali activators used are, sodium hydroxide pellets and sodium silicate liquid. The experimental result indicated that, the addition of fibers affects the workability by 20–30% down. In the mechanical property wise, fibers variation doesn’t affect the compressive strength much. Flexure and tensile strength increase by about 20–40%, compared to other mixes without any fiber’s addition. This increment of strength is due to addition of both the fibers in hybrid way. Using Alkali Activated Concrete helps to reduce emission of carbon dioxide, which happens from manufacturing of cement. Geo polymer concrete make the environment very much sustainable by maintaining global warming in a limit.

Purpose In recent years, fire accidents in engineering structures have often been reported worldwide, leading to a severe risk to life and property safety. The present study is carried out to evaluate the performance of Ground Granulated Blast Furnace Slag (GGBS) and fly ash–blended laterized mortars at elevated temperatures. Design/methodology/approach This test program includes the replacement of natural river sand with lateritic fine aggregates (lateritic FA) in terms of 0, 50 and 100%. Also, the ordinary Portland cement (OPC) was replaced with fly ash and GGBS in terms of 10, 20, 30% and 20, 40 and 60%, respectively, for producing blended mortars. Findings This paper presents results related to the determination of residual compressive strengths of lateritic fine aggregates-based cement mortars with part replacement of cement by fly ash and GGBS exposed to elevated temperatures. The effect of elevated temperatures on the physical and mechanical properties was evaluated with the help of microstructure studies and the quantification of hydration products. Originality/value A sustainable cement mortar was produced by replacing natural river sand with lateritic fine aggregates. The thermal strength deterioration features were assessed by exposing the control specimens and lateritic fine aggregates-based cement mortars to elevated temperatures. Changes in the mechanical properties were evaluated through a quantitative microstructure study using scanning electron microscopy (SEM) images. The phase change of hydration products after exposure to elevated temperatures was qualitatively analyzed by greyscale thresholding of SEM images using Image J software.

Prestressed concrete sleepers [PCS] are widely used in ballasted railway tracks across the world. Sleepers distribute the load coming from the rails to the ballast. PCS have advantages like high durability, stability, and strength compared to other types of sleepers. Concrete sleepers in their life span may undergo utmost loading conditions due to high-speed rails, high-magnitude wheel loads, and rail irregularities. Cracks in sleepers may occur at the rail seat region and mid-span region because of the high positive bending moment and high negative bending moment, respectively. PCS may satisfy the excepted performance standards during short-term serviceability, but long-term durability and premature failures are still an issue. Hence, selecting a suitable sleeper that performs better during harsh loading conditions becomes crucial. In the present study, two kinds of railway sleepers, namely, Indian sleeper (RT2496/60 kg) and Chinese type III prestressed concrete sleeper [CT III PCS], are considered to assess the performance under harsh loading conditions which arise due to modern high-speed or semi-high-speed rails on ballasted tracks. The finite element models of two kinds of sleepers were done using ANSYS, and the performance of the sleepers was assessed. The numerical results show that the CT III PCS performed slightly better than the Indian sleeper that has been studied in the present investigation.

The present study attempts, a detailed evaluation of the strength performance of Alkali Activated Slag based Pervious Concrete (AASPC) mixes, containing fly ash and ground granulated blast furnace slag (GGBS) as binders. Fly ash and GGBS, by-product obtained from thermal power plants and steel industries respectively, is incorporated in the AASPC mixes as a full replacement to ordinary Portland cement (OPC). Initially OPC and AASPC mixes are designed to obtain M30 grade. OPC based pervious concrete is considered as control concrete. Pervious concrete is a type of concrete that has a high-water permeability and a higher void content than regular concrete.

Aims: A detailed and reformed service life prediction model needs to be developed by considering the non-uniform distribution of the porous zone and the non-uniform distribution of the corrosion products layer. Background: The microstructure of the steel-concrete interface (SCI) plays an important role in corrosion initiation and concrete cover cracking. The porous zone around SCI is one of the vital engineering properties that influence the service life of corroding reinforced concrete structures in service life prediction models. Objective: The SCI properties are sensitive to the sample preparation technique of reinforced concrete (RC) samples for studying with the aid of scanning electron microscopy (SEM). A simple step-wise sample preparation technique of RC samples for SEM analysis is proposed where there is minimal damage to the properties of SCI. The development, distribution, and propagation of corrosion products at SCI are investigated for RC samples exposed to the marine environment for different exposure periods. The service life of RC structures was assessed through experimentally determined porous zone thickness (PZT) values. Assuming a uniform and constant value of PZT and uniform distribution of corrosion products around SCI might lead to variation or misinterpretation of the service life of structures. The same is explored in the present study. Methods: In this research investigation, backscattered electron images were obtained for the analysis of porous zone thickness around SCI. The distribution and propagation of corrosion products around SCI were investigated for different mineral admixed reinforced concrete samples exposed to the marine environment. Also, porous zone thickness values were used experimentally measured, and the time from corrosion initiation to corrosion cracking was estimated using a service life prediction model. Results: Results show that porous zone thickness is not uniform around SCI. Once the corrosion is initiated, the corrosion products accumulate in the SCI's porous region. Further, the non-uniform porous zone thickness directly influenced the non-uniform distribution of corrosion products. Assuming a constant or uniform porous zone thickness and uniform distribution of corrosion products around SCI leads to misinterpretation of the service life of corroding reinforced concrete structures. Conclusion: The porous zone thickness values around the steel-concrete interface and corrosion current density play an important role in predicting the service life of reinforced concrete structures exposed to the marine environment.

Thermal power plants produce fly ash and bottom ash as by-products. A total of 70% of by-product from thermal power plants accounts for fly ash and remaining 30% is bottom ash. One of the most common uses of bottom ash at the present scenario is structural fill in its coarser form only, and it is reported that the disposal leads to leaching of heavy metals to the groundwater table. These disposal problems and potential health hazards can be reduced by large usage of bottom ash in construction industry. A larger percentage of usage of the bottom ash in concrete will significantly reduce the potential health hazards and will give solution to disposal problems. With this in view, bottom ash collected from the Udupi thermal power plant was classified into two different levels according to their particle size and replaced against fine aggregates for different replacement levels, in producing M30 grade concrete. The raw bottom ash was coarse and classified as Zone-I after sieve analysis. The classification of bottom ash according to the particle size was carried out into different zones such as Zone-II and Zone-III, according to the specifications from IS 383–1970. The attainment of required compressive strength is directly correlated to particle size of bottom ash. Results show 47% reduction in compressive strength of concrete when raw bottom ash was (Zone-I) was replaced by 50% in place of natural river sand (NRS). A little effort in grading the bottom ash and converting coarser raw bottom ash from Zone-I to finer Zone-II bottom ash has proved beneficial in improving the compressive strength of concrete. It was observed that lower specific gravity of bottom ash directly influences density of concrete, which intern has adverse effect on compressive strength. The bottom graded as Zone-II can be replaced to NRS by 15–20%, with little compromise in compressive strength. Through value addition of 5% extra cement content, there is a possibility to increase the replacement level of Zone-II bottom ash to 30% with similar compressive strength as that of control concrete. Through cost analysis, it was found that 30% replacement of Zone-II bottom ash in place of NRS with 5% extra cement content as value addition was found to be economical.

Interface between steel and concrete is characterized as highly porous and weakest region which influences both mechanical properties and durability of a reinforced concrete structure. The properties of the steel-concrete interface (SCI), especially the porous zone thickness are prime factors in predicting the time for corrosion initiation to corrosion cracking in service life prediction models. Measurement of porous zone thickness of reinforced concrete samples is sensitive to the sample preparation technique for microscopic observations. It is observed that there are hardly any research articles are available in the literature regarding the sample preparation technique of reinforced concrete sample for SCI analysis. In the present study, a detailed and stepwise sample preparation technique is proposed where there is minimal damage found to be observed to SCI. The major focus is on the speed of cutting tool that is being used for obtaining a relatively small size of sample from the bulk reinforced concrete member. The properties such as porous zone thickness and nano mechanical properties around the SCI were determined through scanning electron microscopy and nano-indentation, respectively. A significant variation in porous zone thickness around SCI was observed and measured value of average porous zone thickness is found to be approximately 1.8 times higher from high-speed cutting to low-speed. A similar kind of observation was noticed for nano mechanical properties. In addition to speed of cutting, there found to be other factors such as pressing force for specimen, duration of polishing and heating temperature has significant influence on interfacial properties.

Mineral admixed or blended concretes require more time to attain the desired strength. The present investigation proposes new techniques for enhancing the early-strength development of blended concrete by implementing various thermal curing conditions for blended concretes. Blended concrete of grade M-40 was produced incorporating fly ash and ground granulated blast-furnace slag (GGBS) as partial replacement for ordinary Portland cement (OPC). The replacement levels of fly ash and GGBS were 20, 25 and 30% by weight of OPC. The effect of thermal curing conditions on blended concrete properties was evaluated by compression tests and split tensile strength tests. It was observed that the blended concrete required a minimum curing period of 56-90 d for attaining the desired strength. Under different thermal curing conditions, the desired strength can be achieved within a short duration of curing with the optimum dosage of fly ash and GGBS replacement in blended concrete.

Service life of a reinforced concrete structure depends on its durability in aggressive exposure conditions. In the case of reinforced concrete structures, the phenomenon that directly affects its durability is corrosion of rebar, which has direct influence on the residual service life. Corrosion in reinforced concrete basically initiates at its weakest zone called steel–concrete interface due to its porous nature. The extent of this porous zone is being represented in terms of Porous zone thickness which has been extensively reported by various researchers. This porous zone thickness is one of the key influencing factors in the prediction of residual service life of the reinforced concrete structure. Several mathematical models were proposed by various researchers to estimate the time required for cover cracking of concrete due to rebar corrosion by assuming different values of porous zone thickness (PZT) without any systematic experimental investigation. Assuming a steady value of PZT for all kinds of concrete without any practical justification will misinterpret the predicted residual service life. In the present work, an effort has been made to evaluate an existing analytical model to predict the time to concrete cover cracking by incorporating the experimentally obtained and published data on porous zone thickness. It was found that the porous zone thickness and rate of corrosion have a major role in evaluating the residual service life of reinforced concrete structures.

The Steel-Concrete interface (SCI) is usually regarded as the weakest region, which influences both mechanical properties and durability of reinforced concrete structures. Several researchers have well explored and defined the importance of SCI on the service life of the reinforced concrete structures as it directly affects the durability. The primary objective of this paper is to report and compare a variety of published findings and microstructural analysis on the SCI in one place which appears in reinforced concrete. The information available on the occurrence, formation, properties, various characterizing and analysing techniques of SCI are reviewed for a better understanding of microstructural properties of SCI on the hardened and durability properties of reinforced concrete. It was found that the SCI exhibits significant spatial inhomogeneity along and around as well as perpendicular to the reinforcing steel. Significant factors like quantification of porosity, porous zone thickness and actions that affect the properties of SCI like wall effect, bleeding, settlement and segregation of fresh concrete which were favourable to both initiation and propagation of corrosion are described in this paper. The influence of w/c ratio, hydration age, steel orientation and mineral admixtures on the distribution profiles of hydration products and Engineering properties of SCI is also discussed.

This paper presents the recent research progress on the response of concrete exposed to fire or high temperatures. The main highlight of this review paper is a compilation of previously reported data regarding the variations in mechanical properties and microstructure properties of concrete when exposed to high temperatures. The concrete structures get deteriorated at the macro- and microscopic levels due to high-temperature exposure. The macro-level damages can be measured with degradation in mechanical properties such as the reduction in compressive strength, weight loss, changes in elastic properties, reduction of bond strength in reinforced concrete, etc. The macro-cracks on the surface of concrete causes spalling which can be observed after exposing the concrete samples to more than 300 ℃. The compressive strength of the concrete reduces slightly till 400 ℃, and when the temperature increased to 600 ℃, there was an exponential reduction in the compressive strength of concrete. Another important parameter is bond strength degradation, which plays a crucial role in durability issues. To understand the deterioration phenomenon and changes in mechanical properties, the changes at the level of the microstructure of concrete need to be understood. Dehydration of products causes deterioration of mechanical properties and weight loss of concrete when exposed to high temperatures. At different temperatures, the microstructure changes and the response of hydration products such as calcium hydroxide (CH), CSH gel, unhydrated cement and capillary water reported by previous researchers are compiled and discussed.