Reinforcement Corrosion Research Articles

Effect of silica fume substitution by limestone powder and cement kiln dust on the shrinkage, durability, and sustainability of UHPC.

Silica fume is usually used in UHPC, three times more than that for normal concrete, to enhance mechanical properties and durability. However, silica fume (SF) is an expensive material and has high production costs. This work is aimed at investigating the shrinkage and durability performance of previously developed UHPC mixtures utilizing the two calcareous waste materials, namely limestone powder (LSP) and cement kiln dust (CKD), by partially replacing the silica fume. The optimally selected mixtures of UHPC, having flow and strength above the minimum required, were used for detailed investigation in terms of shrinkage and durability characteristics. The results showed that by replacing SF with up to 20% of LSP and up to 20% of CKD, the mechanical properties of UHPC remained satisfactory compared to the control mixture with 100% SF. However, the ultimate shrinkage was higher for mixtures incorporating LSP or CKD, indicating the need for more volume of steel fibers to compensate for the shrinkage strains. The developed UHPCs also exhibited high resistance against reinforcement corrosion and sulfate attack, making them suitable for use in aggressive exposure conditions. However, special attention needs to be paid to the CKD content, where it is recommended to limit the content of CKD to about 15% or less to control the durability performance of the UHPCs. In addition, the sustainability analysis of developed UHPC mixtures was carried out using the life-cycle assessment and eco-strength intensity index. The results indicated that the UHPC mixtures possess a higher life-cycle and are therefore more sustainable.

Fatigue performance analysis of precast segmental assembled concrete beams

In recent years, assembled bridges have become widely utilized in bridge construction, raising concerns about durability-related bridge diseases over time. These issues significantly impact the fatigue life of assembled bridges, necessitating an in-depth exploration of their fatigue performance. While existing research primarily concentrates on the transverse connection of multiple longitudinal beams, there is a notable dearth of studies on longitudinal precast segmental assembled bridges. This paper addresses this gap by establishing a fatigue benchmark finite element model for segmental assembled concrete beams, building upon existing experiments. The study employs numerical simulation to analyze the entire fatigue process, examining stress distribution, damage development, and considering the influence of reinforcement corrosion. Furthermore, a fatigue life prediction method, based on fatigue residual strength (R), is proposed for predicting the fatigue life (N) of concrete in precast segmental assembled beams. Results reveal that prestressed and ordinary reinforcements experience increasing stress with loading cycles, peaking around 100,000 cycles. Throughout fatigue loading, compressive stress in concrete remains low, preventing fatigue compression failure. However, tensile stress near joints gradually rises, initiating cracks at the mid-span beam’s bottom. With continued cyclic loading, these cracks propagate towards the loading point. The upper and lower limits of fatigue life predicted by the fatigue life prediction method closely align with the compressive fatigue test values of concrete, proposed fatigue life prediction method is efficient and accurate.

Determination of the ability of migrating steel corrosion inhibitors to passivate corroding reinforcement in reinforced concrete structures

Introduction. The corrosion condition of steel reinforcement in reinforced concrete structures and products is the main factor determining their bearing capacity and durability. The alkalinity of the pore liquid of concrete (at pH > 11.8) in reinforced concrete structures and products under normal conditions ensures the passive state of steel reinforcement. In the presence or when chloride, sulfate and other analogous ions enter the concrete, the steel reinforcement of reinforced concrete structures and products depassives, despite the pH value > 11.8, and begins to corrode. In addition, depassivation and subsequent corrosion of steel reinforcement occur during carbonation (neutralization) of the protective layer of concrete due to a decrease in pH < 11.8. One of the promising options for slowing down or stopping the corrosion processes of steel reinforcement is currently the use of migrating corrosion inhibitors.
 
 The aim of the work was to obtain experimental data on the ability of migrating steel corrosion inhibitors to inhibit or completely stop the corrosion of reinforcement in reinforced concrete structures and products initiated by the presence of chloride ions (Cl-) in concrete or neutralization of the protective layer of concrete in relation to steel reinforcement.
 
 Materials and methods. The following types of migrating steel corrosion inhibitors were used for testing:
 
 – Cortec MCI-2020 (manufacturer – KORTEK RUS (KORTEK) LLC, suppliers – Ettrilat LLC, MONUMENT LLC);
 
 – IFKHAN-80 (manufacturer and supplier – IFKHAN LLC);
 
 – Basf Master-Protect 8000 CI (former name Protectosil ® CIT. Suppliers – MBS Construction Systems LLC, MPKM LLC, LKM-FLEET LLC).
 
 The determination of the ability of migrating steel corrosion inhibitors to inhibit or completely stop the corrosion of reinforcement was carried out by accelerated electrochemical research methods in accordance with State Standard 31383-2008 "Protection of concrete and reinforced concrete structures from corrosion. Test methods".
 
 Results. All three types of migrating steel corrosion inhibitors inhibit corrosion of steel reinforcement initiated by the presence of chloride ions in concrete by the age of 90 days. All three types of migrating steel corrosion inhibitors by the age of 30 days do not inhibit the corrosion of steel reinforcement initiated by concrete carbonation.
 
 Conclusions. According to the results of the work, it was revealed that the migrating steel corrosion inhibitors inhibit the corrosion of steel reinforcement initiated by the presence of chloride ions in concrete, while the corrosion initiated by the carbonation of concrete is not slowed down or stopped by migrating steel corrosion inhibitors.

6-Methoxyquinoline immobilized nylon sensor for monitoring chloride concentration in reinforced concrete

An excess in the threshold concentration of chloride in concrete leads to the initiation of reinforcement corrosion, which in turn results in a reduction in the load-bearing capacity of reinforced concrete (RC) structures. Accordingly, the chloride concentration of RC is periodically investigated via a destructive method, but this process is time-consuming, labor-intensive, and costly. In order to overcome the limitations, this study sought to develop an optical chloride sensor that can be used in structural health monitoring. To this end, nylon was functionalized using formaldehyde and epichlorohydrine, after which 6-methoxy quinoline was covalently immobilized to manufacture a sensor. The developed sensor was found to be capable of measuring chloride concentrations (0–5,000 mM) and exhibited rapid responsiveness and reversibility. In addition, the developed sensor also showed a stable response even when exposed to the pH 13.4 environment for three months, and it could detect changes in chloride concentration even inside the mortar.

Degradation Models and Maintenance Strategies for Reinforced Concrete Structures in Coastal Environments under Climate Change: A Review

Modern engineering faces challenges in ensuring technical standards for service, durability, and sustainability. Political, administrative, and budgetary factors, coupled with climate change, pose tasks to structural integrity, affecting industries and economies. Marine infrastructures represent a strategic asset of a country as they handle a large part of the economic exchanges. This article analyzes five essential factors that play a fundamental role in the performance analysis of coastal structures: chloride-induced corrosion, degradation models, maintenance strategies, monitoring, and climate change. We start with reinforcement corrosion, which is considered as the main cause of distress, particularly in coastal zones, for the long-term behavior of structures. Additional pressure from the influences of climate change is becoming evident and extreme, leading to a reduction in capacity. To guarantee the lifespan of infrastructures, degradation models contribute by estimating the long-term performance of the asset as a strategic piece to the development of effective maintenance solutions. Artificial Neural Networks (ANNs) have gained recent prominence in this field due to their ability to learn intricate patterns from historical data, making them valuable instruments for predicting structural deterioration. Additionally, quantifying the condition of the structure from monitoring data plays a crucial part in providing information on the current situation of the structure. Finally, this review summarizes the challenges associated with the maintenance of aging marine structures considering aspects such as corrosion, monitoring, and the future challenges this area will face due to climate change.

Inhibition performance of extract reinforcement corrosion inhibitor from waste Platanus acerifolia leaves in simulated concrete pore solution

In our previous study, the ultrasound-assisted enzymatic extract of Platanus acerifolia leaves (PAL) was confirmed as an efficient corrosion inhibitor of steel. In this study, a new strategy-ultrafiltration-was proposed to further enhance the corrosion inhibition effect of this green steel corrosion inhibitor. To pinpoint the main players in the corrosion-inhibiting performance, the active compounds of the treated PAL extract were further quantitatively characterized via high performance liquid chromatography (HPLC). Electrochemical approaches were employed to investigate the anti-corrosion behavior. The adsorption film and surface morphology of the steel surface were characterized via X-ray photoelectron spectroscopy (XPS) and scanning electron microscope with energy dispersive spectrometer (SEM-EDS), respectively. Furthermore, simulations were carried out to further explore the inhibition mechanisms of the active molecules. The results showed that ultrafiltration significantly removed the polysaccharide impurities, thereby further concentrating the inhibition constituents. Twelve flavonoids and their derivatives were quantitatively traced, among which the procyanidins was the most pronounced ingredient (220 ppm). Ultrafiltration can effectively improve the inhibition performance of the extract. In the presence of chloride ions, the inhibition efficiency of the 1.5 wt% two-step processed extract was equivalent to that of the 5 wt% primary extract. Plus, SEM-EDS observations confirmed that the two-step processed extract was able to effectively mitigate the corrosion degree. XPS and simulation analyses revealed that the flavonoids and their derivatives executed the corrosion inhibition performance by forming a protective carbon-containing organic film on the steel surface via chelation and surface physical adsorption.

Effect of coarse calcareous aggregates on corrosion of steel reinforcement in marine concretes

Finely ground limestone, perhaps as part cement replacement, has been shown to reduce concrete permeability and enhance strength. Whether this holds also for coarse limestone aggregates is of both practical and environmental interest, particularly the effect on corrosion of steel reinforcement. This is confirmed herein with exposure tests over 14 years for a range of concretes exposed to a high chloride environment. Importantly, these concretes also showed delayed initiation of reinforcement corrosion and lower long-term corrosion losses compared with similar concretes made with coarse igneous or siliceous aggregates. The observations are attributed to enhanced bonding between cement-hydration products and the limestone aggregate surfaces. These findings are important both for reducing environmental impacts and greenhouse gasses and for extending the durability of reinforced concrete structures.

Comparative study of models predicting punching shear capacity of strengthened corroded RC slab-column joints

ABSTRACT Degradation in reinforced concrete (RC) members associated with rebar corrosion in old buildings is one major concern that can significantly affect the strength and serviceability of RC structures. Strengthening existing structures using FRP can comprise complex assessment and design processes. This study addresses the critical issue of modeling the behavior associated with steel reinforcement corrosion in RC slab-column joints (SCJs). Three modeling methods, namely artificial neural network (ANN), Eureqa’s symbolic regression algorithm, and analytical modeling, are proposed to predict the punching shear (PS) capacity of corroded RC SCJs by accounting for the changes in material properties due to corrosion and the strengthening provided by different types of FRP. The accuracy of the proposed models is validated through comparisons with experimental results and a verified finite element (FE) model that considers material deterioration and bond degradation. The results demonstrate that the proposed models offer more accurate PS capacity predictions than existing design codes. Among the considered prediction models, the ANN model exhibits superior performance and is recommended for PS capacity prediction. A practical design tool in the form of a graphical user interface (GUI) was created to facilitate the assessment and prediction of the PS behavior of corroded RC SCJs. Engineers can conveniently use this GUI to evaluate and predict the performance of such joints.

The Impact of Climate Change and Carbonation on the Durability of Concrete Structures in Afghanistan

Infrastructure plays an important role in human settlements, offering essential facilities such as buildings, transportation and other necessary systems. However, the impacts of climate change, whether direct or indirect, create various challenges for human settlements and ecosystems. This study investigates the dual impact of climate change and carbonation on the durability of concrete structures in Afghanistan. The durability of reinforced concrete is significantly affected by the corrosion of steel reinforcement, and carbonation is the main factor causing corrosion of steel bars in concrete. With shifting climate patterns influencing environmental conditions, this study aims to analyze how these changes contribute to the carbonation process in concrete and the results will contribute to a deeper understanding of the challenges posed by climate-driven changes and carbonation, thereby providing the basis for necessary measures to minimize the environmental impacts. To facilitate this investigation, (75x75x75mm) concrete cubes were prepared and after 28 days of curing in laboratory conditions, the specimens were exposed in four different regions: Afghanistan, Japan, Indonesia and Malaysia. The carbonation depths were measured at the ages of 6 months and one year. Considering the environmental and climatic conditions of all mentioned regions, despite Kabul's lower humidity and temperature, the carbonation was still significant compared to the other regions. This substantial carbonation poses a threat to structures, emphasizing the need for special attention in the design phase to ensure resilience against climate-induced challenges.

Research on reinforcement corrosion detection method based on the numerical simulation of ground-penetrating radar

Both the reinforcement depth and the electromagnetic properties of the concrete cover dramatically affect the steel reinforcement reflection wave amplitude in ground-penetrating radar (GPR), resulting in significant errors when evaluating the corrosion status of the reinforcement using the reflection wave amplitude. In response to this issue, this paper proposes a normalized amplitude–two-way travel time–relative permittivity (A-TWTT-εr) method, which, compared to traditional single-shot detection methods, enhances the effectiveness of steel reinforcement corrosion detection through 3D space. The amplitude and TWTT parameters are extracted using the A-scan waveform at the vertex of the steel reinforcement, while εr is determined through hyperbolic feature scatter fitting. Finally, the feasibility of the proposed method was verified using COMSOL numerical simulation data. The results showed that the proposed A-TWTT-εr amplitude-correction method could simultaneously correct for the attenuation effect of differences in the reinforcement depth and concrete electromagnetic properties on the amplitude. The proposed method could enable single-shot corrosion detection by GPR, yet further validation is needed in complex experimental and on-site environments.

Monitoring and Accelerating Methods of Corrosion for Reinforced Concrete: A Review

AbstractCorrosion is the irreversible, interfacial reaction of metals in the presence of an electrochemical environment which ultimately results in the deterioration of metals. Corrosion of reinforcement is the major problem in the reinforced concrete (RC) structure. Corrosion of reinforcement is a slow process because of the protective layer of concrete. Even in a severely corrosive environment corrosion process takes time to be initiated and propagated. Since to carry out research work, some techniques are required to accelerate the corrosion process in the shortest period. To overcome this problem, in the past, many researchers use a different method to accelerate the corrosion of steel in concrete. In this paper, a review is presented of various techniques used for accelerated corrosion testing. The suitability of reviewed methods on corrosion acceleration for several research works is presented. After that few case studies review to make use of various predicted empirical models and an experimental technique for predicting corrosion rate and the assessment of the remaining life of the structure. And finally, the paper is concluded by comparing the natural method of corrosion and the accelerated method of corrosion and the future scope of accelerated corrosion.

Experimental and Analytical Investigation of Moment-Carrying Capacities of Reinforced Concrete Frame Systems Corroded by Accelerated Corrosion Method

Technical investigations carried out after the devastating earthquakes in Turkey in the last 25 years show that one of the main causes of damage to reinforced concrete structures is reinforcement bar corrosion. The deterioration caused by reinforcement corrosion in reinforced concrete elements reduces the parameters that define the performance level of the structure, such as ductility, stiffness, bond-slip relationship, load carrying capacity, and energy absorption capacity. Therefore, determining the specified performance levels of reinforced concrete structures exposed to corrosion before any seismic activity occurs is of great importance in preventing loss of life and property. Cross-section behavior in reinforced concrete structures represents the load-bearing element behavior In order to accurately determine the section behavior, the Moment-Curvature relationship must be defined. In this study, the structural behavior of reinforced concrete frames exposed to corrosion was examined experimentally and analytically. For this purpose, 4 of the 5 reinforced concrete frame specimens constructed were corroded at different ratios using the accelerated corrosion method. After the corrosion process was completed, in the experimental part of the study, all specimens were tested under the effect of a 20% constant axial load and reversal-cyclic loading. In the analytical study, as a result of the cross-sectional analyzes carried out by taking into account the material-mechanical properties changing with the effect of corrosion, it was determined that the calculated moment values were in high predicted with the experimentally measured moment values.

Self‐Healing Molecular Biology for Microbial Concrete: A Review

AbstractThe most extensively utilized material in construction is concrete, decreasing life of structure pointing toward loses in structural health. The crack is the major problem faced in the concrete construction. This causes the corrosion in the steel reinforcement. The structure gets deteriorated with the developing cracks; therefore need the proper attention toward this problem. The present work consists of the different self‐healing techniques used by the researchers to inhibit the crack and prevent further deterioration in the structure. The self‐healing mechanism proves advantageous in use of natural fibers to inhibit the corrosion process, to increase compressive strength, and to decrease water absorption is present in this study. The maximum strength increased and the width of crack get healed with the help of these techniques is also mentioned in the study.

Biomimetic-induced hydroxyapatite for rebar corrosion mitigation in self-healing concrete beam

The corrosion of embedded rebar in self-healing concrete is seldom reported on and deserves more intensive attention. This study focuses on utilizing biomimetic-induced hydroxyapatite as a means of achieving autonomous self-healing to target issues associated with rebar corrosion in concrete structures. A comprehensive evaluation of the synthesized supramolecular hydrogel as self-healing agent carrier, the simulated self-healing products, and the reinforcement corrosion behaviour in the upscaled self-healing concrete beams was conducted. Results show that the synthesized 2,6-bis [N-(carboxyethyl carbonyl)amino] pyridine (DAP) hydrogel qualifies as a healing agent carrier with high loading capacity and intelligent response after cracking. The feasibility of hydroxyapatite formation via a combination of phosphate ions released by the supramolecular hydrogel and the available calcium ions leached by the cement matrix has been substantiated. The addition of phosphate as the healing agent is effective in mitigating the corrosion of rebar in the designed self-healing concrete beam. It can be explained by the synergistic effect of surface adsorption of chloride ions by the formed hydroxyapatite and the corrosion inhibitor role of the released phosphate.

Numerical modelling of bridge deck reinforcement corrosion based on analysis of GPR data

AbstractThis study explores the impact of corrosion on Ground Penetrating Radar (GPR) responses through practical experiments and numerical modelling, focusing on rebar diameter reduction, corrosion product layer thickness, crack formation and corrosion product filling in vertical and transverse crack. Practical experiments involved GPR testing of reinforced concrete slab. By analyzing B-scans we identify areas with moderate and severe corrosion. Numerical modelling using the Finite Difference Time Domain (FDTD) Method to model GPR signal propagation in a concrete bridge deck with corrosion is applied. Key finding includes a significant 26.70% increase in reflected wave amplitude when corrosion product filling in vertical crack increased by 400%, highlighting its extensive effect on signal GPR propagation. Reduced rebar diameter led to a 9.79% amplitude decrease and a 0.06 ns arrival time delay. Increased corrosion product layer thickness primarily affected arrival time with a 0.06 ns extension but significantly amplified GPR signal amplitude. These findings offer insights for improving GPR based corrosion detection and assessment methods, leading to more robust systems for concrete bridge deck inspection and maintenance. This paper contributes to understanding how corrosion affects the signal that is detected by GPR. This information can be used to improve the way that we manage and assess corrosion in concrete bridge deck.

Modeling and probabilistic evaluation of repair strategies in the initiation phase of chloride‐induced corrosion of the reinforcement of concrete structures

AbstractChloride ingress is a common issue in concrete structures that can result in reinforcement corrosion. In order to extend the lifetime of a structure, several preventive repair methodologies are available, which reduce the ingress of chlorides. In this work, the computational efficiency of the analytical model for a two‐material diffusion problem has been improved to model the effect of a mortar overlay or partial cover replacement, and is further implemented to model the influence of a coating. This enables the assessment of each repair method in a probabilistic framework using Latin hypercube samples within an acceptable timeframe. A parameter study executed in both a deterministic and probabilistic framework demonstrated the model efficiency and the importance of the timing and quality of the intervention for successful repair when applying a repair intervention in the initiation phase.

An experimental investigation on mitigating cracks and augmenting the endurance of concrete structures in marine environment by bio-mortar immobilised with halophilic bacteria

In coastal areas, built structures encounter hostile conditions and forces that can cause them to deteriorate over time owing to saltwater exposure, tidal forces, reinforcement corrosion, and freeze–thaw cycles. Early age cracks in such structures accelerate the rate of deterioration, and the current research focuses on alleviating such threats. This paper evaluates the performance of a self-healing mortar made by encapsulating expanded perlite with the bacterium Halobacillus Halophilus MCC2188. Mortar cube specimens of size 70.6 mm × 70.6 mm× 70.6 mm were prepared with cement: fine aggregate in 1:3 ratios. A 10% volume of the fine aggregate fraction was substituted with the expanded perlite immobilised with bacterial spores and nutrients. The expanded perlite aggregates were coated with sodium silicate and cement solution to protect the spores from the nonconducive environment. The specimens were subjected to fully and partially submerged marine water curing. The mechanical properties and self-healing potential were evaluated, and the precipitated polymorphs in completely healed cracks were identified and examined by characterisation techniques such as XRD, FEGSEM, FTIR, and TGA-DTG. The marine bacterium under investigation can tolerate the high salt concentrations commonly found in seawater and saline marshy soil and produce calcite through the metabolism of organic compounds, making it a suitable microorganism for self-healing applications. Crack widths of up to 0.84 mm and 92.79% average strength recovery were achieved in 56 days post-cracking, and the pace of healing was quicker in partially submerged curing conditions. The results showed improved self-healing, strength regain and mechanical strength and proved to be an efficient tool for enhancing the endurance of biomortar in severe marine exposure conditions.

Axial compressive behavior and model analysis of BFRP-jacketed corroded and pre-damaged circular reinforced concrete columns

Corrosion of steel reinforcements degrades the structural performance of reinforced concrete (RC) columns under static and seismic loads. Such corroded RC columns are usually retrofitted with fiber-reinforced polymer (FRP). However, existing studies on the retrofitting of RC columns with corrosion and load-induced damage are limited. To confirm the effectiveness of basalt FRP (BFRP) jacketing on the compressive behavior of corroded and pre-damaged RC columns, this study performed axial compression tests on eleven circular RC columns. The columns were fabricated, corroded, pre-damaged, and then jacketed with BFRP composites and reloaded to investigate the effects of BFRP layer number, corrosion ratio, and pre-damage degree. When jacketed by BFRP, the ultimate strength and ultimate strain of RC columns increased with BFRP layer numbers, ranging from 5% to 98% and 448% to 926%, respectively. Further, the ultimate strength and elastic modulus of the jacketed RC columns decreased with the increase in pre-damage degrees and corrosion ratios, while the ultimate strain was little affected. Buckling and corrosion of longitudinal bars significantly reduced the bar stresses at the ultimate state of BFRP-jacketed RC columns and resulted in local rupture of BFRP. This adverse effect became more pronounced as the corrosion ratio increased, but was alleviated by BFRP jacketing. On the other hand, a refined rebar stress-strain model was developed by addressing the effects of buckling, corrosion, and lateral confinement. Further, a feasible constitutive model for corroded hoop-confined columns was determined by validating the existing test results. Finally, models for the ultimate strength, ultimate strain, and stress-strain response of BFRP-jacketed corroded and pre-damaged RC columns were developed.

ПРИЧИНЫ ПОВРЕЖДЕНИЙ БАЛКОННЫХ ПЛИТ ЖИЛЫХ ДОМОВ

The main cause of defects and damage to balcony plates can be considered the so-called temporary factor, which has a far from positive effect on the general state of the structure - the impact of atmospheric-sphere precipitation, strong temperature differences. In addition to the temporary factor, the destruction of the balcony slab can be influenced by mistakes made during installation, no drains and overstrain of the balcony slab due to excessive load on it, which causes the formation of cracks. The basis for the survey was the check of the technical condition of the balcony slabs of a three-story multi-storey brick residential building in order to determine the degree of wear, possible defects and assess the possibility of further operation of the slab. A structural solution analysis was carried out to assess the technical condition of the building structures. Loads acting on the structures, impacts and operating conditions, the quality of structures, materials and connections were established. This also took into account factors such as the geometric dimensions of structures and their sections; presence of cracks, splits and destruction; condition of protective coatings; broken adhesion of reinforcement to concrete; presence of reinforcement rupture; condition of anchoring of longitudinal and transverse reinforcement; degree of corrosion of concrete and reinforcement. As a result of visual and measuring control, defects and damages having the requirements of operation and leading to a malfunction of the structure were revealed. The results set forth in the article may be of interest to specialists of expert organizations who are engaged in the examination of residential apartment buildings in order to assess the actual state of bearing structures, in particular balcony slabs

Effect of incorporating recycled macro fibres on the properties of ultra-high-performance seawater sea-sand concrete

Ultra-high-performance concrete (UHPC) is an ideal material for constructing marine infrastructures, but faces obstacles such as limited local raw materials (i.e., freshwater and river-sand) and corrosion of steel reinforcement. Non-metallic reinforcement is preferable for reinforcing marine UHPC, especially when seawater and sea-sand are used to develop ultra-high-performance seawater sea-sand concrete (USSC). Recently, the authors' group proposed a cost-efficient UHPC reinforced with discrete macro fibres mechanically processed from waste glass fibre-reinforced polymer (GFRP) composites. This present study aimed to explore the potential application of incorporating macro fibres in USSC. A series of tests were conducted to investigate the fundamental properties of macro fibre reinforced USSC with the examined variables including the content (0 %, 2 %, 4 %, and 6 %) and lengths (30 mm and 60 mm) of macro fibres. Comparisons were made between USSC and UHPC with river-sand and freshwater (UTRC), which were both reinforced with macro fibres. The results revealed that incorporating macro fibres in USSC improved the compressive toughness index (CTI) and flexural toughness by up to 84.00 % and 40.15 times respectively, but decreased the workability and compressive strength by up to 42.22 % and 21.45 % respectively. The effect of incorporating macro fibres on the properties of USSC was more prominent than that of its counterpart of UTRC. A theoretical model was then developed for predicting the flexural toughness of various concrete with macro fibres based on the regression analysis on the available test results.