Slurry pipeline transport, the hydraulic conveyance of solid particles suspended in a liquid medium, is essential for bulk material handling in sectors like mining, mineral processing, power generation, dredging, and construction. Development began in the mid-20th century, driven by the need for efficient, continuous, and long-distance transport of ores and industrial by-products. The mining industry was among the earliest adopters, as pipelines offered a cost-effective and environmentally favourable alternative to truck or rail transport for commodities such as coal, iron ore, and limestone [[1], [2], [3]]. Over time, this technology extended beyond mining applications. Today, slurry pipelines are used to transport dredged sediments for marine and river engineering projects [4,5], handle coal ash and combustion residues in thermal power plants [6,7], and transfer processed minerals such as phosphate and limestone from extraction to beneficiation facilities [1,8]. The advantages are clear: pipelines reduce dust and spillage, minimise land use and environmental disturbance, and enable transport over challenging terrain. They also play a critical role in underground backfilling, where waste material is safely deposited to enhance mine stability and support sustainable waste management practices [[9], [10], [11]].

The behaviour of slurries differs significantly from that of single-phase fluids, owing to the interplay between solid particles and the carrier liquid. Their flow characteristics are governed by factors such as solids concentration, particle size distribution (PSD), shape, and interparticle interactions, which are parameters shown to strongly influence rheological behaviour, which in turn governs pressure drop, flow regimes, and energy requirement [[12], [13], [14]]. For example, increasing solids concentration often leads to a shift from Newtonian to shear-thinning or pseudoplastic behaviour, with added yield stress at high loadings [12,14]. Understanding slurry rheology is thus central to the design, operation, and optimisation of pipelines and pumping systems. Recent studies emphasize two major approaches to improving slurry transport performance: (i) the use of bimodal or multimodal particle mixtures to enhance packing density, minimise interstitial fluid volume, and reduce hydraulic resistance [12,13,15], and (ii) the incorporation of chemical additives, both synthetic polymers and emerging bio-based agents, that modify viscosity, yield stress, and suspension stability [14,16]. Together, these strategies have enabled more efficient transport at higher solids loadings, while also mitigating problems such as settling and blockage formation [1,15,17].

In parallel with experimental advances, modelling and simulation techniques have undergone substantial evolution. Early design methodologies relied heavily on empirical correlations, such as those proposed by Durand and Wasp, which remain widely referenced for estimating parameters like critical velocity and pressure drop. However, the inherent limitations of empirical approaches, particularly at high solids concentrations or in heterogeneous particle systems, have motivated the adoption of computational fluid dynamics (CFD). Multiphase CFD frameworks, including Eulerian–Eulerian, mixture, and Eulerian–Lagrangian models, provide greater fidelity in capturing particle–fluid interactions, turbulent modulation, and slip velocities [[18], [19], [20], [21]]. Most recently, hybrid modelling strategies have combined CFD with artificial intelligence (AI) and machine learning (ML), enabling rapid surrogate models that support real-time monitoring and predictive control of industrial pipel1ines. Despite these advances, scaling predictions from laboratory to field conditions remain challenging, primarily due to particle shape variability, nonlinear rheological behaviour, and multiphase complexities that are difficult to capture in deterministic models.

Beyond operational efficiency, sustainability has become an increasingly important dimension of slurry transport research. Modern pipeline design and operation now integrate energy optimisation, environmental compatibility, and lifecycle considerations. Strategies include optimising particle size distribution to reduce pumping power, redesigning pipeline geometries to minimise pressure losses, and introducing vibration-assisted transport to mitigate resistance in fine-grained suspensions [9,18,22]. Novel slurry formulations have also been proposed, including CO₂ hydrate slurries that not only serve as transport media but also contribute to carbon capture and storage initiatives [22]. These innovations reflect a broader trend toward aligning slurry transport practices with global energy and climate objectives.

A particularly active area of research is the use of eco-friendly additives. Conventional synthetic dispersants, surfactants, and polymers are effective in reducing viscosity and preventing particle aggregation, but their long-term environmental impact has raised concerns. Consequently, natural and waste-derived alternatives are receiving significant attention. For example, plant-based biosurfactants such as Sapindus laurifolia extract and biodegradable additives have been shown to improve slurry stability and flowability at high solid concentrations [[23], [24], [25]]. These agents function by reducing surface tension and zeta potential, thereby enhancing dispersion and lowering the risk of sedimentation. Their ecological advantages include reduced toxicity, biodegradability, and decreased emissions during waste disposal, positioning them as promising replacements for synthetic chemicals [24].

Complementary to chemical modification, bio-inspired engineering solutions are also emerging. Bionic pipeline designs incorporating transverse protuberances have been shown to reduce stone accumulation by approximately 35 % compared to conventional smooth pipes, thereby improving transport efficiency in slurry shield systems [26]. Similarly, vibration-induced fluidization has been demonstrated to lower resistance losses in dredging operations, particularly for highly concentrated fine-grained suspensions [5]. At the system level, optimisation of particle size distribution can yield substantial energy savings: for instance, reducing D50 from 300 μm to 100 μm decreased power consumption in iron ore pipelines by 24 % [18]. Pipeline length and diameter also exert strong influences, with longer pipelines increasing energy demand by up to 60 % [18]. Such insights emphasize the need for holistic design strategies that consider particle engineering, hydraulic conditions, and energy efficiency in tandem.

Industrial case studies further illustrate the potential of sustainable practices. Additional advances include the use of rice straw as biodegradable vertical drains in dredged slurry treatment, which performs on par with synthetic alternatives while reducing cost and environmental impact [27]. In phosphate mining operations, the use of tailored modifiers has enabled the transport of highly concentrated pastes (82–84 % solids) at flow rates of 80–100 m3/h, supporting both solid waste utilization and green mining practices [28]. Remote-controlled coal–water slurry systems in underground mines have also demonstrated substantial economic and environmental benefits relative to conventional haulage methods, including reduced greenhouse gas emissions and improved safety [29]. These practical demonstrations validate laboratory-scale findings and underscore the feasibility of translating sustainable slurry transport strategies into industry.

Recent review studies consistently affirm that surfactants and polymers, particularly those derived from natural or waste sources, are effective in stabilising mineral slurries, including iron ore, coal, and limestone systems. In many cases, bio-based agents not only match but surpass the performance of synthetic additives in terms of reducing viscosity, enhancing dispersion, and maintaining stability, while simultaneously lowering environmental burdens [24,30]. This convergence of operational efficiency and ecological responsibility highlights a promising pathway for future research and industrial adoption.

Slurry pipeline transport has evolved into a multidisciplinary field where rheology, particle engineering, additive chemistry, and computational modelling converge to address challenges of efficiency, scalability, and sustainability. The central role of rheology in determining hydraulic behaviour, energy consumption, and flow regimes underscores the need for a systematic understanding of its fundamentals. The multifactorial nature of slurry transport can be conceptualised as shown in Fig. 1. Rheology, particle size distribution, additives, pipeline design, and operating conditions collectively shape the hydraulic behaviour of the system. Their interactions directly influence critical outcomes such as energy efficiency, suspension stability, and environmental sustainability. This systems-level perspective highlights the need for integrated research approaches, where particle engineering, fluid–particle interactions, and design optimisation are addressed in tandem to advance slurry transport technologies.

Building on this foundation, the subsequent sections of this review examine the rheological classifications of slurry flows, the influence of particle-scale properties on bulk behaviour, and the modelling frameworks that underpin current and emerging strategies for optimising slurry transport.