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Controlled low-strength material (CLSM) is known as a self-leveling and self-compacting cementitious
backfill material used for backfilling. The aim of this paper is to give an overview of the research development
and practical application of CLSM for trench backfilling. Widespread application of CLSM is found
around the world including in the Unit...
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Context 1
... and self-leveling cementitious backfill material used in lieu of con- ventional compacted fill [1]. The other terms used to describe this backfilling material includes flowable fill, controlled density fill, flowable mortar, self-compacted backfill material, plastic soil- cement or slurry etc. [1][2][3]. CLSM has a wide range of applications (see Fig. 1) due to its unique characteristics and properties. The principal applications of CLSM include trench backfilling, structural fills, pavement bases, void filling and conduit bedding [4]. Table 1 summarizes the criteria requirements and the essential properties need to be achieved for each different application of ...Context 2
... and self-leveling cementitious backfill material used in lieu of conventional compacted fill [1]. The other terms used to describe this backfilling material includes flowable fill, controlled density fill, flowable mortar, self-compacted backfill material, plastic soil-cement or slurry etc. [1][2][3]. CLSM has a wide range of applications (see Fig. 1) due to its unique characteristics and properties. The principal applications of CLSM include trench backfilling, structural fills, pavement bases, void filling and conduit bedding [4]. Table 1 summarizes the criteria requirements and the essential properties need to be achieved for each different application of ...Citations
... At present, common backfilling projects mainly include the backfilling of foundation pits and fertilizer tanks, the backfilling of comprehensive pipe galleries, and the backfilling of underground pipe networks [1] . These types of projects are often carried out after the completion of the main structure construction. ...
... In practical cases, where it is not possible to attain the maximum dry unit weight, the structures constructed at the site may fail. In conditions where it is hard to accomplish the mandatory compaction characteristics by means of the surface compaction techniques, CLSM was an effective substitute to normally densified fills (ACI 229R-99 2005;Lini Dev and Robinson 2015;Ling et al. 2018). Researchers have considered the use of CLSM in different applications in the field of civil engineering (Ghataora and Alobaidi 2000;Chittoori et al. 2013;Do and Kim 2016). ...
... CLSM is also called flowable fills, flowable mortar, k-crete and unshrinkable fill (Du et al. 2002;Butalia et al. 2004;ACI 229R-99 2005). Other waste products such as recycled aggregates, mine flotation tailings, limestone screenings, cement kiln dust, sewage sludge, bottom ash, waste foundry sand, treated oil sand are also used by various researchers in flowable fill production (Ling et al. 2018;Ibrahim et al. 2022). ...
... The plastic and in-service properties to be considered while utilising CLSM for different applications are flowability, segregation (bleeding), UCS, unit weight, permeability, shear strength and compressibility (ACI 229R-99 2005;Ling et al. 2018). Depending on the applications considered, the properties to be assessed for CLSM varies. ...
The utilization of coal ashes to replace different natural aggregates is a standard procedure adopted nowadays for different civil engineering applications. Reutilization of these industrial waste products generated from the thermal power plants for civil engineering applications is beneficial to society and the environment in various ways. Thus, this research paper deals with the studies done to analyse the effectiveness of using pond ash for controlled low strength materials (CLSM) production. Further, stresses and strains developed on the buried pipelines where CLSM was used instead of the standard aggregate-based bedding layer were also analysed. A comparative study of the stresses and strains developed on the buried pipelines was evaluated using PLAXIS 2D software. The results from the studies showed that the plastic and in-service properties obtained for the pond ash-based CLSM mixtures are equivalent to regular aggregates used in bedding layer applications. Further, the analysis of stresses and strains developed on the buried pipelines using the Plaxis 2D numerical tool showed that the stresses and strains developed on CLSM as bedding layer-based pipelines performed better than the normal bedding layers. Thus, pond ash-based CLSM mixtures can be used as an alternative to normal aggregates as the stresses and strains developed were found to be lesser than that of normal aggregate-based bedding layers.
... The most significant uses of CLSM among various applications include void filling of underground utility ducts, utility trench backfill, reclamation of low-lying areas and structure fill of footing, road bases and pipe bedding (Alizadeh et al. 2014;Blanco et al. 2014;Chompoorat et al. 2021). According to a recent article by Ling et al. (2018), the use of CLSM is growing across all types of construction projects and industries worldwide. Production of CLSM mixture for construction projects requires a considerable amount of fine aggregate, resulting in a shortage of natural resources. ...
Minimizing the utilization of natural resources and recycling industrial by-products on a large scale poses a severe challenge worldwide for sustainable development. Successful utilization of pond ash as a fine aggregate in controlled low-strength material (CLSM) enhances those possibilities. In this paper, laboratory tests were performed to determine the engineering properties of pond ash-based CLSM mixture and its feasibility, along with environmental assessment. The results showed that pond ash could be effectively used as fine aggregate in CLSM production with desired engineering properties. At maximum flowability, the w/c ratio reduces significantly with increased cement content. The strength properties of CLSM mix are exactly related to the percentage of cement content present in the mixture at constant flowability of 300 mm. Low cement content CLSM mixture was more compressible than higher cement content. The leaching concentration of heavy metals in the CLSM mix are within permissible limit according to USEPA threshold limit.
... Based on its requirement of achieving lower strength, CLSM can be produced by solid waste as its cementitious material or aggregate [15,16]. As a consequence, coalbased solid waste can be utilized to substitute the cementitious materials and aggregates of CLSM, reducing the stacking of coal-based solid waste and reducing the pollution to the surrounding environment [17,18]. For instance, Cheng et al. used bottom ash instead of fly ash to study the effect of the ratio of fly ash to bottom ash on the filling material. ...
Recently, controlled low-strength material (CLSM) has been considered an easy-to-mix material, and the raw material is usually derived from solid waste, suggesting lower production costs. Moreover, the resource utilization of waste fosters the sustainable advancement of both society and the environment. In the present work, a CLSM with excellent performance was developed by adopting fly ash, bottom ash, desulfuration gypsum, and cement as the main cementitious materials, as well as gasification coarse slag and coal gangue as aggregates. An orthogonal experiment with three factors and three levels was designed according to the ratio of cement to binder, the contents of water, and the water-reducing agent. Further, the macroscopic properties of flowability, dry density, bleeding, compressive strength, fresh density, porosity, and absorption rate of the CLSM mixtures were tested. To optimize the CLSM proportion, the ranges of three indicators of CLSM were calculated. Experimental results manifested that the fresh and dry densities of the mixtures were within the range recommended by ACI 229. The optimal levels of cement−binder ratio (i.e., the ratio of cement to binder), water content, and water-reducing agent content are 0.24, 248 kg·m–3, and 0.80 kg·m–3, respectively. Under this condition, the flowability was 251 mm, the bleeding was 3.96%, and the compressive strength for 3 d, 7 d, and 28 d was 1.50 MPa, 3.06 MPa, and 7.79 MPa, respectively. Furthermore, the leaching values of eight heavy metals in CLSM and raw materials were less than the standard requirements, indicative of no leaching risk.
... To solve the above-mentioned engineering problems, a new type of fluidized cementsoil backfill technology known as the use of controlled low-strength materials (CLSM), is gradually being adopted in engineering [2]. According to the American Concrete Institute [3], CLSM is defined as a new backfilling material with high flowability, suitable compressive strength, and that can be self-compacted with less vibration under the action of self-weight. ...
... The authors discussed the effects of the differences between native soils on the performance of CLSM and designed a specific mixture ratio for each project. Based on 115 literature articles, Ling et al. [2] summarized that the materials used for the production of CLSM varied from case to case, which in turn has a significant impact on the performance of CLSM and its application in the field. Similarly, Dalal et al. [11] gave a detailed discussion on the recent advances in the development of CLSM with different waste materials, and the effects of material properties on the flowability, strength, and hardening time of CLSM. ...
... When the ash-soil ratio increases from 9% to 12%, the flowability values continuously decrease from 269.75 mm to 212 mm and then to 154.25 mm, with a decrease of 11.1%, 15.8%, and 15.4%, respectively. Those results broadly agree well with previous studies [2], which highlights the critical factors (water content and material properties) affecting the flowability of CLSM. When the cement content increases from 6% to 9%, the flowability of the CLSM decreases by about 11%. ...
When backfilling narrow spaces, controlled low-strength materials (CLSM) can be used to achieve an effective backfilling effect. The pipeline engineering in Yahnghe Avenue of Suqian, China, provides a favorable on-site condition for the use of CLSM. However, no guidance exists for the determination of the material mixture ratio of CLSM for this geological condition. Laboratory tests were performed to investigate the basic physical parameters of excavated soil and the optimal mixture ratio of CLSM. Results indicate that the sand and silt account for 29.76% and 57.23% of the weight of excavated soil, respectively. As the water content increases (from 40% to 50%), the flowability of the CLSM approximately shows a linear increase (slumps values from 154.3 mm to 269.75 mm for 9% cement content), while its compressive strength shows a linear decreasing trend (from 875.3 KPa to 468.3 KPa after curing for 28 days); as the cement content increases (from 6% to 12%), the flowability approximately shows a linear decreasing trend (from 238.8 mm to 178.5 mm for 45% water content), while the compressive strength shows a linear increasing trend (from 391.6 KPa to 987.6 KPa after curing for 28 days). By establishing the relationship between compressive strength/flowability and the water–cement ratio, the optimal material ratio is determined to be 9% cement content and 40–43% water content. The engineering application results indicate that the use of CLSM can achieve efficient and high-quality backfilling effects for pipeline trenches. The findings of this research may provide a reference for the application of CLSM in fields with similar geological conditions.
... The primary factors governing the performance of CLSM are the characteristics of the component materials and their ratios in the combination, including high fluidity and regulated low strength. The grade of the components used in the combination must be lower since CLSMs are made of materials with lesser strength [108]. ...
... CLSMs have demonstrated effectiveness as a backfill material, replacing compacted soil in various countries [2]. The constituents and mix proportions of CLSMs are not explicitly defined, relying on trial and error to achieve the desired properties, such as flowability, strength, and density [3]. ...
This study aims to optimize the sustainable utilization of excavated soil by incorporating it exclusively as a fine aggregate and cement in the formulation of soil-based controlled low-strength materials. The polycarboxylate superplasticizer was introduced to enhance flowability. Various factors, including the cement contents, initial water contents, and curing time, were systematically analyzed for their effects on the fresh properties, mechanical parameters, transverse relaxation time distribution, pore size distribution, porosity, and corrosivity of soil-based controlled low-strength materials. The results indicate that polycarboxylate superplasticizer effectively dispersed clay minerals and cement particles, enhancing the flowability. The unconfined compressive strength increased with the rising cement content and decreased with the increasing initial water content. Additionally, the transverse relaxation time distribution curves of the soil-based controlled low-strength materials exhibited two peaks. These curves shifted to smaller transverse relaxation time values with the increasing cement content, while gradually shifting to larger transverse relaxation time values with the increasing initial water content. An increase in the cement content resulted in higher volume percentages of small and mesopores, while extra-large pores and macropores decreased. The addition of the polycarboxylate superplasticizer had minimal impact on the pore volume percentage distribution. Furthermore, porosity experienced a decline with the rise in the cement content and curing time, in contrast to a notable increase with a higher initial water content. This investigation provides valuable insights into the engineering properties and microstructural characteristics of soil-based controlled low-strength materials, offering a foundation for sustainable waste management practices in geotechnical applications.
... Ling et al. examined 115 reports related to CLSM for backfill and found that the materials used to produce CLSM varied across countries. They reported that the use of different materials has a significant impact on CLSM research and field applications [25]. In particular, as CLSM-related research has become more active, more types of industrial waste for CLSM have been researched. ...
A significant amount of stone sludge is generated as a by-product during the production of crushed stone aggregate, and most of it is disposed of in landfill as waste. In order to recycle this stone sludge, this study evaluated a controlled low-strength material (CLSM) using ultra-rapid-hardening cement and stone sludge for application as backfill and subbase material for road excavation and restoration work. In addition, considering the limited construction time of excavation and restoration work in urban areas, backfill and subbase materials must simultaneously satisfy conditions of fluidity, workability, quick curing time, and certain levels of strength. Therefore, in this study, CLSM was manufactured according to various mixing ratios and flow, slump, and compressive strength tests with age were evaluated. Additionally, the change trend in the microstructure of the CLSM with age was analyzed. Through indoor experiments, the optimal mixing ratios for backfill and subbase CLSM were determined, and field applicability and performance of field samples were evaluated through small-scale field construction. It was concluded that CLSM, which contains a large amount of stone sludge, can be sufficiently applied as a backfill and subbase material for excavation and restoration work if appropriate admixtures are adjusted according to the weather conditions at sites.
... Average flow value is shown in Fig 3, marsh cone and UCS values of GS and GC series are tabulated in Table 3 the flow of GS ranged between 200-385 mm and GC ranged between 200-320 mm [7][8][9][10]. The flow increased with increased percentage of water content and the value is in between 200-300mm hence CLSM mix satisfies self-flowing and self levelling. ...
Road networks play a essential role in transportation systems at the national, state, and local scenario. Ongoing efforts involve construction of new roads and the enhancement of existing ones to improve the overall efficiency of the transportation system. However, highway construction often results in environmental degradation. A more eco-friendly alternative known as CLSM relies significantly on industrial waste in its production process. CLSM, also known as flowable fill, is a self-compacted cementitious material that exhibits properties between concrete and soil. This paper focuses on evaluating the suitability of CLSM mixes in pavement layers and is prepared by combining ground granulated blast furnace slag, cement, and fine aggregates such as crumb rubber and copper slag sand. Flowability and marsh cone tests were conducted to assess the workability of the mixes. California Bearing Ratio (CBR) test, Unconfined Compressive Strength (UCS) to determine the mechanical properties of hardened CLSM. CBR values obtained for CLSM mixes (UCS range 0.28 – 2.42 MPa) was observed to be more than that of conventional pavement subgrade materials. Adoption of such CLSM mixes for pavement subgrade will lead to sustainable road construction.
... CLSM has several benefits frequently highlighted in the literature. The following are the primary benefits of regulated low-strength materials: readily accessible, versatile, strong, durable, lower levels of inspection, allows for an immediate return to traffic, would not settle, improves worker safety, permits building in all weather conditions, simple to place and deliver, needs no storage, easily excavatable, uses less equipment and lowers excavating costs, and allows for by-product utilization [7,[10][11][12]. ...
Fly ash (FA) cement and water make up flowable fill material, which is also generally produced from waste and utilized in place of compacted granular fill as a cost-effective fill or backfill material. The capability to produce mixtures from various inexpensive, locally available by-products is one of the main benefits of flowable fill material. To considerably reduce costs, this study designed flowable fill mixtures utilizing cement, recycled fine aggregate (RFA; recycling waste hardened mortar and ceramic rubbish), FA, superplasticizers (SPs), and water for various uses. Initially, FA, Portland cement, fine natural aggregate, and water were combined to create a control mixture. Recycled aggregate (recycling waste hardened mortar and ceramic rubbish) was used instead of normal aggregate in various mix proportions in weights of 10, 20, 30, 40, and 50%. They performed well and conformed to the requirements of flowable fill material concerning flow consistency, unit weight, compressive strength, direct tensile strength, and thermal conductivity. Finally, when compared to ordinary concrete, flowable fill material can be produced with minimal mechanical criteria, such as a compressive strength of fewer than 5.71 MPa after 60 days and a unit weight between 1,993 and 1,961 kg/m³. Additionally, it was discovered that using more RFA to replace normal fine aggregate in flowable fill materials could result in a relative decrease in thermal conductivity.
