Low Strength Material Research Articles

Development of a new cementless binder for controlled low strength material (CLSM) using entirely by-products

The aim of this study is to develop of a new binder using entirely by-products for a production of CLSM. The new cementless binder, tentatively named Fa-RmLG, was made from fly ash (Fa), lime (L), gypsum (G) and red mud (Rm). Various CSLM mixtures were produced with pond ash and different proportions of the new cementless binder Fa-RmLG. To assess the technical feasibility of this cementless binder in CLSM, three phases corresponding with three mix proportions were performed in this study. A preliminary proportion (phase I) was conducted to evaluate the engineering properties of five proposed CLSM mixtures in which the ratio of gypsum to red mud (G/Rm) varied in the range of 0.4–6.0. Subsequently, the best CLSM mixture was selected to be the control mix for a further study, which investigated the effect of fly ash content (phase II) and lime content (phase III) on the engineering properties of all CLSM mixtures in these phases. The obtained results showed that the engineering properties (flowability, bleeding, setting time, unconfined compressive strength, and microstructural analysis) and environmental impacts (corrosivity, heavy metals) of CLSM made with the proposed cementless binder met the ACI 229R requirements through a control of the cementless binder proportions. In conclusion, it was found a feasibility of using the developed Fa-RmLG binder for the production of CLSM.

Pond Ash–Based Controlled Low-Strength Materials for Pavement Applications

Abstract Cement-based controlled low-strength material, also called flowable fill, is often used as both subbase and subgrade material in pavement construction. This article investigates the properties of a pond ash–based flowable fill with special reference to pavement applications. Properties such as flowability, unconfined compressive strength, California bearing ratio (CBR), and resilient modulus (MR) for different mixes were studied. It was observed that addition of 2–3 % of cement in the pond ash can make a good flowable fill without the need of any other admixtures. Substantial improvement in CBR and resilient modulus values were observed when compared with the compacted pond ash. The results of the study show that the pond-based flowable fill can be used as an effective alternative material for subbase and subgrade layers in pavements.

Evaluation of heavy metal leachability of incinerating recycled aggregate and solidification/stabilization products for construction reuse using TCLP, multi-final pH and EDTA-mediated TCLP leaching tests.

Incinerating recycled aggregate (IRA) produced using bottom ash generated from the incineration of municipal solid wastes can be reused as construction materials and cement-based solidification/stabilization (S/S) can be employed to improve their environmental compatibility. Toxicity characteristic leaching procedure (TCLP) is commonly used to evaluate heavy metal leachability before reuse. However, the applicability of TCLP to IRA and their S/S products can be limited because of their alkaline nature which may cause underestimation of metal release. In this study, the leaching of heavy metals from an IRA and two S/S products, low-strength material (CLSM) and multi-functional regenerated concrete (MRC), were evaluated using TCLP, multi-final pH leaching test and EDTA-mediated TCLP. The results showed that TCLP results generally met the reuse standards. However, the results obtained from multi-final pH leaching test and EDTA-mediated TCLP showed exceedances of reuse standards for Pb and Cu when the final pH was < 5 or in the presence of> 7 mM EDTA. The results suggested that the reuse of IRA or S/S products requires further evaluation of their metal leachability in more harsh environmental conditions. Considering its simplicity, it is suggested that EDTA-mediated TCLP could be used for this purpose.

New approach for proportioning of controlled low strength materials

Controlled Low Strength Material (CLSM) can be a valuable application for the safe and efficient use of recycled and by-product materials. These nonstandard materials affect the mixture properties in less predictable ways, and hence, increase the number of trial batches required to attain the desired CLSM characteristics. In the present study, a laboratory experiment was carried out to explore an efficient methodology for proportioning CLSM mixtures without an extensive trial and error process.In the new methodology, CLSM mixture are proportioned using relative ratios between constituent materials, including the paste volume ratio to the total volume of mixture (PVR), mass ratios of water to cementitious materials (w/cm) and portland cement to cementitiuos materials (pc/cm). These parameters can be adjusted independently, and therefore, the proposed methodology allows for better understanding of the effects of the above parameters on mixture properties.The experimental results showed that the relative ratio parameters can provide adequate control over the relevant CLSM properties in terms of the ability to flow and compressive strength. The PVR parameter had a more significant effect on flowability compared to the w/cm ratio; though, it had little effect on strength development of CLSM mixtures. A mixture design procedure based on the new methodology is provided.

Some observations on failure of austenitic stainless steel: effects of in- and out of plane constraint

Modern engineering design for safety-critical structures demands meticulous failure assessments. While conventional fracture toughness parameters (e.g. JIC or KIC) are perceived as a reliable tool for characterizing the fracture behaviour of many engineering components, excessive plasticity in low-strength materials with high strain hardening capability, such as austenitic stainless steels, can change the predominant failure mode to plastic collapse. In this case, assessing the component integrity assuming fracture can introduce significant conservatism in its estimated load bearing capacity. Low constraint structures such as thin sections or sections with short cracks can suffer from plastic collapse rather than fracture but there is not a measure that can predict the change of failure mechanism. In this study, the effect of crack tip constraint in terms of the thickness and initial crack size on failure behaviour of AISI Type 316L austenitic stainless steel is studied. To this end, several single edge notched bending (SENB) specimen were manufactured with different initial crack lengths and thicknesses to account for in- (i.e. crack length) and out of (i.e. thickness) plane constraint effect. Fracture tests performed according to ASTM E1820-18 except for the sample thickness and crack lengths. The challenges for measuring the crack extension for resistance curve method as a result of deviating from the standard is discussed. The failure of the samples was also assessed by Failure Assessment Diagram (FAD). The results showed that unloading compliance extremely underestimate the crack extension in the presence of significant plastic deformation of the samples. The results also showed that the plastic collapse occurs in all samples before crack starts to grow, in the blunting regime.

Friction behavior of controlled low strength material–soil interface

A controlled low strength material (CLSM) is a highly flowable cementitious material used for trench backfilling. However, when applying vertical loads to backfilled trenches, shear failure or differential settlement may occur at the interface between the CLSM and natural soil. Hence, this study aims to evaluate the characteristics of the interface friction between the CLSM and soils based on curing time, gradation, and normal stress. The CLSM is composed of fly ash, calcium sulfoaluminate cement, sand, silt, water, and an accelerator. To investigate the engineering properties of the CLSM, flow and unconfined compressive strength tests are carried out. Poorly graded and well-graded sands are selected as the in-situ soil adjacent to the CLSM. The direct shear tests of the CLSM and soils are carried out under three normal stresses for four different curing times. The test results show that the shear strengths obtained within 1 day are higher than those obtained after 1 day. As the curing time increases, the maximum dilation of the poorly graded sand–CLSM specimens under lower normal stresses also generally increases. The maximum contraction increases with increasing normal stress, but it decreases with increasing curing time. The shear strengths of the well-graded sand–CLSM interface are greater than those of the poorly graded sand–CLSM interface. Moreover, the friction angle for the CLSM–soil interface decreases with increasing curing time, and the friction angles of the well-graded sand–CLSM interface are greater than those of the poorly graded sand–CLSM interface. The results suggest that the CLSM may be effectively used for trench backfilling owing to a better understanding of the interface shear strength and behavior between the CLSM and soils.

Reuse of volcanic mud to controlled low-strength materials with cement and alkali-activated slag binders

This paper aims to evaluate the applicability of volcanic mud as the fine aggregate for controlled low-strength material (CLSM) by the experimental method. Two types of binder were selected, including cement and alkali-activated slag binders (without cement). The study mainly explored the effects of different addition rates of volcanic mud and different concentrations of alkaline agents (sodium hydroxide) on the engineering properties of CLSM. The test results show that the CLSMs with cement and volcanic mud have better workability and less water bleeding. However, the compressive strength of CLSM decreases as the replacement rate of volcanic mud increases, and the setting time also increases. The replacement rate of volcanic mud is recommended to be 20%. The volcanic mud mixed with the alkali-activated slag binder (without cement) can be successfully made into CLSM. When the concentration of sodium oxide in CLSM is 5%, although the compressive strength is highest at 7 days or 28 days, it cannot be hardened at the early age (before four days) and without compressive strength. CLSM with 20% sodium oxide concentration has poor workability. Its compressive strength is slightly lower than that of the 10% group. Therefore, the amount of calcium hydroxide recommended is 10%.

Evaluation the performance of controlled low strength material made of excess excavated soil

The aim of this work was to investigate the feasibility of partially replacing the sand with excess excavated soil from construction sites in Shanghai to make controlled low-strength material (CLSM). A total of nine mixtures were prepared and tested for its fresh and hardened properties. The experimental results revealed that increasing the soil content can reduce the strength, lower flowability and increase setting time. When sand in the sample was fully replaced by soil, the strength of controlled low-strength material cannot reach 0.35 MPa unless water/cement ratio was lower than 8.5. In addition, the consistence, water stability, and frost resistance of controlled low-strength material decrease as soil content increases. Although too much soil will cause performance degradation, excess excavated soil could be effectively used in controlled low-strength material with proper mix design.

Transforming waterworks sludge into controlled low-strength material: Bench-scale optimization and field test validation

In order to reduce landfill disposal of waterworks sludge (alum sludge) and incinerated sewage sludge ash (ISSA), this study proposed an innovative approach for upcycling them into value-added controlled low-strength materials (CLSM). Waterworks sludge interfered with cement hydration reaction and delayed the stiffening time of CLSM (>10 h) due to its high organics content (5%). The addition of triethanolamine (TEA) with a dosage of 0.1 wt% of binder effectively shortened the stiffening time to 4.5 h. The lab-scale results suggested that the optimal CLSM design (6% cement, 14% ISSA, 8% sludge, and 72% recycled fine aggregate at a water/binder ratio of 1.2) complied with the standard requirement of flowability (>200 mm), stiffening time (<5 h), and compressive strength (0.3–2.1 MPa). The pilot-scale field tests further confirmed that the sludge-incorporated CLSM achieved a high flowability (220 mm), short stiffening time (4 h), low compressive strength (1.38 MPa), and easy re-excavatability after 3 months. This study demonstrated that waterworks sludge can be potentially transformed into sustainable construction materials for urban development.

Impact of planetesimal eccentricities and material strength on the appearance of eccentric debris disks

Context. Since circumstellar dust in debris disks is short-lived, dust-replenishing requires the presence of a reservoir of planetesimals. These planetesimals in the parent belt of debris disks orbit their host star and continuously supply the disk with fine dust through their mutual collisions. Aims. We aim to understand effects of different collisional parameters on the observational appearance of eccentric debris disks. These parameters are the eccentricity of the planetesimal belt, dynamical excitation, and the material strength. Methods. The collisional evolution of selected debris disk configurations was simulated with the numerical code ACE. Subsequently, selected observable quantities are simulated with our newly developed code DMS. The impact of the eccentricity, dynamical excitation, and the material strength is discussed with respect to the grain size distribution, the spectral energy distribution, and spatially resolved images of debris disk systems. Results. The most recognizable features in different collisional evolutions are as follows. First, both the increase of dynamical excitation in the eccentric belt of the debris disk system and the decrease of the material strength of dust particles result in a higher production rate of smaller particles. This reduces the surface brightness differences between the periastron and the apastron sides of the disks. For very low material strengths, the “pericenter glow” phenomenon is reduced and eventually even replaced by the opposite effect, the “apocenter glow”. In contrast, higher material strengths and lower dynamical excitation of the system result in an enhancement of asymmetries in the surface brightness distribution. Second, it is possible to constrain the level of collisional activity from the appearance of the disk, for example, the wavelength-dependent apocenter-to-pericenter flux ratio. Within the considered parameter space, the impact of the material strength on the appearance of the disk is stronger than that of dynamical excitation of the system. Finally, we find that the impact of the collisional parameters on the net spectral energy distribution is weak.

Thermoelastic deformation and failure of rubberlike materials

In many practical applications rubber components are exposed to relatively high operating temperatures yet very few studies can be found in the literature that deal with the temperature influence on deformation and, especially, failure of rubberlike materials. In the present work, we partly fill this gap providing the experimental results on uniaxial tension and bulge tests for nitrile butadiene rubber, neoprene, and silicone for various temperatures in the range from 20°C to 90°C. Based on the results of the tests we develop novel thermoelastic constitutive models, which also incorporate a failure description via the method of energy limiters. Using the developed models, we study the cavitation problem under the elevated temperatures. We find that, generally, the heating might lower material strength while the material stiffness is not necessarily sensitive to the temperature alterations.

Engineering Properties of Controlled Low-Strength Materials Containing Bottom Ash of Municipal Solid Waste Incinerator and Water Filter Silt

The bottom ash of a municipal solid waste incinerator (MSWI) and water filter silt (WFS) were applied to a controlled low-strength material (CLSM) in the present study. The CLSM of the control group was composed of cement, water, and fine aggregates. WFS was first used as a fill material to replace 10% of the volume of natural fine aggregates in the CLSM. MSWI bottom ash was used to replace 0%, 25%, 50%, 75%, and 100% of the volume of the remaining natural fine aggregates with a water-cement ratio of 1.6. The engineering properties of freshness, hardening, and durability were examined. The results revealed that the slump flows of all of the mixture proportions ranged between 50 and 70 cm. The tube flow ranged between 20 and 30 cm, conforming to ASTM D6103 and construction regulations regarding CLSMs stipulated by the Water Resources Agency of the Ministry of Economic Affairs in Taiwan. Increases in the replacement amount of MSWI bottom ash prolonged the time required to achieve a resistance to penetration of 2.74 MPa. The diameter of the drop test ball was less than 7.6 cm, indicating that the mixture proportions had sufficient bearing capacity for successive construction. At an age of 28 d, the compressive strength did not exceed the 8.4 MPa prescribed in ASTM D4832. The ultrasonic pulse velocity and water absorption exhibited identical growth tendencies. In summary, using MSWI bottom ash to create CLSMs is feasible on the condition that the appropriate amount of WFS should be added.

Thermal conductivity of controlled low strength material (CLSM) under various degrees of saturation using a modified pressure plate extractor apparatus – A case study for geothermal systems

Conventionally, controlled low strength material (CLSM) is defined as a self-compacting and self-leveling material. High thermal conductivity CLSM can be, however, used as the heat transfer medium (thermal grout) in geothermal systems due to its good flowability and low shrinkage. Similar to general soils or earlier developed thermal grouts, the degree of saturation of CLSM is strongly related to its thermal conductivity, which is an input parameter in the design of geothermal systems. Hence, this relationship should be explored for the optimum design in these systems. This paper addresses the thermal conductivity of CLSM made with coal ash and excavated soil as a function of the degree. In order to do this, the pressure plate extractor apparatus (SWC-150) was modified by coupling with a single thermal needle probe. In the experimental program, all general properties (e.g. flowability, bleeding, fresh density, initial setting time, and unconfined compressive strength) were performed first. Afterward, thermal conductivity, the degree of saturation, and matric suction were measured simultaneously by the modified apparatus. As a result, all general properties of the prepared CLSM satisfied the specifications of CLSM. In addition, linear relationships between thermal conductivity and degree of saturation of the proposed CLSM mixtures were observed. It is interesting to note that thermal conductivity of CLSM incorporating excavated soil, which works as filler the CLSM mixture, was relatively improved when compared to that of CLSM without excavated soil. Finally, new predictive models for thermal conductivity estimation of CLSM were proposed based on both normalization and regression methods.

Thermal Conductivity of Controlled Low Strength Material (CLSM) Made Entirely from By-Products

Various by-products generated from thermal power plants and chemical industries have considerably economic and environmental impacts in South Korea. This study focuses on evaluating thermal conductivity of controlled low strength material (CLSM) made entirely from by-products (e.g., coal ash, gypsum, red mud). In the experimental program, pond ash is used as a full replacement of natural sand whereas fly ash activated by a little lime, red mud, and gypsum is the main binder in the production of CLSM. Various laboratory tests including flowability, bleeding, initial setting time, and unconfined compressive strength were performed on the prepared CLSM mixtures to determine its general characteristics. Thermal conductivity is then measured subjected to saturated curing condition (SC) and room temperature curing condition (RTC). As a result, all general characteristics meet the specification of CLSM reported in ACI 229R by controlling the ratio of gypsum to red mud. In particular, the good flowability of higher than 20 cm is observed as the G/Rm ratio of smaller than 1.33. The bleeding values, ranging from 0.30% to 2.70%, fall into the bleeding requirement of CLSM of less than 5%. Moreover, the initial setting time and strength results are also in the acceptable specification of general CLSM in ACI 229R. Eventually, the thermal conductivity of the proposed CLSM was in the range of 0.84–0.87 (W/mK) and these values were considerably affected by the saturation states and curing conditions rather than binder proportion.

Dynamic Properties of Controlled Low-Strength Materials with Treated Oil Sand Waste

AbstractThe use of controlled low-strength materials (CLSM) is rapidly expanding in many geotechnical applications as designer backfill, especially foundations subjected to dynamic loading. This pa...

The study of material flow behaviour in dissimilar material FSW of AA6061 and Cu-B370 alloys plates

Friction stir welding is a solid-state joining process which proved to be very effective for similar low strength materials. However, the joining of dissimilar materials is far complex than the similar materials because of divergent material properties. The need to study friction stir welding of dissimilar materials is inevitable due to increasing demand of modern industries. In the current study, the joining of aluminium alloy (AA-6061) and copper alloy (Cu-B370) plates is accomplished for studying the material flow movement throughout welding zone. A novel material flow model for dissimilar material friction stir welding is proposed based on the temperature and strain rate dependent material properties. The model used the volume of fluid (VOF) approach in the commercial FVM package ANSYS fluent 14.5. Experiments are also conducted to validate the model with thermal profiles and optical micrographs. Furthermore, the effect of tool rotational and the welding speed are studied on the material movement. It is found that process parameter had a huge impact on the nugget zone formation during the welding. The tool rotaion and welding speed directly affect the amount of platisized material mixing.

Controlled Low Strength Material for Emergency Restoration Using Bottom Ash and Gypsum

Controlled Low Strength Material for Emergency Restoration Using Bottom Ash and Gypsum

A CFD simulation of CLSM filling with piping on Herschel–Bulkley rheological model

In order to study and predict the flowing behaviour of controlled low-strength material (CLSM) slurry filling with piping transportation, a three-dimensional computational fluid dynamics simulation is carried out based on the Herschel–Bulkley (H-B) rheological model. The simulation is validated by L-pipe flow experiments of CLSM on the flow time and flow pattern. The analysis results show that it is reliable to use the H-B model to simulate the flow of the CLSM slurry. On this basis, simulations are performed to predict the dynamic characteristics of CLSM slurry filling with piping transportation and analyse the velocity distribution and pressure variation in pipeline. The simulation results are consistent with the basic law of power flow, which proves the rationality and effectiveness of the method. The study on the filling characteristics of CLSM slurry pipeline lays a theoretical foundation for the realisation of low-cost, safe and efficient filling of abandoned pipelines.

The Performance of Controlled Low-strength Material Base Supporting a High-volume Asphalt Pavement

A lack of proper base and subbase materials in pavement construction is one of the common problems in the tropical region worldwide. In many countries such as Thailand, cementitious materials are usually used for ground improvement. Controlled Lowstrength Material (CLSM) was considered in this study as a pavement base material. The CLSM mixes were prepared by varying cement, fly ash and fine aggregate content. Each mixed component was studied for their physical and chemical properties. After mixing, properties of the CLSM were investigated based on the standard testing of fresh concrete and cement-treated base material. The flowability, setting time and bleeding were checked to ensure that the CLSM were self-compacting. The mechanical properties of hardened CLSM were determined by means of CBR, unconfined compressive strength and resilient modulus tests. The resilient modulus results were used in the analytical design of flexible pavement with CLSM base. The critical traffic data under high-volume road collected by the Thailand Department of Highway was adopted in this study. Results show that the CLSM base considerably increased the performance as well as design life of asphalt pavement compared with the conventional crush rock base pavement.

Potential of Rice Husk Ash (RHA) as a Supplementary Cementitious Material in Concrete

Abstract Supplementary cementitious material (SCM) is often used to make concrete more durable by improving its mechanistic properties. Rice husk ash (RHA) has the potential of being a SCM because of its pozzolanic activity. Arkansas produces a huge amount of RHA, which mostly originates from the world’s largest rice miller, Riceland Foods, Inc. The RHA produced here is treated as an agricultural waste product and stored in nearby temporary storages, resulting in costly disposal processes as well as environmental hazards. Because the potential of this local RHA as a SCM has not been studied in the past, the present research study aims at exploring the potential of RHA as SCM through laboratory-based experiments. Three different graded RHA (600-RHA, 150-RHA, and 44-RHA) were incorporated in this study. The 600-RHA and 150-RHA were coarse in nature as they had a particle size of 600 μm and 150 μm, respectively, and did not meet the AASHTO M 321-04, Standard Specification for High-Reactivity Pozzolans for Use in Hydraulic-Cement Concrete, Mortar, and Grout, specification. The 600-RHA sample was collected from a plant site and was further ground to produce the 150-RHA sample. The 44-RHA sample was obtained from a commercial industry, and it was incorporated in this study for comparative analyses. Each type of RHA with two different percentages (10 % and 20 %) of replacement of Type I Ordinary Portland Cement (OPC) was investigated in this research. It was found that coarser RHA-modified concrete (600-RHA and 150-RHA) showed reduced strength properties while finer RHA (44-RHA) exhibited improved concrete properties. As a result, 44-RHA can be used as SCM in replacement of the OPC. The coarse RHA could be utilized in backfill and flowable fill as controlled low strength material. Further grinding of the coarse RHA followed by burning may improve the properties of modified concrete.