Cement-stabilized Aggregate Research Articles

Utilization of Tunnel Waste Slag for Cement-Stabilized Base Layers in Highway Engineering.

The rapid expansion of highway infrastructure in the mountainous regions of China has led to a significant increase in tunnel construction, generating substantial amounts of tunnel waste slag. Concurrently, the development of transportation infrastructure has created a critical shortage of natural aggregates, necessitating the exploration of alternative sustainable sources. This study aimed to conduct a comprehensive evaluation of the physical and mechanical properties of tunnel waste slag and explore its potential for utilization in cement-stabilized base courses for highway engineering applications. The uniaxial compressive strength of the parent rock (tunnel waste slag) ranged from 81 MPa to 89 MPa in the desiccated state, indicating its suitability for use as a construction material. This study also determined the maximum dry density (2.432 g/cm3) and optimal moisture content (5.4%) of cement-stabilized mixtures incorporating recycled aggregates derived from tunnel waste slag. The splitting tensile strength of these mixtures at 28 days varied from 0.48 MPa to 0.73 MPa, demonstrating robust mechanical performance. Moreover, the unconfined compressive strength of these mixtures escalated from 7.0 MPa at 7 days to 11.0 MPa at 90 days, signifying a substantial enhancement in strength over time. These results validate the viability of utilizing tunnel waste slag in highway engineering and furnish valuable insights for designers, concrete manufacturers, and construction firms engaged in the development of cement-stabilized aggregate base courses.

Effect of Public Fillers on Cement-Stabilized Recycled Mixes of Road Performance: Mechanical Properties, Microstructure, and Durability.

In order to address the challenges of resource utilization posed by construction waste, the substitution of natural aggregate (NA) with public fill (PF) contents was investigated for load reclamation and road grassroots applications. A comprehensive assessment of road performance for the recycled mixture was conducted, focusing on parameters such as unconfined compressive strength, splitting strength, compressive resilience modulus, dry shrinkage, and frost resistance. Additionally, the impact of incorporating PF at various types and replacement ratios on the microstructure of cement-stabilized aggregate (CSA) was analyzed. The results indicated that the unconfined compressive strength of cement-stabilized recycled mixture with varying PF contents meets the base strength requirements for heavy, medium, and light traffic pavement on secondary and sub-secondary roads in China. Notably, the unconfined compressive strength and resilience modulus follow a similar pattern, reaching their peak at a 25% PF content. Microscopic examination reveals that an appropriate PF content leads to the predominant formation of C(N)-A-S-H, hydrotalcite, Ca(OH)2, and CaCO3 as paste reaction products. As the replacement of public fill increases from 0% to 25%, there is a gradual stacking of gel products, which enhances the compactness of the microstructure by cementing together unreacted particles. Consequently, this process reduces dry shrinkage strain and effectively mitigates the formation of reflection cracks. Applying large quantities of public fill to road construction can effectively deal with various waste accumulation problems and produce a novel road material with significant social, economic, and environmental benefits.

Freeze–Thaw Performance Trends of Short-Term Cured Cement-Stabilized Aggregate Quarry By-Product Materials

Recent research studies conducted at the Illinois Center for Transportation focused on sustainable applications of quarry-by-products (QB) as pavement foundation materials and demonstrated the superior durability performance of dolomitic aggregate materials exposed to long-term cementitious reaction and repeated freezing and thawing. This study investigated the influence of QB chemical composition on the strength of cement-stabilized samples exposed to freeze–thaw cycles. Dolomitic QB materials from different quarries in Illinois and with different magnesium oxide (MgO) content, and a control limestone sample were chemically characterized by X-ray fluorescence and X-ray diffraction techniques. The QB materials were then stabilized with 3% cement and subjected to a 7-day curing period, followed by freeze–thaw conditioning. Unconfined compressive strength and resonant frequency tests were conducted to examine how the percentage of MgO and dolomitic minerals could alter the strength/stiffness with freeze–thaw cycles. Optical microscopy analysis was also performed to observe the extent of microstructure damage with freezing and thawing. Over the course of the applied freeze–thaw cycles, no notable minerology effect on strength or stiffness characteristics was observed for the short-term curing. Instead, performance was predominantly governed by physical properties, such as the particle size distribution, which played a more significant role after short-term curing. Well-graded QB materials with optimum packing, following Talbot’s equation with a 0.45 exponent, consistently exhibited the highest strength after any freeze–thaw cycle. The next phase of research, focusing on long-term curing, is expected to provide more insights into the chemical and mineralogical effects of QB materials on durability performance.

Use of waste rubber particles in cement-stabilized aggregate for the eco-friendly pavement base layer construction: Laboratory performance and field application

The waste tires were utilized for cement-stabilized aggregate (CSA), which could alleviate the environmental problems caused by waste tires and improve the durability of CSA. In this study, rubber particles with sizes ranging between 2.36 ∼ 4.75 mm were added to the CSA and replaced natural aggregate. The rubberized cement-stabilized aggregate (RCSA) was designed in the laboratory and verified in the field test road. The CSA and RCSA specimens were prepared by static pressure compaction and vertical vibration compaction in the laboratory and from field cores. The unconfined compressive strength test, indirect tensile strength test, fatigue test, dry shrinkage test, and temperature shrinkage test were adopted to evaluate the performance of RCSA. The results showed that the addition of rubber reduced the compressive and indirect tensile strength of CSA. However, the vibration compaction method could significantly alleviate the negative impact of rubber on strength reduction. The rubber particles could improve the deformation capacity and fatigue performance of CSA, and the maximum increase in ultimate failure strain was 21.5%. The dry shrinkage strain and dry shrinkage coefficient of CSA were reduced by 12.0% and 18.4%, respectively. The temperature shrinkage strain and temperature shrinkage coefficient decreased by 29.2% and 28.4% after adding rubber particles, respectively. Rubber could improve the durability and cracking resistance of CSA. The RCSA provided an option for an environmentally friendly pavement base layer.

Evaluation of the shrinkage crack resistance of cement-stabilized aggregate by predicting the crack spacing

Shrinkage cracks are a major issue in the manufacture of cement-stabilised aggregate (CSA) bases. This study proposes a novel mechanical method to predict the stress and crack spacing caused by shrinkage in CSA bases. Its effectiveness was found to be 71% by using field data collected from several expressways in Jiangsu Province, China. The predicted maximum crack spacing was used to evaluate the shrinkage crack resistance of CSA with different cement contents, gradations, and forming methods. The results suggest that for a specific gradation, an optimal cement content exists that leads to the best shrinkage crack resistance. The shrinkage crack resistance of a large stone base course (LSBC) filled with CSA was found to be 30% less than that of a typical gradation. Moreover, the shrinkage crack resistance of CSA specimens was improved significantly by vibration compaction forming compared with static pressure forming.

Rubberized cement-stabilized aggregates: Mechanical performance, thermal properties, and effect on temperature fluctuation in road pavements

Temperature change is one of the critical issues causing shrinkage cracking in cement-treated bases. This study aimed to evaluate the effect of incorporating rubber aggregates into cement-stabilized aggregate on temperature fluctuation in semi-rigid pavements. To estimate temperature change, the thermal property test was firstly conducted on rubberized cement-stabilized aggregates, in which the aggregate component (0.425 mm to 9.5 mm) was replaced by rubber aggregates (3–6 mm) at varying volume percentages of 0%, 5%, 10%, and 20%. The experimental results showed that increasing rubber aggregate content reduced the thermal diffusivity, thermal conductivity, and specific heat capacity of the rubberized cement-stabilized base materials. A good correlation between the thermal properties and surface temperature was also observed. These obtained thermal properties were then used in numerical simulations using the ANSYS program. The modelling results demonstrated the potential of rubberized cement-stabilized aggregates in reducing both temperature and temperature fluctuation within semi-rigid pavement structures. Furthermore, despite the detrimental impacts of rubber aggregates on compressive and splitting tensile strengths and compressive resilient modulus, the rubberized cement-stabilized aggregates still met the requirements for pavement bases.

Resurfacing Performance Evaluation of Recycled Mixture with High Content of Iron Tailings Sand

ITS is the main component of industrial solid waste, of which there are about 2 billion metric tons in China. A large number of ITS not only occupy land resources and pollute the environment but also pose major security risks. This study, based on a road resurfacing project in Shanxi Province, China, focused on the “iron tailings sand (ITS) plus reclaimed inorganic binder stabilized aggregate (RAI)” solid waste treatment method, which uses special cementitious material to stabilize ITS and RAI as a new base course material and aims to replace new aggregates by 100% to apply in the renovation project through testing the road performances of the recycled mixture. Although it does not comply with the conventional grading range, the new ITS and RAI mixture (the recycled mixture) can achieve excellent compressive performance from the material composition, and it can meet different levels of design strength under various load conditions by adjusting the mixing ratio (ITS content can reach up to 70%). The pavement performance of the recycled mixture was compared with that of cement-stabilized aggregate (the traditional base course material), and it was evaluated by testing its anti-water damage, frost resistance (dry and wet freeze), shrinkage, and fatigue characteristics. A total of 380 mixtures were tested. The results showed that, at the same strength level, the anti-water damage and frost resistance properties of the recycled mixture were better than those of cement-stabilized aggregate, whereas its shrinkage and fatigue properties were inferior. For anti-water damage properties, the water stability coefficient of the recycled mixture is about 2%~5% higher than that of cement-stabilized aggregate. For the frost resistance property, the wet frost coefficient of the recycled mixture is about 10%~15% higher, and the dry frost coefficient is about 5%~10% higher. The dry shrinkage strain of the recycled mixture is about 50 × 10−6~300 × 10−6 higher than that of cement-stabilized aggregate, and the temperature shrinkage coefficient is about 10 × 10−6~20 × 10−6 higher. Thereafter, the reduction of carbon emissions in engineering applications per kilometer was compared between the recycled mixture and cement-stabilized aggregate. The engineering application in Shanxi Province shows that the carbon reduction is approximately 18.869 t of CO2. In a word, the recycled mixture has excellent pavement performance and reduces carbon emissions.

Fatigue damage calculation of cold recycled asphalt pavement considering measured temperature field and traffic volume distribution

<abstract> <p>A finite element simulation method for fatigue damage calculation and life prediction of pavement structures under the influence of temperature and traffic distribution factors was proposed in this study. Relying on the test cold recycled asphalt pavement structure, the existing distress, pavement structure forms, field monitored temperature and strain were first introduced and analyzed. Then, in constructing the numerical model, the viscoelastic constitutive model was introduced to characterize the effect of temperature and loading conditions on the mechanical response of the hot mix asphalt (HMA) layers and the emulsified asphalt cold recycled (EACR) layer. The damage variables are defined by fatigue equations, and the damage accumulation can be determined by Miner's linear fatigue accumulation theory. To reflect the distribution of traffic volume, the total traffic volume of a year was divided into 144 axle load groups according to the monthly and hourly distribution conditions. Accordingly, based on the monthly maximum and minimum temperature, 12 representative days were selected to represent the climate characteristics of 12 months, respectively. Then, each representative day's measured structural temperature data were extracted every 2 hours and linearly interpolated to obtain 144 representative temperature fields corresponding to 144 axle load groups. Through the above method, simulation calculations were performed for cold recycled asphalt pavement structures with different cement-stabilized aggregate (CSA) base stiffnesses. The results show that the fatigue damage accumulation of the EACR layers reaches its highest value in winter and midday hours, owing to the temperature variation and traffic distribution. Due to the weak fatigue resistance of EACR mixtures, it is not recommended to be paved EACR layers directly on top of the CSA base with poor bearing capacity. Otherwise, fatigue cracking is likely to occur first. For this reason, recommendations for ensuring the durability of the cold recycled pavement structure were also proposed in the study.</p> </abstract>

Meso-cracking characteristics of rubberized cement-stabilized aggregate by discrete element method

As a sustainable solution, embedding rubber inclusions in the semi-rigid pavement base course can ensure the consumption of a large amount of waste tire pollution and improve the mechanical properties of cement-treated base materials. The rubber modification has a potential effect on reducing the possibility of pavement reflective cracks caused by base cracking. This paper aims to investigate the meso-cracking characteristics of rubberized cement-stabilized aggregate (RCSA) mixtures and to quantitatively evaluate the influence of rubber inclusion content and particle size through numerical simulation. The rubber particle size of 0.6–4.75 mm was selected. The virtual RCSA samples were prepared by replacing similar-size aggregates with rubber particles based on the reference mixtures without rubber. Five volumetric replacement contents (20%, 40%, 60%, 80% and 100%) of three gradation ranges (0.6–1.18 mm, 1.18–2.36 mm, and 2.36–4.75 mm) were adopted. An indirect diametric tensile (IDT) simulation test was adopted to obtain the investigated performance of IDT strength, static stiffness, toughness and toughness index. The simulation results show that the incorporation of rubber inclusion has a negative effect on the IDT strength of the RCSA sample. However, material extensibility and post-peak toughness are improved and stiffness is reduced with increasing rubber replacement percentage. The optimal rubber content of the investigated mixtures should be controlled within 80% of the corresponding aggregate gradation volume, which is conducive to controlling the reduction of the overall strength and the play of the extensibility. The strength reduction and ductility improvement of modified concrete are positively correlated with the particle size of rubber inclusion. The modified RCSA mixture with a smaller rubber particle size could ensure a higher IDT strength and extensibility. For the investigated sample, the best comprehensive modification effect can be obtained using the finer rubber substitute with a particle size of 0.6–1.18 mm. The rubber inclusion acts similarly to a cavity defect, which will result in fracture preferring to occur adjacent to the rubber aggregate. Ignoring the adverse effect of strength, the practical implication of rubber incorporation is to improve the ductile behaviour of the RCSA mixture and reduce base cracking. The present numerical simulation methods have the potential to investigate the meso-cracking mechanism of RCSA. It also provides a theoretical guidance for the gradation design of rubberized mixtures.

Study on the Properties and Mechanisms of a Cement-Stabilized Aggregate Mixture With Vibration Mixing

In order to understand the influence of the vibration mixing method on the performance of cement-stabilized aggregate mixture (CSAM), in this study, an unconfined compressive strength test, drying shrinkage test and the influence of gradation characteristics on compressive strength were used to systematically analyze the performance of CSAM based on vibration mixing. At the same time, the influence mechanism of vibration mixing on the interface transition zone of cement aggregate was analyzed by use of a scanning electron microscope (SEM), and the influence of the mixing method on cement dispersion uniformity was studied by the ethylene diamine tetraacetic acid (EDTA) titration method. The results show that 7 days of unconfined compressive strength and crack resistance of the CSAM with vibration mixing is better than those of the ordinary mixing, and the aggregate grade has a great influence on the compressive strength of the CSAM. Vibration mixing can improve the micro-water-cement ratio uniformity of CSAM and significantly improve the bonding condition of the interface transition zone between cement paste and aggregate, thus enhancing the structural compactness of CSAM. The dispersion uniformity of cement under the vibration mixing is better than that of ordinary mixing.

Field Calibration of Fatigue Models of Cementitiously Stabilized Pavement Materials for Use in the Mechanistic-Empirical Pavement Design Guide

The use of cementitiously stabilized materials (CSM), such as lean concrete, cement-stabilized aggregate, and soil stabilized with cement, lime, fly ash, or combinations thereof in the subgrade, sub-base, and base layers of flexible and rigid pavement structures, is a widely accepted practice by many state highway agencies. However, the bottom-up fatigue cracking models of cementitiously stabilized layers (CSL) described in the AASHTO Interim Mechanistic-Empirical Pavement Design Guide Manual of Practice (referred to as the MEPDG) have not been calibrated for CSM based on their field performance. In addition, top-compression fatigue as well as the effects of increases in the modulus and strength values of CSM over time, erosion, and freeze–thaw and wet–dry cycles on the fatigue properties of CSM are not considered in the MPEDG. To address these deficiencies, this research calibrated the bottom-up fatigue model, and developed and calibrated the top-compression fatigue model, with consideration of modulus and strength growth, erosion, and freeze–thaw and wet–dry cycles. Reasonable correlations between the predicted modulus values and measured modulus values are found for CSL. Further study is needed to refine the calibration and validate the models based on a larger population of field data that covers different material types, climatic zones, and traffic conditions.

Characterization of rubberized cement bound aggregate mixtures using indirect tensile testing and fractal analysis

The main focus of this paper is to investigate the tensile properties of virgin and rubberized cement bound granular mixtures. This was conducted using indirect tensile testing with lateral displacement measurements, nondestructive resonant frequency testing, X-ray CT and quantitative assessment for cracking pattern using fractal analysis. The investigated properties were density, compacity, indirect tensile strength (ITS), indirect tensile static modulus, toughness, dynamic modulus of elasticity, dynamic modulus of rigidity, dynamic poison’s ratio, fractal dimension and fracture energy. To keep the same aggregate packing, the natural aggregate was replaced by waste tyres’ crumb rubber of similar gradation. Four volumetric replacement percentages (0%, 15%, 30% and 45%) of the 6mm fraction size were utilized. This adjustment was observed to affect the material density not only due to the lower specific gravity, but because it also affects the compactibility of the mixture negatively due to the damping action of the rubber particles. In addition, strength was also affected detrimentally. However, material toughness was improved and stiffness was mitigated. The latter findings were supported by quantitative assessment of the cracking pattern which revealed more tortuosity and a higher fractal dimension as a result of rubber content increasing. A failure mechanism for this type of mixture was suggested and support by examining the internal structure of failed samples using X-ray CT. Overall, construction of cement-stabilized aggregate base with a small percentage of added crumb rubber may ensure a more sustainable and environmental-friendly pavement material and, at the same time, improve the properties of stabilized layers. However, behaviour of these mixtures under cyclic loading and evaluation of their durability should be assessed to fully validate their use.

The bending fatigue performance of cement-stabilized aggregate reinforced with polypropylene filament fiber

Cement-stabilized aggregate reinforced with polypropylene filament fiber (CAPFF) is a new material for road base course of semi-rigid pavements whose bending fatigue performance has been rarely studied. The paper studied the bending fatigue performances of CAPFF (including two types of CAPFF, i.e., cement-stabilized macadam and gravel respectively reinforced with polypropylene filament fiber) with low mixing content, and then established their bending fatigue equations. Results show that, when under the same stress level, the fatigue life of CAPFF is improved by 1.0–4.2 times comparing with that of ordinary cement-stabilized aggregate. Meanwhile, the analysis of the fatigue equations indicates that, when using fibers, the bending fatigue strength of mixtures is appreciably improved, respectively about 30% in case of CMPFF and about 20% for CGPFF. When the stress level is under 0.75, the enhancement of fiber to cement-stabilized macadam is better than to cement-stabilized gravel; when the stress level is higher than 0.75, a reverse conclusion can be obtained. Ultimately, by the results from microtopography analysis by scanning electron microscope (SEM), the enhancement of the polypropylene filament fiber to the bending fatigue resistance of the cement-stabilized aggregates is analyzed.

The Shrinkage Performance of Flexible Fiber Reinforced Cement-stabilized Aggregate Base

The Shrinkage Performance of Flexible Fiber Reinforced Cement-stabilized Aggregate Base

Study on Freeze-Thaw Performance of Polypropylene Fiber Reinforced Cement-Stabilized Aggregate

Study on Freeze-Thaw Performance of Polypropylene Fiber Reinforced Cement-Stabilized Aggregate

Study on Freeze-Thaw Performance of Polypropylene Fiber Reinforced Cement-Stabilized Aggregate

In this paper, the authors study the anti-freeze-thaw performance of a new type of semi-rigid base material named polypropylene fiber reinforced cement-stabilized aggregate, and freeze-thaw mass loss rate, freeze-thaw compressive strength, freeze-thaw splitting strength are used to evaluate the effect of polypropylene fiber on the anti-freeze-thaw performance, and the relationship of polypropylene fiber content, polypropylene fiber length with the anti-freeze-thaw performance are analyzed. The test after 10 freeze-thaw cycle shows that the mix of polypropylene fiber increase the freeze-thaw compressive strength and freeze-thaw splitting strength, and decrease the mass loss rate greatly. At the same time, the paper also determine the reasonable fiber content and fiber length, under this mix proportion, the mass loss rate reduce by 80%, the freeze-thaw compressive strength increase more than 12.1% and freeze-thaw splitting strength increase more than 13.4%. This research has laid an important foundation for the follow-up research and practice.

Evaluation of the Impact of Fines on the Performance of Lightly Cement-Stabilized Aggregate Systems

The impact of increasing fines content on the performance of unbound (unstabilized) and lightly stabilized aggregate systems was evaluated. The aggregate systems analyzed varied in amount of mineral fines, the moisture state during curing and at the time of testing, and the amount of portland cement used to stabilize the blend. The evaluation was based on measurements of anisotropic resilient properties, permanent deformation, and unconfined compressive strengths of aggregate systems. In addition, the nonlinear anisotropic resilient properties of the aggregate blends were used in a finite element program to determine critical pavement responses. Aggregate systems with higher fines content were, as expected, more sensitive to moisture than control systems with standard fines content. The increase in the fines content in the unbound systems when molding moisture was wet of optimum dramatically diminished the quality of performance. However, the aggregate systems with higher fines benefited considerably from low percentages of cement stabilizer. It was found that with the proper design of fines content, cement content, and moisture, the performance of the stabilized systems with high fines content can perform equivalent to or even better than the systems with standard fines content. This was clearly evinced by enhancing the resilient properties (increase in stiffness and decrease in anisotropy), decreasing the rate and magnitude of permanent deformation, and increasing compressive strength. The beneficial use of mineral fines will result in benefit to the aggregate industry.