Cement Stabilized Base Course Research Articles

Investigation of the performance of cement-stabilized magnesium slag as a road base material

The harmless, resource-saving, and large-scale utilization of magnesium slag (MS) from industrial waste has become an important topic for road research. The use of MS as a substitute for aggregate is a practical and efficient way to dispose of it. However, there is a lack of systematic research on how to standardize its use in road construction. The objective of this study was to investigate the applicability and feasibility of using MS for cement stabilized base course materials. The influence of different cement dosages, curing age, and gradation on the strength, stiffness and stability of cement-stabilized magnesium slag mixture (CMSM) was investigated, and the actual road performance of CMSM was analyzed by paving a test road. The results showed that the mechanical properties of the CMSM met the requirements for road base courses under medium-to-light traffic when the cement dosage was above 5%. The unconfined compressive strength loss rate of the CMSM was less than 13% for an immersion time of 1 to 7 days, and after 5 freeze–thaw cycles, the frost resistance coefficient of the CMSM was more than 85%. The performance of the CMSM was most affected by cement dosage and curing age, closely followed by mixture grading type. MS can enhance the development of the pozzolanic reaction, resulting in improved strength and compactness of CMSM. Overall, CMSM exhibited exceptional road performance and could reduce aggregate costs by 25% to 35%. The use of MS as an aggregate for road base courses offers a sustainable solution that not only maximizes the use of solid wastes, but also avoids the potential safety hazards and environmental pollution caused by improper disposal and stockpiling of MS.

Research on Water-saving, Moisture-keeping and Curing Technology of Cement Stabilized Base Course of Highway

The cement stabilized macadam base has excellent road performance and economy, and it is widely used. However, cement stabilized macadam also has some shortcomings such as poor anti-scour ability and insufficient frost resistance. To solve this problem, this study uses Scanning Electron Microscope (SEM) to analyze the micro-morphology of the specimen surface under four curing methods, namely moisturizing film, sack, polyethylene film and curing room, explaining the mechanism of curing methods affecting the anti-scour performance of cement stabilized macadam. Through the experimental study of anti-scour performance, it was found that the water-saving and moisturizing film was the closest to the experimental condition of curing in the curing room; the scour rates of the specimens of health-preserving sacks and polyethylene films were both high, and they were respectively 12.1g and 16.7g at 15m; through the experimental study of frost resistance, it was found that these curing methods had little influence on the frost resistance of cement stabilized macadam, and the ratio of compressive strength exceeded 0.6%.

Evaluating Cement Treated Aggregate Base Containing Steel Slag: Mechanical Properties, Volume Stability and Environmental Impacts.

Steel slag has been commonly used in road engineering as cementitious material; however, its application in base course is not widely reported. Four contents of steel slag (0%, 30%, 50%, 75% by volume) were blended into different cement (3%, 4%, 5%, 6% by weight)-treated aggregates. Mechanical properties, volume stability, economic benefits and environmental influences of steel slag mixtures were investigated for the feasibility of applying steel slag in semi-rigid base course. Abrasion, crushing and elongated particle content were compared against limestone aggregate, showing that steel slag has the potential of replacing natural aggregate in concrete. Steel slag is beneficial for reinforcement of the strength and stiffness. The mixture has the highest strength and stiffness when bended with 50% steel slag at 4% cement content. By treating steel slag with CH3COOH or adding silica fume, volume expansion of steel slag can effectively be controlled. Larger size steel slag (>4.75 mm) and higher cement content are recommended due to heavy metal leaching risk, especially in salty humid areas. Steel slag has sound economic benefits due to the relatively low price. Environmental benefits can also be achieved given that the transport CO2eq emission of steel slag is accounted for. With proper control in production process, steel slag is a very promising alternative material to be utilized in cement-stabilized base course in road engineering.

Experiment on Gyratory Compaction of Cement Stabilized Base Course Materials

Experiment on Gyratory Compaction of Cement Stabilized Base Course Materials

Shrinkage Characteristics and Modeling of Cement Stabilized Road Pavement Bases: A Compaction Delay Investigation

One of the main failure modes of a cement-stabilized road pavement base is the shrinkage cracking which could lead to negative consequences up to the failure of road pavements. The compaction time delay and cement content inherently affect to the shrinkage characteristics of the cement stabilized base course. This research aims to investigate the shrinkage characteristics with respect to the compaction time delay of a cement-stabilized base material through laboratory experiments. A series of shrinkage tests were performed on cement stabilized base samples with varying 3%, 4% and 5% of cement contents under controlled compaction delay periods varied from 0.5 hours to 1 day. The results of this study showed that shrinkage values of the study cement stabilized base increase with longer compaction time delay periods and cement contents. In addition, during an early stage (1-14 days) of shrinkage tests, shrinkage sharply increases before reaching the stage of a relatively constant rate after 14 days of testing. It would also be further notice that around 80% of the maximum shrinkage values from all tests gains in a test period between 14-21 days out of 42 days of a total shrinkage measurement period. Finally, the mathematic shrinkage model was formulated based on the test results of the study. In the model, the main factors of compaction delay time, cement content, and curing periods were used as the model variables. Shrinkage values can be predicted with a reliability of the R2 value of 0.6755.

Characteristics of dry shrinkage and temperature shrinkage of cement-stabilized steel slag

The objective of the present study was to investigate the characteristics of dry shrinkage and temperature shrinkage of cement-stabilized steel slag (CSS). The steel slag was intended to be utilized to replace the macadam in cement-stabilized base course to reduce dry shrinkage and temperature shrinkage of semi-rigid base materials. Dry shrinkage and temperature shrinkage tests were performed to analyze the water loss rate, dry shrinkage strain, dry shrinkage coefficient and temperature shrinkage strain of CSS and cement-stabilized macadam (CSM) as functions of time, cement content and gradation types of the material. The water loss rate of CSS increased with the rise in time, and then tended to be flat on about 10th days. The hygroscopicity of coarse gradation CSS was larger than those of intermediate gradation and fine gradation CSS. With the same gradation, the more the cement content was, the greater the water loss rate was. It was suggested that the cement content of CSS should not be more than 4%, which can obviously reduce the dry shrinkage strain. Compared with CSM, CSS with rational adjustment of gradation owned a smaller dry shrinkage strain and would not produce a larger temperature shrinkage strain. It is feasible to replace the base macadam with waste steel slag, which is beneficial to improve the characteristics of dry shrinkage and temperature shrinkage of semi-rigid base material and utilization of waste steel slag. This paper aims to provide a solid theoretical foundation to popularize the wide utilization of CSS in engineering applications.

Dynamic Modulus Measurements of Bound Cement-Treated Base Materials

One of the most common methods used in road-pavement construction is the stabilizing of the conventional pavement base course layer. This is achieved by adding cement or lime to gain better material performance. However, obtaining modulus input parameters from a cement-stabilized base course layer for pavement-response analysis under real traffic conditions has proven difficult in that, to date, only ambiguous results have been produced. Using the flexural modulus or elastic modulus in the response analysis has certain limitations in embracing real pavement behavior under traffic and temperature conditions. Accordingly, a more reliable modulus input parameter for pavement analysis under traffic (cyclic) loads is required to obtain more precise and reliable outputs. Moreover, there is, at present, no test protocol to determine a suitable modulus for a cement-stabilized base material under the cyclic loading regime. This study aims to examine the real dynamic responses of cement-stabilized base course materials with a view to adapting the asphalt mixture performance tester (AMPT), a specifically designed dynamic modulus test machine used on asphalt concrete material. The AMPT dynamic modulus test has as an advantage in that loading and temperature regimes based on real pavement conditions can be rationally simulated and directly applied to the test samples. As such, the dynamic moduli of a cement-stabilized base course material can be obtained under different temperature and loading rates. Moreover, the effects of the dynamic strain range, cement content, and curing duration on the dynamic responses of a cement-stabilized base course material may also be examined. Cement-stabilized base course materials of 4 %, 5 %, and 6 % cement contents (by mass) were used as the study materials. The findings of this study indicate that curing durations and cement contents significantly influence the dynamic modulus values of cement-stabilized base course materials. However, the dynamic modulus is insignificantly affected by the changes in temperature and loading rates within a specific range of testing conditions in this study. The test results also reveal that cement-stabilized base course materials under examination behave in the manner of an elastic material when subjected to an axial compressive deformation of 45–105 μstrains. This is because of the dynamic modulus having no impact upon changes in the dynamic strain ranges or on the magnitudes of cyclic loads. Moreover, the dynamic moduli from this study were found to be much higher than the elastic moduli suggested by previous studies. However, the flexural moduli, which are derived from standard flexural tests, demonstrated close values to those of the dynamic moduli obtained in this study. In the study, the dynamic modulus of cement-stabilized base course materials, derived from the dynamic modulus using AMPT, could more reasonably embrace the dynamic responses of a material under traffic-loading conditions. This leads to a somewhat more reliable modulus input for the cement-stabilized base course materials used in a rational pavement design and analysis method.

Development and Validation of a Mechanistic Recursive-Incremental Deterioration Model for Cement-Stabilized Base Courses

Contemporary pavement analysis and design is increasingly relying on recursive–incremental analysis in the prediction of pavement performance. This paper describes the development and calibration of a model for the prediction of deterioration of cement-stabilized base course layers. The model was developed on the basis of full-scale testing of six pavements with different aggregate compositions and strength characteristics. The model was then validated against measured performance on actual motorway sections, and it was found that it could be applied directly without any shift factor functions. The result is a central estimate recursive–incremental model suited for application in performance-simulation design systems and a generalized set of equations defining mechanistic–analytical design criteria.

Development and Validation of a Mechanistic Recursive-Incremental Deterioration Model for Cement-Stabilized Base Courses

Contemporary pavement analysis and design is increasingly relying on recursive-incremental analysis in the prediction of pavement performance. This paper describes the development and calibration of a model for the prediction of deterioration of cement-stabilized base course layers. The model was developed on the basis of full-scale testing of six pavements with different aggregate compositions and strength characteristics. The model was then validated against measured performance on actual motorway sections, and it was found that it could be applied directly without any shift factor functions. The result is a central estimate recursive-incremental model suited for application in performance-simulation design systems and a generalized set of equations defining mechanistic-analytical design criteria.

Behavior of Fiber-Reinforced Cement-Stabilized Fly Ashes

A laboratory experimental study was carried out on two Indian fly ashes to investigate their compressive strength and flexural behaviors as cement-stabilized and fiber-reinforced base course materials. The cement content was chosen to comply with the criteria specified by the Electric Power Research Institute. The fiber reinforcement was in the form of randomly oriented polymeric fibers. Unconfined compression tests and flexure tests were conducted on specimens stabilized with cement alone and with both cement and fibers. The experimental program included the determination of the chemical composition of the raw fly ashes, and scanning electron microscopy and x-ray diffraction tests of the raw and stabilized fly ashes. The study showed that, in general, the fiber inclusions improved the performance of the cement-stabilized fly ash specimens.

Sulfate Attack on Cement-Stabilized Sand

A 3.5-km (2.2 mi) section of a road in Georgia developed unexpected transverse bumps within 6 months after construction. The source of the bumps appeared to be expansion within the cement-stabilized base course. Laboratory examination of samples from areas showing distress revealed the presence of ettringite, a calcium sulfoaluminate the formation of which can be accompanied by severe expansion. This expansive materials was the probable cause of the volume changes causing the transverse bumps. The calcium and alumina needed to form ettringite ware available from the portland cement and the stabilized soil`s clay minerals. The source of the sulfur was identified as the well water that was mixed with the cement-stabilized base. Sulfate attack of cement-stabilized soils is a relatively infrequent problem, but it is highly destructive when it occurs. Currently, there are no firm criteria for identifying when sulfate attack of a cement-stabilized soil is a potential problem nor are there established methods of preventing the attack.

Soil properties and pavement performance in the Niger Delta

Abstract The pavement conditions of roads in the Niger Delta and the geotechnical properties of the soil materials used in constructing them were studied in an attempt to find permanent solutions to the recurrent widespread pavement failures in the region. The most severe surface deformations, pavement cracking and failures occur in the seasonally flooded fresh/salt water swamps because of the high water table, poor drainage and the very fine-grained (> 70 0.000000ines) silty clays/clays used. It is suggested that a pavement design consisting of well compacted, subgrade/sub-base, cement stabilized base course, paved shoulders and good drainage would ensure good performance and avoid the expensive haulage of better base materials from long distances.