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Soil Cement


Published on Nov 24, 2016

Abstract

Soil-cement is a highly compacted mixture of soil/aggregate, portland cement, and water. Soil-cement differs from Portland cement concrete pavements in several respects. One significant difference is the manner in which the aggregates or soil particles are held together. A Portland cement concrete pavements mix contains sufficient paste (cement and water mixture) to coat the surface area of all aggregates and fill the void between aggregates.

In soilcement mixtures, the paste is insufficient to fill the aggregate voids and coat all particles, resulting in a cement matrix that binds nodules of uncemented material. It is widely used as a low-cost pavement base for roads, residential streets, parking areas, airports, shoulders, and materials-handling and storage areas. Its advantages of great strength and durability combine with low first cost to make it the outstanding value in its field. A thin bituminous surface is usually placed on the soil-cement to complete the pavement.

The cost of soil-cement compares favorably with that of granular-base pavement. When built for equal load-carrying capacity, soil-cement is almost always less expensive than other low-cost pavements. Economy is achieved through the use or reuse of in-place or nearby borrow materials. No costly hauling of expensive, granular- base materials is required; thus both energy and materials are conserved. The major engineering benefits of cement stabilization are increased strength, stiffness, better volume stability and increased durability.

The improvement of the unconfined compressive strength (UCS) of LSC composite was also evaluated. As regards the application aspect, the results shows that cement mixed lateritic soils are suitable for base course construction. The investigation also shows that increase in UCS was attributed to the cement hydration within soil mass, resulting in the formation of reaction products as analyzed by XRD. It was also found that UCS was proportionally increased with the amount of the major reaction products such as calcium silicate hydrate (CSH). They used the Portland cement is a popular additive for stabilization. They carried out unconfined compression test and UCS of composite soil cement was determined at various curing ages. From this they observed that UCS increased with increasing cement content as well as with increasing time of curing.A quantitative assessment of soil mineral composition was performed using X-RAY diffractometer, XRD, PHILIPS X’Pert MPD, Netherlands.

Soil Cement

Objective of the Work

 To study about soil cement roads.

 To study about construction methods.

 Discuss about various properties of soil cement roads.

 Discuss about advantages and disadvantages of soil cement roads.

Soil Cement Road

Soil-cement is a highly compacted mixture of soil/aggregate, Portland cement, and water. Soil-cement differs from Portland cement concrete pavements in several respects. One significant difference is the manner in which the aggregates or soil particles are held together. A Portland cement concrete pavements mix contains sufficient paste (cement and water mixture) to coat the surface area of all aggregates and fill the void between aggregates. In soilcement mixtures, the paste is insufficient to fill the aggregate voids and coat all particles, resulting in a cement matrix that binds nodules of uncemented material. It is widely used as a low-cost pavement base for roads, residential streets, parking areas, airports, shoulders, and materials-handling and storage areas. Its advantages of great strength and durability combine with low first cost to make it the outstanding value in its field.

A thin bituminous surface is usually placed on the soil-cement to complete the pavement. material used for soil cement are soil cement and water. The use of soil-cement can be of great benefit to both owners and users of commercial facilities. Its cost compares favorably with that of granular-base pavement. When built for equal load carrying capacity, soil-cement is almost always less expensive than other low-cost site treatment or pavement methods. The use or reuse of in-place or nearby borrow materials eliminates the need for hauling of expensive, granular-base materials; thus both energy and materials are conserved.

Performance of Soil Cement

Soil-cement thicknesses are less than those required for granular bases carrying the same traffic over the same subgrade. This is because soil-cement is a cemented, rigid material that distributes loads over broad areas. Its slab-like characteristics and beam strength are unmatched by granular bases. Hard, rigid soil-cement resists cyclic cold, rain, and spring-thaw damage. Cement stabilizes soil in two ways. First, it reduces soil plasticity, especially for the soil in which there is high amount of clay particles.

The second is cementation which is very important because clay is not its main composition. In fine grained silty and clayey soils, the hydration of cement develops strong linkages between the soil aggregates to form a matrix that effectively encases the soil aggregates. Old soil-cement pavements in all parts of the continent are still giving good service at low maintenance costs. Soil-cement has been used in every state in the United States and in all Canadian provinces. Specimens taken from roads show that the strength of soil-cement actually increases with age; some specimens were four times as strong as test specimens made when the roads were first opened to traffic. This reserve strength accounts in part for soil-cement’s good long-term performance.

Types of Soil Used

The soil material in soil-cement can be almost any combination of sand, silt, clay, gravel, or crushed stone. Local granular materials, such as slag, caliche, limerock, and scoria, plus a wide variety of waste materials including cinders, fly ash, foundry sands, and screenings from quarries and gravel pits, can all be utilized as soil material. Old granular-base roads, with or without bituminous surfaces, can also be reclaimed to make great soil-cement. Soil-cement is sometimes called cement-stabilized base, or cement-treated aggregate base. Regardless of the name, the principles governing its composition and construction are the same. But it is not suitable for all types of soil such as organic soil, acid soil, sulfate soil and uniform sand.The soil becomes stabilized because the cement reacts chemically with the soil particles and bind them together. But these above soil containing component prevent the chemical reaction.

Proportioning / Spreading

The cement shall be applied in one operation to the required width, grade and cross section. Cement shall be evenly applied at the designated rate and shall not vary more than 10 percent on any area. The percent cement is based on the in-place dry weight of the soil to be treated or as determined by the engineer. The calibrated spreader able to provide a uniform distribution of the cement throughout the treatment area shall apply cement. The cement shall be added in a dry state and every precaution shall be taken to prevent dusting outside the treatment area.

Tailgate application of cement will not be permitted. Tailgating is defined as having manual control of the spread rate, rather than automatic. The spreader truck shall demonstrate the ability to maintain a consistent spread rate over variable travel speeds. The contractor will demonstrate the consistency of the application rate by conducting multiple pan tests. The pan test consists of placing a 3 square foot pan on the grade in front of the spreader truck. After cement has been applied, the cement is weighed to determine the rate of application in pounds per square foot. No traffic other than the mixing equipment or other related construction equipment will be allowed to pass over the exposed cement until after completion of mixing. The figure 5.1 shows the speading of cement using spread truck.

Soil Cement

Conclusion

The use of soil-cement can be of great benefit to both owners and users of commercial facilities. Its cost compares favorably with that of granular-base pavement. When built for equal load carrying capacity, soil-cement is almost always less expensive than other low-cost site treatment or pavement methods. The use or reuse of in-place or nearby borrow materials eliminates the need for hauling of expensive, granular-base materials, thus both energy and materials are conserved. It is not only benefit to the human but also benefit to the environment.

The crushed rock production process consumes a considerable amount of energy for mining, transportation, burning and which contributes to the total CO2 emissions to the atmosphere. The environmental issues to be addressed include the need to reduce the levels of CO2 emissions. The major engineering benefits of soil cement roads are increased strength, stiffness, better volume stability and increased durability.