Abstract
Some natural resources such as gravel are not renewable, therefore, it is necessary to reduce the use of such resources and replace them with other recycled, economic, and environmentally friendly materials. Recycled crushed concrete aggregates demolished from old buildings and blocks of waste concrete can be used to replace the natural aggregates. The present study focused on using recycled crushed concrete in improvement the chemical and geotechnical properties of soft soil having undrained shear strength of 6.78 kPa. The soft soil samples were mixed with 5, 10, and 15% of crushed concrete. The blocks of waste concrete are grinded by mills to get crushed concrete which passing sieve no. 4. Such aggregates are lighter than natural aggregates and provide a good deformation modulus when mixed with soil. In Iraq, there are hundred thousand tons of concrete blocks used as fences and now considered wastes after removing these security fences, so it’s important to interest from recycling of such materials to be used in the improvement wide region of soft soils in Iraq. The results of tests showed increasing the undrained shear strength of soft soil by 175-193.5% and reduced the compressibility of soft by 25-31% measured in terms of compression index.
Highlights
The design of the foundations of different structures such as buildings, dams, bridges etc. requires knowing the geotechnical properties of the foundation soil, therefor, laboratory tests are performed to investigate the geotechnical properties of soil
The improvement of the mechanical properties of base and subbase layers when stabilized with recycled concrete aggregates (RCA) mixed with limestone aggregates (LSA) have been evaluated by the unconfined compressive strength (UCS) which is influenced by cement content, curing time, and dry density [13]
Definition Soft soil sample Recycled crushed concrete Soft soil mixed with 5% of recycled crushed concrete Soft soil mixed with 10% of recycled crushed concrete Soft soil mixed with 15% of recycled crushed concrete
Summary
The design of the foundations of different structures such as buildings, dams, bridges etc. requires knowing the geotechnical properties of the foundation soil, therefor, laboratory tests are performed to investigate the geotechnical properties of soil. The results showed that the cement stabilized soil has a good resistance to shear failure compared to an equivalent layer of compacted sand fill and the unconfined compressive strength of the cement stabilized soil is increased with increasing the cement content and increasing the curing time up to 28 days [9]. Melbouci (2009) studied the shear strength and compaction properties of recycled concrete aggregates experimentally and concluded that the mechanical behavior of the material can be improved by the addition of 10% cement, 6% bricks, and 5% sand particles of sizes smaller than 0.125 mm. The improvement of the mechanical properties of base and subbase layers when stabilized with recycled concrete aggregates (RCA) mixed with limestone aggregates (LSA) have been evaluated by the unconfined compressive strength (UCS) which is influenced by cement content, curing time, and dry density [13]. The soft soil is mixed with several percentages of crushed concrete to measure the improvement of geotechnical properties of soft soil
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