An Investigation on the Strength of Road Base Materials made of Recycled Construction Debris

In recent years the recycling of concrete to produce aggregates suitable for non-structural applications, such as road construction materials, is emerging as an environmentally viable and technically feasible operation. While studies on the engineering properties of concrete made by recycled concrete aggregate abound only limited data are available on performance of crushed brick aggregate in road construction. This paper is an attempt to understand the physical properties of recycled masonry bricks and cement mortar or concrete made of natural aggregate. The study also provides the laboratory basic test results required to assess the mechanical performance of the unbound aggregates for use in road construction. In the present research study, the possibility of demolition debris recycling and its utilization in base and sub-base layers of roads, directly or after improvement, is investigated. A vast variety of physical and chemical tests has been carried on crushed bricks, mortar cement, concrete or different combinations of these materials. Freezing and thawing, durability, compaction and CBR tests are the most important tests to be executed for evaluation of the performance of these materials for use in construction of road layers. The initial test results indicate that these materials may be considered as sub-base materials for second degree (immediate traffic) roads. To enhance the quality of the recycled materials, two methods were employed. In the first method, different fractions of recycled construction debris were replaced with high performance materials. This led to an increase in CBR amount, i.e. increasing the new material performance. At the second method, cement with different percentages was added to the recycled materials including brick and cement mortar. Again, this resulted an increase in compressive strength of new materials. Also complementary experiments indicated increased quality of construction debris as base course material in highway construction.