Alireza Mohammadinia

Laboratory evaluation of the use of cement-treated construction and demolition materials in pavement base and subbase applications

AbstractConstruction and demolition (C&D) materials constitute a major proportion of waste materials present in landfills worldwide. With the scarcity of high-quality quarry aggregates, alternative materials, such as C&D materials, are increasingly being considered as a replacement for traditional road-construction materials, particularly as the sustainable usage of these C&D materials has significant environmental benefits. In this research, an extensive laboratory evaluation was carried out to determine the engineering properties of cement-treated C&D materials. The C&D materials investigated were reclaimed asphalt pavement (RAP), recycled concrete aggregate (RCA), and crushed brick (CB). The geotechnical properties of cement-treated C&D materials were evaluated to assess their performance in pavement base/subbase applications. The effect of curing duration on the strength of the C&D materials was analyzed by conducting unconfined compression strength and repeated load triaxial tests. The RAP required 2...

Stabilization of Demolition Materials for Pavement Base/Subbase Applications Using Fly Ash and Slag Geopolymers: Laboratory Investigation

AbstractThe use of recycled construction and demolition (C&D) materials in unbound and cement stabilized pavement base/subbase applications has generated growing interest in recent years. C&D materials consisting of crushed brick (CB), recycled crushed aggregate (RCA), and reclaimed asphalt pavement (RAP) have been investigated in unbound and cement stabilized pavement base/subbase applications. However, the high carbon footprint of using cement for pavement base/subbase stabilization has led to this research to seek alternative low-carbon binders. This study evaluates the behavior of C&D materials when stabilized with geopolymers. Fly ash (FA) and ground granulated blast furnace slag (S) were used as pozzolanic binders and a different alkaline activator solution to pozzolanic binder ratio was tested. A maximum of 4% of dry weight of soil was used for geopolymer stabilization of the C&D materials. The binders used were either 4% FA, 2% FA+ 2% S, or 4% S. The geotechnical engineering and strength propertie...

Effect of fly ash on properties of crushed brick and reclaimed asphalt in pavement base/subbase applications

Fly Ash (FA), an abundant by-product with no carbon footprint, is a potential stabilizer for enhancing the physical and geotechnical properties of pavement aggregates. In this research, FA was used in different ratios to stabilize crushed brick (CB) and reclaimed asphalt pavement (RAP) for pavement base/subbase applications. The FA stabilization of CB and RAP was targeted to improve the strength and durability of these recycled materials for pavement base/subbase applications. The Unconfined Compressive Strength (UCS) and resilient modulus (MR) development of the stabilized CB and RAP aggregates was studied under room temperature and at an elevated temperatures of 40°C, and results compared with unbound CB and RAP. Analysis of atomic silica content showed that when the amount of silica and alumina crystalline was increased, the soil structure matrix deteriorated, resulting in strength reduction. The results of UCS and MR testing of FA stabilized CB and RAP aggregates indicated that FA was a viable binder for the stabilization of recycled CB and RAP. CB and RAP stabilized with 15% FA showed the highest UCS results at both room temperature and at 40°C. Higher temperature curing was also found to result in higher strengths.

Strength Development and Microfabric Structure of Construction and Demolition Aggregates Stabilized with Fly Ash–Based Geopolymers

The reuse of recycled construction and demolition (C&D) aggregates in civil engineering infrastructure applications has been considered a low-carbon solution to replace conventional pavement aggregates. Evaluating the strength development mechanism and interparticle flow of forces in geopolymer stabilized C&D aggregates will provide fundamental understanding of the behavior of stabilized C&D aggregates. The C&D aggregates studied are reclaimed asphalt pavement (RAP), recycled concrete aggregate (RCA), and crushed brick (CB). The performance of alkali-activated fly ash (geopolymer) on the stabilization of C&D aggregates, under different curing conditions and sample preparation methods were studied. Fly ash was used as the precursor for the alkali-activated binder that was used to stabilize the C&D aggregates. The effect of low and high content of fly ash–based geopolymers on strength development of recycled materials is investigated for the first time. Sodium silicate and sodium hydroxide were used, with different ratios, to intensify the alkaline environment for fly ash to accelerate the strength development of the mixture. The effect of static and dynamic compaction on the density and strength development was investigated for both low-content fly ash and high-content fly ash. Temperature treatment of geopolymer stabilized C&D aggregates up to 40°C and humidity curing in the moisture chamber for 7 days indicated improvement of the strength development of the mixture. The results of unconfined compressive strength (UCS) and resilient modulus testing of geopolymer-stabilized C&D aggregates indicate that alkali-activated fly ash is a viable binder for the stabilization of C&D aggregates.

A Review of the Sand Castle Test for Assessing Collapsibility of Filters in Dams

The Sand Castle (SC) test is a simple test for recognition of collapsibility and self-healing in filter materials. The rather qualitative outcomes and dissimilar techniques implemented in conducting the test complicate judgment about filter performance from the viewpoint of crack-holding propensity. This paper reviews earlier research concerning SC testing and highlights its governing principles. Results of comprehensive SC tests with different methodologies are presented, and the role of various parameters in results of SC tests is elaborated. The influence of basic soil properties (such as water content, relative density, fines content, and plasticity of the fines) on the ability of filters to hold a crack are assessed. Recommendations for appropriate conduct of SC tests and acceptance criteria in relation to field performance are provided.

A new approach for determining resilient moduli of marginal pavement base materials using the staged repeated load CBR test method

The selection of marginal materials to construct workable and durable pavement base materials requires an understanding of their resilient moduli properties. Empirical formulations have been developed previously based on quality quarried material with known performance-based behaviour. However, in recent years, there has been an increasing demand to use locally available marginal materials, which do not necessarily meet road authority specification requirements; hence it is imperative to evaluate the performance of these non-standard materials. In this study, the geotechnical properties of two marginal materials, namely limestone (Ls) and sandstone (Ss), were evaluated and compared with a high-quality rhyolite (Rh) crushed rock. In order to improve the performance of the marginal materials, each of Ls and Ss was blended with 20% Rh and 50% Rh. The geotechnical properties of individual and blended materials which were investigated included: particle size distribution, particle density, Atterberg limits, Los Angeles value, modified compaction test, California bearing ratio (CBR) and repeated load triaxial test. A novel test method termed repeated load CBR (RL-CBR) was used to investigate the performance properties of the individual materials and blends. The RL-CBR test was further developed to study the stress-dependent behaviour of the materials, termed as staged RL-CBR test. An in-depth analysis of the staged RL-CBR test confirmed the capability of this test method to determine the resilient modulus of marginal pavement base materials.

Performance evaluation of semi-flexible permeable pavements under cyclic loads

ABSTRACT Traditional permeable pavements are constructed with rigid aggregates and have low load-bearing capacity. The crack development due to loads and unpredicted ground movements reduces their service life. The widespread cracks on the surface of conventional asphalt accelerate the pavement structure deterioration and reduce the overall service life. In this research, the end-of-life tyre products shredded to tyre-derived aggregates (TDAs) were utilised along with crushed rock (CR) in different fractions of a porous structure to enhance the flexibility of permeable pavement whilst maintaining the minimum load-bearing capacity for use in footpath and low-volume roads. The transitional behaviour from a semi-rigid structure owing to the rigidity of CR aggregates to a more flexible structure for mixtures at higher TDA content was investigated. The impact of rigid-rigid and flexible-rigid inter-particular contacts at low and high stress levels is investigated. The plastic and recoverable deformations of the flexible-rigid blends under monotonic and repeated loadings are compared. Also, the impact of polyurethane binder content on improving the mixtures flexural strength is investigated. The lightly bonded flexible-rigid mixtures are a viable replacements for traditional porous pavements to improve the load-bearing mechanism and increase the flexibility of pavement.

Geotechnical Properties of Lightly Stabilized Recycled Demolition Materials in Base/Sub-Base Applications

Conventionally, high quality quarry materials are used for base and sub-base materials of the pavements. Traditional road building materials are becoming scarce in some regions. Moreover, rate of consumption of high strength aggregates is increasing rapidly in different industries. The use of traditional quarry materials at current rate of consumption is unsustainable from both environmental and cost perspective. The engineering characteristics of various cement-treated recycled Construction and Demolition (C&D) materials obtained from extensive laboratory testing are presented in this paper. Unconfined Compression Strength (UCS) tests shows that cement treated recycled material can be considered satisfactorily as a pavement base or sub-base material in the field. The Laboratory result shows that conditions of temperature and humidity curing play a very important role in strength development in cement-treated materials. The Los Angeles abrasion loss tests indicated that the cement treated recycled materials are durable.