Characterization of cement-modified base course materials for Western Australia roads

The cement-modified soil (CMS) is described as a soil that has been treated with a relatively small amount of cement in order to improve its engineering properties so that it is suitable for construction. This soil stabilization technique is employed for the typical base course material in Western Australia named “Hydrated Cement Treated Crushed Rock Base (HCTCRB)”. In present, the mechanistic approach of pavement design and analysis become more important and widely used internationally but HCTCRB has been created from the empirical approach empirical approach point of view. In order to be able to use this material effectively relating to the new pavement design method, its shear strength, resilient modulus, and permanent deformation characteristics need to be more investigated and deeply understood. This study aimed to perform the results of the laboratory testing which was carried out to assess the mechanical characteristics of HCTCRB. Our findings show that HCTCRB can be characterized as a relevant cohesive granular material with significant shear strength parameters. Based on the laboratory results, the suitable models of the resilient modulus characteristics and the permanent deformation characteristics were determined and introduced

Evaluation of a stabilized sand residue for use as roadway materials

Australia produces approximately 40% of the world’s bauxite and over 30% of the world’s alumina. Each year, about 25 million tons of sand residues are produced in Australia. The management and containment of large impoundment areas are costly. The sustainable use of coarse sand residues for road construction is an attractive option with a high potential for large volume reuse. During the extraction of alumina from bauxite ore using the Bayer process, a fine residue is produced called red mud. In Western Australia, Darling Range bauxite deposits contain high levels of quartz, which results in a coarse residue fraction also being produced. This study focuses on whether a coarse sand residue is a viable option for use as a road base material in Western Australia. The soil stabilization technique, a pozzolanic- stabilized mixture, was used to improve the properties of a coarse sand residue to satisfy minimum requirements of road bases. The intent of this stabilization technique is to use potential by-products from industry in Western Australia as stabilizing materials. A pozzolanic - stabilized mixture consisting of Class F fly ash, a by-product from a coal power station, and activators, the by-product from the quicklime manufacturing in terms of lime kiln dust, were employed to develop pozzolanic activity.Once the appropriate mixture of a coarse sand residue, fly ash, and activators was established (based on a maximum dry density and a value of unconfined compressive strength), a set of laboratory tests were performed. These included an unconfined compressive strength test, a resilient modulus test, and a permanent deformation test. Comparisons were made between the stabilized residue and the conventional road base material in West Australia (crushed rock with the addition of 2% General Purpose (GP) Portland Cement.). The results of this study show that the performance of the stabilized residue is superior to that of the standard use material. Our findings indicate that stabilized residue can provide improved performance when used as road base material in Western Australia

Sustainable use of construction and demolition (C&D) waste as A road base material

Crushed concrete waste is a by-product from building demolition and constitutes a principal component of municipal solid waste consisting of concrete, sand, brick, rock, metals and timber. Over 50% of this waste is commonly sent to land-filled sites, resulting in the impact on the limited capacity of land-filled sites. Nowadays, the sources of virgin natural aggregates are depleted by increasing in demand of using a virgin material in building and infrastructure construction and maintenance facilities. This depletion leads to the utilisation of crushed concrete waste to replace natural aggregates in road and highway construction. Of key significance of this study is to present alternative materials for road and highway construction on the production of the proper guideline for road base by using crushed concrete waste. Sophisticated tests were conducted to investigate the mechanical responses of compacted crushed concrete subjected to applied loads simulated from traffic loads. Unconfined compressive strength, shear strength parameters, resilient modulus and permanent deformation of such material were determined. Our findings showed that crushed concrete waste is able to utilise as a road base material. The results of this study will enhance increased use of crushed concrete waste in road and highway construction and will, therefore, alternatively reduce consumption and costs in manufacturing virgin aggregates

Unbound granular base course with shallow foundation concept

This study aims to introduce alternative design procedures for a flexible pavement base course by utilizing the ultimate strength criteria with sophisticated laboratory results of base course materials. Current pavement design mostly avoids all complicated behaviours of an unbound granular base layer considered only as a layer transferring traffic loads to underneath layers regardless of the base course deterioration. Based on the design protocol, there are only the design criterion of the horizontal tension and the vertical compression occurring at the bottom of asphalt layer and at the top of subgrade, respectively. The real behaviour of a base course under traffic loads has been rarely accounted for in pavement design protocol. Nowadays, traffic is growing in terms of magnitudes and quantities and causing premature deterioration in a base course layer leading to major damage in pavements. The study presents theoretically the more suitable approach of the stress and strain distribution in a flexible pavement using the finite element method. An example of a conventional pavement structure consisting of a surfacing, a base course, a sub base course and a subgrade with a single wheel load of 750 kPa standard pressure was selected was established to investigate all pavement phenomena. The effects of uniform design pressure and material attributes which were generated by traffic were investigated. Moreover, the new design criteria for an unbound granular layer were defined as the ultimate strength design and the bearing capacity factor resulting from the application of the shallow foundation bearing capacity concept within the California Bearing Ratio (CBR) results. Our findings were reported and used to draw up the guideline and recommendation on the current pavement analysis and design

Cracking and flexural behaviors on cement treated crushed rock for thin flexible pavement

Fatigue cracking is considered to be one of the most important types of distress affecting the performance of flexible pavements on major highways. This report analyses the results of a laboratory study of the static and fatigue response of a typical Western Australia Cement Treated Base (CTB) to evaluates its mechanical parameters i.e. flexural strength, flexural stiffness and tensile strains. Five different series of cement content were evaluated in the mix of 1%, 2%, 3%, 4% and 5%. Two major types of testing were conducted for the purpose of this study, i.e. Flexural Fatigue Tests (dynamic loading) and Flexural Beam Tests (static loading). The flexural fatigue tests were carried out with strain control mode. From the tests, the flexural stiffness for each specimen was calculated. The flexural stiffness was obtained from maximum tensile strains on the bottom of the specimens. The outcomes of the paper are as summarized as follow: First, 1% to 3% CTB was found out to be classified as modified material while 4% and 5% CTB are categorized as stabilized materials. Second, fatigue cracking phenomenon can be seen in stabilized materials (4% and 5% CTB) while other types of distress may affect the behavior of modified materials (1 to 3% CTB). Third, 4% cemented material is observed to be the most suitable material to perform under fatigue loading conditions. Fourth, a series of recommendations are presented for further research i.e. the Flexural Fatigue Test be conducted at a suitable (lower) strain value instead of the 400 µe magnitude used in this research. © 2012 Taylor & Francis Group

Recycled concrete aggregate as a base course material in Western Australian road

Recycled crushed concrete and demolition materials have been trailed successfully as a road construction material in a number of locations in Western Australia, but industry acceptance of the material has been minimal. Specifications of such materials currently in use have been modified from commonly used specifications for new quarried products, and remarkably, there have been some doubts about the long term performance and quality control of such recycled products. This paper analyses the performance of recycled concrete pavements that have been constructed in Western Australia, and details the extensive laboratory testing program undertaken to model the product and compare its performance to conventional quarry products. Field testing demonstrates good quality control and performance of recycled crushed concrete and demolition materials superior to conventional quarry products and the laboratory results shows very close characteristics between both materials. © 2012 Taylor & Francis Group