Hydrated Cement Treated Crushed Rock Base （HCTCRB） is widely used as a base course in Western Australian pavements. HCTCRB has been designed and used as a basis for empirical approaches and in empirical practices. T...Hydrated Cement Treated Crushed Rock Base （HCTCRB） is widely used as a base course in Western Australian pavements. HCTCRB has been designed and used as a basis for empirical approaches and in empirical practices. These methods are not all-encompassing enough to adequately explain the behaviour of HCTCRB in the field. Recent developments in mechanistic approaches have proven more reliable in the design and analysis of pavement, making it possible to more effectively document the characteristics of HCTCRB. The aim of this study was to carry out laboratory testing to assess the mechanical characteristics of HCTCRB. Conventional triaxial tests and repeated load triaxial tests （RLT tests） were performed. Factors affecting the performance of HCTCRB, namely hydration periods and the amount of added water were also investigated. It was found that the shear strength parameters of HCTCRB were 177 kPa for cohesion （c） and 42~ for the internal friction angle （~）. The hydration period, and the water added in this investigation affected the performance of HCTCRB. However, the related trends associated with such factors could not be assessed. All HCTCRB samples showed stress-dependency behaviour. Based on the stress stages of this experiment, the resilient modulus values of HCTCRB ranged from 300 MPa to 1100 MPa. CIRCLY, a computer program based on the multi-layer elastic theory was used in the mechanistic approach to pavement design and analysis, to determine the performance of a typical pavement model using HCTCRB as a base course layer. The mechanistic pavement design parameters for HCTCRB as a base course material were then introduced. The analysis suggests that the suitable depth for HCTCRB as a base layer for WA roads is at least 185 mm for the design equivalent standard axle （ESA） of 10 million.展开更多
In the past decade alone, the BITRE has indicated an increase of 40% in road users, escalating demands for quality pavements to service tmprecedented traffic conditions. An abundance of crushed rocks are available in ...In the past decade alone, the BITRE has indicated an increase of 40% in road users, escalating demands for quality pavements to service tmprecedented traffic conditions. An abundance of crushed rocks are available in Western Australia but do not meet strength requirements for road construction. However, cement treatment of crushed rocks, forming Cement Treated Crushed Rocks （CTCR）, improves the mechanical properties of the material, allowing wider application. In order to streamline the mix design of CTCR, the classification of its behaviour is pivotal. Austroad classifies cement treated pavement materials as either being modified or bound based on its Unconfined Compressive Strength （UCS） and performance attributes. Bound materials are def＇med by its susceptibility to fatigue failure which, in the mechanistic-empirical design for flexible pavements, is dictated by the flexural modulus. However, in the study of damage mechanics, fatigue life is suggested to be an accumulation of micro-scale damage in lieu of dependency to ultimate stresses. Strain dependent damage functions are used phenomologically to explain the evolution of fatigue for various engineering materials. This paper therefore investigates a theoretical relationship between strain and fatigue life prediction supported by a laboratory investigation on the use of UCS for classification. This is achieved by providing regression analysis with strain parameters used in fatigue life prediction. The Indirect Tensile Strength （ITS） test is also employed to this end. It is observed that strain at onset of micro-cracking coalescence （ε30） is independent of test type undertaken and potentially capable of acting as a more superior blanket classification for cemented materials.展开更多
文摘Hydrated Cement Treated Crushed Rock Base （HCTCRB） is widely used as a base course in Western Australian pavements. HCTCRB has been designed and used as a basis for empirical approaches and in empirical practices. These methods are not all-encompassing enough to adequately explain the behaviour of HCTCRB in the field. Recent developments in mechanistic approaches have proven more reliable in the design and analysis of pavement, making it possible to more effectively document the characteristics of HCTCRB. The aim of this study was to carry out laboratory testing to assess the mechanical characteristics of HCTCRB. Conventional triaxial tests and repeated load triaxial tests （RLT tests） were performed. Factors affecting the performance of HCTCRB, namely hydration periods and the amount of added water were also investigated. It was found that the shear strength parameters of HCTCRB were 177 kPa for cohesion （c） and 42~ for the internal friction angle （~）. The hydration period, and the water added in this investigation affected the performance of HCTCRB. However, the related trends associated with such factors could not be assessed. All HCTCRB samples showed stress-dependency behaviour. Based on the stress stages of this experiment, the resilient modulus values of HCTCRB ranged from 300 MPa to 1100 MPa. CIRCLY, a computer program based on the multi-layer elastic theory was used in the mechanistic approach to pavement design and analysis, to determine the performance of a typical pavement model using HCTCRB as a base course layer. The mechanistic pavement design parameters for HCTCRB as a base course material were then introduced. The analysis suggests that the suitable depth for HCTCRB as a base layer for WA roads is at least 185 mm for the design equivalent standard axle （ESA） of 10 million.
文摘In the past decade alone, the BITRE has indicated an increase of 40% in road users, escalating demands for quality pavements to service tmprecedented traffic conditions. An abundance of crushed rocks are available in Western Australia but do not meet strength requirements for road construction. However, cement treatment of crushed rocks, forming Cement Treated Crushed Rocks （CTCR）, improves the mechanical properties of the material, allowing wider application. In order to streamline the mix design of CTCR, the classification of its behaviour is pivotal. Austroad classifies cement treated pavement materials as either being modified or bound based on its Unconfined Compressive Strength （UCS） and performance attributes. Bound materials are def＇med by its susceptibility to fatigue failure which, in the mechanistic-empirical design for flexible pavements, is dictated by the flexural modulus. However, in the study of damage mechanics, fatigue life is suggested to be an accumulation of micro-scale damage in lieu of dependency to ultimate stresses. Strain dependent damage functions are used phenomologically to explain the evolution of fatigue for various engineering materials. This paper therefore investigates a theoretical relationship between strain and fatigue life prediction supported by a laboratory investigation on the use of UCS for classification. This is achieved by providing regression analysis with strain parameters used in fatigue life prediction. The Indirect Tensile Strength （ITS） test is also employed to this end. It is observed that strain at onset of micro-cracking coalescence （ε30） is independent of test type undertaken and potentially capable of acting as a more superior blanket classification for cemented materials.
