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Variability in unconfined compression strength of pavement materials stabilised with cementitious binders
Conference paper   Open access

Variability in unconfined compression strength of pavement materials stabilised with cementitious binders

Gregory W White and C Gnanendran
Proceedings of the 21st ARRB and 11th REAAA Conference, p.18P
21st ARRB Transport Research and 11th Road Engineering Association of Asia and Australia Conference, 2003 (Cairns, Australia, 18-May-2003–23-May-2003)
ARRB Group
2003
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Abstract

Civil Engineering Transportation and Freight Services binders cement compressive strength curing and setting agents laboratory tests materials pavements portland cement testing variables
This paper examines the variability of strength in stabilized pavement materials and some of the causes of such variation. The variation of Unconfined Compressive Strength (UCS) of new quarried materials is compared with that of reclaimed road base, both stabilized with cementitious binders. The effect of binder type (slag-lime blends versus General Purpose (GP) Portland cement) on the stabilized material's UCS variability is also discussed. The paper presents the information and findings from the laboratory tests. When conducting laboratory investigations into the strength, modulus and fatigue life of stabilized materials, the inherent variability must be low enough to ensure that meaningful and reliable relationships between the characteristics of interest can be drawn. However, if the variability is not too high, use of reclaimed material would be preferred as it more readily mirrors the actual field conditions. A review of literature found that typical laboratory prepared and tested samples indicated UCS values to have coefficients of variation ranging between 10 and 25%. This typically increases to around 40% for field-cured samples that are cored from actual pavements. The UCS testing conducted in this research produced coefficients of variation of between 10 and 18% for 9 sample batches and this is comparable to those reported in the literature from other laboratory testing programs. When comparing a new and reclaimed material stabilized with 7% slag-lime binder, the new material had a UCS of around double that of the reclaimed material but also had a higher (about twice the amount of) standard deviation. However, the difference in coefficient of variation in UCS between the two host materials was negligible. When comparing batches of identical reclaimed material stabilized with different binders (one with 7% slag-lime and one with 3.5% GP cement), the UCS values obtained were very similar. The standard deviation of the GP cement stabilized material is, however, around double and therefore the coefficient of variation is significantly higher (around double). This is thought to be due to the low binder content making it difficult to ensure uniform binder distribution and, therefore, higher variability in the UCS and other properties. For the remaining laboratory testing program the authors will utilize the reclaimed material, stabilized with 7% slag-lime binder as it does not increase the variability above that determined from using a new crushed rock host material and better models the field characteristics of an insitu stabilized pavement material with cementitious binder. Where GP cement is utilized to compare with the slag-lime stabilized materials, 7% binder content will be used to ensure more uniform binder distribution.

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