Numerous projects on crushed rocks for hydrated cement based on trial sections have gone through an investigation in Western Australia.
Introduction Of Hydrated Cement
The main purpose of this phase is to study the operation of experimental sections of the base of hydrated cement rubble (HCTCRB) in the Greater Perth area.
This includes monitoring performance, comparing HCTCRB specifications, reviewing current design practices, and providing a possible project roadmap for further research.
HCTCRB has been used in numerous projects in Western Australia, with performance testing ongoing on some key road sections.
This report focuses on the HCTCRB sections of the Kwinana Freeway, the Mitchell Freeway, and the Reid Highway.
Performance monitoring for this project includes deflection, rutting and roughness measurements associated with traffic counting and visual evaluations.
Types And Models Of Hydrated Cement
Visual assessments will not be discussed in this report due to limited inspection data available only on the Kwinana Freeway and assessed for rutting only.
General specifications are acceptable for the roads and sites in this report, which include base thicknesses from 123mm to 200mm and cement grades from 1% to 2%.
Sections of the Reid Highway are almost 21 years old, while the other two roads are 8 to 9 years old.
Available roughness and rutting data do not predict any clear wear relationships.
All maximum deflection results are still below 0.5mm indicating good ground conditions.
The curvature values are also lower than calculated and indicate sufficient rigidity of the upper layer according to the MRWA criteria.
Specification Of Hydrated Cement
The curvature results in Section 5 of the Reid show that 1% cement grade can work as well as 2%, and Section 1 shows that a base thickness of 123 mm can be considered a design thickness with similar characteristics to a base thickness of 200 mm, with the same total pavement thickness for less loaded roads.
If other sections of the HCTCRB have broken in the past, these sections should be examined to determine the exact mechanism by which they break.
At this stage, no such partitions are currently reported.
Cost Of Hydrated Cement
Bitumen Stabilized Limestone (BSL) was used as a preliminary response to the poor performance of raw CRB and performed well with minimal problems.
MRWA subsequently developed HCTCRB as a low-cost alternative to BSL and as a less moisture sensitive, higher modulus alternative to untreated CRB.
The use of HCTCRB is currently limited to high traffic areas where asphalt pavement is normally required.
However, HCTCRB floors have not been built since 2009 due to industry fears of premature damage associated with the technology.
Design considerations such as curing the HCTCRB prior to compaction are believed to have a significant impact on performance (e.g., fatigue cracking).
Helpful Advice About The Best Hydrated Cement
Examination of these sections showed that in most cases the untreated crushed stone base was either of poor quality or weakened due to moisture penetration during operation.
In addition, structural design methods for HCTCRB need further development or validation.
These combined risks have prompted the MRWA to limit the use of HCTCRB to construction contracts only and where the asphalt has a 15-year fatigue life.