by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
Concrete In Australia : March 2012
32 Concrete in Australia Vol 38 No 1 were not impacted by the increase from 5% to 7.5% limestone mineral addition. e limited results available for 24 hour strengths also indicated that average strength of 7.5% and 5% limestone mineral addition were equivalent (site temperature was not considered but this is a known factor impacting early age strengths). One shrinkage sample was taken during the trial period and one immediately following. e shrinkage value of the sample of concrete taken using 7.5% limestone mineral addition cement was 20% higher than the result of the concrete containing 5% limestone mineral addition cement. While this single result and the test method AS1012.13 is prone to high variability, the significant difference will require further investigation. Customer feedback for the period 5-17 September did not highlight any adverse concrete performance attributable to the higher limestone mineral addition cement. Notably some sites supplied from multiple concrete plant were unable to differentiate the finishing and set times of the concretes from plants running the trial and standard concrete mixes. Factors such as the impact of cement temperature at the time of delivery and the impact of cement temperature on concrete setting were not evaluated during this trial but will be included in future testing. 5.0 CONCLUSION Laboratory evaluations of limestone mineral addition levels above the currently approved 7.5% ceiling imposed by Australian Standards have shown additional scope to increase mineral additions up to 10% and beyond without compromise to key performance requirements. Field concrete has been successfully placed without incident at 7.5% limestone mineral addition. Additional work planned for 2012 will further extend the available data on field concretes beyond the existing trials undertaken at 7.5% and seek to answer a number of durability questions requiring further investigation. REFERENCES Aitcin, P.-C. (2000). Cements of yesterday and today Concrete of tomorrow. Cement and Concrete Research, 1349-1359. Bonavetti, V., Donza, H., Menendez, G., Cabrera, O., & Irassar, E. F. (2000). Limestone filler cement in low w/c Figure 7. Combined trial (7.5% limestone) and control (5% limestone) strength data at 4 days and 28 days in the 32 MPa mix supplied from the Sydney trial plant.