The use of Portland-Limestone Cement (PLC), or Type IL, has gained widespread acceptance across the world, including the United States. Additional ground limestone added to portland cement for use in concrete has demonstrated to have improved strength and consistent properties with traditional portland cement. The reactive elements in ground limestone make it a beneficial supplementary cementitious material in a concrete mix where the percentage of portland cement is typically 7% to 15%. However, the effect of PLC on soil-cement applications is considered to be generally different, with the percentage of portland cement in road base stabilization (cement-treated base and full-depth reclamation) averaging at around 5% and the percentage of portland cement in soil stabilization (cement-modified soil and cement-stabilized subgrade soil) averaging at around 3%. This makes the corresponding ground limestone percentages in stabilization efforts to be around 0.54% and 0.32%, respectively. It is logical and reasonable to conclude that these quantities of ground limestone are unlikely to have any effect when used in soil-cement applications. The ground limestone would be essentially an inert material in the whole mass of the agglomerations of bound materials that make up a cement-treated road base or cement-treated soil. Soil-cement efforts benefit from the mass production of PLC, which is more commonly used in concrete. It would not be economically feasible to provide widespread availability of portland cement for stabilization that does not have the ground limestone component.
The growing demand from the public and private sector interests for cement that is manufactured in ways that reduce greenhouse gas emissions is spurring the expansion of PLC use. In April 2022, the Portland Cement Association (PCA) reported that most of the state DOTs in the country are either allowing or considering allowing the use of PLC for soil-cement applications. With most cement producers switching to PLC, the universal use in soil-cement applications is inevitable. There is very little research on the effect of PLC on cement-treated road bases and soil because its widespread use has continued with no reports of problems.
Reference
State DOT Acceptance of PLC for Soil-Cement Applications, Portland Cement Association, G. Halsted, 2022
