Three new reports from the CP Tech Center offer up-to-date assessments of internal curing (IC) for pavements. What are the best ways to supply additional curing water to a concrete mixture? How does internal curing of concrete affect performance and long-term stability of concrete? Funding for the work came from the Federal Highway Administration (FHWA), the Iowa Highway Research Board, and the Iowa Department of Transportation (Iowa DOT).
1 – Guide Specifcation for Internally Curing Concrete
Internal curing (IC) is a practical way of supplying additional curing water throughout the concrete mixture. This water can improve the hydration of cement, reduce autogenous shrinkage, and improve durability. The purpose of this document is to provide guidance for the development of project specifications for internally cured concrete projects. The guidance in this document is designed to supplement the agency’s standard specifications for concrete pavement. If the standard specifications are outdated, modifications other than those provided in this document may be necessary to produce a high-quality, long-lasting concrete. This document contains IC specification language, references to IC resources, references to IC instructional videos, and references to tools that can be used for IC of concrete or providing quality control. For the PDF of this report, please go to: https://intrans.iastate.edu/app/uploads/2018/09/IC_guide_spec_w_cvr.pdf
2 – Impacts of Internal Curing on the Performance of Concrete Materials in the Laboratory and the Field
Internal curing is a technique to prolong cement hydration by providing internal water reservoirs in a concrete mixture. These reservoirs do not affect the initial water-to-cementitious materials (w/cm) ratio, but do provide water for curing throughout the thickness of the element.
Benefits of this approach include improved mechanical properties as well as reduced risk of moisture gradients, thus reducing the potential for warping.
The aim of this work was to assess whether joint spacings could be increased in slabs containing lightweight fine aggregate (LWFA) as a source of internal curing. For the PDF of this report, please go to: https://intrans.iastate.edu/app/uploads/2018/07/impacts_of_IC_on_contraction_joint_spacing_w_cvr.pdf
3 – Lifecycle Cost Analysis of Internally Cured Jointed Plain Concrete Pavement
Internal curing is a technique that has been developed to prolong cement hydration by providing internal water reservoirs in a concrete mixture that do not adversely affect the concrete mixture’s fresh or hardened physical properties. Internal curing grew out of the need for more durable structural concretes that were resistant to shrinkage cracking.
This report covers an investigation into the relative costs and benefits of internal curing using a lifecycle cost analysis (LCCA) that compares internally cured (IC) jointed plain concrete pavement to conventionally cured (CC) pavement. This analysis was based on a pavement designed for use in Dubuque, Iowa.
According to the analysis, IC concrete makes it possible to design pavement with decreased thickness or increased joint spacing or to reduce the required maintenance over the analysis period, which results in savings in initial construction cost. Even if the thickness does not change, IC pavement requires less maintenance than a comparable CC pavement to provide satisfactory performance over its service life. However, the initial construction cost of IC pavement is about 3.2% higher than that of CC pavement with the same thickness. Considering all of the evidence, the net present value of IC pavement is less than that of CC pavement. For the PDF of this report, please go to: https://intrans.iastate.edu/app/uploads/2018/07/lifecycle_cost_analysis_of_IC_JPCP_w_cvr.pdf