详情

Durability of Rapid Hardening Cement Concrete

项目名称：	Durability of Rapid Hardening Cement Concrete
摘要：	Certain high importance paving applications such on-ramps and intersections or maintenance operations such as full depth pavement repair benefit from the application of high early strength materials that require minimal lane down time by allowing traffic in a matter of hours. These concrete mixtures can be produced using Type III Portland cement with accelerating admixtures, but concrete mixtures with other modern rapid hardening cement formulations are also likely to be suitable. Rapid hardening hydraulic cement is specified in the KDOT Standard Specification, Section 2009. Section 1716 specifies pre-packaged rapid hardening patching materials. Depending on the particular paving or repair operation being conducted, concrete mixtures may be required to achieve a minimum of 1,800 pounds per square inch (psi) in compressive strength or 380 psi in flexural strength before the road is opened to traffic, as listed in Section 833 of the Kansas Standard Specifications for State Road & Bridge Construction (KDOT 2015). These novel cements have varying chemical formulations and are governed by ASTM C1600. The rapid hardening cements are able to easily meet the strength requirements within a few hours however to date there has been little testing to evaluate the durability of ASTM C1600 cement concrete and the testing that has been performed shows mixed results with significant vulnerabilities for certain conditions. KDOT requires ASTM C666 testing for such mixtures with Durability Factor not less than 90% nor expansion greater than 0.1%. It is assumed that the same mechanisms that affect portland cement concrete freezing and thawing durability are also relevant for rapid setting cement concrete and similar techniques for combatting these mechanisms will be effective. In particular, air entrainment, the use of otherwise durable aggregates, and low mixture permeability after drying are all expected to beneficially impact freeze-thaw durability. Given the mixed results in evaluating the durability of high early strength portland cement concrete, investigating the suitability of ASTM C1600 cement concrete for paving operations in Kansas appears well justified. Furthermore, with commercially available rapid hardening cement concrete in the Kansas City metro area, developing the technical basis to evaluate the expected durability of these materials for KDOT is required. In the KTRAN project KSU-17-2, the durability of representative high early strength mixtures was assessed by measuring freeze-thaw resistance according to KTMR-22 procedures. Interestingly, only one tested mixture achieved the KDOT required KTMR expansion threshold and only three of six passed the required relative dynamic modulus of elasticity threshold. While this supported the field based observations that high early strength mixtures are not durable, the research offers few solutions to help KDOT better specify concrete patching mixture requirements. Additionally, it was observed that the calcium chloride accelerator significantly confused the interpretation of resistivity based measurements for the concrete by “short-circuiting” the resistivity test. Finally, it was anecdotally observed that achieving repeatable air content values with these mixtures was very difficult. In the ongoing project, KSU-20-5, the durability of high early strength concrete mixtures with non-calcium chloride accelerators are being assessed. In addition, the inclusion of highly active pozzolons such as metakaolin, microsilica, and ultra-fine fly ash are being evaluated to further reduce the cement quantity and permeability of the resultant concrete. Internal curing via the use of saturated lightweight aggregates is also under evaluation.
状态：	Active
资金：	46676
资助组织：	Kansas Department of Transportation
项目负责人：	Wadley, Dan
执行机构：	Kansas State University Transportation Center
开始时间：	20200815
预计完成日期：	20220215
主题领域：	Highways；Maintenance and Preservation；Materials；Pavements