Stringline Effects on Concrete Pavement Construction

Abstract

Modern concrete pavement construction typically uses slipform paving equipment, especially on major highways and airfields. This equipment commonly is guided by its sensing of a stringline set in advance by an engineering survey. Although use of stringline guidance has improved the smoothness of pavement, some limitations of this technique are known to exist. Three of these limitations are explored in detail. The effects on concrete pavement smoothness from the chord effect, the sag effect, and random survey error are described both conceptually and analytically. Of these three effects, random error introduced during the engineering survey is found to be the most pronounced. Furthermore, this analysis shows that contradictions exist within what is sometimes considered good practice for concrete pavement construction; the belief that improved smoothness can be obtained by simply using shorter spacing of the stringline stakes is not always correct. In fact, it is demonstrated that optimum stringline spacing can be realized by recognizing each of the effects described, including the associated costs of mitigation.