Research Activities: 2010

 Field Evaluation of Alternative and Cost-Efficient Bridge Approach Slabs



Complete                          View Final Report: PDF                          


Sequential Number


Identification Number


Matching Research Agency


Missouri Department of Transportation


Principal Investigator

Ganesh Thiagarajan, Ph.D., Associate Professor, Civil Engineering Department
University of Missouri-Kansas City
5100 Rockhill Road
Kansas City, MO  64110
p 816-235-1288
f 816-235-1260

Student Involvement



Project Objective

The main objective of the proposed project is to evaluate and compare the field performance of recommended BAS designs, their constructability, and their impact on cost and schedule to the current MoDOT BAS design. Based on collected field data, researchers will recommend improvements in terms of construction practices, sequencing, design details, and other issues for a successful implementation of the new BAS designs in the future.

Economic feasibility of using a flowable fill mixture as a base for bridge approach slabs will be evaluated. Prior and on-going research has investigated the environmental impact of using fly ash products for road construction and for CLSM mixtures (Folliard et al. 2008, Wang 2009). Results of these studies will be considered in terms of the selection process for the CLSM material used in this study. If found to be economically feasible, researchers will collaborate with MoDOT, contractors, and Missouri ready mixed concrete suppliers to use a suitable flowable fill mixture under one of the new BAS designs constructed in this project. Impact of using flowable fill on BAS performance, cost, and schedule will also be documented.


Project Abstract

Recently Missouri Department of Transportation (MoDOT) in collaboration with Missouri Transportation Institute (MTI) and the National University Transportation Center (NUTC) funded a study to develop cost efficient alternative bridge approach slab (BAS) designs (Thiagarajan et al. 2010). After surveying the cost and performance of different bridge approach slabs being used by Departments of Transportation (DOT) around the country, performing numerical modeling and simulations, and analyzing cost data, the study has recommended three new BAS designs for possible adoption and implementation by MoDOT

a) 20 feet cast in place (CIP) slab with sleeper slab - for new construction on major roads

b) 25 feet precast prestressed slab with sleeper slab - for replacement and new construction applications on major and minor roads, and

c) 25 feet modified BAS without a sleeper slab for new CIP construction on minor roads.

Additionally, the use of Controlled Low Strength Materials (CLSM), aka flowable fill, as a backfill material behind bridge abutments under the BAS was suggested as a possibility to solve problematic bridge approach slab issues, such as excessive settlement, loss of support due to erosion, and others. A preliminary short study was performed to evaluate feasibility of producing low cost CLSM mixtures suitable for this application.

In this project, researchers propose to collaborate with MoDOT engineers to evaluate the field performance of the BAS designs, recommended by the earlier study, through their implementation on a series of pilot projects. Field performance of the new designs and their impact on construction duration and cost will be evaluated using a variety of methods including visual evaluation, profilograph studies, surveying, field instrumentation, collection of actual cost and duration data from the field engineers, and project close out interviews with the field engineers.


Anticipated Benefits




Project Start Date: 01/01/2011
Project End Date:



Project Deliverables

The project will result in a final report documenting the detailed cost and duration of construction for the new BAS designs. Performance will be monitored through visual inspection and field instrumentation. The final report will include all the collected data and analysis of data. Based on the results, researchers will recommend improvements in terms of construction practices and sequencing, design detail, connection details, and other issues. The results of the proposed project will provide the necessary data and final design improvements for state wide implementation of the new BAS designs and possibly provide recommendations for approved flowable fill designs and materials.


Technology Transfer Activities



Transportation Research Board Keywords