The nondestructive, in-situ testing of early-age concrete properties is a crucial point for the progress of many construction projects in the building sector. The application of such techniques can establish e.g. the earliest possible form removal from concrete construction elements, thereby opening highways to traffic or releasing prestress from steel...
The setting and hardening process of concrete is considered to be the most critical time period during the life of a concrete structure. Previous research has been conducted on an ultrasonic wave reflection method that utilizes a steel plate embedded in the concrete to measure the reflection loss of shear...
The gradual evolution of the material properties of a cement-based material, i.e. the stiffness of cement paste, is the result of the continuous change of the microstructure with the progress of the hydration process. Based on an existing micromechanical model for the simulation of the shear and elastic modulus of...
The setting and hardening process of concrete can be considered as the most critical time period during the life of a concrete structure. To assure high quality and avoid problems in performance throughout the life of the material, it is essential to have reliable information about the early age properties...
This presentation contains information on the keynote paper "Health Monitoring of Early Age Concrete". The presentation was delivered by Surendra P. Shah at CONSEC'04 in Seoul, Korea on June 30, 2004.
The concrete currently used in the slip-form paving process is a low slump concrete that requires both internal and external vibration in order to achieve satisfactory compaction. The use of vibrator fingers for the internal vibration often leads to trails on the surface of the pavement and to segregation around...
The paper deals with the behavior of fluid cement pastes, formulated from Self Consolidating Concretes (SCCs), and the experimental correlation of fundamental rheological properties, such as the yield stress and the viscosity, with measurements from field tests, such as the mini-cone slump flow test. As a matter of fact, several...
This presentation contains information on the project "Aligning Data to Support Transportation Decisions, Emerging Challenges & Opportunities for the Data World". The presentation was delivered by Joseph L. Schofer at Transportation Research Board – AASHTO Peer Exchange meeting on May 15-16, 2008.
This presentation contains information about the project "The future of transportation... and how we'll pay for it" by Joseph L. Schofer, Department f Civil & Environmental Engineering. The presentation was delivered at the 40th Anniversary Seminar Day at Northwestern University on April 18, 2009.
This presentation provides information on the project "Safety Concrete - a Material Designed to Fail" by Jeffrey J. Thomas, Julie Gevrenov, Hamlin Jennings, and Edward O'Neil. The presentation was delivered at the 106th Annual Meeting & Exposition of The American Ceramic Society, Indianapolis, Indiana in 2004.
The objective of this program is to measure the changes in the properties of the C-S-H gel phase in cement paste as a function of the Ca/Si ratio. The motivation is to better understand the hydration products that form in blended cements with lower Ca/Si ratios than portland cement. The...
A study is conducted to determine the effects on the early hydration kinetics and
compressive strength by seeding of Portland cement and alkali-activated blast furnace
slag with a pure form of calcium silicate hydrate (C-S-H). The effects of C-S-H seeding
during the early nucleation and growth period of each type...
This presentation provides information on the progress report of the project "Empirical Study of Life-Cycle Cost Analysis for Bridges" by Ahmad Hadavi, 2003.
Non-destructive evaluation (NDE) techniques have been used for a number of years to provide quality control of construction procedures for drilled shafts and driven concrete piles. In particular sonic echo and impulse response methods have been used extensively to check lengths and continuity of newly-installed foundations. In recent years, the...
An empirical procedure for fitting a complementary error function (erfc) to settlement and lateral ground movement data in a direction parallel to an excavation support wall is proposed based on extensive optical survey data obtained around a 12.8 m excavation in Chicago. The maximum ground movement and the height and...
Several three-dimensional effects were observed in the performance monitoring data collected during excavation for the Ford Engineering Design Center (FEDC) in Evanston, Illinois. These responses are related to lateral deformations of the soil around the excavation walls, forces in the cross-lot and diagonal bracing that supported the temporary wall and...
This paper presents the results of 159 finite element simulations conducted to define the effects of excavation geometry, i.e., length, width and depth of excavation, wall system stiffness, and factor of safety against basal heave on the 3-dimensional ground movements caused by excavation through clays. The results of the analyses...
Successful use of monitoring data to update performance predictions of supported excavations depends equally on reasonable numerical simulations of performance, the type of monitoring data used as observations, and the inverse analysis techniques used to minimize the difference between predictions and observed performance. This paper summarizes each of these factors...
Two numerical procedures are described that quantitatively identify a set of constitutive parameters that best represents observed ground movement data associated with a deep excavations in urban environments. This inverse problem is solved by minimizing an objective (or error) function of the weighted least-squares type that contains the difference between...
This paper describes developments of integrated tools for predicting, monitoring, and controlling ground movements associated with excavations in urban areas. Successful use of monitoring data to update performance predictions of supported excavations depends equally on reasonable numerical simulations of performance, the type of monitoring data used as observations, and the...