Laboratory Testing: Concrete setting evaluation

Case study: SOFO, ADAM System

Prediction of compressive strength evolution
Strength-maturity curves
Autogenous deformation
Thermal expansion coefficient
Drying deformation

Project Description

Summary: This research project involved developing a methodology for monitoring concrete during the hardening phase in order to determine key material characteristics (compressive strength, thermal expansion coefficient etc.) as a function of maturity.

Clients: IMAC - EPFL

Place: EPFL, Lausanne (Switzerland)

Period: 2002 - 2005

Installation: IMAC - EPFL

Structure's short description: In order to develop the method different types of concrete specimens were tested using Standard SOFO sensor, Concrete Setting SOFO Sensor and for a purpose developed slim sensor. The specimens were mostly cylindrically and rectangularly shaped with various border conditions in terms of strain, temperature insulation and humidity insulation. In order to keep the cost limited specially designed re-usable moulds were developed.

Aim of monitoring: The overall objective of this project was to develop a methodology for predicting mechanical properties and for separating important phenomenon in hardening materials, such as commercial concrete and mortar, to be ultimately applied in real time and in situ.

Number of sensor: 80

Main Results: Results confirm the hypothesis that relative hardening curves obtained using early age measurement of standard and setting SOFO sensors are related with properties of concrete such as activation energy, rate of reaction and equivalent age. The work performed in this project demonstrates that compressive strength evolution can be predicted and that a decomposition of the total deformation into the effects of physical phenomena is possible in real-time and in-situ. More specifically, during this work the following results have been achieved: ? Compressive strength evolution have been successfully predicted for seven very different types of concretes after only three days of measurements ? Strength-maturity curves obtained can be reused for the same mix to determine, by instance, save removal times for shores and moulds, cable release in prestressed units (see Figures 1 and 3) ? A prototype of testing equipment have been developed. It allows to reuse sensors, reducing laboratory expenses ? Autogenous deformation, thermal expansion coefficient and drying deformation have been calculated for six types of concrete mixes and one type of mortar ? A new, low axial stiffness sensor has been developed ? Software for the treatment and interpretation of data has been implemented

A prototype of the reusable sensor mould with a slim sensor

The strength-maturity prediction obtained using Concrete Setting and Standard SOFO sensors

Evolution of Thermal expansion coefficient obtained using Concrete Setting and Standard SOFO sensors

Bibliography:

Monitoring of concrete at very early age using stiff SOFO? sensor , B. Glisic, N. Simon, Cement and Concrete Composite, Elsevier, Vol 22, No 2, p 115-119, 2000

Fibre optic sensors and behaviour in concrete at early age, B. Glisic, EPFL, Lausanne, Switzerland, Ph.D. Thesis No. 2186, 2000

Monitoring and modelling of construction materials during hardening, Marco Viviani, EPFL, Doctoral Thesis No. 3168, 2005

Three day prediction of concrete compressive strength evolution , Viviani, M., Glisic, B., Smith, I. F.C., ACI Materials J., July 2005, pp. 231-236, 2005

Separation of thermal and autogenous deformation at varying temperatures using optical fiber sensors , M. Viviani, B. Glisic, I.F.C. Smith, Cement & Concrete Composites, Elsevier, Vol. 29, pp 435-447, 2007

Equivalency points: Predicting concrete compressive strength evolution in three days, M. Viviani, B. Glisic, K.L. Scrivener, I.F.C. Smith, Cement and Concrete Research, No. 38, pp.1070-1078, 2008