Journal of Materials and Engineering Structures

Number 1, 2014

2-10
Influence of re-dispersible powder on the properties of mortars

Authors: Van Tien PHAN

Abstract

View in PDF

Number of views: 465

This paper presents an experimental study on the effect of a re-dispersible powder on the properties of cement mortars in both fresh and hardened state. The effects of varying contents of re-dispersible powder on the adhesive properties and rheological behavior of mortar in fresh state and on the flexural strength of mortar in hardened state have been investigated. To determine the adhesive properties the probe tack test was used. The tack test results have been exploited to identify the adhesion strength, the cohesion strength and the support’ adherence force. The rheological behavior of the mortars was also considered. It is found that the influence of re-dispersible powder on the properties of fresh mortar is quite small. Re-dispersible powder seems to have only indirect and minor effects on the fresh properties through increase of air content. The flexural strength of mortar is determined by three-point bending test at the age of 2, 7, 14 and 28 days. The results indicate that re-dispersible powder decreases the flexural strength of mortar at early-age. However, it improves the flexural strength of hardened mortar, at which the polymer film has fully formed and spans all the materials.

11-21
Effect of different curing methods on the compressive strength development of pulverized copper slag concrete

Authors: Daniel Mensah Boakye, Herbert Chidozie Uzoegbo, Nonhlanhla Mojagotlhe, Moeti Malemona

Abstract

View in PDF

Number of views: 593

The results of laboratory studies conducted to evaluate the effects of different curing conditions on the compressive strength development of concrete made with pulverized copper slag as partial replacement for ordinary Portland cement (OPC) is presented. Concrete cube specimens were made with copper slag replacing cement in the following proportions; 2.5, 5, 10 and 15% compared to the control (0%) specimen under normal laboratory conditions and cured in three different conditions, namely; water, solar chamber and ambient air up 90 days. Test performed included X-ray Fluorescence (XRF) and sieve analysis respectively for the chemical oxide composition and fineness for both the pulverized copper slag and ordinary Portland cement. Specimens were tested for compressive strength up to 90 days of curing, with the temperature and humidity of the surrounding curing environment recorded for each of the three curing method used. The experimental results indicate a significant drop in the compressive strength as the copper slag content increases for all curing methods. Moreover, for the control samples, the percentage decrease in the compressive strength for the 3-day curing for water cured sample, compared to the solar chamber and ambient air were respectively 31% and 28%. However, beyond 28 up to 90 days of curing, the water cured samples yielded a higher compressive strength, followed by the solar chamber and ambient air. The percentage increase in the compressive strength up to 90 days of curing for water cured specimen, compared to the solar chamber and ambient air were respectively 8.5% and 12%. This trend was similar for all percentage replacement of cement with the pulverized copper slag

22-31
Measurement Points selection strategy to update models in frequency domain

Authors: Farid Asma

Abstract

View in PDF

Number of views: 512

In model updating procedures, the experimental data provide information for a configuration error modelling. The selection of the measurement DOFs in the experimental frequency response function should make the updating procedure as capable as possible of detecting configuration mismodelling in the initial model. The selection of the measurement DOFs should be sensitive to the effects of the possible configuration mismodelling in the model. For the model updating procedure, the experimental data should be measured in such a way that the modified model resulting from the updating procedure is the most likely to be reckoned as an updated model. This paper proposes a technique for selecting measurement points that should provide the best structural information for updating. The selected measurement points would define the defects that can be detected. The proposed method is based on the derivative of the frequency response function which materializes the participation of each element on the variation of the measured frequency response.

32-45
Coupling Neumann development and component mode synthesis methods for stochastic analysis of random structures

Authors: Driss Sarsri

Abstract

View in PDF

Number of views: 521

In this paper, we propose a method to calculate the first two moments (mean and variance) of the structural dynamics response of a structure with uncertain variables and subjected to random excitation. For this, Newmark method is used to transform the equation of motion of the structure into a quasistatic equilibrium equation in the time domain. The Neumann development method was coupled with Monte Carlo simulations to calculate the statistical values of the random response. The use of modal synthesis methods can reduce the dimensions of the model before integration of the equation of motion. Numerical applications have been developed to highlight effectiveness of the method developed to analyze the stochastic response of large structures.