Effect of substitution of lime stone in CPJ45 by Jorf Lasfer fly and bottom ash on the hydration of cement and on the mechanical proprieties of mortar

K Nabih,Ángeles G De La Torre,F Cherkaoui El-Moursli,K Kada,O Sassi,R Barbacha,A Diouri,N Khachani,M Alami Talbi

doi:10.1051/matecconf/20141101046

Abstract

The study undertaken in this work indicates that it is possible to exploit the industrial by products such as fly ash and bottom ash from the combustion of coal in Jorf lasfar thermal power and valorize them as additive in the construction materials. Because in addition to their poozolanic activity, these ashes have technical, economical and ecological compelling interests.In this work we have studied the effects of substitution of limestone in the CPJ45 cement by fly ash or bottom ash on the mechanical properties of prepared mortars, on the grinding time and on the hydration of the new cements.Different analysis techniques were undertaken to determine the physico-chemical characteristics of the starting materials.X-ray fluorescence (XRF) had permitted the classification of fly ash and bottom ash in the class F from their levels on major oxides. Rietveld quantitative phase analysis (RQPA) allowed us to compare the percentages of clinker phases with that calculated with bogue formulas. The result showed that the values found by RQPA of C 3 S and C 3 A were much higher than those calculated, while for the C 2 S the values given by RQPA were much lower.The isothermal conduction micro calorimeter was used to measure the heat evolution during the hydration of the cements prepared. We noticed that the additions of fly ash or bottom ash have accelerated the hydration of C 3 A and have delayed that of C 3 S.The tests performed by substituting limestone in CPJ 45 by different proportions of fly ash or bottom ash have shown that the effect of these ashes on the mechanical properties of cement CPJ 45 . We have observed that the 28days mechanical strengths of the mortar went for a maximum with the substitution of lime stone by 6% of fly ash and 7% of bottom ash;We have also observed that increasing the amount of substitution of lime stone by fly ash had decreased the grinding time and had eliminated the clogging of the cement on the mill balls.

Highlights

The Moroccan cement industry is a major player in the development of the country because growing needs for cementing products for the construction of buildings and communication infrastructures are considerable
Kokubu established that partial replacement of cement by a good quality fly ash increases the workability. typically, to produce a concrete with the same 28-days strength as one made using a pure Portland cement [3].Uchikawa reviewed rheological studies of Fly ash containing a high proportion of coarse ash (>45 um) and mentioned that these materials are unsuitable for blending but may be suitable for inter grinding, because the effect of the latter is largely to separate particles present in agglomerates and to break up some of the larger cenospheres [4]
In Morocco, the production of fly ash from thermal power plants is estimated at 570 000 tons per year (400,000 tons are recoverable in the dry state)

Summary

Introduction

The Moroccan cement industry is a major player in the development of the country because growing needs for cementing products for the construction of buildings and communication infrastructures are considerable. Among the goal chosen to optimize the production of cement is the focus more towards the manufacture of cement with addition of industrial by products such as fly and bottom ash, that are known to be of great interest in cement and concrete These ashes have hydraulic and poozolanic activities and have the potential to improve the durability of concrete [1,2]. In Morocco, the production of fly ash from thermal power plants is estimated at 570 000 tons per year (400,000 tons are recoverable in the dry state) The use of these ashes in cement can protect the environment by reducing the CO2 emissions [5] and conserving the raw materials. Such utilization of these by products is a good example to provide a solution to environment problems for the storage of these wastes and improve the thermal balance in an area of high energy consumption

Methods

Results

Conclusion