Effect of partial replacement with thermally processed sugar cane bagasse on the properties of mortars

Augusto Cesar Da Silva Bezerra,Conrado De Souza Rodrigues,Sérgio Luis Costa Saraiva,Maria Teresa Paulino Aguilar,Maria Cecília Novaes Firmo Ferreira,Luis Felipe Dos Santos Lara,Romero Cesar Gomes,Laurenn Wolochate Aracema De Castro

doi:10.1590/s1517-707620170001.0117

Abstract

Sugar cane bagasse is a residue of the sugar-alcohol industry, and its main destination is represented by burning boilers for power generation. The bagasse cogeneration of power produces a sugar cane bagasse ash (SCBA) residue that does not have a useful destination. Ashes are commonly studied as pozzolan in Portland cement production. International Standards indicate the use of pozzolan with up to 50% substitution. In the present work, we investigate the use of SCBA as an addition in Portland cement. For this purpose, Portland cement was prepared by substituting cement with 0, 10, 20, and 30% processed SCBA in volume. The ashes were processed by re-burning and grinding and were then characterized by scanning electron microscopy, Xray diffraction, laser granulometry, X-ray fluorescence spectrometry, the Chapelle method, and pozollanic activity. To evaluate the cement with substitution, we used the mortar recommended by NBR 7215. The mechanical properties of the cements with replacement were analysed through tests of the compressive strength and flexural strength of mortars. The results appear interesting and support the possible use of SCBA in the production of cement from the aspect of mechanical properties evaluated.

Highlights

In 2013, Brazil produced approximately 70 million tons of cement [1]
Evaluating the results of the particle size of sugar cane bagasse ash (SCBA) RG, it is perceived that the presented size of particles smaller than those of the Portland cement used has met the parameters of ASTM C618 [28]
It is believed in clear pozzolanic reaction SCBA, since the pozzolanic reaction is characterized by calcium hydroxide reaction released in the cement hydration reaction of Portland and oxide silicon on non-crystalline form, and others (SiO2 + Al2O3+Fe2O) present in the pozzolan

Summary

Introduction

In 2013, Brazil produced approximately 70 million tons of cement [1]. Cement consumes 5.5 GJ of energy and releases approximately 1 ton of CO2 per t of clinker, corresponding to between 5 and 8% of the total CO2 emitted annually into the atmosphere [2]. An alternative to mineral addition is represented by sugar cane bagasse ash (SCBA). It is important to highlight that while the bagasse combustion releases CO2, the CO2 emission balance is essentially zero when the complete cycle is considered because photosynthesis restores the burned biomass in the sugar cane crop. After the sugar cane combustion process, approximately 0.7% of the initial mass remains in the form of residual ash, the equivalent of 4.8 million tons in just 2009 [3]. Considering that only 93% of the bagasse is used as fuel in the boilers, the amount of residual ash would be approximately 0.58% of the sugar cane’s total mass, which amounts to a production of nearly 4 million tons of ash [4].

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