Use of Slag/Sugar Cane Bagasse Ash (SCBA) Blends in the Production of Alkali-Activated Materials

Abstract

Blast furnace slag (BFS)/sugar cane bagasse ash (SCBA) blends were assessed for the production of alkali-activated pastes and mortars. SCBA was collected from a lagoon in which wastes from a sugar cane industry were poured. After previous dry and grinding processes, SCBA was chemically characterized: it had a large percentage of organic matter (ca. 25%). Solutions of sodium hydroxide and sodium silicate were used as activating reagents. Different BFS/SCBA mixtures were studied, replacing part of the BFS by SCBA from 0 to 40% by weight. The mechanical strength of mortar was measured, obtaining values about 60 MPa of compressive strength for BFS/SCBA systems after 270 days of curing at 20 °C. Also, microstructural properties were assessed by means of SEM, TGA, XRD, pH, electrical conductivity, FTIR spectroscopy and MIP. Results showed a good stability of matrices developed by means of alkali-activation. It was demonstrated that sugar cane bagasse ash is an interesting source for preparing alkali-activated binders.

Mechanical and durability properties of alkali-activated mortar based on sugarcane bagasse ash and blast furnace slag

“…Mortars cured at 65ºC for 3 and 7 days presented compressive strength values in the range 42.8 -53.5 MPa, depending on the proportion of BFS/SCBA (85/15, 75/25 and 60/40). In the same way, mortars cured at room temperature for long curing times presented higher compressive strength than mortars cured at 65ºC and the total porosity of these mortars was also reduced [11]. Recently, Castaldelli et al [12] presented another paper where the use of fly ash/SBA was reported.…”

“…Castaldelli et al [11] studied the use of SBA generated in a sugar factory for preparing alkaliactivated systems based on binary systems of blast furnace slag (BFS)/SBA. According to the authors, even presenting a high proportion of organic matter (about 25%) and high percentage of impurities (calcite and quartz), SBA from a sugar factory can be an interesting material for producing alkali-activated binders.…”

Study of the binary system fly ash/sugarcane bagasse ash (FA/SCBA) in SiO2/K2O alkali-activated binders

“…This original ash (non-calcined ash), in a first approach, was tested for preparing geopolymeric mixtures. However, some problems in setting and hardening were observed, since the residue presents a high amount of organic matter [28]. Thus, in order to remove it, the original ash was calcined at 650°C for 2 hours.…”

“…Afterwards, the sugarcane bagasse ash was dried at 105°C and milled for 20 minutes in a ball mill in order to increase its reactivity [28]. This original ash (non-calcined ash), in a first approach, was tested for preparing geopolymeric mixtures.…”

“…After the burning process, approximately 2.5% (by mass) of the bagasse remains as ashes, called sugarcane bagasse ash [26]. Nowadays, this waste is being researched as a pozzolanic material [27], but there are fewer studies on its use in alkali-activated binders [28,29].…”