Effects of sand addition on production of lightweight aggregates from Tunisian smectite-rich clayey rocks

The effect of additives on the properties of lightweight aggregates produced from clay

“…For example the addition of amorphous SiO 2 in form of cullet powder to sewage sludge ash for the production of LWA was reported to enhance the bloating behaviour of the material [11]. Other studies reported the addition of quartz sand to be beneficial for the production of LWA from smecite-rich claystone-marlstone rocks or the addition of waste glass to lignite coal fly ash leading to LWA with advanced physical and mechanical properties [4,12]. The addition of CaO (a flux) to water reservoir sediments led to an enhanced expansion and pore growth during firing but resulted in a LWA with decreased strength [13].…”

“…which severely complicates the assessment of strength variation due to pore distribution alone. The addition of SiO 2 in form of quartz sand and cullet powder (amorphous SiO 2 ) was reported to have positive effects on firing temperature, expansion and mechanical properties of different types of LWA [4,11]. In the present study amorphous SiO 2 in the form of silica fume and crystalline SiO 2 in the form of quartz powder were used as additives.…”

“…Different types of raw materials of natural and artificial origin are used for the production of lightweight aggregates (LWA) [1][2][3][4][5]. The chemical composition of the raw material determines the bloating (expansion) behaviour and the properties of the product [6].…”

Microstructure and mineralogy of lightweight aggregates manufactured from mining and industrial wastes

“…The Si0 20 Ah03 and FeD + Fe203 contents mainly corresponded to quartz and phyllosilicates (illite, kaolinite and smectite) present in both samples. Na20 and K 2 0 contents were mainly attributed to the interlayer cations of clay minerals and to feldspars [15]. In the SS, the main compound is Ah03 (Table 2 ) along with amorphous compounds and{or organic matter [14].…”

“…Bloating Index (BJ) expresses the volume change after firing of LWAs and it was determined following the equation: BI= 100 x (d 2 -d 1 )fd 1 , where d 1 and d 2 are the diameters of pellets before and after firing respectively [15]. DI)' particle density (Pd) is the relationship between the mass of a sample of aggregates dried in an oven and the volume these aggregates occupy in water, including the watertight internal pores and the available pores to water [17].…”