Synthese et caractérisation des matériaux géopolymeres a base des métakaolins et des rebus de briques de terres cuites

Abstract

Waste fired bricks from MIPROMALO, located in Yaoundé. The kaolins used in this work were collected in the West and Littoral regions of Cameroon. The standard metakaolin denoted MK-BALCO from BALCO (Italy) were used as aluminosilicate sources in this work for the synthesis of geopolymer materials. Bauxite calcined at 600°C and rice husk ash were used as semi-crystalline alumina and silica sources, respectively. Calcium aluminate hydrate, calcium hydroxide and calcium silicate hydrate prepared from calcined eggshells and rice husk ash were used as additives. Commercial sodium waterglass and sodium waterglass from rice husk ash containing a molar SiO /Na O ratio kept constant at 1.6 and a phosphoric acid solution (10M) 22 were used as hardeners. The synthesised geopolymer materials were characterised by measuring their compressive strengths, X-ray diffractometry, Fourier Transform Infrared spectrometry and scanning electron microscopy. The geopolymer materials based on waste fired bricks obtained using a commercial sodium waterglass, sodium waterglass from rice husk ash and a phosphoric acid solution have compressive strengths equal to 40.84, 47.82 and 56.44 MPa, respectively. The coexistence of the poly(phospho-siloxo) network and calcium phosphate on the compressive strengths of geopolymer materials synthesised in an acidic medium were studied. It can be observed that the compressive strengths of the geopolymer materials obtained with the addition of 10, 20, 40 and 50 g of calcined eggshells to waste fired bricks are 30.15, 22.85, 21.16 and 13.47 MPa, respectively. Those resulting from the addition of calcium aluminate hydrate are 32.62, 31.58, 17.83 and 16.33 MPa, respectively. While those resulting from the addition of calcium silicate hydrate are 44.02, 42.71, 40.19 and 18.59 MPa, respectively. A comparative study of the properties of geopolymer materials from standard and local metakaolins have compressive strengths of 44.46 and 40.32 MPa, respectively, while that of waste fired bricks is around 42.82 MPa. The behaviour of semi-crystalline alumina added to waste fired bricks and metakaolin during the geopolymerization process was also carried out. Calcined bauxite (0, 25, 50, 75 and 100 g) were added to 250 g of waste fired brick and metakaolin. The compressive strengths and microstructural properties of geopolymer materials using metakaolin as aluminosilicate source are improved by adding 25, 50 and 75g of semi- crystalline alumina. After the addition of semi-crystalline alumina, those of the geopolymer materials obtained by using waste bricks as the source of aluminosilicate decrease.