Characterization of alkali activated kaolinitic clay

Low cost building materials have been developed by chemical activation of Jordanian Hiswa kaolinite with a sodium hydroxide solution. The effect of the main parameters of synthesis and processing on the development of compressive strength was studied. An investigation of the physical, thermal, mineralogical and microstructural properties was performed. A compressive strength of 32 MPa was obtained for a mixture cured at 80 °C for 24 h. The mineralogical and microstructural results on the hardened material indicate the formation of sodium zeolite phases and feldspathoids with a Na/Al ratio of one. The high compressive strength observed is directly related to the formation of the new phases that fill the pore spaces and bind the matrix.

► Kaolinite can be alkali activated.
► Zeolite-like reaction products are formed.
► Compressive strengths above 40 MPa can be obtained.
► The environmental impact (CO2 emission) is smaller than for geopolymers.