Research paperDurability of alkali activated cement produced from kaolinitic clay
Graphical abstract
Introduction
Alkali activated cements (AAC) are inorganic polymers (IP) that are generated from activation of solid aluminosilicate material to form a new class of three-dimensionally network of alkali alumino-silicates (Ingles, 1970, Patfoort and Wastiels, 1989, Davidovits, 1991, Davidovits and 383–397, 1994, Van Jaarsveld et al., 2002, Rowels and O'Connor, 2003, Duxson et al., 2007, Slaty et al., 2013, Lemougna et al., 2014). These materials are an attractive alternative to Portland cement as they have a comparable compressive strength, hardness, and chemical stability, but less energy is consumed and less greenhouse gases are emitted during production (Patfoort and Wastiels, 1989, Steveson and Sagoe-Crentsil, 2005, Xu and Van Deventer, 2000).
The quality of the alkali activated cement is an important criterion for their use as a new construction material (Rovnanik, 2010). Different construction materials show different degrees of durability depending on the chemical composition and on the external environment (Miller, 2005). Since AAC are alkaline in nature, stability and durability aspects present similarities with more traditional cements like Portland or Blast Furnace cement (Puertas et al., 2003). Durability is an important parameter, which reflects the resistance of materials to short and long term performance under weathering action, chemical attack, and abrasion while maintaining its desired properties (Detwiler and Taylor, 2005). A specific class of alkali activated cements are geopolymers. Previous publications investigated the durability characteristics of geopolymers and other AAC from different raw materials like latosoils (Gogo, 1990), clay (Diop and Grutzeck, 2008), cement based repair materials (Al-Zahrani et al., 2003, Thomas and Keralia, 2004), fly ash (Jimenez et al., 2006, Rangan, 2008) blast furnace slag and metakaolinite (Palomo et al., 1999, Zhang et al., 2010a, Zhang et al., 2010b). The durability has been tested under different conditions such as aggressive environments and alkali–silica reaction. The results indicated that these materials have a good resistance against drying (low shrinkage), sulfate and acid attack.
The purpose of this research is to study the durability of a newly generated inorganic polymer by chemical activation of kaolinite from south Jordan with a NaOH solution. The durability tests are carried out under different environmental and chemical conditions that include: drying shrinkage, ambient conditions (dry conditions at room temperature), wet conditions in de-ionized water, wetting–drying conditions, chemical attack (sea water and sodium sulfate solution), acid attack, and alkali–silica reaction.
Section snippets
Experimental procedure
The used materials for fabrication of the geopolymer specimens are: Jordanian Hiswa kaolinite (JHK) as aluminosilicate source and Jordanian silica sand from south Jordan as a filler material (JSS); NaOH from Merck with 99% purity was used in the form of pellets to prepare the alkali solution with distilled water.
Table 1 gives the chemical composition as detected by Bruker System S4 Pioneer X-ray fluorescence (XRF) analysis of JHK and JSS materials. The results indicated that the Jordanian
Drying shrinkage
Drying shrinkage is the reduction in volume which is primarily caused by the loss of water during the drying process. The amount of volume change can vary, based on mixture proportions and material properties of constituents. Generally, materials containing higher fine content exhibit greater potential change than those containing higher content of coarser materials (Wallah, 2009). The type of clay mineral also influences the material properties. The materials that have expandable minerals such
Conclusions
The durability of a kaolinite/NaOH inorganic polymer (IP) or geopolymer using Jordanian Hiswa clay was studied. The results have indicated that the addition of sand filler has improved the compressive strength and the durability of the IP under all experimental conditions. The IP has indicated very low drying shrinkage and very good performance under ambient, de-ionized water, sodium sulfate, and seawater conditions. These conditions did not negatively influence the mechanical properties. This
Acknowledgments
The authors are indebted to VLIR-UOS for the financial support via the project “Chemical stabilization of natural geomaterials for construction and industrial applications”, number ZEIN2006PR33.
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