Study On Alkali-Activated-Carbonatites Cementitious-Grouting Material

Saving resources and energy, protecting ecological environment, and improvingdurability are the three primary essentials for sustainable development of buildingmaterial industry. Because the production of traditional cementitiousmaterial-Portland cement, has led to increasingly severe environmental deteriorationand resource problems, it is of strategic meaning to develop new types ofcementitious materials using "low-grade"raw materials. In this paper, a initiativeresearch of the "Alkali-Activated-Carbonatites Cementitious Materials (AACCM)for grouting engineering was presented, in which, the reaction thermodynamics, thereaction products, the mechanism of structure formation, the influence factors, andselection and manufacture of raw materials were studied in detail. Besides, themanufacture process, the properties and performance, and the influence factors ofAACCM were also studied. A simulated grouting experiment was carried out basedon the systematic work above.Thermodynamics investigation indicate that the reaction between carbonatiteand sodium silicate solution, forming hydration calcium (magnesium) silicate gel,can occur at normal temperature. Kinetics studies show that the rate and degree ofthe reaction are influenced by several factors: the composition of carbonatites, thecrystallinity and crystal size of dolomite in carbonatites, the mole ratio of SiO2/Na2O,the concentration and pH value of sodium silicate solution and the reactiontemperature, etc. When some specific carbonatites, with MgO content ranging from10 to 20% and the particle portion of less than 5μm diameter taking up over 80%,was selected to react with certain industrial water-glass, which was modified andwith modulus ranging between 1.6 and 2.0, Baume degree being about 40, pH valuevarying from 13 to 13.5, the reaction could be accelerated and AACCM with certainstrength was obtained.It is of important significance to determine the reaction products of sodiumsilicate solution and carbonatites reaction for this new type of cementitious material.But it is very difficult to ascertain these amorphous products with only one anyanalyze and characterization techniques. Therefore, using the combination of SEM,XPS (X-ray photoelectron spectroscopy for element quantitative analysis), IR, XRD,DTA and (29)~Si NMR ((29)~Si nuclear magnetic resonance) to analyze the reaction...