Study On The Influence Of Composition Of Static Demolition Agent On Its Properties

Static demolition agent(SDA) is a kind of cementious material that expanding greatly during hydration, when static demolition agent mixed with water and been filled in the boreholes that for demolishing the brittle materials, the volume expansion occurred with hydration makes brittle boulders cracking and demolishing. During static demolition agent hydrating, the expansive force increasing peacefully and bringing little environmental problems such as noise, viabration, dust and flying debris which usually coming with explosion. Static demolition agent is not dangerous or toxic, and so it is not a product restrained by public security ordinance, and it also have the advantages of low costing and convenient to use. Therefore, static demolition agent used more and more nowadays and it is the complementarity of conventional blasting.Through the study of setting times, expansive pressure and hydration temperature raising of C-S, C-A, C-F two-phase-system and C-S-A-F four-phase-system SDA, the following results were concluded. When silicate phase, ferrite phase and mixed phase used as the assistant phase of SDA, setting times increasing, expansive pressure decreasing with the content of assistant phase raising; when aluminate phase used as assistant phase, setting times decreasing with the raising of assistant phase content, as well as expansive pressure. During 1400 to 1500℃, setting times and expansive pressure are benefit from clinker calcined temperature of two-phase-system SDA increasing, and the proper calcining temperature for two-phase-system SDA clinker is 1450~1500℃; and for the four-phase-system SDA, setting times prolongs with clinker calcined temperature raising, but expansive pressure is opposite, decreases with clinker calcined temperature raising, and the proper clinker calcining temperature for this system SDA is 1400~1450℃. When the f-CaO content and clinker calcined temperature are constant, setting times decreases with the silicate phase increasing and the ferrite phase reducing, or with the aluminate phase increasing and the ferrite phase reducing, but expansive pressure varies oppositely. Through the study on the influence of admixture of different types and different dosage on the properties of SDA, the following conclusions can be made. Mixing gypsum to SDA has notably effect on setting times and expansive pressure of SDA, and its proper dosage of gypsum is 2~3%; Sodium tripolyphosphate retards SDA effectually, and its dosage shall not exceed 0.6%; Citric acid has less retarding effect on SDA, and the dosage also shall not exceed 0.6%; Calcium gluconate retards SDA less than citric acid, but the dosage can reach 1%. Through the fluidity experiment of static demolition agent with different admixture, the following conclusions can be made: polycarboxylate superplasticizer has best water reducing effect, and the dosage will not suitable to exceed 0.4%; SM superplastizer reducing less water than polycarboxylate superplasticizer, and its dosage shall not exceed 0.8%; FDN superplastizer has moderate water reducing rate, and the dosage shall not exceed 0.8, too; Sodium ligninsulfonate has bad water reducing effect.