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Durability of Concrete Products
Категория: Стр. тех. и арх. |
Новость от: Admin |
27-12-2005
1. Provision of durability of concrete products and reinforced-concrete structures.
2. Field of application – construction. Obtained practical results were introduced for the construction of navigation facilities in the Far East: for erection of reinforced structures at different chemical factories of Armenia and also for design of refractory concrete mix of various purposes.
3. Besides physical and mechanical properties it is necessary to take into account the conditions of service, that is, to provide chemical resistance for any medium. Parameter of chemical stability, e.g. for reinforced structures, where the concrete must protect steel reinforcement from corrosion, it is necessary to have alkaline medium with pH not less than 11.8. In other cases, e.g. for hydro technical and refractory concretes, specifically in case of aggressive medium (soleplate and others) this coefficient should be minimized as much as possible. Predication and correction of this coefficient being caused by the amount of tree lime should be performed on the stage of choice of concrete mixture according to proposed formula [1]
C= YZ – AP kg/m3
C – Is amount of free hydroxide where calcium in choice concrete mixture kg/m3
Y - The amount of Ca (OH)2 extracted by 1 kg cement in conversion to CaO, kg;
Z – The amount of cement obtained during the choice of concrete mixture, kg/m3
A - Chemical or “hydraulic” activity of the applied sand kg CaO /kg;
P – The amount of the sand estimated for the choice of concrete mixture kg/m3.
Correction of the choice mixture should be performed regardless of the formula for the concrete mixture selection for the aggregate activity is not taken account for any of existing formulae. Moreover, the correction doesn’t significantly Influence on design physical and mechanical parameters of concrete.
1. The coefficient of chemical activity, (A) that is the amount of lime for in chemical interaction with reactive constitutes of aggregates is defined in accordance with special method [2].
2. In comparison with existing methods the advantage of the developed one is for direct quantitative estimation of the reacted Ca (OH)2 regardless of fineness modulus of the aggregate. Other methods are based on changing of lime motor concentration during heating and reliable results can’t be obtained.
3. According to the developed method activity parameters were revealed for a number of volkanites of various composition, shape phase and mineralogical compound of Armenia, Kamchatka, Georgia and artificial aggregates (lightweight aggregates, agglomerates and others) Russia, Ukraine, Azerbaijan and others. Coefficient is obtained for retardation and braking of cement hydration while using plasticized admixtures. It is equal to 0,7.
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Добавил: Wilton
Дата: 2024-09-01 08:34:58
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