High Calcium Fly Ash-to Silica Fume-to Slag Sand Ratio Versus Compressive Strength and Density of Cementless Concrete


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Title: High Calcium Fly Ash-to Silica Fume-to Slag Sand Ratio Versus Compressive Strength and Density of Cementless Concrete

Author(s): S.I. Pavlenko, L.P. Myshlyaev, V.F. Evtushenko, A.V. Soin and Yu. M. Bazhenov

Publication: Special Publication

Volume: 178


Appears on pages(s): 1117-1126

Keywords: fly ash; silica fume; slag sand; mathematical models .

Date: 6/1/1998

The Siberian State Academy for Mining and Metallurgy (SSAMM) has developed a cementless fine-grained ash-slag concrete consisting of high calcium fly ash and slag sand from thermal power plants and containing silica fume. The also composition and technology of the concrete has been patented. The compressive strength of the concrete is 5 to 20 MPa. It does not contain any natural or artificial aggregates (gravel, sand, claydit, polystiren). High-calcium fly ash combined with silica fume is used as a binder. The influence of the ratio of the above mentioned three components on the compressive strength and density of the concrete developed was studied using a computing technique. As result, a three-dimensional integral scheme was designed for proportioning the concrete of a required strength class (5 to 20MPa) and density (2000 to 2500 kg/m3). The optima1 mixture proportions for concrete of 20 MPa strength class were as follows: Fly Ash 30-40% Slag Sand 3 O-40% Silica Fume 3-4% Water (60-80°C) the rest Concrete with optimum mixture proportions was used to investigate optimization of schedules of concrete heat treatment carried out in an automatic steam-curing chamber. Here, the three-dimensional system was involved as well: previous curing before heat treatment of 3, 6 and 12 hours; three schedules of a heat treatment i.e.,3(6)3, 3(9)3 and 3(12)3 hours cycles where (6), (9) and (12) hours are holding periods; three isothermal temperatures of 60, 80 and 100°C. A computerized analysis of the results of the investigation showed that heating of concrete during 9 to 10 hours at 80 to 1OO’C with 6 to 7 hours of curing provided the best strength characteristics of the concrete.