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During the last decades, the concrete industry has been widely developing in many ways such as the methods of pouring concrete in order to achieve high quality concrete and low cost. Some new concretes have been produced which is completely defer from the conventional concrete in the method of mixing, pouring and no need for the normal compaction methods that require more labors, tools and cost more. This paper presents two special types of concrete; Two-Stage Concrete and Rock Filled Concrete and presents the advantages and special requirements for each of the two special types of concrete and their uses.
Advances in concreting methods (PDF Download Available). Available from: https://researchgatepublication/266376395_Advances_in_concreting_methods [accessed May 4, 2016].
One of the disadvantages of conventional concrete is the high self weight of concrete. Density of the normal concrete is in the order of 2200 to 2600 kg/m3. This heavy self weight will make it to some extent an uneconomical structural materials. Attempts have been made in the past to reduce the self weight of concrete to increase the efficiency of concrete as a structural material. The light-weight concrete as we call is a concrete whose density varies from 300 to 1850 kg/m3.
The strength of light-weight concrete depends on the density of concrete. Less porous aggregate which is heavier in weight produces stronger concrete particularly with higher cement content. The grading of aggregate, the water/cement ratio, the degree of compaction also effect the strength of concrete.
WORKABILITY :-
Light-weight concrete exhibits higher moisture movement than the normal weight concrete. Considerable attention is required to be given to the workability aspect for structural light weight concrete.
MIXING :-
Cement content : 325 to 550 kg/m3
W/C Ratio : 0.4 to 0.6
Percentage of same to total aggregate : 50% to 100%
Maximum aggregate size : 10 mm
Air-content : 6% to 9%
Fibre content : 0.5 to 2.5 % by volume of mix
: Steel --- 1% 78kg/m3
: Glass --- 1% 25kg/m3
: Nylon --- 1% 11kg/m3.