5.1 DEVELOPMENT OF THE OPTIMAL COMPOSITION AND ECONOMIC JUSTIFICATION FOR THE USE OF SELF-COMPACTING CONCRETE IN MONOLITHIC STRUCTURES

Abstract

The study aims to develop an optimal composition of self-compacting concrete (SCC) for use in monolithic structures. The effects of various additives and proportions on concrete properties such as strength, fluidity and durability are considered. An economic justification for the use of SCC is also provided, including an assessment of production and placement costs. It is expected that the use of SCC will improve the efficiency of construction processes and reduce labor costs.

Key words: self-compacting concrete, optimization of the composition, monolithic structures, economic justification , strength characteristics

As a result of the experiments, the dependences of strength on the composition of the concrete mixture were determined. Based on the data obtained, the following composition of self-compacting concrete with a complex additive was proposed, providing the necessary characteristics of the concrete mixture for its use in monolithic construction in our region:

• Portland cement Holcim M500 CEM II/ A-I 42.5;
• 50% crushed sand from granodiorites + 50% Kama sand;
• crushed stone of fraction 5-10 mm;
• 10% microsilica instead of Portland cement;
• 10% fly ash instead of Portland cement;
• superplasticizer Polyplast SP-4.

The concrete mixture contains 10% microsilica - this allows to compact the structure of the cement stone and increase the strength of the concrete, also this amount of MK allows to avoid "overstressing" the concrete to avoid the formation of cracks.

The addition of 10% fly ash increases the mobility of the concrete mixture. The use of microsilica and fly ash allows the reaction of aluminosilicates and silicates to start with calcium hydroxide in cement, resulting in the formation of low-base  calcium hydrosilicates CSH ( 1) and high-strength concrete is obtained.

Polyplast SP-4 was used as a plasticizer ; in combination with fly ash, it allows for the production of a self-compacting mixture, while reducing the price (in comparison with the use of a polycarboxylate- based hyperplasticizer ).