New compositions of self-compacting fiber–reinforced concrete mixtures

Abstract

 One of the topical problems of recent years is the repair and reconstruction of hydraulic structures of the water management and reclamation complex, and underwent considerable destruction during the long-term operation. One of the promising materials for repair and restoration of reinforced concrete hydraulic structures is self-priming concrete mixes (SPCM), which allow efficient concreting of structures of complex configuration saturated with reinforcement and in areas of restricted access by casting without the use of vibration sealing.

SPCM are obtained by modifying traditional concrete mixtures with organo-mineral additives. Organo-mineral additives are complex modifiers, which are combinations of organic and mineral additives. The organic component in such additives is represented by a superplasticizer (SP), the mineral component is a silica-containing component: microsilica, metakaolin or fly ash. When joint application of SP and microsilica or metakaolin is performed, a synergistic effect is manifested, that is, the total effect of their combined effect, which far exceeds the effect of each component separately.

Recent research has focused on the development of multifunctional modifiers, which include an organo-mineral modifier and additives that increase the fracture toughness and adhesion strength of concrete. In our opinion the combination of an organo-mineral modifier with polymer dispersions (latex) and polypropylene reinforcing fibers.

The influence of the content of polycarboxylate superplasticizer, polymer latex and polypropylene fiber on the mobility of concrete mixtures and on the physical and mechanical properties of concrete on their basis at constant values of the water-cement ratio (V/C) and the content of metakaolin: compressive strength f_{сm cube}, bending strength f_сtd, adhesion strength f_adg, impact strength f_imp, water absorption W_m.

The research results show that the superplasticizer and polymer latex are positively influenced by the mobility of concrete mixtures under the predominant influence of the superplasticizer. The mobility of concrete mixtures is significantly reduced when the content of polypropylene fibers in the mixture increases. The strength of compression of concrete slightly increases with increasing the content of superplasticizer and polypropylene fibers in a concrete mixture.  Polymer latex negatively affects the strength of compression of concrete. Superplasticizer, polymer latex and polypropylene fiber have a positive effect on bending strength, adhesion and impact strength of concrete and reduce its water absorption.

The area of optimal formulations is in the range (% of cement mass): polycarboxylate superplasticizer — 1,4 … 1,8, polymer latex — 2,5 … 5,0, polypropylene fiber 0,45 … 1,80 at the content of Metakaolin 10% of the mass of cement, the consumption of cement 450 kg / m3, the flow rate of sand with a modulus of fineness 1.49 — 940 kg/m³, the consumption of crushed stone 5-10 — 940 kg/m³, W/C = 0.4