Development of nanomodified rapid hardening clinker-efficient concretes based on composite Portland cements

Abstract

It has been shown that significant reduction of «carbon trace» in construction technology is achieved by production of clinker-effective concretes based on composite Portland cements. Studies have shown that uneven distribution of grain fractions of the filler mix and their increased specific surface area lead to growth of water demand, stratification, bleeding in the concrete mix and a decrease in concrete strength. To achieve higher grain packing density, an approach based on optimizing particle size distribution in the concrete mix components was implemented. It was found that increased early strength of concretes based on low-emission composite cements is achieved by introduction of polycarboxylate (PCE) superplasticizers and alkaline-sulfate activation. To establish connection between environmental and technical properties of concretes, clinker efficiency in concrete was determined. An increase in strength of modified concrete based on composite Portland cement CEM II/B-M 32.5 R (clinker factor 0.65) create the possibility for a significant reduction of specific consumption of clinker per unit strength, up to 4.5…3.0 kg/(m 3 MPa); accordingly, CO 2 intensity 3.9...2.6 kg CO 2 /(m 3 MPa). Significant intensification of the processes of early structure formation in nanomodified clinker-efficient concretes is ensured by a comprehensive approach: optimization of the component mix, introduction of the PCE superplasticizer and nanomodifiers. Using the laser diffraction method, it was proved that main contribution to development of specific surface of the nanomodified cementing matrix is made by ultrathin particles ( K isa =761.2 μm –1 vol. %) of nano-SiO 2 . It was established that synergistic combination of mineral additives in composite Portland cement and complex nano-SiO 2 +C-S-H-PCE nanomodifier provide increased early strength (after 12 hours – R c =6.4 MPa) and obtaining rapid hardening concrete class C50/60 ( f cm 2 / f cm 28 =0.51). Thus, there are reasons to argue that it is advisable to develop nanomodified clinker-efficient concretes in order to ensure rapid construction and solve problems connected with necessity of implementation of a strategy of low-carbon development