The chemical additives in the prefabricated reinforced concret technology

Usov Boris Aleksandrovich, Okol'nikova Galina Erikovna

Moscow State University of Mechanical Engineering, Moscow, Russia

Abstract:

The article presents research data of concrete with chemical admixtures for precast concrete. To the additives are hardening accelerators, systems-based accelerators, plasticizers and air-entraining additives. The authors studied the effect of the addition of electrolytes (NаСl, Nа₂SО₄ СаСl₂, Са(NO₃)₂), complex additives (on the basis of the electrolytes and plasticizers, air-entraining additives SPD and mikrokremnezema) on properties of concrete, strength of concrete steamed and some of its properties. By accelerating the effect of electrolyte additives studied were located in the sequence: СаСl₂ > NаСl > Nа₂SO₄ > Са(NO₃)₂. It is noted that the increase of concrete strength with electrolytes increases with decreasing the duration of heating and the content of aluminates in Portland cement, which allows for 40...50% reduction in the warm-up of concrete or 5...15% of cement consumption. Complex agent (on their basis), irrespective of the Mineralogy of the cement is more efficient and reduce the cement consumption by 10...15%, superplasticizers up to 20%, but long-term modes and regardless of the type of Portland cement. The article contains a material with strength in different curing regimes, the indicators of reduction of consumption of cement and frost resistance of concrete with the introduction of air-entraining additives. Empirical formula to calculate the reduction of the duration of isothermal heating regime during heat treatment of concrete.

Keywords:

The induction period of hydration, the potential of cement, electrolytes, air-entraining additives, capillary-porous structure of concrete steamed, accelerated hardening of concrete.