The use of superplasticizers in a self-compacting concrete mix without the addition of a foaming agent in practice leads to a well-known problem associated with increased air entrainment and promotes the formation of harmful large bubbles, high-void content, and ununiform appearance. This paper presents research on the properties of cement paste consisting of Ordinary Portland Cement (OPC), powder based on ground granulated blast furnace slag (GBBS), and superplasticizer. The methodology of this study was the estimation of flow diameter and flow time, as well as the evaluation of the rheological characteristics. The influence of ground granulated blast furnace slag and polycarboxylate plasticizer on the flowability and viscosity of cement paste was studied. The effect of superplasticizer (SP) based on polycarboxylate esters (PCE) anti-foaming agent (AFA) based on a glycol ester and air-entraining admixture (AEA) based on an amphoteric surfactant on flowability, viscosity, rheological properties and the strength of the cement paste was evaluated. It was found that the increase of slag content in cement paste (25%) with the presence of superplasticizer (0.64%) significantly changes the flowability and viscosity. It was stated that the addition of 0.04% anti-foaming agents increases flowability (20%) and reduces viscosity (44%) of cement paste. It was stated that the addition of small dosages of glycol ester-based anti-foaming agent (0.02 and 0.04%) significantly changes the rheological properties, decreases the shear yield stress by 2.1–2.8 times, the plastic viscosity by 2.4–2.6 times and apparent viscosity 1.6–2.5 times, improves the compressive strength at the age of 1 and 7 days by 2.5 and 1.4 times, respectively. The addition of air-entraining admixture led to a decrease in the plastic viscosity by 1.2–1.4 times. It was stated that the presence of air-entraining admixture assists in increasing the apparent viscosity by 1.7–2.4 times. It was shown that the presence of complex admixtures of various origins, purposes, and mechanisms of action would assist in predicting the behavior of concrete mixtures under the conditions of the building site and reduce the consumption of polycarboxylate esters due to the enhancing plasticizing effect of anti-foaming agent and air-entraining admixture.

The use of self-compacting concretes has become widespread in recent years. To achieve high flowability in mixtures, highly effective polycarboxylate based plasticizers are used. However, the use of superplasticizers in self-compacting concrete mixes without adding a defoamer can lead to a well-known problem: increased air entrainment and the formation of air bubbles. This can cause deterioration in the surface appearance. This article presents studies on the effects of various defoaming agents and air-entraining additives on the basic technological and rheological properties of plasticized by polycarboxylate plasticizers cement pastes, made from a blended binder which includes Portland cement and a microfiller based on ground blast-furnace granulated slag, in proportions of 25% and 40% respectively. The aim of this study was to investigate the spread diameter, expiration time, and dynamic viscosity of the cement paste with and without chemical additives, as well as to determine the type of defoaming agent that was most effective. The results of the experiments showed that a glycol ester-based defoamer was the most efficient. This type of agent reduced the number of surface pores in the paste. Optical microscopy was used to measure the size of these pores. It was found that glycol-ether defoamers were the most effective when used in concentrations of 0.02% and 0.04% in a cement mixture containing ground blast furnace slag (25%) and a polycarboxylate plasticizer. These additives changed the size and number of surface pores. It was also found that increasing the content of glycol-ether additives increased the mobility of the cement paste, but did not change the viscosity. There was a slight increase in average density and decrease in pore size and number by 0.28–0.29%, respectively. The study showed that using a defoaming agent in combination with a polycarboxylic acid ester-based additive can help reduce consumption and enhance plasticizing effects, thus predicting concrete behavior during construction.