Durability Evaluation of Cement Paste with Ginger by Adding Defoaming Agent

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.

When chloride ions ingress and carbonation take place simultaneously in concrete, chloride ions that have been fixed in cement hydrates will be unfixed and become soluble due to the deterioration of cement hydrates caused by carbonation. It has been observed that chloride ions concentrate in the region where carbonation has not occurred. Therefore, for concrete subjected to both chloride ions ingress and carbonation the corrosion of steel bars in it may take place at an early stage and the rate of corrosion may also increase. Therefore, when chloride ions ingress and carbonation are co-existed the prediction of the distribution of chloride ions in concrete is essential to the evaluation of concrete durability. This study is aimed to estimate the effect of carbonation on chloride penetration in concrete through an investigation into the immobilization of chloride ions in cement hydrates and the release of them when alteration of cement hydrates occurs due to carbonation. The available potential for hydrates to immobilize chloride ions and the carbonation-induced release of chloride ions is determined using artificially synthesized cement hydrates, which are immersed in an artificial pore solution. Based on these above experiments, a model characterizing the process of immobilization and release of chloride ions is established and its validity is verified by comparing calculated data with data from tests on cement paste and mortar specimens. The effect of change in micro-structure due to carbonation on chloride penetration was also evaluated in this study.

Organic superplasticisers improve the flow properties of cement, offering operational advantages for the disposal of radioactive wastes. However, there are concerns that they could increase the mobility of encapsulated contaminants significantly. The effect of polycarboxylate ether superplasticisers on the solubility of Ni(II), Am(III), Pu(IV) and U(VI) in two cement-equilibrated waters (ordinary Portland cement/pulverised fuel ash (OPC/PFA) and OPC/ground granulated blast-furnace slag (GGBS)) has been assessed. The study included four commercial superplasticisers, three adjuncts (a de-foaming agent, biocide and viscosity modifier) and a bespoke, synthesised superplasticiser from which residual monomer had been removed by dialysis. The commercial products (0·5% w/w dosage) had a much greater effect on metal solubility than the dialysed equivalent, increasing solubility by 2–3 orders of magnitude. As the adjuncts alone showed no effect, the difference between the commercial and synthesised superplasticisers is attributed to small molecules, primarily residual monomers, in the commercial formulations owing to incomplete polymerisation. The distribution of radionuclides in hardened cement pastes corresponds closely to the distribution of superplasticiser, as shown by 14C-labelling in combination with digital autoradiography and accounting for the bleed observed for certain slag-rich formulations.

Durability, mechanical, and chemical properties evaluation: A review on plug & abandonment materials