How to deal with mildew of Polycarboxylate Superplasticizer
As the third generation of high-performance water reducer, polycarboxylate water reducer is often combined with a small amount of retarding components, air-entraining components, defoaming components, and viscosity modifying components to meet different concrete technical performance requirements. Use after compounding. However, in summer, the temperature is high, and the water reducer added with retarding components (such as Sodium Gluconate, sucrose) is prone to deterioration, which seriously affects the use effect. How to solve it?
1. Metamorphism and its causes
(1) Ingredients cause mildew
In the initial stage of deterioration of Polycarboxylate Superplasticizer, there are light-colored fluffy or cotton-like plaques on the liquid surface, and then develop into floating objects in the form of discrete islands, and strings of bubbles emerge from time to time; when the deterioration is severe, the plaques It will cover the entire liquid surface, and there will be thick green, brown, and black suspended matter in the solution, accompanied by the generation of corrupt sour odor gas. This deterioration is mainly caused by mildew.
The deterioration of polycarboxylate water reducer is mainly caused by the compounded Sodium Gluconate. In industrial production, Aspergillus niger is generally used to ferment Sodium Gluconate. After the fermentation of Aspergillus niger, a large amount of Aspergillus niger cell residues will be produced, and its wet weight is 2%-3% of the total amount of Sodium Gluconate solution. Aspergillus niger residue contains nutrients and various components.
In the production of sodium glucose, if the production control is not strict, it is inevitable that there will be residues of glucose and Aspergillus niger, which also provide nutrients for the reproduction of microorganisms. Under suitable natural conditions (nutrients, temperature, humidity, oxygen, pH value), microorganisms have an astonishing reproduction rate, and one generation can be reproduced within about (20-30) minutes. The phenomenon of "mold explosion" occurs when extremely rare breeding conditions are once encountered and superimposed on each other. The blackening of the deteriorated water reducer is caused by the fermentation of Aspergillus niger in unqualified sodium glucose products.
(2) The storage environment causes mildew
The mildew of the Polycarboxylate Superplasticizer is also related to its storage environment. Higher temperature will intensify the movement of macromolecular chains. Once the dissociation energy of chemical bonds is exceeded, chain decomposition, random fracture and thermal decomposition will occur, resulting in accelerated deterioration of polymers. Similarly, the higher the temperature, the greater the activity of microorganisms, and the faster the mildew of the water reducer will be. There are also literatures showing that improper storage conditions, such as severe temperature rise in the storage space, lack of ventilation, and humidity, lead to the melting of large monomers, and the local temperature of monomers is too high, which accelerates the rearrangement reaction of related monomers, resulting in large single The amount of double bonds in the body decreases seriously, and the performance deteriorates seriously.
2. Precautions against spoilage
The mildew of the polycarboxylate water reducer will affect its quality, and in severe cases, it will lead to concrete quality accidents. The following measures are recommended.
(1) Select high-quality Sodium Gluconate as the retarding component
At present, there are many manufacturers of Sodium Gluconate on the market. Manufacturers with a strict production control system can effectively control the residual amount of glucose and Aspergillus niger in the production process, thereby reducing the risk of spoilage of the Polycarboxylate Superplasticizer compounded with sodium gluconate.
(2) Compound a certain amount of preservatives
Compounding a certain amount of preservatives in the production process of Polycarboxylate Superplasticizer can effectively prevent the deterioration of Superplasticizer Polycarboxylates. Preservatives currently on the market mainly include sodium nitrite, sodium benzoate and isothiazolinone. Among them, isothiazolinone is a relatively broad, efficient, low-toxicity, non-oxidizing fungicide with a wide range of applicable pH values, and is ideal for anti-mold and sterilization of water reducing agents. The amount of preservative added is 0.5-1.5 kg per ton of polycarboxylate water reducer.
(3) Pay attention to the storage environment
Try to store the Polycarboxylate Superplasticizer in a cool, ventilated place without direct sunlight. A test has been done, and one part of the polycarboxylate water reducer was placed in a cool storage bottle without direct sunlight, and the other was placed in a storage bottle that could be exposed to direct sunlight. It was found that the storage bottle placed in direct sunlight The water reducing agent in the water will soon become moldy and black.
In addition, the polycarboxylate water reducer storage container should be made of non-metallic materials as much as possible, otherwise the corrosion of metal materials will also cause the water reducer to change color or even deteriorate. For example, the stainless steel tank will turn the stored water reducer red, the iron tank will turn the stored water reducer green, and the copper tank will turn the stored water reducer blue.
(4) Reasonably estimate the amount of polycarboxylate water reducer used in the project
Due to the influence of project progress, weather environment and other factors, the use speed of polycarboxylate superplasticizer is often difficult to control. Some Polycarboxylate Superplasticizer have been placed on the construction site for more than 3 months or even longer, and corruption and deterioration occur from time to time. Therefore, the medicine fully researches the progress and cycle of product use, so as to achieve planned procurement, and ensure that the consumption and replenishment of polycarboxylate-based water-reducers are in a dynamic balance.
3. Treatment of deteriorated polycarboxylate water reducer
For the mildewed Polycarboxylate Superplasticizer, there are also related methods for treatment and recovery, such as heat treatment or methods of adding hydrogen peroxide or liquid caustic soda. The research conclusions of relevant literature show that after treatment, the mildewed Polycarboxylate Superplasticizer can restore its original performance, the color is close to the original product, and the peculiar smell can be removed.
