Gypsum has features such as light weight, sound insulation, fireproof, etc., and is a green building material highly developed all over the world. The industrial by-product, phosphogypsum/ desulfurization gypsum has also been widely used in gypsum boards, gypsum blocks and interior wall coatings. In practice, the water consumption of gypsum commonly reaches 65%~80%, and the water-cement ratio is too high, which seriously affects the strength of gypsum products, so a certain amount of water reducer mixing into plaster to reduce the water consumption and improve the strength is necessary
1. Application advantages of polycarboxylate(PCE) superlasticizer in phosphogypsum
Phosphogypsum is a waste product resulting from the action of sulfuric acid with phosphate rock in the wet production of phosphoric acid. The use of phosphogypsum can effectively reduce the consumption of natural gypsum, a non-renewable resource. It is of great significance to explore the action characteristics of chemical admixture water reducer and phosphogypsum for the wide application of phosphogypsum.
And different types of water reducing agents have different adaptability to phosphogypsum, among which polycarboxylic acid water reducing agent has better effect, naphthalene water reducing agent and melamine have the second best effect. Polycarboxylic acid water reducing agent has good retardation effect on phosphogypsum, small fluidity loss and high strength enhancement effect. And naphthalene water reducing agent has the characteristics of promoting coagulation, large loss of mobility over time and certain strength enhancement for half-water phosphogypsum. It should be noted that, when using polycarboxylic acid water reducing agent to gypsum-based materials, it is necessary to test its adaptability, because the water reducing agent applicable to cement is not necessarily applicable to gypsum-based materials.
2. Application advantages of PCE superlasticizer in desulfurization gypsum
Dispersibility
In the application of desulfurization gypsum, in order to achieve the same water reducing effect, there is a big difference in the dosage of different types of water reducing agents. Specific types of water reducing agents are sulfonated melamine, naphthalene water reducing agent, calcium lignosulfonate and polycarboxylic acid water reducing agent, among which sulfonated melamine SM has the highest dosage and its dispersing effect is also the poorest; naphthalene water reducing agent needs a slightly lower dosage than calcium lignosulfonate M, but the dispersing property of naphthalene water reducing agent NSF is better than that of calcium lignosulfonate M; polycarboxylic acid water reducing agent PCE has the lowest dosage, and has excellent dispersing property.
Setting time
As for the setting time of desulfurization gypsum, the selection of naphthalene water reducing agent will not affect the initial setting time of gypsum, but can effectively shorten the final setting time; while melamine basically does not affect the setting time of gypsum; the polycarboxylic acid water reducing agent will only slightly extend the final setting time of gypsum slurry; and calcium lignosulphonate has a significant prolongation of both the initial setting time and the final setting time of gypsum, and shows a stronger retardation effect.
Strength
Water-paste ratio is the main parameter affecting the strength of gypsum, and among the water reducing agent types, polycarboxylic acid water reducing agent PCE increases the strength most obviously.
Economic benefit analysis
In the production process of desulfurization gypsum products, if the water reduction ratio is higher and the water consumption is less, the less water needs to be removed to dry the gypsum products to a constant weight, and the time needed is also shorter, which will surely significantly reduce the energy consumption of the gypsum products in the drying process. Increasing the dosage of polycarboxylic acid water reducing agent PCE can effectively reduce the water consumption of desulfurization gypsum powder, which can greatly improve the production efficiency and reduce the production energy consumption, and has significant economic benefits.
Huaxuan High-tech company expert in Construction chemical admixture with more than 16 years, main products encompasses a group of polycarboxylate based, high performing, water-reducing concrete admixtures. From conventional to high-strength, self-consolidating materials our products are specially formulated to provide full range water reduction with a variety of cementitious materials
