Technical Field

The present disclosure relates to material science or material engineering. Background

In a construction industry, there is a need for a new wall system to replace an existing or conventional wall system that requires typical brick work and labor intensive. The new wall system has been developed and shows its advantages including shorter amount of construction lead time, consistency in quality of finished work, durability and other desirable properties such as flame retardant properties, heat insulation, sound insulation, or light weight properties.

There is a previous wall system that uses plaster slurry to fill between the gap of the frame-panel structures to form a wall system. However, such present wall system has its limitation such as inability to paint the wall after filling plaster slurry for 7 days. This is because, when plaster slurry is injected to fill the gap along the entire height of the wall and is allowed for setting, excess water generated from plaster reaction will gradually move to dryer region at the outer surface of the panel and then evaporate. Excess water causes difficulty and problems in wall panel painting and delay the entire construction process. More particularly, excess water causes low paint adhesion to the surface or wall panel, resulting in paint wear-off and paint swelling. In case of allowing the excess water to completely evaporate followed by painting step, this will delay the entire construction process. Moreover, excess water may corrode the frame structure. Even when the frame material structure can relatively well withstand corrosion such as zinc galvanized steel structure, prolong contact with excess water or moisture can still cause metal corrosion. Accordingly, there exists a need to develop an enhanced plaster formulation to be used in a wall system and a new wall system having improved plaster slurry to accelerate construction process and solve limitation of existing wall system.

Summary of the Invention

The present invention discloses gypsum composition for construction work comprising plaster, lightweight aggregrate, and pozzolanic materials. The gypsum composition can further comprise of a filler, a group of additives selected from a retarder, a superplasticizer, a water retaining agent, a foaming agent, and an activator at the appropriate ratio or amount. The present invention is directed towards a wall system, in which the plaster slurry is added to reduce or minimize excess water and reduce corrosion of metal structure in the wall system to solve wet surface problem. In addition, a wall structure system having gypsum as one of the composition has heat insulation and flame retarding properties.

Detailed Description

The present invention discloses gypsum composition for construction work comprising plaster, lightweight aggregrate, and pozzolanic materials. The gypsum composition can further comprise of a filler, a group of additives selected from a retarder, a superplasticizer, a water retaining agent, a foaming agent, and an activator as described in details in the following:

Plaster (or its chemical name as calcium sulfate hemihydrates) serves as an adhesive material or substance to bind particles and form a solid mass and provide material strength. Embodiments of the present disclosure have plaster at the amount of 20-60% by weight of the main composition.

Plaster can be obtained from natural or synthetic gypsum such as gypsum obtained from desulfurization process of flue gas (flue gas desulfurization gypsum, FGD), phosphogypsum, or gypsum obtained from sodium citrate manufacturing process. Gypsum is heated and reacted in order to obtain plaster. Plaster can be categorized into 2 forms, namely beta-plaster and alpha-plaster. Each form of beta- or alpha-plaster can be selected for various applications based on their different properties such as strength, water absorption/desorption ability of plaster. Embodiments of the present disclosure can use beta-plaster and/or alpha-plaster depending upon required mechanical performance. For instance, alpha-plaster has especially high strength and hardness, requires low amount of water during mixing, slow setting, and good heat resistance.

Light weight aggregate is added into gypsum composition for construction work to decrease slurry density, which consequently decreases plaster usage per square meter value. Additionally, some light weight aggregate such as rice husk ash or fly ash, which are industrial wastes, are cheap sources. Therefore, light weight aggregate can decrease raw material cost and manufacturing cost without compromising other desirable properties and simultaneously develop an environmentally friendly product.

Light weight aggregate, as defined in the present disclosure, is a low density material, which has bulk density less than 800 kilogram/cubic meter, and particle size less than 5 millimeter. Light weight aggregate that can be used in the present disclosure can come from natural source or synthetic source; for instance, expanded polystyrene, expanded perlite, expanded vermiculite, expanded Shale, expanded clay, expanded cell polymer, closed hollow balloon made up from ceramic materials, polymer materials, glass such as fly ash balloon, Cenosphere, glass sphere, or any material in a closed hollow balloon shape, volcanic ash, microsphere, diatomaceous earth, cork, palm kernel shell, ash obtained from agricultural waste; for instance, rice husk ash, sugar cane ash, wood chip ash, wood ash, and other biomass ashes.

Lightweight aggregate present in embodiments of the present disclosure can be in the form of single substance or in combination of any substances as described above as representative examples. Embodiments of the present disclosure have light weight aggregate at the amount of 5-25% by weight of the main composition.

Pozzolanic material acts as a binding or adhesive material similarly to plaster and increase strength of the composition for construction work in the present disclosure. Another characteristic of pozzolanic material is that pozzolanic reaction occurs much more slowly than plaster reaction. Pozzolanic material constituted in the composition in the present disclosure can therefore use excess water generated from plaster reaction for the pozzolanic reaction. This pozzolanic characteristic can therefore aid in internal drying phenomenon.

Pozzolanic material is a material having silica (Si02) as a major component and can react with calcium hydroxide and water to generate a product known as C-S-H in a similar manner to hydration reaction of Portland cement. Representative examples of pozzolanic material are silica fume, metakaolin, crushed volcanic ash, rice husk ash, bagasse ash, fly ash, foamed blast furnace slag, and crushed glass. Embodiments of the present disclosure can have pozzolanic material at the amount of 10-60% by weight of the main composition.

Particular pozzolanic materials such as rice husk ash can decrease overall slurry density due to bar-shaped and porous particle. However, said pozzolanic materials require more water for mixing to form slurry.

Fillers are materials added into an admixture to add up or constitute in the slurry without having any reaction involved and can also decrease raw material cost, which is part of manufacturing cost. Fillers used in the present disclosure can have particle size in the range of 0-1 millimeter. Representative examples of filler materials are sand, crushed rock, and the like such as calcium carbonate, crushed sand, and talc. Embodiments of the present disclosure can have filler at the amount of 0-45% by weight of the main composition. Additives are used to mix in the composition to improve certain quality of slurry obtained from mixing gypsum composition with water. . Embodiments of the present disclosure can have additives at the amount of 0-5% by weight of the main composition added into the main composition. Representative examples of additives are described in the following;

- Retarders such as citric acid, tartaric acid, malic acid, water soluble salt, Diethylene Triamine Pentaacetic Acid (DTP A), and calcium tartrate.

- Superplasticizers such as Melamine sulfonate, Melamine sulfonate formaldehyde, Lignosulfonate, Naphthalene sulfonate, Naphthalene sulfonate formaldehyde, Polycarboxylic acid, certain copolymers such as copolymer of Oxyalkylene-alkyl ether, and Dicarboxylic acid

- Water retaining agents including modified cellulose such as Methylcellulose, Hydroxypropylmethyl cellulose, Methylhydroxyethyl cellulose or modified starch such as pre-gel starch, and starch ether

- Foaming agents and/or air entraining agents such as Sodium Lauryl Sulfate (SLS), polyethylene glycol alkyl ether, protein based foam agent, or foam generated from a reaction of phosphoric and calcium carbonate.

- Activators such as calcium hydroxide, calcium chloride. Activators react with pozzolanic materials during pozzolanic reaction to create new crystal substances to bind various particles and consequently increase strength and durability in long term. Additionally, activators can include calcium sulfate dehydrates, which accelerates gypsum reaction.

Gypsum composition according to the present disclosure can be applied in various construction systems, processes, applications. Embodiments of the present disclosure further include a wall system with gypsum composition as described above filling therein. More particularly, a wall system according to the present disclosure comprises of a frame structure, at least one fiber-reinforced cement panel coupled to the front and back sides of the frame structure to form a gap within a panel or between the panels, and slurry of gypsum composition filling in the said gap. Slurry of gypsum composition filling in the said gap will set, be hardened, and form a wall or wall system as designed.

Below are some representative examples of the composition according to the present disclosure.

Example 1

Embodiments of the present disclosure can provide a gypsum composition comprising;

Part 1 : Main composition

Plaster 25-60% by weight of the main composition

Pozzolanic materials 10-60% by weight of the main composition Lightweight aggregates 5-25% by weight of the main composition Fillers 0-45% by weight of the main composition

Part 2: Additives

Retarder 0.5-2% wt added of the main composition

Superplasticizer 0-0.3% wt added of the main composition Water retaining agents 0.1-0.5% wt added of the main composition Foaming agent 0.05-3% wt added of the main composition

Activator 0-5% wt added of the main composition

Example 2

Embodiments of the present disclosure can provide a gypsum composition comprising;

Part 1 : Main composition having fillers

Plaster 30-50%) by weight of the main composition

Fly ash 10-30% by weight of the main composition

Perlite 7-11% by weight of the main composition Crushed lime 15-30% by weight of the main composition

Or Part 1: Main composition without fillers

Plaster 30-45% by weight of the main composition

Fly ash 40-60% by weight of the main composition

Perlite 7-11% by weight of the main composition

Or Part 1: Main composition without fillers

Plaster 30-45% by weight of the main composition

Fly ash 35-55% by weight of the main composition

Rice Husk Ash 8-18% by weight of the main composition

Part 2: Additives

Retarder 0.5- 1.5% wt added of the main composition

Superplasticizer 0-0.3% wt added of the main composition

Water retaining agents 0.15-0.35% wt added of the main composition

Foaming agent 0.05-0.2% wt added of the main composition

Activator 0-3% wt added of the main composition

When plaster with above described composition is mixed with water to obtain plaster slurry slump diameter of 60-65 millimeter. The water required for mixing is in the range of 25-55 gram per mixed plaster 100 gram. The properties of slurry obtained are: density of 0.7-1.4 gram/cm3, initial setting time in the range of 1-3 hours, final setting time in the range of 3-8 hours, and absorption diameter less than 60 millimeter.