GB2525454A

GB2525454A - Construction material

Info

Publication number: GB2525454A
Application number: GB1412756.7A
Authority: GB
Inventors: Dominic Dillon; Richard Elliott
Original assignee: ENVIROMATE Ltd
Current assignee: ENVIROMATE Ltd
Priority date: 2014-07-17
Filing date: 2014-07-17
Publication date: 2015-10-28
Also published as: GB201412756D0

Abstract

A construction material is disclosed, and in particular a construction material comprising waste plastic material. The construction material may be used in a range of applications to replace traditional concrete or cement. The construction material comprises cementitious material and particulate aggregate, the cementitious material being 20-30% by volume of the dry ingredients of the construction material and the particulate aggregate being 70-80% by volume of the dry ingredients of the construction material, and wherein the particulate aggregate comprises 25-100% by volume particles of a plastics material, and the aggregate comprises 10-75% by volume particles having a size of 0.1-2 mm and 25-90% by volume particles having a size of 2-10 mm.

Description

Construction Material

BACKGROUND

a. Field of the Invention

This invention relates to a construction material, and in particular to a construction material comprising waste plastic material. The construction material may be used in a range of applications to replace traditional concrete or cement.

b. Related Art Cementitious construction materials, such as concrete, are used in a wide variety of applications. There are, however, a number of disadvantages related to both the production and use of these materials. These disadvantages include, for example, damage to the environment due to quarrying and the release of CO2 during the production of cement. Additionally, concrete has a number of drawbacks due to its low strength to weight ratio and its susceptibility to cracking.

There is, therefore, an ongoing need to find materials that can replace traditional cement and concrete, and which offer both environmental and structural advantages.

SUMMARY OF THE INVENTION

According to the present invention there is provided a construction material comprising cementitious material and particulate aggregate, the cementitious material being 20-30% by volume of the dry ingredients of the construction material and the particulate aggregate being 70-80% by volume of the dry ingredients of the construction material, and wherein the particulate aggregate comprises 25-100% by volume particles of a plastics material, and the aggregate comprises 10-75% by volume particles having a size of 0.1-2 mm and 25-90% by volume particles having a size of 2-10 mm.

The particulate aggregate preferably comprises particles of at least one of sand, rubber, glass and stone. The construction material may comprise limestone.

In preferred embodiments the particulate aggregate comprises rubber having a particle size of between 2 mm and 10 mm. In some embodiments the particulate aggregate comprises rubber and the rubber is coated with a sealant to prevent penetration of water into the rubber particles.

In embodiments in which the particulate aggregate comprises glass, the glass preferably has a particle size of between 0.1 mm and 2 mm.

The particulate aggregate may comprise stone particles having a particle size of between 6 mm and 10mm.

In order to improve the adhesion of the cementitious material to the particles of a plastics material, the construction material may further comprise a chemical admixture.

In some embodiments 100% of the particulate aggregate is particles of a plastics material.

The construction material may further comprise between 10% and 30% by volume fibres, which are preferably made from a plastics material or stainless steel.

DETAILED DESCRIPTION

The construction material of the present invention may be used to form pre-cast construction elements such as slabs, panels, posts and blocks or, alternatively, may be cast or moulded in situ, depending on the application. A bagged dry mix for use as a light weight topping or filling material is also proposed.

The construction material includes, as its primary components, plastic particles and a cementitious material. These dry ingredients can then be mixed with water to form a castable material that may be used as a replacement for traditional cement, concrete or mortar. The ratio of plastics material to cementitious material, by volume, is generally between 0.6:1 and 3.5:1, with greater volumes of plastics material providing reduced density and greater toughness. In some embodiments the dry ingredients of the construction material consist entirely of plastics material and a cementitious material.

The plastics particles typically have dimensions or a diameter less than 10 mm, and preferably less than 6 mm. In particularly preferred embodiments the plastics material has particle sizes between 1 mm and 6 mm. The particle sizes may be between 1 mm and 3 mm, or between 3 mm and 6 mm. For commercial and environmental reasons the plastics material is preferably recycled or waste material, however, virgin plastics material may also be used when this is available.

The plastics material may be of any suitable type, for example, polyethylene terephthalate (PET), high density polyethylene (HDPE), low density polyethylene ([DPE), polyvinyl chloride (PVC), polypropylene (PP) and polystyrene (PS), and may be a mixture of different types of plastics.

In some embodiments the plastics material includes particles having dimensions less than 2 mm, such that this plastics material is equivalent to a sand or silt material. In the following description the plastics material will be classified in two grades, plastics particles having dimensions in the region of 2 mm to 6 mm and plastics silt having dimensions in the region of 0.1 mm to 2 mm. It will, of course, be appreciated that plastics material having a continuous distribution of particle sizes can be used in the construction material of the present invention, and plastics material having particle sizes outside of these ranges may also be included.

The plastics particles and silt may be of different colours and, as such, in some embodiments the plastics material may be selected so as to impart a chosen colour to the resultant construction material.

The cementitious material will typically be a standard cement such as Ordinary Portland cement. In some embodiments, however, the cementitious material may be a cement replacement material such as banahCEMTM which is based on a geopolymer binder system. Accordingly, references to a cementitious material also include cement replacement materials such as geopolymers that act as a binder in the construction material.

In some embodiments it may be beneficial to add a liquid chemical additive or admixture to improve the adhesion of the cementitious material to the plastics particles (Type 1 in Table 1 below). These chemical additives will typically include a copolymer to aid adhesion, as well as providing improved workability of the material and/or increased strength. Possible chemical additives include ViscoBond (RTM) and Plastiment (RTM), both made by Sika AG.

In some embodiments, in order to alter the physical properties of the construction material or to improve the cohesion of the construction material, other aggregates are added to the cementitious material in addition to the plastics material. These aggregates may be selected from rubber, sand, glass, stone and limestone.

Rubber aggregate will typically have a particle size of less than 25 mm, and more preferably less than 10 mm. The rubber is preferably recycled rubber and may comprise chopped up or shredded vehicle tyres. The rubber may be treated or coated with a sealant that minimises or prevents absorption of water or other liquid into the rubber. In some embodiments the rubber pieces are pre-treated by applying a chemical admixture to the rubber and leaving the rubber to absorb at least some of the chemical admixture. In preferred embodiments the chemical admixture (Type 2 in Table 1 below) is selected from an air-entraining chemical admixture, a water-reducing chemical admixture, a retarding chemical admixture, an accelerating chemical admixture, and a plasticizer or superplasticizer chemical admixture.

The rubber provides the resultant construction material with improved flexibility, resilience and toughness. Embodiments of the construction material comprising plastics material and rubber may be particularly suited to forming playing surfaces such as playgrounds and tennis courts. These materials may also find use in the construction of vibration or shock resistant structures and noise barriers.

Glass aggregate preferably has a particle size of less than 2 mm and, as such, provides an alternative to sand in the construction material. The glass is, preferably, recycled glass. As with the plastics material, the colour of the glass may be selected to impart a particular colour to the resultant construction material.

In some embodiments, and in particular in embodiments comprising primarily plastics material and rubber, it may be beneficial to include a stone aggregate to increase the strength of the resultant construction material. The stone aggregate may include natural stone material or gravel, or may comprise a recycled or waste material, such as blast furnace slag, having equivalent physical properties. The stone aggregate typically has a particle size range of between 6 mm and 10 mm.

The construction material may also include other components such as fly ash, limestone or fibres.

The fly ash can be used to replace some of the cementitious material or may be used as a sand replacement material.

Fibres may be included to increase the toughness, tensile strength and flexural strength of the resultant material and improve the bonding between the constituent components. The fibres may be made from a plastics material or steel, and in preferred embodiments the fibres are made from polypropylene or stainless steel.

In other embodiments the fibres may comprise an absorbent material. The volume percentage of fibres included in the construction material may be between 10% and 30%.

The incorporation of fibres provides increased flexural and tensile strength to panels and slabs in structural applications. Furthermore, the benefits of the porosity and low density of the construction material for applications such as retaining wall panels, boundary fences/partitions, tilt-up wall panels and noise barriers can be utilised without compromising the integrity of the material compared to traditional steel reinforced concrete materials. Additionally, in embodiments in which plastics fibres or stainless steel fibres are included, panel thickness can also be reduced compared to that of conventional reinforced concrete as it is not necessary to fully cover the reinforcement to prevent corrosion.

Additional liquid additives may be included in the construction material of the present invention. These liquid additives may include plasticizers and water reducing agents, such as Simeplast Qblock (TM) manufactured by DMB-Farkon.

Table 1 lists some example embodiments of the construction material comprising different relative quantities of aggregates and cementitious material. The numerical quantities are shown as volume percentages of the dry ingredients of the construction material. The table lists two bonding admixtures. As described above, Type 1 is an additive included to improve the adhesion between the cement and the plastics material and Type 2 is an additive used to treat the rubber.

Table I

Cementitious Material Aggregate Bonding Admixture Plastic Plastic Fibms Cement Geopolymer 2-6mm 0.1-2mm Sand Glass Rubber Stone Limestone Type 1 Type 2 0 20 30 20 0 0 0 0 No Yes No 0 30 40 0 0 0 0 0 No Yes No 0 40 0 30 0 0 0 0 No No No 0 0 20 0 0 40 10 0 Yes No No 0 0 20 10 0 30 10 0 Yes No No 0 50 20 0 0 0 0 0 No Yes No 0 55 15 10 0 0 0 0 No Yes No 0 60 10 0 0 0 0 0 No Yes No 0 65 10 0 0 0 0 0 No Yes No 0 25 15 0 25 0 15 0 No Yes No 0 45 20 0 0 0 20 0 No Yes No 0 55 20 0 0 0 0 10 No Yes No 0 25 40 0 0 0 0 20 No Yes No 0 0 45 0 0 0 0 40 No Yes No 0 55 0 0 0 0 35 0 No Yes No 0 45 0 0 0 0 45 0 No Yes No 0 15 45 0 0 0 0 30 No Yes No 0 30 0 0 0 0 0 60 No Yes No 0 20 10 10 20 0 40 0 0 Yes No Yes 0 20 15 30 0 10 25 0 0 No No Yes 0 20 25 45 0 10 0 0 0 No No Yes A sandwich panel or slab may be formed by placing a geogrid (such as those manufactured by Tensar International Limited) between layers of the construction material. This composite construction improves the tensile and flexural strength of the resultant structure. The hardened cementitious material in the construction material effectively anchors the geogrid and provides a significant increase in tensile and flexural capacity. In these embodiments the construction material of the present invention is effectively replacing compacted granular fill above the geogrid which would traditionally be used to anchor it in an improved or stabilized foundation application. This has particular application in civil construction to provide a strong yet flexible layer over weak foundation material. The sandwich panel or slab provides a strengthened layer capable of supporting heavy superimposed loads on weak foundation material. The sandwich panel or slab also reduces the volume of good quality compacted granular material or stone required for heavy duty pavement construction and is effective in reducing the quantity of imported fill required.

The present invention, therefore, provides a construction material that can replace traditional cement and concrete, and which offers both environmental and structural advantages.

Claims

CLAIMS1. A construction material comprising cementitious material and particulate aggregate, the cementitious material being 20-30% by volume of the dry ingredients of the construction material and the particulate aggregate being 70- 80% by volume of the dry ingredients of the construction material, and wherein the particulate aggregate comprises 25-100% by volume particles of a plastics material, and the aggregate comprises 10-75% by volume particles having a size of 0.1-2 mm and 25-90% by volume particles having a size of 2-10 mm.
2. A construction material as claimed in Claim 1, wherein the particulate aggregate comprises particles of at least one of sand, rubber, glass and stone.
3. A construction material as claimed in Claim 1 or Claim 2, wherein the particulate aggregate comprises rubber having a particle size of between 2 mm and 10mm.
4. A construction material as claimed in any preceding claim, wherein the particulate aggregate comprises rubber and the rubber is coated with a sealant to prevent penetration of water into the rubber particles.
5. A construction material as claimed in any preceding claim, wherein the particulate aggregate comprises glass having a particle size of between 0.1 mm and2mm.
6. A construction material as claimed in any preceding claim, wherein the particulate aggregate comprises stone particles having a particle size of between 6 mm and 10 mm.
7. A construction material as claimed in any preceding claim further comprising a chemical admixture for improving the adhesion of the cementitious material to the particles of a plastics material.
8. A construction material as claimed in Claim 7, wherein 100% of the particulate aggregate is particles of a plastics material.
9. A construction material as claimed in any preceding claim further comprising between 10% and 30% by volume fibres made from a plastics material or stainless steel.
10. A construction material further comprising limestone.
11. A construction material substantially as herein described.