Rebounding track board made of magnesium-based cement and system comprising same

Abstract

A rebounding track building board made essentially from a magnesium oxychloride hydrated cement, a magnesium oxysulfate hydrated cement, a mixture of the two materials, and / or a magnesium phosphate cement, the cement preferably comprising one or more high modulus fibrous materials distributed in the cement and one or more low modulus fibrous materials distributed in the cement; a method of manufacturing the rebounding track building board and a rebounding track system comprising the rebounding track building board.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of construction material manufacturing. In particular, the present invention relates to the use of magnesia based cement as ballistic impact resistant panel in buildings or other structures where ballistic protection is required. The invention also relates to a particularly advantageous formulation of magnesia based cement for such applications. BACKGROUND

[0002] Resistance to high velocity impact of projectiles such as bullets and fragments plays an important role in the ability of protective building structures to directly protect people or to provide a longer time frame for evacuation in the event of impact disasters such as terrorist attacks, gun attacks, crashes, building collapses, etc.

[0003] Based on the impact velocity, the impact phenomena resulting from the impact of these projectiles, including ballistic impact, are generally classified as "low velocity", "high velocity" and "ultra-high velocity". In the case of projectile impact, these three categories are generally defined as: below 50 m / s; between 50 m / s and 1000 m / s; in the range of 2000 m / s to 5000 m / s.

[0004] Among these, ballistic impact and small projectile impact in the high velocity impact category are of the most interest in the present invention, especially those caused by light weapons fire.

[0005] The United States Department of Defense Unified Facilities Criteria UFC-4-023-07 (2008) defines "light weapons" as including ballistic weapons such as handguns, rifles, shotguns and submachine guns with a caliber of no more than 12.7 mm (0.50 caliber). Some anti-tank weapons are also included, but not limited to: shoulder-fired rockets such as the Russian RPG-7, RPG-18 and RPG-22 and the American M-72 light antitank weapon (LAW).

[0006] During the impact of the impact body with the target, an impact stress wave propagation occurs in the target material. The response of the target to such impact stress wave propagation depends on its mechanical strength, its stress-strain behavior, the stiffness of the surrounding structural elements and the type and velocity of the impact body.

[0007] In low velocity impact, the impact time is longer, characterized by the relatively slow generation of stress waves which are distributed from the impact point outwards towards the supports or periphery of the target. This results in the transmission of vibrations and stress waves to the supports.

[0008] Impact bodies with higher velocities have a shorter time of contact with the target, so the impact wave distribution can not reach the periphery of the target or the supports. High velocity impact tends to destroy the local structural elements of the impact area and is more likely to cause perforation of the target.

[0009] Furthermore, the dynamic impact response of a target object depends not only on its mechanical strength and geometry, but also on the impact velocity, mass, shape and type of the impacting projectile.

[0010] Several ballistic impact resistant materials for various purposes are available on the market, such as metals, plastics, glass, composites (resin-based, metal-based, ceramic-based, cementitious composites) and construction products (such as walls, doors, windows, etc.). However, the high cost of these materials limits their ability to be widely used in both civilian and military fields.

[0011] Among the impact resistant construction materials, ordinary Portland cement (OPC) based products are slightly cheaper compared to other impact resistant construction materials. The OPC cementitious category is used for civilian residential, commercial buildings, and protective structures. This category is generally defined as in-situ concrete walls, concrete blocks (e.g. coal cinder blocks), fiberglass composite panels, brick veneer, etc. cast in place and precast. These products can be designed to withstand a certain degree of ballistic impact, but apart from being heavy non-portable structures, they are often expensive and time consuming to build.

[0012] Despite the cost advantage of OPC cementitious products, their inherent brittleness is a major obstacle to solving the problem of providing thinner / lighter products and easier construction while maintaining ballistic resistance. When OPC construction products are impacted by high speed small projectiles, they tend to break due to their inherent brittleness. Therefore, OPC cement structures, whether reinforced or not, must be built as large structures to meet the required ballistic performance, for example, UF4-3 shows the thickness required for selected materials to achieve the designed ballistic rating.

[0013] Therefore, it is an object of the present invention to provide a ballistic resistant material that improves at least some of the problems associated with the prior art. SUMMARY

[0014] According to a first aspect of the present invention, there is provided the use of a magnesium oxychloride hydrate cement (MOC), a magnesium oxysulphate hydrate cement (MOS), a magnesium phosphate cement (MPC), a magnesium based activated cement (MAC); or a mixture of two or more of said materials; as a substrate in the manufacture of a ballistic resistant construction panel.

[0015] According to a second aspect of the present application, there is provided a ballistic resistant building panel made substantially from a combination of Magnesium oxychloride hydrate cement (MOC), Magnesium oxysulfate hydrate cement (MOS), Magnesium phosphate cement (MPC) and / or Magnesium based activated cement (MAC).

[0016] The magnesium based cement according to the present application is made from known compositions and is modified to improve impact resistance. MOC, MOS, mixtures of the two materials, MPC and / or MAC can be employed and can advantageously include one or more of the following: high and low modulus fibres and / or fine and coarse aggregates (such as stone chippings, river aggregate or sand) and / or fillers (such as rice husks, perlite, vermiculite, dolomite etc).

[0017] Preferably, the ballistic resistant building panel includes one or more of the following: high modulus fibres and / or stone chippings, preferably granite chippings; and low modulus fibres; the fibres and / or chippings being distributed in the cement.

[0018] As shown in Figure 1 Magnesium cements according to the present application have high impact resistance and high flexibility compared to OPC products which tend to shatter during impact due to their inherent brittleness.

[0019] The impact response characteristics of a cement depend not only on its own mechanical properties but also on the impact velocity, type and shape of the projectile. While conventional magnesium cement products exhibit some impact resistance at certain threat levels, they tend to be unable to resist high velocity projectile impacts as shown in Figure 2

[0020] The benefit of the high flexibility magnesium cement according to the present application is that it provides a substantially intact post-impact surface on both the impact side and the far side of a panel made from the material.

[0021] The present application therefore provides a relatively lightweight, thin, transportable and cost effective magnesium cementitious building panel which is impact resistant, particularly with respect to ballistic impacts. This allows ballistic resistant buildings to be constructed without the need for heavy construction techniques and allows relatively rapid installation and de-installation. Furthermore, the panel can be reused.

[0022] In the present application, various examples of magnesium cement are modified for ballistic resistant performance. To improve stiffness and impact resistance, the magnesium cement includes industrial by-product binders, low and / or high modulus fibres, organic fibres, fine aggregates, coarse aggregates and additives.

[0023] ​The modulus of elasticity represents the stiffness of a material. High modulus of elasticity fibres have high material stiffness, but can undergo permanent deformation under stress or strain, low modulus of elasticity fibres are longitudinally flexible or "stretchable". Preferably, the high modulus fibres are one or more materials selected from the group comprising: carbon fibres, steel fibres, copper fibres, Kevlar, titanium, graphite and glass fibre staple. Preferably, the low modulus material is selected from the group comprising: Polyvinyl Alcohol (PVA), Polypropylene (PP) and Polyethylene (PE). Preferably, the building panel further comprises coarse aggregate, preferably stone chips having a Mohs hardness in the range of 5-7 and a maximum dimension of 1 mm to 20 mm; the stone material is preferably granite, blue metal and / or basalt.

[0024] Preferably, the high modulus fibres material or coarse aggregate is included in an amount of 0.5% to 1.0% by mass of the cement; the low modulus fibres material is included in an amount of 1.2% to 2.0% by mass of the cement.

[0025] Preferably, the building panel comprises one or more of: expanded perlite; organic waste fibres; alumina particles having a dimension of between 1 mm and 5 mm; and exfoliated vermiculite.

[0026] The present invention provides an improved magnesium cement having superior properties associated with high velocity impact response, in particular with respect to the mechanical strength, ductility and toughness of the matrix.

[0027] Amongst the various failure modes induced by high velocity small projectile impact, perforation is a major problem for magnesium cement panels, and the present invention provides a panel having higher mechanical flexibility, which in turn reduces the risk of fragmentation and perforation failure.

[0028] According to another aspect of the present invention, there is provided a structure comprising a ballistic resistant panel, the ballistic resistant panel being at least partially formed from a ballistic resistant building panel according to any of the above.

[0029] According to another aspect of the present invention, there is provided the use of a magnesium cement in the construction of a ballistic resistant building panel; wherein the magnesium cement is selected from one or more of: a magnesium oxychloride hydrate cement; a magnesium oxysulfate hydrate cement; a mixture of the two materials; and / or a magnesium phosphate cement; the cement further comprising one or more high modulus fibres material distributed in the cement and one or more low modulus fibres material distributed in the cement.

[0030] According to another aspect of the application, there is provided a method of manufacturing a magnesium cement, wherein the magnesium cement is selected from one or more of: magnesium oxychloride hydrate cement; magnesium oxysulfate hydrate cement; a mixture of the two materials; and / or magnesium phosphate cement; the method comprising including in the cement one or more high modulus fibrous materials distributed in the cement and one or more low modulus fibrous materials distributed in the cement. Preferably, the method further comprises the step of including any stone particles having a Mohs hardness greater than 5, or wherein the average hardness of the stone particles is greater than 5 Mohs hardness. Preferably, the stone is blue stone, basalt or granite. The method preferably further comprises the step of including in the cement one or more materials selected from the group comprising: expanded perlite; organic by-product fibres; aluminium oxide particles; perlite and expanded vermiculite.

[0031] According to another aspect of the application, there is provided the use of magnesium oxychloride hydrate cement, magnesium oxysulfate hydrate cement, magnesium phosphate cement; or a mixture of one or more of the materials; as a substrate in the manufacture of a ballistic resistant building panel.

[0032] According to another aspect of the application, there is provided a ballistic resistant building panel made substantially from: magnesium oxychloride hydrate cement; magnesium oxysulfate hydrate cement; a mixture of the two materials; and / or magnesium phosphate cement; the cement further comprising one or more of: high modulus fibres and / or stone chippings, preferably granite chippings; and low modulus fibres; the fibres and / or chippings being distributed in the cement.

[0033] According to another aspect of the application, there is provided a structure comprising a ballistic resistant panel, the ballistic resistant panel being formed at least in part from a ballistic resistant building panel according to any of the above.

[0034] According to another aspect of the application, there is provided the use of a magnesium cement in the construction of a ballistic resistant building panel; wherein the magnesium cement is selected from one or more of: magnesium oxychloride hydrate cement; magnesium oxysulfate hydrate cement; a mixture of the two materials; and / or magnesium phosphate cement; the cement further comprising one or more high modulus fibrous materials distributed in the cement and one or more low modulus fibrous materials distributed in the cement.

[0035] According to another aspect of the application, there is provided a method of manufacturing a magnesium cement, wherein the magnesium cement is selected from one or more of: magnesium oxychloride hydrate cement; magnesium oxysulfate hydrate cement; a mixture of the two materials; and / or magnesium phosphate cement; the method comprising including in the cement one or more high modulus fibrous materials distributed in the cement and one or more low modulus fibrous materials distributed in the cement.

[0036] Preferred embodiments of the present application will now be described, by way of specific, non-limiting examples, with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 a to Figure 1 f shows failure modes of (50 mm thick OPC and engineered cementitious composite (ECC) panels) under high velocity small projectile impact according to the prior art: (a) front and (b) back of OPC 45 grade panel at 312 m / s impact velocity; (b) front and (c) back of OPC 45 grade panel at 441 m / s impact velocity; (e) front and (f) back of hybrid fiber ECC panel at 524.5 m / s impact velocity.

[0038] Figure 2 a and Figure 2 b shows ballistic impact of UBIQ INEX 19 mm thick non-rebound ballistic magnesium cementitious panel by.22 long rifle (impact velocity 178 J),.22 Magnum rifle (impact velocity 439 J) and 30-30 Winchester rifle (impact velocity 2390 J) respectively; (a) front, (b) back.

[0039] Figure 3 shows a ballistic cladding system according to the present application - structural insulated panel (SIP) panel and solid panel.

[0040] Figure 4 shows a magnesium based armor (Armor-MAG) cladded SIP panel system according to the present application.

[0041] Figure 5 a and Figure 5 b shows perforation failure mode of inventive Armor-MAG sample: (a) spalling present on impact surface, (b) flaking present on distal surface with large intact surface.

[0042] Figure 6 shows a schematic of an air gun impact testing apparatus.

[0043] Figure 7 shows a setup of a high speed steel ball impact air gun.

[0044] Figure 8 shows absorbed energy and thickness of Armor-MAG under steel ball projectile impact.

[0045] Figure 9 Toughness and thickness of Armor-MAG subjected to steel ball projectile impact.

[0046] Figure 10 a to Figure 10 f shows post-failure mode: 36 mm-Armor-MAG solid panel for steel projectile impact velocity limit: (a) and (d) are front surface, (b) and (e) are distal surface; (c) and (f) show non-rebound bullets after impact of samples without steel fiber inclusions (417 m / s) and with steel fiber inclusions (412 m / s), respectively.

[0047] Figure 11 Post-impact observation of Armor-MAG 4x22 solid layer at 816 m / s impact velocity is shown.

[0048] Figure 12 A schematic of a ballistic test apparatus according to AS / NZS 2343-1997 is shown.

[0049] Figure 13 A ballistic test apparatus according to AS / NZS 2343-1997 is shown.

[0050] Figure 14 SIP 22-22 Armor-MAG panels subjected to ballistic impact: G1 (AS / NZS 2343) and UL Class 3 are shown.

[0051] Figure 15 SIP 44-22 Armor-MAG panels subjected to ballistic impact: G2 (AS / NZS 2343), UL Class 7 and AK-47 are shown.

[0052] Figure 16 SIP 88-22 and 66-22 Armor-MAG panels subjected to ballistic impact: S0 (AS / NZS 2343) and UL Class 8 (North Atlantic Treaty Organization, NATO) are shown.

[0053] Figure 17 Various SIP panels with permanent metal template (in this test, 0.55 bmt colour-bond) are shown, subjected to S1, R1 and NATO (AS / NZS 2343) threat levels testing.

[0054] Figure 18 A setup of a 25-25 SIP panel according to the present invention is shown, with permanent template for fire resistance testing.

[0055] Figure 19 Results of 4-hour fire rating tests of 25-25 SIP panels are shown. Figure 18

[0056] Figure 20 A flow chart showing the basic MOC manufacturing process. DETAILED DESCRIPTION

[0057] The present invention relates most broadly to the use of magnesium cements, such as magnesium oxychloride hydrate cement, magnesium oxysulfate hydrate cement, mixtures of the two materials, magnesium phosphate cement, and / or activated magnesium cement, for use as a base for panels or other building components in buildings intended to have ballistic properties.

[0058] More specifically, the present invention provides for the modification of the magnesium cements to improve impact resistance and to enhance the ballistic properties of such cements to a degree that such materials have not been able to achieve to date in the prior art.

[0059] The magnesium cements modified according to the present invention have been shown to have superior properties compared to conventional OPC, especially in terms of flexural and tensile rebound, which are important characteristics in resisting ballistic impact failure modes such as spalling, bulking, and chipping after high velocity impact.

[0060] Impact failure modes observed in OPC cement panels subjected to high velocity small projectile impact are: (1) perforation, (2) penetration, (3) bulking, (4) spalling, (5) chipping, (6) matrix cracking, (7) delamination, (8) microcracking, and (9) spider webbing.

[0061] The advantage of using magnesium cements according to the present invention is that the inventors have demonstrated superior flexural and tensile strength compared to OPC cement, the effect of which during small projectile impact is to significantly reduce most of these failure modes (except for penetration and perforation) with comparable sample thickness. In addition, the high flexural performance of the magnesium cement eliminates the microcracking and "spider webbing" failure modes that occur in the prior art.

[0062] The use of the hitherto unknown properties of magnesium cements in ballistic performance, combined with further reinforcement of the fiber reinforcement technology, results in a significant improvement in the high velocity impact performance of the building materials manufactured according to the present invention.

[0063] 5In other aspects, the present invention provides a new formulation for a high velocity impact resistant magnesium cement building product that is relatively lightweight, thin, and portable, while having superior ballistic properties.

[0064] ​According to the preferred embodiment, the primary magnesium cement binder in the present invention is a combination of light-burned magnesium oxide (MgO) powder and one or more salt solutions of magnesium salts, which can include: magnesium chloride (MgCl2), magnesium sulfate (MgSO4), and sodium or potassium phosphates, potassium phosphate-based or phosphoric acid, and MgO powder with or without activators in magnesium-activated cement with silica-rich cementitious materials.

[0065] Although all types of magnesium cement can be adjusted to enhance ballistic performance, the preferred material properties of the primary binder in the present invention are given below.

[0066] The light-burned magnesium oxide used in the present invention is preferably calcined at a temperature of 700-1000°C, with a purity of 80-95% and an average particle size of less than 45 pm to increase the contact area with water and thus accelerate the hydration process, achieving early high strength. The activity level of the magnesia (MgO) powder is between 50-70%.

[0067] In one embodiment, for the ballistic performance of MOC cement, a salt solution with a solid salt concentration of 22-33% is preferred. In the case of using this crystalline form, magnesium chloride hexahydrate (MgCl2·6H2O) crystals are dissolved in water to form an aqueous solution with the desired solid concentration 24 hours before its use in cement production.

[0068] In another embodiment, the preferred solid content of magnesium sulfate (MgSO4) in the solution is in the range of 18% to 26%. In the case of using magnesium sulfate heptahydrate (MgSO4·7H2O) crystals, it is necessary to prepare the solution 24 hours before its use in cement production. In another embodiment, a combination of the two salt solutions described above is used in combination with phosphoric acid and / or other additives and phosphates (such as sodium monofluorophosphate, sodium hexametaphosphate, magnesium phosphate, silane, etc.).

[0069] The preferred molar ratio of MgO to magnesium salt is in the range of 5 to 11. In this case, the magnesium salt refers to magnesium chloride or magnesium sulfate, or a combination of both.

[0070] According to the present invention, the preferred water / cement mass ratio is 0.35 to 0.6.

[0071] In another embodiment, the magnesium-activated cement comprises magnesium oxide powder and silica-rich cementitious materials, preferably silica fume / microsilica and ground granulated blast furnace slag (GGBFS). When water is added to the MgO and SiO2 powders, a magnesium silicate hydrate (M-S-H) binder is formed. Activators or additives accelerate the hydration process but do not produce significant changes in the formation of the M-S-H system.

[0072] In other embodiments of the application, the formulation can include one or more combinations of cementitious / volcanic ash industrial by-products such as: fly ash, microsilica (silica fume) and / or ground granulated blast-furnace slag (GGBS). These tend to enhance the mechanical properties of the cement, and hence the toughness and durability of the substrate, by reducing water absorption. Preferably, F-class fly ash with an average particle size of 45 pm is added to the composition in an amount of 20% or less of the dry mix mass. Silica fume with an average particle size of less than 2 pm and GGBFS with an average particle size of less than 10 pm are included in the composition in a weight proportion of 5-15% of the dry mix mass. If MAC is used, a 1 : 1 molar ratio of MgO:SiO2is used.

[0073] In alternative embodiments, a plasticizer or high strength water reducer can be included in the composition to improve the processability of admixtures during production if required.

[0074] The uniform substrate reduces the likelihood of delamination and potential cracking between the interfaces of the substrate layers that will be subjected to high velocity impact. The cohesiveness of the structural elements makes the substrate stronger. Furthermore, this provides a simpler and more efficient production line during manufacturing. In the present application, one or more combinations of fibres are preferably applied to achieve a preferred balance of high modulus materials and low modulus materials in the uniform substrate to achieve uniform propagation of compressive and tensile stress waves in the event of high velocity small projectile impact on the substrate.

[0075] Preferably, the high modulus fibres are one or more materials selected from the group comprising: carbon fibres, steel fibres, copper fibres, Kevlar, titanium, graphite and glass fibre chopped strands. Preferably, the low modulus materials are selected from the group comprising: PVA, PP, PE and banana fibres.

[0076] In some embodiments, the fine and coarse aggregates include, but are not limited to: river sand, river stone, granite, basalt, lapis lazuli, etc. The quantity and particle size should be selected according to the mix design and the thickness of the wall substrate.

[0077] The magnesium cement can also include fillers such as: sawdust, rice husk, perlite, vermiculite, dolomite, alumina oxide, etc. Other additives can include: phosphoric acid, citric acid, phosphates, water repellents, siloxane functional groups, and corrosion inhibitors such as sodium monofluorophosphate, sodium polyphosphate, sodium nitrate, sodium and potassium chromate, sodium phosphate, etc.

[0078] Some examples of magnesium cement and ballistic test results are presented in the following sections. Ballistic tests were performed in simulated airgun tests as well as ballistic tests defined in AS / NZS 2343 and Underwriters Laboratories standards.

[0079] Low modulus fibres (such as PVA or PE fibres) exhibit high ultimate tensile strain behaviour, which in turn significantly improves ductility, while also exhibiting high strain hardening behaviour. Thus, the inclusion of low modulus fibres in cement enhances the energy absorption capacity of the cement. This also reduces the width of any fractured cracks caused by a projectile and provides enhanced bridging strength across any fractures for the matrix. However, low modulus fibres exhibit low ultimate tensile strength.

[0080] Thus, a balance of high modulus fibres (or stone chips, such as granite chips) and low modulus fibres in a cementitious body provides higher toughness and resilience to a projectile impact by enhancing the ability of the cement to absorb impact energy. During high velocity impact, penetration resistance is directly related to the tensile strength and toughness of the sample, while energy absorption depends on the strain capacity of the cementitious body.

[0081] In embodiments of the invention, chopped strand fibres are preferably included for a more uniform matrix. However, a fibreglass mesh can also be included as a reinforcing material for the panel.

[0082] Low modulus REC-15-polyvinyl alcohol (PVA) fibres having a diameter of 39 μm and a length of 8-12 mm can be used as low modulus fibres in the cementitious body.

[0083] High modulus copper coated steel fibres (SE) having a diameter of 0.2 mm and a length of 8-12 mm can be used as high modulus fibres in the cementitious body.

[0084] Alternatively, copper fibres (Cu) having a diameter of 0.2 mm and a length of 6-8 mm can be used as high modulus fibres in the cementitious body.

[0085] Alternatively, chopped strand glass fibres having a diameter of 6-12 μm and a length of 6-8 mm can be used as high modulus fibres in the cementitious body.

[0086] Alternatively, other fibres can be used to provide the desired high modulus or low modulus effect in the cementitious body, such as: polyethylene, polypropylene, carbon, graphite, Kevlar, titanium, etc.

[0087] Toughness (i.e. the ability of the cement to absorb energy before failure) is one of the most important properties of the impact resistance of a material when subjected to ballistic impact. It can be represented by the area under the stress / strain curve, and therefore, in order to optimize this property, the strength and strain hardening properties should be balanced.

[0088] In a preferred embodiment of the application, steel fibres and / or granite chippings coarse aggregate are used in the composition to enhance the toughness of the cementitious body.

[0089] In an alternative embodiment, natural stone chippings (e.g. granite chippings) can be used to replace steel completely or partially as high modulus fibres, as the application of steel in magnesium cement without any corrosion protection can be subject to corrosion problems (such as concrete cancer) later in the life of the material. The use of these granite chippings allows the cementitious body to exhibit comparable impact performance to the steel fibre reinforced materials described above.

[0090] Other inclusions in the matrix can be used for specific purposes. Organic waste fibres (such as rice or barley husks) can be included as lightweight fillers; alumina particles of 1-5mm can be included as aggregate for strength enhancement; expanded perlite can be included as lightweight aggregate; expanded vermiculite can be included as lightweight filler.

[0091] Example - method of manufacture Referring to the materials specified in Table 1 below, a preferred manufacturing process for the ballistic resistant magnesium cementitious panel according to the application is shown in the flow chart of Figure 1. Figure 20

[0092] Table 1 - Material specifications Step 1 : As described above, prepare a brine of one or more magnesium salts in solution with the required concentration at least 24 hours before preparing the composition (if prepared from a crystalline form of the salt). The brine temperature should be between 22°C and 30°C.

[0093] Step 2: Add the brine to a mixer, followed by the additives. The addition of these ingredients does not change the pH of the brine, which is approximately 6.5 to 8.0. Mix them until fully dispersed in the solution.

[0094] Step 3: Add the MgO, cementitious material, fly ash, silica fume and slag to the alkaline aqueous solution prepared in Step 2 and mix until fully dispersed in the mixer. For magnesium activated cement, Step 3 precedes Step 2.

[0095] ​Step 4: Add the fillers and aggregates (such as reinforcing fibres, rice husks (optionally with expanded perlite and / or vermiculite)) and the above fine and coarse aggregates to the mixture prepared in Step 3, followed by dispersing the chopped fibres in the mixture (5 to 10 minutes).

[0096] Step 5: Check the viscosity and temperature of the slurry before placing into the mould (either a temporary or permanent mould).

[0097] Step 6: Once cast in the mould, the wet sample / product is allowed to set at room temperature with a relative humidity (RH) between 60% to 70%. The curing temperature should not be less than 20°C for the first 24-48 hours.

[0098] Step 7: The product is de-moulded and placed in a curing room at 45°C ± 3°C for 3 to 5 hours. In the case of using a permanent mould, the product is placed in the curing room without de-moulding.

[0099] As mentioned above, the mechanical properties of the resulting board were measured to have a compressive strength greater than 34 MPa and a flexural strength greater than 10 MPa. The strength tests were conducted in accordance with ASTM C0109M-16A and ASTM C348-18, respectively.

[0100] Table 2 below shows alternative example compositions of the protective magnesium oxide cementitious body according to the present application.

[0101] Table 2 - Example compositions As shown in Table 3 below, the properties of some examples of the cementitious samples according to the present application were: compressive strength in the range of 40 MPa to 70 MPa and flexural strength in the range of 12 MPa to 19 MPa.

[0102] Table 3 - Mechanical properties of samples After being submerged in water for 24 hours, the water absorption of the samples was in the range of 0.2% to 0.5% and the retention of compressive and flexural strength was in the range of 80% to 110% (i.e. some compositions showed an increase in strength under water).

[0103] High velocity impact testing The test regime comprised two parts: • high velocity steel ball projectile impact testing; and • ballistic impact testing in accordance with AS / NZS 2343 and Underwriters Laboratories standards.

[0104] The inventors have observed that a 40 grade INEX magnesium cement panel according to the present invention exhibits excellent flexibility under impact of a 30-30 Winchester bullet with an impact energy of 2329 J. The target panel with a thickness of only 19 mm shows only a small amount of spalling and delamination after the bullet perforation and a large intact area is visible. As shown in Figure 1 , a 50 mm thick OPC panel breaks after impact of a small projectile with an impact energy of 730 J.

[0105] A 40 grade high flex and thin ballistic INEX magnesium cement panel with a thickness of 19 mm exhibits high flexibility and tensile strength of the matrix by observing small local failures and large intactness on the impact surface and the back surface when subjected to ballistic impact, see Figure 2 .

[0106] The INEX 19 mm sample did not exhibit perforation when subjected to a 0.22 long rifle impact (bullet 40 grains (2.6 g) at an impact velocity of approximately 317 m / s with an impact energy of 179 J). As a sandwich structure with layered glass fiber reinforcement, some delamination occurred on the back surface.

[0107] Post-impact observations of the INEX 19 mm sample after being subjected to a 0.22 Magnum rifle (40 grains (2.6 g)) and a 3030 Winchester rifle impact showed that both impacts resulted in perforation of the sample with impact energies of 439 J and 2390 J, respectively. The higher impact of the 3030 Winchester rifle resulted in greater delamination and spalling damage, including the outermost glass fiber layer. However, no radial cracks were observed around the damage, as shown in Figure 2 , with large intact surfaces on both sides.

[0108] In a preferred embodiment of the present invention, the inventors further enhance the flexibility and compressive strength of the magnesium cement by including a distributed composition of one or more fiber reinforcement materials in the matrix. Thus, the resistance to the propagation of compressive and tensile stresses caused by high velocity impacts is improved.

[0109] In the present invention, a mixed combination of fibers (such as PVA, PP, PE, carbon fibers, steel fibers, copper fibers, and glass fiber short-cut strands) has been used to achieve a balance of high modulus fibers and low modulus fibers.

[0110] One of the important results of the preferred embodiment of the present invention is to improve the toughness of the magnesium cement product, making it flexible rather than brittle, and thus more likely to absorb impact energy before perforation failure occurs. To this end, steel fibers and / or granite chips are included in the magnesium cement matrix.

[0111] Granite chips can also be used as a substitute for high modulus steel or copper fibers to improve resistance to high velocity impacts.

[0112] Thus, with the increase in flexibility and toughness of the magnesium cement according to the present invention, the modified magnesium cement panel according to the present invention exhibits significantly high ballistic resistance in the range of 44mm-110mm thickness. The inventive panel can withstand different levels of ballistic impact up to 3400J of impact energy according to NATO R2 level of AS / NZS 2343-1997 and US- underwriter Laboratory Standard (UL) level 8. 3

[0113] The following ballistic impact tests are in accordance with AS / NZS 2343 and US- underwriter Laboratory Standard.

[0114] Magnesium cement test samples were manufactured according to the above-mentioned methods. They were subjected to various forms of high velocity impact testing, including various thicknesses and configurations (such as solid form, solid laminated form and SIP panel). Some examples of samples are shown in Figure 3 When tested as thin solid panels, two or more panels of the preferred inventive material were laminated together - for example, “2x22” means two 22mm thick panels fixed together without a gap.

[0115] SIP panels according to the present invention are formed similar to a cladded wall system, where one or more 22mm thick panels are separated by steel or timber framing, which includes a gap of 70mm to 90mm between the panels. When used as a building material, insulation material can be filled inside the gap, as shown in Figure 4

[0116] Tests were performed on panels of thickness 13mm to 50mm, solid laminates of 2x22, 3x18, 3x22, 4x22 and SIP panels of 22-22 (22mm impact panel separated by a 22mm distal panel) to 88-22 (laminates of 4x22mm impact panels separated by a 22mm distal panel).

[0117] 1. High velocity steel ball projectile impact test of diameter 12mm High velocity small projectile impact was performed using a single barrel air gun. Steel ball projectiles of diameter 12mm and mass 7.05g were propelled by compressed helium gas to achieve impact velocities in the range of 400m / s to 815m / s. The air gun test set-up is shown in Figure 6 and Figure 7

[0118] Impact test data is shown in Table 4 below, where the panels according to the present invention are referred to as “Armor-MAG”.

[0119] ​​​​Table 4: High velocity small projectile impact test results As Figure 8 shown, for plate thicknesses less than 22 mm, the plates absorbed a maximum energy in the range of 400 J to 500 J at the point of perforation failure (as Figure 5 shown) with small areas of delamination and spalling. The 36 mm, 50 mm and 66 mm plates absorbed energy in the ranges of 600 J - 830 J, 1200 J - 1500 J and greater than 2000 J, respectively.

[0120] In addition to the inherent high compressive and flexural strength of the material according to the present application, the impact toughness of the material also depends on the thickness and the impact velocity. When the impact velocity is high, the compressive strain wave propagates to the edge of the sample more quickly and the projectile tends to penetrate the thickness of the sample.

[0121] When a projectile strikes the surface of a sample, compressive waves are generated at the impact surface and a corresponding depth of the sample. Later, these waves are converted to tensile stress waves near the far surface. When the residual energy of the projectile is still sufficient to cause damage after it has traveled along the depth of the sample, the tensile waves cause the perimeter of the sample to bulge outward until it breaks. This is known as perforation failure.

[0122] As Figure 9 shown, plates with thicknesses less than 22 mm had a toughness rating in the range of 400 kJ / m 3 to 520 kJ / m 3 when subjected to impact velocities of 400 m / s - 420 m / s. The toughness rating of the 36 mm thick plate was 380 kJ / m 3 and 520 kJ / m 3 at impact velocities of 410 m / s and 500 m / s, respectively. When the plate thickness was 50 mm, the toughness rating was in the range of 600 kJ / m 3 - 800 kJ / m 3 at impact velocities between 500 m / s and 800 m / s.

[0123] Tables 5a, 5b and 5c list the ballistic test results for each of the solid and SIP plates according to the present application. Table 5a shows the results for plates without permanent formers, while Table 5b shows the results for plates with 0.55 bmt color coated steel plate permanent formers. Table 5c represents the ballistic performance of the joint system of the wall to a MgO board blocker that is as thin as 19 mm. As can be seen, each of the plates passed the required tests for use as a ballistic resistant plate.

[0124] Table 5a: Ballistic test results for Armor-MAG plates without permanent formers Figure 10 Photographs showing the post-failure mode of a 36mm solid panel with or without steel fibre reinforcement according to the present application. Views (a), (b) and (c) show the front impact surface, the distal surface and the embedded non-jumping bullet after impact on a sample without steel fibres respectively. Views (d), (e) and (f) show the front impact surface, the distal surface and the embedded non-jumping bullet after impact on a sample with steel fibres according to the present application respectively.

[0125] The ballistic limit (i.e. the impact energy or velocity at which the sample perforates before failing) of the 36mm panel including steel fibres was 412m / s, while the ballistic limit of the panel without steel fibres was 417m / s. The bulged mode of the distal surface is shown in Figure 10 (b) and (e). The panel according to the present application absorbed 591J, while the panel without steel fibre inclusion absorbed 609J. In terms of impact toughness, the sample without steel fibre inclusion was 276kJ / m 3 , slightly higher than the 268kJ / m 3 of the sample with steel fibre inclusion.

[0126] Table 5(b): Ballistic test results for Armor-MAG panel with 0.55mm bmt permanent formwork of painted steel sheet Table 5(c): Ballistic test results for Armor-MAG panel joint system with 0.55mm bmt permanent formwork of painted steel sheet The 4x22 solid layer of the panel according to the present application was observed to be unperforated at an impact velocity of 816m / s and an impact energy of 2350J, and the sample without steel fibres exhibited higher resistance, with an intact distal surface, as shown in Figure 11 . Ballistic impact tests were in accordance with AS / NZS 2343 and Underwriters Laboratories standards, as shown in Tables 6 and 7 respectively.

[0127] The panel sample configuration according to the present application is shown in Figure 3 and Figure 4 . The ballistic test apparatus schematic is shown in Figure 12 and Figure 13 .

[0128] Table 6 - Ballistic test conditions - Table B1 - AS / NZS 2342-1997 The test failed if the witness card was damaged by the bullet or fragments thereof during impact, depending on the test conditions. The test passed only if the bullet did not perforate the panel or did not damage the witness card during impact.

[0129] Panels having a thickness of less than 110 mm manufactured according to the present invention have passed the highest ballistic threat rating of R2 Class - NATO (AS / NZS 2343) or UL Class 8.

[0130] The 22-22 SIP panel system withstood a.357 Magnum SJFN (nominal 158 grains) G1 class ballistic threat at an impact velocity of 450 m / s without perforation and without spalling or bulging on the front side surface, as shown in Figure 14

[0131] Table 7: US Standard UL-752 (Underwriters Laboratories) Protection Rating Rating The same panel withstood a.44 Magnum LSWC (nominal 240 grains) impact at an impact velocity of 412 m / s without perforation but with slight bulging on the distal surface. However, no damage to the witness card was observed and thus the test passed the requirements of UL-Class 3, as shown in Figure 14

[0132] The 44-22 SIP panel system according to the present invention withstood a 5.56 FMJ, M193 type bullet (nominal 55 grains) impact at an impact velocity of 969 m / s and a.44 Magnum SJSP (nominal 240 grains) impact at an impact velocity of 477 m / s. No perforation was observed and the surfaces remained substantially intact. No damage to the witness card was observed and thus the test passed UL-Class 7 and G2 class, as shown in Figure 15

[0133] The 22-22 SIP panel according to the present invention withstood a 12 gauge SG shot (32 grains) impact at an impact velocity of 407 m / s without perforation and without rebound of the projectile but with the projectile remaining inside the sample. Thus, the panel passed S0 class, as shown in Figure 16

[0134] ​​​​A 66-22 SIP panel according to the present application withstood a NATO Protection Level - 308 Winchester Calibre FMJ, M80 round (150 grains) at an impact velocity of 849 m / s without perforation and a bullet penetration depth of 66 mm. No witness card damage was observed and the bullet was stuck inside the sample by absorbing all the impact energy. Thus, a 110 mm solid panel or an 88-22 SIP panel passed the test after being subjected to a ballistic threat of Class R1 or equivalent to UL Level 8 with minimal impact damage as shown in Figure 16

[0135] Figure 17 Various SIP panels with permanent metal stencils (0.55 bmt colour coated steel sheet in this test) were shown to withstand threat levels of S1, R1 and NATO (AS / NZS 2343).

[0136] Further development of the 44-22 SIP ballistic panel with permanent stencils according to the present application showed that it passed the ballistic test according to the NATO Protection Level of AS / NZS 2343. The 35-35 SIP panel with permanent stencils also passed the same test.

[0137] In addition, the joint area of the SIP panels also achieved significant ballistic resistance. The 22-22 SIP panel (with permanent stencils) joint withstood the UL L3 level of protection, while the 25-25 SIP panel joint with permanent stencils withstood the S1 class.

[0138] The inventors also conducted a pilot fire test on a 25-25 SIP panel with a 19 mm magnesium panel joint firestop which achieved a 4 hour fire rating (as shown in Figure 18 and Figure 19 ).

[0139] The person skilled in the art will understand that the above embodiments are only one example of how to implement the inventive concept. It is understood that other embodiments can be envisaged, although differing in their details, but falling within the same inventive concept and representing the same invention.​

Claims

1. A rebound road building panel, which is essentially made of: magnesium oxychloride hydrated cement; magnesium oxysulfide hydrated cement; a mixture of the two materials; and magnesium phosphate cement.

2. The rebound track building material according to claim 1, wherein, The cement further comprises one or more of the following: high elastic modulus fibers and / or stone chips, preferably granite chips; and low elastic modulus fibers; the fibers and / or chips are distributed in the cement.

3. The building panel according to claim 2, wherein, The high-modulus fiber material is one or more materials selected from the group consisting of: carbon fiber, steel fiber, copper fiber, Kevlar, titanium, graphite, alkali-coated C-glass, glass fiber, and chopped glass fiber filaments.

4. The building panel according to claim 2, wherein, The low-modulus material is selected from the group consisting of polyvinyl alcohol (PVA) fibers, polypropylene (PP) fibers, and polyethylene (PE) fibers.

5. The building panel according to any one of the preceding claims, wherein, The stone chips are granite chips with a maximum size between 1 mm and 20 mm, preferably less than 10 mm; the stone chips preferably have a Mohs hardness in the range of 6-7; and the specific gravity is preferably 2000 kg / m³. 3 Up to 3000 kg / m 3 between.

6. The building panel according to any one of the preceding claims, wherein, The high-modulus fiber content ranges from 0.5% to 1.0% of the cement by mass, while the low-modulus fiber content ranges from 1.0% to 2.0% of the cement by mass.

7. The building panel according to claim 6 further comprises expanded perlite.

8. The building material according to claim 6 further comprises organic waste fiber.

9. The building panel according to claim 6 further comprises alumina particles with a size between 1 mm and 5 mm.

10. The building material according to claim 6 further comprises one or more of the following: expanded vermiculite, rice husk, banana tree trunk fiber, expanded perlite, and dolomite.

11. The building panel according to claim 6 further comprises one or more of the following: lightly calcined magnesium oxide; magnesium salts; and cement industrial by-products.

12. The building panel according to claim 11, wherein, The magnesium salt includes one or more of the following: magnesium chloride hexahydrate, magnesium sulfate heptahydrate, and magnesium phosphate.

13. The building panel according to claim 11, wherein, The molecular ratio of lightly calcined magnesium oxide to magnesium salt is in the range of 7 to 11.

14. The building panel according to claim 11, wherein, The lightly calcined magnesium oxide has a MgO purity greater than 80%, an activity of 58% to 70%, and a particle size of less than 45 μm.

15. The building panel according to claim 11, wherein, The cementitious material is one or more materials selected from the group consisting of: fly ash, silica fume, and finely ground blast furnace slag.

16. The building panel according to any one of the preceding claims, wherein, The water-to-dry-mix ratio of the cement is between 0.30 and 0.60 by weight.

17. The building panel according to any one of the preceding claims further comprises one or more of the following: phosphate additives, moisture-proof and corrosion-resistant agents, such as phosphoric acid, sodium monofluorophosphate, sodium hexametaphosphate, high-performance water-reducing agents, active cationic organic groups, and silane-based waterproofing agents.

18. A rebound deck building panel system comprising two or more building panels according to any one of the preceding claims, the building panels being spaced apart by gaps held by a support frame.

19. A structure comprising a rebound paving panel made at least in part of a rebound paving panel according to any of the preceding claims.

20. A rebound road building panel comprising any one of the following: magnesium oxychloride hydrated cement; magnesium oxysulfide hydrated cement; or magnesium phosphate cement; or a combination of said materials.

21. The use of magnesium cement in the construction of paving stone building panels, wherein, The magnesium cement is selected from one or more of the following: magnesium oxychloride hydrated cement; magnesium oxysulfide hydrated cement; a mixture of the two materials; and magnesium phosphate cement.

22. The use according to claim 21, wherein, The cement further comprises one or more high-modulus fiber materials and one or more low-modulus fiber materials distributed in the cement.

23. The use according to claim 21, wherein, The cement further comprises one or more of the following: high elastic modulus fibers and / or stone chips, preferably granite chips; and low elastic modulus fibers; the fibers and / or chips are distributed in the cement.

24. The use according to claim 22, wherein, The high-modulus fiber material is one or more materials selected from the group consisting of: carbon fiber, steel fiber, copper fiber, Kevlar, titanium, graphite, alkali-coated C-glass, glass fiber, and chopped glass fiber filaments.

25. The use according to claim 22, wherein, The low-modulus material is selected from the group consisting of polyvinyl alcohol (PVA) fibers, polypropylene (PP) fibers, and polyethylene (PE) fibers.

26. The use according to any one of claims 21 to 25, wherein, The stone chips are granite chips with a maximum size between 1 mm and 20 mm, preferably less than 10 mm; the stone chips preferably have a Mohs hardness in the range of 6-7; and the specific gravity is preferably 2000 kg / m³. 3 Up to 3000 kg / m 3 between.

27. The use according to any one of claims 21 to 26, wherein, The high-modulus fiber content ranges from 0.5% to 1.0% of the cement by mass, while the low-modulus fiber content ranges from 1.0% to 2.0% of the cement by mass.

28. The use according to claim 27, wherein, The sheet material also contains expanded perlite.

29. The use according to claim 27, wherein, The building materials also contain organic waste fibers.

30. The use according to claim 27, wherein, The building material also contains alumina particles with a size between 1 mm and 5 mm.

31. The use according to claim 27, wherein, The building materials also include one or more of the following: expanded vermiculite, rice husks, banana tree trunk fibers, expanded perlite, and dolomite.

32. The use according to claim 27, wherein, The building material also includes one or more of the following: lightly calcined magnesium oxide; magnesium salts; and cement industrial byproducts.

33. The use according to claim 32, wherein, The magnesium salt includes one or more of the following: magnesium chloride hexahydrate, magnesium sulfate heptahydrate, and magnesium phosphate.

34. The use according to claim 32, wherein, The molecular ratio of the lightly calcined magnesium oxide to the magnesium salt is in the range of 27 to 31.

35. The use according to claim 32, wherein, The lightly calcined magnesium oxide has a MgO purity greater than 80%, an activity of 58% to 70%, and a particle size of less than 45 μm.

36. The use according to claim 32, wherein, The cementitious material is one or more materials selected from the group consisting of: fly ash, silica fume, and finely ground blast furnace slag.

37. The use according to any one of claims 21 to 36, wherein, The water-to-dry-mix ratio of the cement is between 0.30 and 0.60 by weight.

38. The use according to any one of claims 21 to 37, wherein, The building materials also include one or more of the following: phosphate additives, moisture-proof and corrosion-resistant agents, such as phosphoric acid, sodium monofluorophosphate, sodium hexametaphosphate, high-performance water-reducing agents, active cationic organic groups, and silane waterproofing agents.

39. A method for manufacturing magnesium cement suitable for use according to any one of claims 21 to 38, wherein, The magnesium cement is selected from one or more of the following: magnesium oxychloride hydrated cement; magnesium oxysulfide hydrated cement; a mixture of the two materials; and / or magnesium phosphate cement; the method includes including one or more high-modulus fiber materials and one or more low-modulus fiber materials distributed in the cement.

40. The method of claim 39, further comprising the step of: The cement contains stone chips, preferably granite chips, with a maximum size between 1 mm and 20 mm, preferably less than 10 mm; the granite chips preferably have a Mohs hardness in the range of 6-7; and the specific gravity is preferably 2000 kg / m³. 3 Up to 3000 kg / m 3 between.

41. The method of claim 39, further comprising the step of: The cement contains one or more materials selected from the group consisting of: expanded perlite; organic waste fibers; alumina particles with a size between 1 mm and 5 mm; and expanded vermiculite.

42. The use of granite chips in the manufacture of paving pavement panels, the paving pavement panels being substantially made of: magnesium oxychloride hydrated cement; magnesium oxysulfide hydrated cement; a mixture of the two materials; and / or magnesium phosphate cement, to completely or partially replace high modulus steel fibers, thereby improving corrosion resistance without significantly reducing paving pavement performance.

43. Use of one or more of a high-modulus fiber and / or stone chips, preferably granite chips, and a low-modulus fiber in the manufacture of a rebound pavement slab, the rebound pavement slab being substantially made of: magnesium oxychloride hydrated cement; magnesium oxysulfate hydrated cement; a mixture of the two materials; and / or magnesium phosphate cement, to eliminate or reduce the occurrence of multiple cracks and / or spiderweb failure modes under projectile impact.

44. Use of a magnesium oxychloride hydrated cement, magnesium oxysulfide hydrated cement, magnesium phosphate cement, or one or more of said materials as a base material in the manufacture of a rebound paving board.

45. A rebound road building panel, which is substantially made of materials selected from the group consisting of: magnesium oxychloride cement (MOC); magnesium oxysulfide cement (MOS); a mixture of MOC and MOS; and magnesium phosphate cement.

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