Lightweight concrete compositions

Abstract

A lightweight concrete composition containing from 10 to 90 volume percent of a cement composition, from 10 to 90 volume percent of particles having an average particle diameter of from 0.2 mm to 8 mm, a bulk density of from 0.03 g/cc to 0.64 g/cc, an aspect ratio of from 1 to 3, and from 0 to 50 volume percent of aggregate; where the sum of components used does not exceed 100 volume percent, and where after the lightweight concrete composition is set it has a compressive strength of at least 1700 psi as tested according to ASTM C39 after seven days. The concrete composition can be used to make concrete masonry units, construction panels, road beds and other articles.

Description

REFERENCE TO RELATED APPLICATION

This application
N_b represents the number of expanded beads.

A LWC test specimen with diameter D and height H (usually 2″×4″ or 6″×12″), containing dispersed expanded polymer beads of average expanded bead diameter B, and a given volume fraction V_d contains an amount of expanded polymer beads N_b given by equation 1:

Note that N_b is inversely proportional to the cube of the expanded polymer bead diameter. The constant of proportionality, K=1.5 V_dHD², is a number that is dependent only on the sample size and the volume fraction of expanded polymer beads. Thus for a given sample size, and known expanded polymer bead volume fraction, the number of beads increases to a third power as the bead diameter decreases.

As a non-limiting example, for a 2″×4″ LWC specimen, at 90 pcf (lb/ft³) (corresponding to expanded polymer bead 43% volume fraction with pre-puff bulk density of 1.25 pcf), the number of beads increases fourfold and sevenfold moving from a 0.65 mm bead to 0.4 mm and 0.33 mm beads respectively. At 2.08 pcf, the increase in the number of beads is sixfold and sevenfold for 0.4 mm and 0.33 mm beads respectively. At 5 pcf, the increases are twofold and threefold respectively. Thus, the density correlates to the bead size. As shown below, the density also affects the cell wall thickness. The strength of a concrete matrix populated by expanded beads is typically affected by the cell wall stiffness and thickness.

In an embodiment of the invention, where monodisperse spherical cells are assumed, it can be shown that the mean cell diameter d is related to the mean wall thickness 6 by equation 2:

$\begin{array}{cc}d=\delta /\left(\frac{1}{\sqrt{1-\rho /{\rho }_s}}-1\right)& \left(2\right)\end{array}$
where ρis the density of the foam and ρ_s, is the density of the solid polymer bead.

Thus for a given polymer, depending on the particular expansion process used, one can obtain the same cell wall thickness (at a given cell size) or the same cell size at various values of δ. The density is controlled not only by the cell size but also by varying the thickness of the cell wall.

The table below exemplifies the variation of expanded polymer bead density with bead size for three classes of beads.

		Foam Particle	Expansion	Average Number of
Bead Size,	Density	Size	factor	beads for 43% volume
microns	(pcf)	(mm)	(cc/g)	fraction
650	2.00	1.764	31	96,768
650	3.00	1.541	21	145,152
650	4.00	1.400	16	193,536
400	2.00	1.086	31	415,233
400	3.00	0.949	21	622,849
400	4.00	0.862	16	830,466
330	2.00	0.896	31	739,486
330	3.00	0.783	21	1,109,229
330	4.00	0.711	16	1,478,972

Desirable microstructures and/or morphologies can fall into distinct classes. The first is a bicontinous or co-continuous composite with special interfaces and the second includes special inclusions in a connected matrix. The effective properties of both bicontinous and singly connected microstructures are described by known optimal cross-property bounds.

In many cases, the smaller the beads, the greater the number of beads required to maintain the same expanded polymer bead volume fraction as described by equation 1. As the number of beads increases exponentially, the spacing between the beads decreases.

The optimal bounds can be described by a number of relations representing critical numbers or limits. As a non-limiting example, for a given volume fraction, there is often a critical bead size corresponding to a critical number of beads that can be dispersed to provide a desired morphology such that all the beads are isolated and the concrete is singly connected. It is also possible to form a morphology where all of the beads are non-isolated but contacting.

Finite element analysis of a 2-dimensional cross section was performed using ANSYS® (a finite element analysis program available from ANSYS Inc., Canonsburg, Pa.). In the finite element mesh of the cross-section, the beads are modeled as non-contacting or isolated circles in a singly connected concrete matrix.

The results demonstrate that under loading, the stresses build up in a direction perpendicular to the load axis. The maximum stress concentrations are at the horizontal boundary between the expanded polymer beads, which tend to be deformed from a circular shape to an elliptical shape.

In a particular embodiment of the invention, the concrete composition contains at least some of the expanded polymer particles or prepuff particles arranged in a cubic or hexagonal lattice.

In an embodiment of the invention, the present LWC composition is substantially free of air entraining agents, which are typically added to create air cells or voids in a batch of concrete.

In another embodiment of the invention, the LWC composition can include reinforcement fibers. Such fibers act as reinforcing components, having a large aspect ratio, that is, their length/diameter ratio is high, so that a load is transferred across potential points of fracture. Non-limiting examples of suitable fibers include fiberglass strands of approximately one to one and three fourths inches in length, although any material can be used that has a higher Young's modulus than the matrix of the cementitious mixture, polypropylene fiber and other fibers as described above.

The LWC compositions according to the invention can be set and/or hardened to form final concrete articles using methods well known in the art.

The density of the set and/or hardened final concrete articles containing the LWC composition of the invention can be at least 40 lb/ft³ (0.64 g/cc), in some cases at least 45 lb/ft³ (0.72 g/cc) and in other cases at least 50 lb/ft³ (0.8 g/cc) lb/ft³ and the density can be up to 130 lb/ft³ (2.1 g/cc), in some cases 120 lb/ft³ (1.9 g/cc), in other cases up to 115 lb/ft³ (1.8 g/cc), in some circumstances up to 110 lb/ft³ (1.75 g/cc), in other circumstances up to 105 lb/ft³ (1.7 g/cc), in some instances up to 100 lb/ft³ (1.6 g/cc), and in other instances up to 95 lb/ft³ (1.5 g/cc). The density of the present concrete articles can be any value and can range between any of the values recited above. The density of the LWC composition is determined according to ASTM C 138.

In a particular embodiment of the invention, the LWC composition contains containing from 10 to 60 volume percent of a cement composition that includes type III Portland Cement; from 20 to 78 volume percent of expanded polymer particles having an average particle diameter of from 0.2 mm to 5 mm, a bulk density of from 0.032 g/cc to 0.56 g/cc, and an aspect ratio of from 1 to 2; from 5 to 35 volume percent of one or more aggregates; and from 0.1 to 1 volume percent of one or more additives selected from anti-foam agents, water-proofing agents, dispersing agents, set-accelerators, set-retarders, plasticizing agents, superplasticizing agents, freezing point decreasing agents, adhesiveness-improving agents, colorants and combinations thereof; where the sum of components used does not exceed 100 volume percent and where after the lightweight cementitious composition is set, it has a compressive strength of at least 2000 psi as tested according to ASTM C39 after seven days.

The LWC compositions can be used in most, if not all, applications where traditional concrete formulations are used. As non-limiting examples, the present LWC compositions can be used in structural and architectural applications, non-limiting examples being party walls, ICF or SIP structures, bird baths, benches, shingles, siding, drywall, cement board, decorative pillars or archways for buildings, etc., furniture or household applications such as counter tops, in-floor radiant heating systems, floors (primary and secondary), tilt-up walls, sandwich wall panels, as a stucco coating, road and airport safety applications such as arresting walls, Jersey Barriers, sound barriers and walls, retaining walls, runway arresting systems, air entrained concrete, runaway truck ramps, flowable excavatable backfill, and road construction applications such as road bed material and bridge deck material.

Additionally, LWC articles according to the invention readily accept direct attachment of screws, as a non-limiting example drywall screws and nails, which can be attached by traditional, pneumatic, or powder actuated devices. This allows easy attachment of materials such as plywood, drywall, studs and other materials commonly used in the construction industry, which cannot be done using traditional concrete formulations.

When the LWC compositions of the invention are used in road bed construction, the polymer particles can aid in preventing and or minimizing crack propagation, especially when water freeze-thaw is involved.

In an embodiment of the invention, the set and/or hardened LWC compositions according to the invention are used in structural applications and can have a minimum compressive strength for load bearing masonry structural applications of at least 1700 psi (119.5 kgf/cm²), in other cases at least 1800 psi (126.5 kgf/cm²), in some instances at least 1900 psi, and in other instances at least 2000 psi (140.6 kgf/cm²). For structural lightweight concrete the compositions can have a minimum compressive strength of at least 2500 psi (175.8 kgf/cm²). Compressive strengths are determined according to ASTM C39 at seven days.

Although ASTM C39 can be consulted for precise details, and is incorporated by reference herein in its entirety, it can be summarized as providing a test method that consists of applying a compressive axial load to molded cylinders or cores at a rate which is within a prescribed range until failure occurs. The testing machine is equipped with two steel bearing blocks with hardened faces, one which is a spherically seated block that will bear on the upper surface of the specimen, and the other a solid block on which the specimen rests. The load is applied at a rate of movement (platen to crosshead measurement) corresponding to a stress rate on the specimen of 35±7 psi/s (0.25±0.05 Mpa/s). The compressive load is applied until the load indicator shows that the load is decreasing steadily and the specimen displays a well-defined fracture pattern. The compressive strength is calculated by dividing the maximum load carried by the specimen during the test by the cross-sectional area of the specimen.

The compositions of the invention are well suited to the fabrication of molded construction articles and materials, non-limiting examples of such include wall panels including tilt-up wall panels, T beams, double T beams, roofing tiles, roof panels, ceiling panels, floor panels, I beams, foundation walls and the like. The compositions exhibit greater strength than prior art LWC compositions.

In an embodiment of the invention, the molded construction articles and materials can be pre-cast and/or pre-stressed.

As used herein, “pre-cast” concrete refers to concrete poured into a mold or cast of a required shape and allowed to cure and/or harden before being taken out and put into a desired position.

As used herein, “pre-stressed” concrete refers to concrete whose tension has been improved by using prestressing tendons (in many cases high tensile steel cable or rods), which are used to provide a clamping load producing a compressive strength that offsets the tensile stress that the concrete member would otherwise experience due to a bending load. Any suitable method known in the art can be used to pre-stress concrete. Suitable methods include, but are not limited to Pre-tensioned concrete, where concrete is cast around already tensioned tendons, and post-tensioned concrete, where compression is applied after the pouring and curing processes.

A particular advantage that the present invention provides is that the set concrete composition and/or molded construction articles formed from such compositions can be readily cut and/or sectioned using conventional methods as opposed to having to use specialized concrete or diamond tipped cutting blades and/or saws. This provides substantial time and cost savings when customizing concrete articles.

The compositions can be readily cast into molds according to methods well known to those of skill in the art for, as non-limiting examples, roofing tiles, paver, or other articles in virtually any three dimensional configuration desired, including configurations having certain topical textures such as having the appearance of wooden shakes, slate shingles or smooth faced ceramic tiles. A typical shingle can have approximate dimensions of ten inches in width by seventeen inches in length by one and three quarters inches in thickness. In the molding of roofing materials, the addition of an air entrainment agent makes the final product more weatherproof in terms of resistance to freeze/thaw degradation.

When foundation walls are poured using the LWC compositions of the invention, the walls can be taken above grade due to the lighter weight. Ordinarily, the lower part of the foundation wall has a tendency to blow outwards under the sheer weight of the concrete mixture, but the lighter weight of the compositions of the invention tend to lessen the chances of this happening. Foundation walls prepared using the present LWC compositions can readily take conventional fasteners used in conventional foundation wall construction.

In an embodiment of the invention, the concrete compositions according to the invention are formed, set and/or hardened in the form of a concrete masonry unit. As used herein, the term “concrete masonry unit” refers to a hollow or solid concrete article including, but not limited to scored, split face, ribbed, fluted, ground face, slumped and paving stone varieties. Embodiments of the invention provide walls that include, at least in part, concrete masonry units made according to the invention.

In an embodiment of the invention, the molded construction articles and materials and concrete masonry units described above are capable of receiving and holding penetrating fasteners, non-limiting examples of such include nails, screws, staples and the like. This can be beneficial in that surface coverings can be attached directly to the molded construction articles and materials and concrete masonry units molded construction articles and materials and concrete masonry units.

In an embodiment of the invention, a standard 2½ inch drywall screw can be screwed into a poured and set surface containing the present light weight concrete composition, to a depth of 1½ inches, and is not removed when a force of at least 500, in some cases at least 600 and in other cases at least 700 and up to 800 pounds of force is applied perpendicular to the surface screwed into for one, in some cases five and in other cases ten minutes.

The present invention is also directed to buildings that include the LWC compositions according to the invention.

The present invention also provides a method of making an optimized lightweight concrete article that includes:

• • identifying the desired density and strength properties of a set lightweight concrete composition;
  • determining the type, size and density of polymer beads to be expanded for use in the light weight concrete composition;
  • determining the size and density the polymer beads are to be expanded to;
  • expanding the polymer beads to form expanded polymer beads;
  • dispersing the expanded polymer beads in a cementitious mixture to form the light weight concrete composition; and
  • allowing the light weight concrete composition to set in a desired form.

The desired density and strength properties of the set and/or hardened LWC composition are determined based on the intended application.

In an embodiment of the invention, the type, size and density of polymer beads to be expanded and the size and density the polymer beads are to be expanded to can be determined based on empirical and/or published data.

In another embodiment of the invention finite element analysis can be used to determine the type, size and density of polymer beads to be expanded and the size and density the polymer beads are to be expanded to.

The resulting lightweight concrete composition is allowed to set and/or harden to provide LWC articles and concrete masonry units as described above.

The present invention will further be described by reference to the following examples. The following examples are merely illustrative of the invention and are not intended to be limiting. Unless otherwise indicated, all percentages are by weight and Portland cement is used unless otherwise specified.

EXAMPLES

Unless otherwise indicated, the following materials were utilized:

• • Type III Portland Cement
  • Mason Sand (165 pcf bulk density, 2.64 specific gravity, fineness modulus=1.74)
  • Potable Water—ambient temperature (˜70° F./21° C.)
  • Expandable Polystyrene—M97BC, F271C, F271M, F271T (NOVA Chemicals Inc., Pittsburgh, Pa.)
  • EPS Resin—1037C(NOVA Chemicals, Inc.)
  • ½ inch Expanded Slate (Carolina Stalite Company, Salisbury, N.C.—89.5 pcf bulk density/1.43 specific gravity)

Unless otherwise indicated, all compositions were prepared under laboratory conditions using a model 42N-5 blender (Charles Ross & Son Company, Hauppauge, N.Y.) having a 7-ft³ working capacity body with a single shaft paddle. The mixer was operated at 34 rpm. Conditioning was performed in a LH-10 Temperture and Humidity Chamber (manufactured by Associated Environmental Systems, Ayer, Mass.). Samples were molded in 6″×12″ single use plastic cylinder molds with flat caps and were tested in triplicate. Compression testing was performed on a Formey FX250/300 Compression Tester (Formey Incorporated, Hermitage, Pa.), which hydraulically applies a vertical load at a desired rate. All other peripheral materials (slump cone, tamping rods, etc.) adhered to the applicable ASTM test method. The following ASTM test methods and procedures were followed:

• • ASTM C470—Standard Specification for Molds for Forming Concrete Test Cylinders Vertically
  • ASTM C192—Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory
  • ASTM C330—Standard Specification for Lightweight Aggregates for Structural Concrete
  • ASTM C511—Standard Specification for Mixing Rooms, Moist Cabinets, Moist Rooms, and Water Storage Tanks Used in the Testing of Hydraulic Cements and Concretes
  • ASTM C143—Standard Test Method for Slump of Hydraulic-Cement Concrete
  • ASTM C1231—Standard Practice for Use of Unbonded Caps in Determination of Compressive Strength of Hardened Concrete
    Cylinders
  • ASTM C39—Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens Cylinders were kept capped and at ambient laboratory conditions for 24 hours. All cylinders were then aged for an additional 6 days at 23±2° C., 95% relative humidity. The test specimens were then tested.

Example 1

Polystyrene in unexpanded bead form (M97BC—0.65 mm, F271T—0.4 mm, and F271 M—0.33 mm) was pre-expanded into EPS foam (prepuff) particles of varying densities as shown in the table below.

		Prepuff Particle
	Bead	Bulk
Bead	Mean Size,	Density,		Standard deviation,
Type	μm	lb/ft3	Mean Size, μm	μm
F271M	330	2.32	902	144
F271M	330	3.10	824	80
F271M	330	4.19	725	103
F271T	400	2.40	1027	176
F271T	400	3.69	1054	137
F271T	400	4.57	851	141
M97BC	650	2.54	1705	704
M97BC	650	3.29	1474	587
M97BC	650	5.27	1487	584

The data show that the prepuff particle size varies inversely with the expanded density of the material.

Example 2

Polystyrene in unexpanded bead form (0.65 mm, 0.4 mm, and 0.33 mm) was pre-expanded into prepuff particles with a bulk density of 2 lb/ft³ as shown in the table below. The prepuff particles were formulated into a LWC composition, in a 3.5 cubic foot drum mixer, that included 46.5 wt. % (25.3 vol. %) Portland cement, 16.3 wt. % (26.3 vol. %) water, and 1.2 wt. % (26.4 vol. %) prepuff particles. The resulting LWC compositions had a concrete density of 90 lb/ft². The average compressive strength (determined according to ASTM C39, seven day break test) is shown in the table below.

		Prepuff Particle	Concrete
	Bead	Bulk Density,	Density,	Compressive
	Mean Size, μm	lb/ft3	lb/ft3	Strength, psi
	650	2.00	90	1405
	400	2.00	90	1812
	330	2.00	90	1521

The data show that as the mean unexpanded bead size decreases, at a constant prepuff particle density, that surprisingly higher compressive strength does not necessarily result from ever decreasing unexpanded bead size as suggested in the prior art. More particularly, the data show that an optimum unexpanded bead size with respect to compressive strength at 2.00 pcf exists when loaded to obtain 90 pcf concrete density. This optimum appears to be between 330 microns and 650 microns for this particular formulation.

Example 3

Since the prepuff particle density also impacts the overall concrete density, changing the EPS density requires a change in the EPS loading level to maintain a constant concrete density. This relationship holds only as long as the total amount of prepuff particles is not so large as to compromise the strength of the surrounding concrete matrix. The relationship between the prepuff particle density and loading level provides additional opportunities to optimize concrete strength while controlling the overall concrete density.

Polystyrene in unexpanded bead form (0.65 mm) was pre-expanded into prepuff particles having varying densities as shown in the table below. The prepuff particles were formulated into LWC compositions containing the components shown in the table below, in a 3.5 cubic foot drum mixer, and each having a concrete density of 90 lb/ft³.

	Sample A	Sample B	Sample C
Prepuff Particle Bulk Density	1.26	3.29	5.37
(lb/ft3)
Portland Cement, wt. %	46.7	(28.5)	46.2	(22.1)	45.8	(18.9)
(vol. %)
Water, wt. % (vol. %)	16.4	(29.8)	16.2	(23)	16.1	(19.7)
EPS, wt. % (vol. %)	0.7	(16.8)	1.8	(35.6)	2.6	(44.9)
Sand, wt. % (vol. %)	36.2	(24.9)	35.8	(19.3)	35.5	(16.5)

The following data table numerically depicts the relationship between prepuff density and concrete strength at a constant concrete density of 90 lb/ft³.

			Concrete
	Bead	Prepuff Particle	Density,	Compressive
	Mean Size, μm	Bulk Density, lb/ft3	lb/ft3	Strength, psi
Sample A	650	1.26	90	1463
Sample B	650	3.29	90	1497
Sample C	650	5.37	90	2157

The data show that as the prepuff particle density increases, the compressive strength of the LWC composition also increases at constant concrete density.

Example 4

Polystyrene in unexpanded bead form (0.65 mm) was pre-expanded into prepuff particles having a bulk density of 1.11b/ft³ as shown in the table below. The prepuff particles were formulated into LWC compositions, in a 3.5 cubic foot drum mixer, containing the components shown in the table below.

	Sample D	Sample E	Sample F
Prepuff Particle Bulk Density	1.1	1.1	1.1
(lb/ft3)
Portland Cement, wt. %	46.8	(21.6)	46.3	(18.9)	46.1	(16.6)
(vol. %)
Water, wt. % (vol. %)	16.4	(22.5)	17	(20.6)	17	(18.2)
EPS, wt. % (vol. %)	0.6	(37)	0.9	(44)	1.1	(50.8)
Sand, wt. % (vol. %)	36.2	(18.9)	35.9	(16.5)	35.8	(14.5)

The following data table numerically depicts the relationship between prepuff loading, concrete strength and concrete density.

			Concrete
	Bead	Prepuff Particle	Density,	Compressive
	Mean Size, μm	Bulk Density, lb/ft3	lb/ft3	Strength, psi
Sample D	650	1.1	89.6	1252
Sample E	650	1.1	80.9	982
Sample F	650	1.1	72.4	817

The data show that as prepuff particle loading in the LWC composition increases at constant foam particle density, the light weight concrete density and compressive strength decreases.

Example 5

Polystyrene in unexpanded bead form (0.65 mm) was pre-expanded into prepuff particles having various densities as shown in the table below. The prepuff particles were formulated into LWC compositions, in a 3.5 cubic foot drum mixer, containing the components shown in the table below.

	Sample G	Sample H	Sample I	Sample J
Prepuff Particle	1.1	2.3	3.1	4.2
Bulk Density
(lb/ft3)
Portland Cement,	46.8	(21.6)	46.8	(26.8)	46.8	(28.4)	46.8	(29.7)
wt. % (vol. %)
Water, wt. %	16.4	(22.5)	16.4	(28)	16.4	(29.6)	16.4	(31)
(vol. %)
EPS, wt. %	0.6	(37)	0.6	(21.8)	0.6	(17.2)	0.6	(13.4)
(vol. %)
Sand, wt. %	36.2	(18.9)	36.2	(23.4)	36.2	(24.8)	36.2	(25.9)
(vol. %)

The following table numerically depicts the relationship between prepuff density and concrete strength at a constant concrete prepuff loading based on the weight of the formulation.

			Concrete
	Bead	Prepuff Particle	Density,	Compressive
	Mean Size, μm	Bulk Density, lb/ft3	lb/ft3	Strength, psi
Sample G	650	1.1	89.6	1252
Sample H	650	2.32	109.6	1565
Sample I	650	3.1	111.7	2965
Sample J	650	4.2	116.3	3045

The data show that as prepuff particle density in the light weight concrete composition increases at constant prepuff particle loading (by weight), light weight concrete density and compressive strength increases.

Example 6

Polystyrene in unexpanded bead form (0.65 mm) was pre-expanded into prepuff particles having various densities as shown in the table below. The prepuff particles were formulated into LWC compositions, in a 3.5 cubic foot drum mixer, containing the components shown in the table below.

		Sample L	Sample M
	Prepuff Particle Bulk Density	1.1	3.1
	(lb/ft3)
	Portland Cement, wt. % (vol. %)	46.3	(18.9)	46.2	(21.4)
	Water, wt. % (vol. %)	17	(20.6)	16.2	(22.3)
	EPS, wt. % (vol. %)	0.9	(44)	1.8	(37.5)
	Sand, wt. % (vol. %)	35.9	(16.5)	35.8	(18.7)

The following table numerically depicts the relationship between prepuff density and concrete strength at a constant concrete density.

			Concrete
	Bead	Prepuff Particle	Density,	Compressive
	Mean Size, μm	Bulk Density, lb/ft3	lb/ft3	Strength, psi
Sample L	650	1.1	80.9	982
Sample M	650	3.1	79.8	1401

The data show that as prepuff particle density in the LWC composition increases at constant concrete density, the compressive strength of the LWC increases.

Example 7

Polystyrene in unexpanded bead form (0.65 mm) was pre-expanded into prepuff particles having various densities as shown in the table below. The prepuff particles were formulated into LWC compositions, in a 3.5 cubic foot drum mixer, containing the components shown in the table below.

		Sample N	Sample O
	Prepuff Particle Bulk Density	3.9	5.2
	(lb/ft3)
	Portland Cement, wt. % (vol. %)	46	(21.5)	45.6	(21.4)
	Water, wt. % (vol. %)	16.1	(22.4)	16	(22.3)
	EPS, wt. % (vol. %)	2.3	(37.3)	3	(37.5)
	Sand, wt. % (vol. %)	35.6	(18.8)	35.4	(18.7)

The following data table numerically depicts the relationship between prepuff density and concrete strength at a constant concrete density.

	Bead	Prepuff Particle	Concrete
	Mean Size,	Bulk Density,		Compressive
	μm	lb/ft3	Density, lb/ft3	Strength, psi
Sample N	650	3.9	85.3	1448
Sample O	650	5.2	84.3	1634

The data show that as prepuff particle density in the LWC composition increases at constant concrete density, the compressive strength of the LWC increases.

Example 8

The following examples demonstrate the use of expanded slate as an aggregate in combination with the prepuff particles of the present invention. Polystyrene in unexpanded bead form was pre-expanded into prepuff particles having various densities as shown in the table below. The prepuff particles were formulated into LWC compositions, in a 3.5 cubic foot drum mixer, containing the components shown in the table below.

	Mixed expanded
	slate/EPS runs	Example P	Example Q
	Bead Mean Size,	0.33	0.4
	micron
	Prepuff Particle Bulk	5.24	4.5
	Density, pcf
	Weight %
	Cement	19.84%	21.02%
	EPS	1.80%	1.44%
	Expanded slate	42.02%	39.07%
	Water	6.96%	7.36%
	Volume %
	Cement	9.53%	10.34%
	EPS	22.71%	21.74%
	Expanded slate	41.91%	39.91%
	Water	9.95%	10.78%
	LWC density (pcf)	90.9	93.7
	LWC strength (psi)	1360.0	1800.0

The data show that desirable light weight concrete can be obtained using the prepuff of the present invention and expanded slate as aggregate in light weight concrete compositions.

Example 9

The following examples demonstrate the use of expanded slate as an aggregate used in combination with the prepuff particles of the present invention. Polystyrene in unexpanded bead form was pre-expanded into prepuff particles having various densities as shown in the table below. The prepuff particles were formulated into LWC compositions, in a 3.5 cubic foot drum mixer, containing the components shown in the table below.

	Example R	Example S	Example T	Example U	Example V	Example W
Bead size (mm)	0.5	0.4	0.4	0.4	0.4	0.4
Prepuff density (lb./ft3)	40	3.4	3.4	3.4	3.4	3.4
	(unexpanded)
Weight %
Cement	34.4%	35.0%	36.2%	37.3%	35.9%	37.1%
Sand	0.0%	23.2%	9.9%	0.0%	15.8%	1.9%
EPS	25.0%	1.5%	1.4%	0.6%	1.5%	1.3%
Slate	25.9%	26.3%	38.1%	47.1%	32.4%	44.7%
Water	14.6%	14.0%	14.5%	14.9%	14.4%	14.9%
Total	100.0%	100.0%	100.0%	100.0%	100.0%	100.0%
water/cement	0.43	0.40	0.40	0.40	0.40	0.40
Volume %
Cement	15.8%	16.1%	16.1%	18.3%	16.1%	16.1%
Sand	0.0%	12.1%	5.0%	0.0%	8.0%	1.0%
EPS	39.5%	27.3%	24.4%	11.9%	26.4%	23.4%
Slate	24.7%	25.2%	35.3%	48.0%	30.3%	40.3%
Water	20.0%	19.2%	19.2%	21.8%	19.2%	19.2%
total	100.0%	100.0%	100.0%	100.0%	100.0%	100.0%
compressive strength	3813	2536	2718	4246	2549	2516
(psi)
density (pcf)	89.3	91.1	90.7	98.0	89.7	89.9

Example 10

One-foot square, 4 inch thick concrete forms were made by pouring formulations prepared according to examples X and Y in the table below into forms and allowing the formulations to set for 24 hours.

		Example X	Example Y
	bead size (mm)	0.4	0.65
	Prepuff density (lb/ft3)	3.4	4.9
	wt %
	Cement	35.0%	33.1%
	Sand	23.2%	45.4%
	EPS	1.5%	2.9%
	Slate	26.3%	0.0%
	Water	14.0%	13.2
	total	100.0%
	water/cement	0.40	40.0%
	Volume %
	Cement	16.1%	16.0%
	Sand	12.1%	24.7%
	EPS	27.3%	40.3%
	Slate	25.2%	0.0%
	Water	19.2%	19.1%
	total	100.0%
	compressive strength	2536	2109
	(psi)
	density (pcf)	91.1	90.6

After 7 days, a one-foot square, ½ inch sheet of plywood was fastened directly to the formed concrete. A minimum of one-inch penetration was required for adequate fastening. The results are shown in the table below.

Fastener	Example X	Example Y
7 d coated nails
attachment	No penetration when	100% penetration and
	slate is encountered	attachment
removal	Easily removed	Could not be manually
		removed from the concrete
		without mechanical
		assistance
2½ inch
standard
dry wall screw
attachment	No penetration when	100% penetration and
	slate is encountered	attachment. Screw broke
		before concrete failed.
removal	Easily removed	Could not be manually
		removed from the concrete
		without mechanical
		assistance. Screw could be
		removed and reinserted with
		no change in holding power.

The data demonstrates that the present light-weight concrete composition, without slate, provides superior gripping capability with plywood using standard fasteners compared to traditional expanded slate formulations, while slate containing concrete did not readily accept fasteners. This represents an improvement over the prior art as the time consuming practice of fixing anchors into the concrete to enable the fasteners to grip thereto can be eliminated.

Example 11

One-foot square, 4 inch thick concrete forms were made by pouring the formulations of Examples X and Y into forms and allowing the formulations to set for 24 hours. After 7 days, a one-foot square, ½ inch sheet of standard drywall sheet was fastened directly to the formed concrete using standard 1¾ inch drywall screws. A minimum of one-inch screw penetration was required for adequate fastening. The results are shown in the table below.

Fastener	Example X	Example Y
1¾ inch
standard dry
wall screw
attachment	No penetration when slate	100% penetration and
	encountered	is attachment. Screw could
		penetrate through the
		drywall.
removal	Easily removed.	Could not be manually
		removed from the concrete
		without mechanical
		assistance. Screw could be
		removed and reinserted with
		no change in holding power.

The data demonstrates that the present light-weight concrete composition, without slate, provides superior gripping capability compared to traditional expanded slate formulations, which did not readily accept fasteners. This represents an improvement over the prior art as the time consuming practice of fastening nailing studs to the concrete to allow for attaching the drywall thereto can be eliminated.

Example 12

Two-foot square, 4 inch thick concrete forms were made by pouring the formulations Examples X and Y into a form and allowing the formulations to set for 24 hours. After 7 days, a three foot long, 2″×4″ stud was fastened directly to the formed concrete using standard 16d nails. A minimum of two-inch nail penetration was required for adequate fastening. The results are shown in the table below.

Fastener	Example X	Example Y
16 d nail
attachment	No penetration when slate	100% penetration and
	is encountered	attachment.
removal	Easily removed.	Could not be manually removed
		from the concrete without
		mechanical assistance.

The data demonstrates that the present light-weight concrete composition, without slate, provides superior gripping capability compared to traditional expanded slate formulations, which did not readily accept fasteners. This represents an improvement over the prior art as the expensive and time consuming practice of using TAPCON® (available from Illinois Tool Works Inc., Glenview, Illinois) or similar fasteners, lead anchors, or other methods known in the art to fasten studs to concrete can be eliminated.

Example 13

Concrete without additional aggregate was made using the ingredients shown in the table below.

	Ex. AA	Ex. BB	Ex. CC	Ex. DD	Ex. EE	Ex. FF	Ex. GG	Ex. HH	Ex. II
Starting Bead	F271T	F271C	M97BC	F271T	F271C	M97BC	F271T	F271C	M97BC
bead size (mm)	0.4	0.51	0.65	0.4	0.51	0.65	0.4	0.51	0.65
Density (pcf)	1.2	1.3	1.5	3.4	3.3	3.4	5.7	5.5	4.9
Prepuff size (mm)	1.35	1.56	2.08	0.87	1.26	1.54	0.75	1.06	1.41
Expansion Factor	48	48	48	18	18	18	12	12	12
wt %
Cement	33.0	35.8	35.0	33.0	33.0	35.0	33.0	33.0	33.1
Sand	51.5	47.2	50.1	50.3	50.4	48.9	49.0	49.2	45.3
EPS	0.6	0.8	0.9	1.8	1.7	2.2	3.0	3.0	2.9
Water	14.9	16.1	14.0	14.8	14.8	14.0	14.9	14.8	13.2
Volume %
Cement	16.0	16.0	16.0	16.0	16.0	16.0	16.0	16.0	16.0
Sand	28.1	23.7	25.8	27.5	27.5	25.2	26.8	26.9	24.7
EPS	34.5	38.8	39.1	35.1	35.1	39.8	35.8	35.7	40.2
Water	21.4	21.4	19.1	21.4	21.4	19.1	21.4	21.4	19.1
compressive	1750	1650	1720	1770	2200	1740	1850	2400	2100
strength (psi)
density (pcf)	93	87	89	90	92	88	89	90	90

The data shows that the average prepuff size required to provide maximum compressive strength compositions is dependant, to some degree, on the expansion factor of the prepuff. Focusing on average prepuff size alone does not provide a good indicator of maximum potential concrete strength. This point is illustrated by comparing examples BB and FF. Example FF (1.54 mm size) does not provide maximum compressive strength at an 18× expansion factor, yet it is near the maximum strength that can be obtained from beads expanded 48×.

Using a combination of prepuff size and expansion factor can provide an indicator for maximum concrete strength. As an example, example AA (prepuff size, 1.35 mm and expansion factor 48) provides 93 pcf concrete with a compressive strength of 1750 psi while a similarly sized prepuff, example 11 (prepuff size 1.41 mm and expansion factor 12) provides 90 pcf concrete with a significantly higher compressive strength of 2100 psi. Thus smaller prepuff size and a lower expansion factor can provide higher compressive strength in the present light weight concrete composition within an optimum range of prepuff particle size.

Example 14

Concrete with expanded slate as an aggregate was made using the ingredients shown in the table below.

	Ex. JJ	Ex. KK	Ex. LL	Ex. MM	Ex. NN	Ex. OO	Ex. PP	Ex. QQ	Ex. RR
Starting Bead	F271T	F271T	F271T	F271T	F271T	F271T	F271T	F271T	F271T
bead size (mm)	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4
Density (pcf)	3.4	3.4	3.4	3.4	3.4	3.4	3.4	3.4	3.4
Prepuff size (mm)	0.87	0.87	0.87	0.87	0.87	0.87	0.87	0.87	0.87
Expansion Factor	18	18	18	18	18	18	18	18	18
wt %
Cement	35.9	33.0	30.5	35.9	33.0	30.6	35.9	33.0	30.6
Sand	0	8.2	15.6	10.6	18.0	24.3	21.1	27.7	33.2
EPS	1.1	0.8	0.5	1.3	1.0	0.7	1.6	1.2	0.9
Exp. Slate	48.7	44.8	41.3	37.8	34.8	32.2	27.0	24.9	23.0
Water	14.4	13.2	12.2	14.4	13.2	12.2	14.4	13.2	12.2
Volume %
Cement	16.0	16.0	16.0	16.0	16.0	16.0	16.0	16.0	16.0
Sand	0	4.5	9.3	5.3	9.8	14.3	10.6	15.1	19.6
EPS	19.9	15.5	10.7	24.6	20.2	15.7	29.3	24.9	20.4
Exp. Slate	45.0	45.0	45.0	35.0	35.0	35.0	25.0	25.0	25.0
Water	19.1	19.1	19.1	19.1	19.1	19.1	19.1	19.1	19.1
7-day	3220	3850	4070	2440	2890	3745	2300	2625	3695
strength (psi)
Density (pcf)	92.8	98.5	102.7	90.7	96.8	101.5	88.1	94.5	101.3

The data indicates that while the EPS volume required to maintain approximately 90 pcf density concrete decreases somewhat linearly as the slate concentration increases; the present light weight concrete's strength increases exponentially as the amount of slate in the formulation increases. This relationship highlights the potentially significant impact of including aggregates in the present light weight concrete formulation and demonstrates the potential for optimizing the amount of EPS and aggregates in the formulation to maximize strength at a desired density. In addition, the cost of various components can also be included in such a design and the light weight concrete formulation can be optimized for both maximum strength and lowest cost.

Example 15

Concrete with unexpanded EPS (1037C) and no additional aggregate was made using the ingredients shown in the table below.

		Ex. JJ	Ex. KK	Ex. LL
	bead size (mm)	0.51	0.51	0.51
	Density (pcf)	40	40	40
	Expansion	1	1	1
	Factor
	wt %
	Cement	38.7	33.0	28.8
	Sand	0	21.6	37.8
	EPS	43.9	30.4	20.4
	Water	17.4	14.9	13.0
	Volume %
	Cement	16.0	16.0	16.0
	Sand	0	11.8	23.6
	EPS	62.6	50.7	38.9
	Slate	21.4	21.4	21.4
	Water	16.0	16.0	16.0
	compressive	2558	2860	3100
	strength (psi)
	density (pcf)	76	89	100

The data show that unexpanded polystyrene resin beads (˜40 pcf bulk density) can provide a light weight concrete composition having surprisingly high compressive strength (2500-3200 psi) at low density (76-100 pcf).

Example 16

Prepuff from F271T bead expanded to 1.2 lb/ft³, F271C bead expanded to 1.3 lb/ft³ and M97BC bead expanded to 1.5 lb/ft³ were evaluated using scanning electron microscopy (SEM). The surface and inner cells of each are shown in FIGS. 1 and 2 (F271T), 3 and 4 (F271C), and 5 and 6 (M97BC) respectively.

As shown in FIGS. 1, 3 and 5, the external structure of the prepuff particles was generally sphereical in shape having a continuous surface outer surface or skin. As shown in FIGS. 2, 4 and 6, the internal cellular structure of the prepuff samples resembles a honeycomb-type sturcture.

The size of the prepuff particles was also measured using SEM, the results are shown in the table below.

	T prepuff
(microns)	(1.2 pcf)	C prepuff (1.3 pcf)	BC prepuff (1.5 pcf)
Outer diameter	1216	1360	1797
Internal cell size	42.7	52.1	55.9
Internal cell wall	0.42	0.34	0.24
Cell wall/cell size	0.0098	0.0065	0.0043
		C prepuff (3.4 pcf)	BC prepuff (3.1 pcf)
Outer diameter	—	1133	1294
Internal cell size	—	38.2	31.3
Internal cell wall	—	0.26	0.47
Cell wall/cell size	—	0.0068	0.0150

Taken with all of the data presented above, the data provide an indication that internal cellular structure might affect the strength of a light weight concrete formulation.

When used in light weight concrete compositions, the prepuff particles can impact the overall strength of the concrete in two ways. First, the larger particles, which have a lower density, change the concrete matrix surrounding the prepuff particle and secondly, the lower density prepuff particle is less rigid due to the cell structure of the foamed particle. Since the strength of the concrete depends, at least to some extent, on the strength of the prepuff particles, increased prepuff particle strength should result in greater light weight concrete strength. The potential strength increase can be limited by the extent to which it impacts the concrete matrix. The data in the present examples suggest that the original bead particle size can be optimized to provide an optimally sized prepuff particle (which is controlled by the prepuff density), which results in the highest possible lightweight concrete strength.

In other words, within an optimum prepuff particle size and optimum density range, the wall thickness of the prepuff will provide sufficient support to allow the present light weight concrete composition to have better strength than light weight concrete compositions in the prior art.

The data presented herein demonstrate that unlike the presumption and approach taken in the prior art, expanded EPS particles can do surprisingly more than act simply as a void space in the concrete. More specifically, the structure and character of the prepuff particles used in the present invention can significantly enhance the strength of the resulting light weight concrete composition.

Example 17

This example demonstrates the use of fasteners with the present light weight concrete composition and related pull-out strength. This evaluation was used to compare the load capacity of a screw directly installed in the present light weight concrete (approximately 90 pcf) with conventional concrete fasteners installed in normal weight and traditional lightweight concrete.

Fastener pullout testing was performed on three types of concrete: normal weight, 143 pcf (sample MM, 140 pcf normal concrete), lightweight concrete using expanded slate (123 pcf) (sample NN, 120 pcf LWC), and lightweight concrete with EPS (87 pcf) (sample OO, 90 pcf LWC) made as described above according to the formulations in the following table.

	Sample MM	Sample NN	Sample OO
	140 pcf	120 pcf	90 pcf
EPS bead size (mm)	—	—	0.51
density (pcf)	—	—	3.37
wt %
cement	20.2	24.8	32.9
sand	34.6	36.4	52.7
EPS	—	—	1.86
⅜″ pea gravel	37.6	—	—
½″ expanded slate	—	29.4	—
Water	7.7	9.41	12.51
vol %
cement	16.0	16	16
sand	30.9	26.5	28.9
EPS	—	—	37
⅜″ pea gravel	35.0	—	—
½″ expanded slate	—	39.4	—
Water	18.1	18.1	18.12
compressive	4941	9107	2137
strength (psi)
density (pcf)	143	123	87

An apparatus was built that allowed weights to be hung vertically from each fastener using gravity to apply a load in line with the axis of the fastener. The 90 pcf LWC had 2½″ standard drywall screws directly installed to approximately 1½″ depth. The 120 pcf LWC had two types of fasteners installed into predrilled holes:2¾ TAPCON® metal screw-type masonry fastening anchors (Illinois Tool Works Inc., Glenview, Ill.) installed approximately 2″ deep and standard 2¼″ expanding wedge-clip bolt/nut anchors installed approximately 1¼″ deep. The 140 pcf normal concrete also had two types of fasteners installed into predrilled holes: 2¾″ TAPCON anchors installed approximately 2″ deep and standard 2¼″ expanding wedge-clip bolt/nut anchors installed approximately 1¼″ deep. One of the drywall screws in the light weight concrete was backed out and re-installed into the same fastener hole for testing. Also one of the TAPCON screws was removed and reinstalled to evaluate any loss in capacity. The following tables show the data and loadings for each anchor/fastener tested.

90 pcf LWC Drywall Screw
	Screw		Extract and
Stone 1:	Length (in)	Exposed (in)	re-install (in)	Strength (lb)
Screw B	2.5	0.594	1.906	700 @ 30 sec.
90 pcf LWC Drywall Screw
	Screw
Stone 2:	Length (in)	Exposed (in)	Installed (in)	Strength (lb)
Screw C	2.5	1.031	1.469	>740 > 10
				min.
120 pcf LWC TAPCON Screws
	Screw		Extract and
Stone 3:	Length (in)	Exposed (in)	re-install (in)	Strength (lb)
Screw C	2.75	0.875	1.875	>740 > 10 min.
120 pcf LWC Bolt/Sleeve/Nut
	Anchor
Stone 4:	Length (in)	Exposed (in)	Installed (in)	Strength (lb)
Anchor D	2.25	0.875	1.375	>740 > 10 min.
140 pcf normal concrete TAPCON Screws
	Screw		Extract and
Stone 5:	Length (in)	Exposed (in)	re-install (in)	Strength (lb)
Screw C	2.75	0.906	1.844	>740 > 10 min.
140 pcf normal concrete Bolt/Sleeve/Nut
	Anchor
Stone 6:	Length (in)	Exposed (in)	Installed (in)	Strength (lb)
Anchor C	2.25	1.094	1.156	>740 > 10 min.

The holding power of the drywall screws in the 90 pcf LWC was surprisingly high as they did not easily break or tear from the concrete. The drywall screws were easy to install, only requiring a standard size electric drill. The gripping strength of the drywall screws in the 90 pcf LWC was such that if the applied drilling torque was not stopped before the screw head reached the surface of the concrete, the head of the screw would twist off. All of the fasteners held the 740 lbs. of load for at least 10 minutes except the backed out and re-inserted drywall screw in the 90 pcf LWC, which held 700 lbs. for 30 seconds before tearing loose from the concrete. This drywall screw did not break at the failure point, but pulled out of the concrete.

Taking the above data as a whole, it has been demonstrated that an optimum prepuff bead size exists (as a non-limiting example, approximately 450-550 μm resin beads expanded to an expansion factor of approximately 10-20 cc/g to a prepuff diameter of approximately 750 to 1400 μm for 90 pcf lightweight concrete) to maximize the compressive strength of the present light weight concrete formulations. The compressive strength of the present light weight concrete formulations can be increased by increasing the present EPS prepuff bead density. Unexpanded polystyrene resin (˜40 pcf bulk density) yields LWC of high compressive strength (2500-3200 psi) considering the low density (76-100 pcf). Aggregates can be used in the present light weight concrete formulations. The present light weight concrete formulations, without course aggregates, provide a concrete composition, which may be directly fastened to using standard drills and screws. When the EPS prepuff beads are expanded to low bulk densities (for example <1 pcf), the beads have a weak internal cellular structure, which creates a weaker foam, and in turn provides a light weight concrete composition having a lower compressive strength.

The present invention has been described with reference to specific details of particular embodiments thereof. It is not intended that such details be regarded as limitations upon the scope of the invention except insofar as and to the extent that they are included in the accompanying claims.

Claims

1. A pre-cast and pre-stressed construction article containing a lightweight concrete composition comprising

from 10 to 90 volume percent of a cement composition,

from 10 to 90 volume percent of particles having an average particle diameter of from 0.2 mm to 3 mm, a bulk density of from 0.028 g/cc to 0.48 g/cc, an aspect ratio of from 1 to 3, and have a continuous outer layer,

from 0 to 50 volume percent of aggregate, and

less than one percent by weight with respect to total weight of the composition of air-entraining agents;

2. A lightweight concrete article made according to a method comprising:

identifying the density and strength properties of a set lightweight concrete composition;

determining the type, size and density of polymer beads to be expanded for use in the lightweight concrete composition;

determining the size and density the polymer beads are to be expanded to;

expanding the polymer beads to form expanded polymer beads;

dispersing the expanded polymer beads in a cementitious mixture containing a hydraulic cement composition to form the lightweight concrete composition; and

allowing the lightweight concrete composition to set in a desired form;

3. A pre-cast construction article containing a concrete composition comprising

from 10 to 90 volume percent of a cement composition,

from 10 to 90 volume percent of particles having an average particle diameter of from

0.2 mm to 3 mm, a bulk density of from 0.028 g/cc to 0.48 g/cc, an aspect ratio of from 1 to 3, and have a continuous outer layer,

from 0 to 50 volume percent of aggregate, and

less than one percent by weight with respect to total weight of the composition of air-entraining agents;

4. The construction article according to claim 3, wherein the particles comprise expanded polymer particles having an inner cell wall thickness of at least at least 0.15 μm.

5. The construction article according to claim 3, wherein the particles comprise expanded polymer particles comprising one or more polymers selected from the group consisting of homopolymers of vinyl aromatic monomers; copolymers of at least one vinyl aromatic monomer with one or more of divinylbenzene, conjugated dienes, alkyl methacrylates, alkyl acrylates, acrylonitrile, and/or maleic anhydride; polyolefins; polycarbonates; polyesters; polyamides; natural rubbers; synthetic rubbers; and combinations thereof.

6. The construction article according to claim 3, wherein the particles comprise expanded polymer particles prepared by expanding a polymer bead having an unexpanded average resin particle size of from about 0.2 mm to about 2 mm.

7. The construction article according to claim 3, wherein the cement composition comprises one or more materials selected from the group consisting of Portland cements, pozzolana cements, gypsum cements, aluminous cements, magnesia cements, silica cements, and slag cements.

8. The construction article according to claim 3, wherein the concrete composition comprises sand, fine aggregate, coarse aggregate, plasticizers and/or fibers.

9. The construction article according to claim 8, wherein the fibers are selected from the group consisting of glass fibers, silicon carbide, aramid fibers, polyester, carbon fibers, composite fibers, fiberglass, combinations thereof, fabric containing said fibers, and fabric containing combinations of said fibers.

10. The construction article according to claim 3, wherein a standard 2 ½ inch drywall screw, screwed into the formed and set concrete composition to a depth of 1 ½ inches, is not removed by applying 500 pounds of force perpendicular to the surface screwed into for one minute.

11. The construction article according to claim 2, wherein the particles comprise expanded polymer particles prepared by expanding a polymer bead having an unexpanded average resin particle size of from about 0.2 mm to about 2 mm.

12. The construction article according to claim 11, wherein the particles comprise polystyrene.

13. The construction article according to claim 2, wherein the coarse aggregate is selected from the group consisting of stone, gravel, ground granulated blast furnace slag, fly ash, glass, expanded slate, clay; pumice, perlite, vermiculite, scoria, diatomite, expanded shale, expanded clay, expanded slag, pelletized aggregate, extruded fly ash, tuft, macrolite, slate, expanded blast furnace slag, sintered fly ash, coal cinders, and combinations thereof.

14. The construction article according to claim 2, wherein the fine aggregate comprises sand.

15. The construction article according to claim 2, wherein the lightweight concrete composition comprises from 0.1 to 1 volume percent of one or more additives selected from the group consisting of anti-foam agents, water-proofing agents, dispersing agents, set-accelerators, set-retarders, plasticizing agents, superplasticizing agents, freezing point decreasing agents, adhesiveness-improving agents, colorants and combinations thereof.

16. The construction article according to claim 1, wherein the particles comprise expanded polymer particles prepared by expanding a polymer bead having an unexpanded average resin particle size of from about 0.2 mm to about 2 mm.

17. The construction article according to claim 1, wherein the construction article comprises prestressing tendons.

18. The construction article according to claim 1, wherein the lightweight concrete composition comprises from 0.1 to 1 volume percent of one or more additives selected from the group consisting of anti-foam agents, water-proofing agents, dispersing agents, set-accelerators, set-retarders, plasticizing agents, superplasticizing agents, freezing point decreasing agents, adhesiveness-improving agents, colorants and combinations thereof.

19. The construction article according to claim 1, wherein the lightweight concrete composition is free of air entraining agents.

20. The concrete article according to claim 2, wherein the lightweight concrete composition is free of air entraining agents.

21. The construction article according to claim 3, wherein the lightweight concrete composition is free of air entraining agents.

22. A dry mixture comprising:

10 to 90 volume percent of a cement composition,

10 to 90 volume percent of expanded particles having an average particle diameter of from 0.2 mm to 3 mm, a bulk density of from 0.028 g/cc to 0.52 g/cc, an aspect ratio of from 1 to 3, and a continuous outer layer,

0 to 50 volume percent of one or more aggregates, and

0 to 1 volume percent of one or more additives;

wherein the sum of components used does not exceed 100 volume percent;

wherein the dry mixture is packaged for future use;

wherein after the dry mixture is mixed with a sufficient amount of water to cause the mixture to set and bind, the resulting concrete composition has a density of from 90 to about 130 lb./ft³ and a seven day compressive strength of at least 1700 psi as determined according to ASTM C39.

23. The mixture according to claim 22, wherein the expanded particles comprise one or more polymers selected from the group consisting of homopolymers of vinyl aromatic monomers; copolymers of at least one vinyl aromatic monomer with one or more of divinylbenzene, conjugated dienes, alkyl methacrylates, alkyl acrylates, acrylonitrile, and/or maleic anhydride; polyolefins; polycarbonates; polyesters; polyamides; natural rubbers; synthetic rubbers; and combinations thereof.

24. The mixture according to claim 22, wherein the particles comprise expanded polymer particles prepared by expanding a polymer bead having an unexpanded average resin particle size of from about 0.2 mm to about 2 mm.

25. The mixture according to claim 22, wherein the cement composition comprises a hydraulic cement composition.

26. The mixture according to claim 25, wherein the hydraulic cement comprises one or more materials selected from the group consisting of Portland cements, pozzolana cements, gypsum cements, gypsum compositions, aluminous cements, magnesia cements, silica cements, and slag cements.

27. The mixture according to claim 22, wherein the cementitious mixture comprises fine aggregate, coarse aggregate, plasticizers and/or fibers.

28. The mixture according to claim 27, wherein the fibers are selected from the group consisting of glass fibers, silicon carbide, aramid fibers, polyester, carbon fibers, composite fibers, fiberglass, combinations thereof, fabric containing said fibers, and fabric containing combinations of said fibers.

29. The mixture according to claim 22 comprising one or more materials selected from the group consisting of stone, gravel, ground granulated blast furnace slag, fly ash, glass, silica, expanded slate, clay; pumice, perlite, vermiculite, scoria, diatomite, expanded shale, expanded clay, expanded slag, fumed silica, pelletized aggregate, extruded fly ash, tuft, macrolite, slate, expanded blast furnace slag, sintered fly ash, coal cinders, and combinations thereof.

30. The mixture according to claim 22, wherein the additives are selected from the group consisting of anti-foam agents, water-proofing agents, dispersing agents, set-accelerators, set-retarders, plasticizing agents, superplasticizing agents, freezing point decreasing agents, adhesiveness-improving agents, colorants and combinations thereof.

31. The mixture according to claim 22, wherein the expanded particles are expanded polystyrene particles.

32. The mixture according to claim 31, wherein the cement composition is present at from 10 to 60 volume percent and comprises a Portland cement; the expanded polystyrene particles are present at from 20 to 78 volume percent, the aggregates are present at from 5 to 35 volume percent, and one or more additives are present at from 0.1 to 1 volume percent.

33. A dry mixture for mixing later with water to form a concrete structure comprising:

22 to 90 volume percent of cement;

10 to 90 volume percent of expanded particles having

an average particle diameter of from 0.2 mm to 3 mm,

a bulk density of from 0.028 g/cc to 0.52 g/cc,

an aspect ratio of from 1 to 3, and

a continuous outer layer,

0.5 to 5 volume percent of fibers;

0 to 60 volume percent of one or more aggregates,

0 to 3 volume percent by weight of an ethylene/vinyl acetate copolymer;

0 to 3 volume percent of an anti-foam agent;

0 to 3 volume percent of a water reducer; and

0 to 3 volume percent of a plasticizer;

wherein the sum of components used does not exceed 100 volume percent;

wherein after the dry mixture is mixed with a sufficient amount of water to cause the mixture to set and bind, the resulting concrete composition has a density of from 90 to about 130 lb./ft³ and a seven day compressive strength of at least 1700 psi as determined according to ASTM C39.

34. The mixture according to claim 33, wherein the cement composition comprises a hydraulic cement composition.

35. The mixture according to claim 33, wherein the hydraulic cement comprises one or more materials selected from the group consisting of Portland cements, pozzolana cements, gypsum cements, gypsum compositions, aluminous cements, magnesia cements, silica cements, and slag cements.