Modular precast wall system with mortar joints

A modular construction system (10) which is directed toward the construction of structural walls (26). The construction system (10) employs precast wall units (12) and a variety of spacer/tensioning, spacer, tensioning, and extension assemblies (14, 16, 18, and 20). The wall units (12) contain a plurality of cavities (44) and are made of concrete with side walls (36) reinforced with prestressed tension wires (48). In the process of constructing a wall (26), the wall units (12) are stacked one upon the other onto threaded wall bars (24) that extend upwardly from a foundation (22). The spacer/tensioning assembly (14) and the spacer assembly (16) provide alignment during the stacking process and also create mortar joints (52). The spacer/tensioning assembly (14) and the tensioning assembly (18) are utilized in conjunction with the wall bars (24) to tension the wall units (12) onto lower wall units (12) and the foundation (22). When stacked, the internal structure of the wall units (12) creates vertically and horizontally extending passages (85 and 86) into which grout (84) is poured to create a monolithic wall (26).

TECHNICAL FIELD 
The present invention relates generally to the field of construction, and 
more particularly to a construction system employing precast block units 
for the construction of walls and other structures in which mortar joints 
are desired. 
BACKGROUND ART 
Shelter is a basic need, and human ingenuity has arrived at numerous and 
sophisticated methods and materials to meet this need. Among the many 
methods include those employing precast concrete units that are assembled 
to create a building or other structure. These methods encompass 
construction systems incorporating a wide range of precast unit designs 
that vary from the simple to the very complex. The most elementary precast 
unit designs are those used in basic, concrete masonry. While concrete 
masonry units (CMU's) may be designed for a variety of applications, they 
can result in structures that are structurally inferior to those created 
with larger, reinforced concrete units. Smaller CMU's can crack and chip 
as well. Construction with small CMU's also requires a specialized labor 
force. As a result, building methods utilizing CMU's can create high labor 
costs, and it can be difficult to find a qualified work crew. 
More sophisticated construction systems use concrete columns, beams, and 
foundation members to create a superstructure. A beam and column joining 
assembly is set forth in U.S. Pat. No. 4,583,336, issued to Shelangoskie, 
et al. on Apr. 22, 1986. U.S. Pat. No. 5,103,613 issued to Satoru 
Kinoshita on Apr. 14, 1992 teaches foundation members interconnected by a 
binding member having mortises therein for receiving tenons on the bottom 
of a column. U.S. Pat. No. 4,124,963 issued to Tadayasu Higuchi on Nov. 
14, 1978 sets forth a precast unit for providing a footing for a building. 
While the above patents describe a superstructure they provide no 
teachings on the construction of walls or the like. In addition, the 
precast units of the inventions provide little flexibility for increasing 
structural integrity of the larger structure. 
Two U.S. patents present precast units in which wall members are also 
employed. U.S. Pat. No. 4,328,651 issued to Manuel Gutierrez on May 11, 
1982 shows a system having a number of precast units including footing 
boxes, grade beams, roof beams and a wall panel. The Gutierrez system sets 
forth an intricate system of interconnecting parts. The intricacies of the 
design limit the flexibility of the system, however. The beams and wall 
panels described therein would have to be formed to custom lengths and 
heights in order to meet the needs of differing structures. In addition, 
the wall panels lack flexibility for increasing structural strength. The 
second patent is U.S. Pat. No. 5,081,805 issued to M. Omar A. Jazzar on 
Jan. 21, 1992. This patent teaches precast units of half-story height that 
include steel reinforcements. The Jazzar invention requires substantial 
lifting equipment, however, and is also limited in versatility. 
Furthermore, building designs departing from preformed dimensions require 
a second, expensive mold, or considerable custom work to arrive at the 
desired shape. 
Authors David A. Sheppard and William R. Phillips illustrate unitary 
load-bearing or non-load-bearing precast panels in their book Plant-Cast 
Precast & Prestressed Concrete--A Design Guide, Third Edition, McGraw-Hill 
Inc., 1989, (see pages 311-13). The same book also illustrates the use of 
very large, precast, concrete "voided" bearing walls at page 340. The 
large bearing walls and precast panels, like those in the Gutierrez 
patent, must be custom formed and require large custom molds, a large site 
slab, and very large lifting equipment. In addition, the immense size of 
the walls makes them impractical for smaller construction projects. 
Illustrated in a commercial brochure of American ConForm Industries, Inc. 
(1993), is a modular construction system that employs stackable 
polystyrene units. Concrete is poured within the stacked units to create 
walls for different applications. The design of the units allows for the 
placement of reinforcing steel, but the units themselves are 
non-structural. Such a system suffers from a number of problems, including 
those inherent in having to pour large quantities of concrete, such as 
delays due to inclement weather conditions and the creation of clutter and 
debris at the work site. Moreover, strict engineering tolerances are 
difficult to obtain without skilled workers. 
To the inventors' knowledge, no building system employing preformed 
building units has been developed that provides versatility in design, can 
accommodate a variety of reinforcement designs for great structural 
strength, requires relatively small lifting equipment, allows for the 
rapid construction of buildings, and that does not suffer from the 
limitations of poured concrete systems. 
DISCLOSURE OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a 
construction system using precast units that can be used for the 
construction of a variety of building forms and designs. 
It is another object of the invention to provide a construction system that 
can be used to rapidly construct buildings while achieving a very high 
quality of construction and great structural strength. 
It is a further object to provide a construction system, using precast 
units, that can accommodate a wide range of reinforcement designs. 
It is yet another object to provide a construction system using precast 
units, which system allows for the introduction of conventional mortar 
joints. 
It is still a further object to provide a construction system that does not 
require a large amount of specialized erection equipment. 
It is yet another object to provide a construction system that does not 
require a crew having specialized skills. 
It is yet a further object to provide a construction system, using precast 
units, that includes alignment aids. 
It is still another object to provide a construction system using precast 
units which can be easily cut to size. 
It is still a further object of the present invention to provide a 
construction system that is cost effective for residential and 
light-commercial projects. 
Briefly, the preferred embodiment of the present invention is a modular 
construction system employing precast wall units and a variety of spacer, 
tensioning, and extension assemblies for the construction of walls. The 
wall units contain cavities and are made of concrete and reinforced with 
prestressed steel wires. In the process of constructing a wall, the wall 
units are stacked onto threaded wall bars that extend upwardly from a 
foundation, the wall bars being inserted into the cavities of the wall 
units. The stacking is performed with the aid of the spacer, tensioning, 
and extension assemblies. When stacked, the structure of the preferred 
wall units creates both vertically and horizontally extending passages 
within the resulting wall. Reinforcement rods or bundles of rods may be 
placed within both the vertical and horizontal passages. The tensioning 
assemblies utilize the vertically extending wall bars and the horizontally 
positioned reinforcement rods to tension the wall units onto lower wall 
units and onto the foundation. The extension assembly provides the 
capacity to extend the height of the wall bars and therefore the height to 
which the wall units may be stacked. Grout is poured within the vertical 
and horizontal passages of the stacked wall units to create a monolithic 
wall of great structural strength. 
The spacer assemblies provide spaces between wall units for conventional 
mortar joints and also assist in the alignment of the wall units during 
their stacking. One variety of spacer assembly provides a tensioning 
capability in addition to providing mortar joint spaces and assisting in 
alignment. This spacer assembly includes a bracket which spans most of the 
width of the wall unit and which has an aperture for receiving a wall bar. 
The bracket also includes upwardly and downwardly extending pairs of 
vertical alignment fins which are inserted within the side walls of the 
wall units to give a precise stacking of the wall units. The bracket is 
tensioned down onto a wall unit by torquing a nut onto the threaded wall 
bar and bracket. The bracket is hidden from view by the mortar joint since 
it does not extend the full width of the wall unit side walls. 
A second variety of spacer assembly provides mortar joint spaces and 
assists in alignment of the wall units. This spacer assembly includes two 
bracket halves removably joined together with a bolt. Each bracket half 
has an upwardly and downwardly extending alignment fin. The side walls of 
wall units are inserted between the alignment fins of the mated bracket 
assembly to give precision stacking. After completion of the wall, the 
outer bracket half is removed and a simple patch of mortar is applied to 
fill the void. The inner bracket half is then hidden from view. This 
spacer assembly may be modified to include a wall brace fin which extends 
perpendicularly outward from the outer bracket half and wall. The wall 
brace fin includes an aperture to which external bracing may be connected 
to provide support for the wall during its construction where necessary. 
An advantage of the present invention is that the construction system 
allows for a significantly more rapid and easy assemblage of walls and 
building forms than is possible by either conventional cast-in-place 
concrete or CMU construction methods. 
Another advantage of the invention is that the construction system provides 
for the building of structures with significantly more uniform and 
accurate dimensions than is possible by either conventional cast-in-place 
concrete or CMU construction methods. 
Yet another advantage is that the construction system allows for the 
introduction of more reinforcing material and therefore a greater 
structural strength than is possible with conventional CMU walls, with a 
strength that can approach that of a conventional cast-in-place concrete 
wall. 
A further advantage is that the construction system allows a wall to be 
engineered and built as a conventional CMU wall and with the convenience 
thereof. 
Yet a further advantage is that walls made with the construction system are 
significantly less water permeable than CMU construction methods. 
Still another advantage of the invention is that the construction system 
allows for engineers to utilize the sidewalls of precast wall units as 
part of the overall structural wall thickness in their calculations for 
CMU-built walls. 
Yet another advantage is that the precast units of the construction system 
may be stockpiled for immediate use. 
A further advantage is that the precast units of the invention may be 
stocked in varying sizes for a wide range of applications. 
Yet another advantage is that construction with the present invention may 
be carried out in inclement weather. 
Still another advantage is that the construction system can be implemented 
by smaller work crews than are typically employed. 
Yet a further advantage is that the construction system generates very 
little debris. 
A still further advantage is that the construction system of the present 
invention does not require a superstructure. 
These and other objects and advantages of the present invention will become 
clear to those skilled in the art in view of the description of the best 
presently known mode of carrying out the invention as described herein and 
as illustrated in the several figures of the drawings.

BEST MODE FOR CARRYING OUT THE INVENTION 
The preferred embodiment of the present invention is a modular construction 
system employing precast block units and providing for mortar joints 
between the block units. The construction system of the preferred 
embodiment is directed toward the creation of structural walls and is set 
forth in FIG. 1, where it is designated therein by the general reference 
character 10. 
Referring to FIG. 1 of the drawings, the construction system 10 is shown to 
include a number of wall units 12, a combination spacer/tensioning 
assembly 14, a spacer assembly 16, a modified spacer assembly 17, a 
tensioning assembly 18, and a wall bar extension assembly 20. A base 
structure or foundation 22 provides a number of upwardly projecting wall 
bars 24 that are received by the wall units 12. As illustrated in FIG. 1, 
the wall units 12 of the preferred embodiment are designed to be stacked, 
one on top of the other, to create a vertical wall 26. 
The structure of the wall units 12 is detailed in FIGS. 2-4. As shown in 
the side elevational view of FIG. 2 and the end cross-sectional view of 
FIG. 3, the wall units 12 have a generally rectangular solid shape that 
includes a wall unit top surface 28, a wall unit bottom surface 30, two 
wall unit side surfaces 32, and two wall unit end surfaces 34. As 
indicated in the various figures, the wall unit side surfaces 32 are 
considerably longer than the wall unit end surfaces 34, typical wall unit 
12 lengths and widths being on the order of 3.0 to 18.3 m (10 to 60 ft) 
and 20 to 30 cm (8 to 12 in) respectively. Typical wall unit 12 heights 
are on the order of 46 to 91 cm (18 to 36 in). The wall units 12 of the 
preferred embodiment 10 are precast, prestressed masonry forms composed of 
any of a variety of concrete mixes and additives depending on the strength 
required and the climate anticipated. In addition to various structural 
additives, the inclusion of color additives and waterproofing additives 
are contemplated as well. Furthermore, the wall units 12 may be provided 
with a variety of architectural finishes during the casting process (e.g., 
using a patterned form-liner, or adding aggregate). Commercially available 
insulation cores may be incorporated as well. 
Each integrally molded wall unit 12 has two rectangular, parallel, opposing 
wall unit side walls 36. The wall unit side walls 36 are joined by a 
number of cavity walls 38. As best illustrated in FIGS. 1 and 4, the 
cavity walls 38 are perpendicular to, and integral with, the wall unit 
side walls 36. In the preferred embodiment of the construction system 10, 
a cavity wall top surface 40 and a cavity wall bottom surface 42 are each 
recessed approximately 15 cm (6.0 in) from the wall unit top and bottom 
surfaces (28 and 30) for reasons as will be explained later herein. The 
wall unit side walls 36 and cavity walls 38 of the preferred wall unit 12 
have thicknesses of approximately 3.8-4.4 cm (1.5-1.8 in) and 5.1 cm (2.0 
in) respectively, with center to center distances of approximately 30.5 cm 
(12 in) between cavity walls 38. Although not indicated in the drawings, 
the various interior surfaces of the wall units 12 have slight tapers 
which are introduced during the formation of the wall units 12 to allow 
for the easy removal of the patterns used to mold the wall units 12. The 
inclusion of such tapers or "drafts" is well-known in the art. 
The resulting structure comprised of wall unit side walls 36 and cavity 
walls 38 creates a number of vertically extending cavities 44 within the 
wall unit 12. As best shown in FIGS. 1 and 3, each cavity 44 extends for 
the height of the wall unit 12, opening onto both the wall unit top 
surface 28 and the wall unit bottom surface 30. The molded design and 
incorporation of cavities 44 into the wall unit 12 provides for both 
structural integrity and a substantial reduction in weight for the wall 
unit 12. This reduced weight permits the rapid erection of walls 26 using 
lifting equipment of a relatively smaller size than would otherwise be 
possible. 
Contained within each wall unit 12 of the construction system 10 of the 
preferred embodiment is a reinforcement structure 46. The reinforcement 
structure 46 is illustrated in the partial cutaway view of FIG. 1 and the 
cross-sectional views of FIGS. 3 and 4. The reinforcement structure 46 is 
comprised of three parallel tension wires 48 that are horizontally 
disposed within each wall unit side wall 36. The tension wires 48 are 
pre-tensioned and cast in place when the wall units 12 are formed. The 
tension wires 48 place the entire wall unit 12 under compression upon 
formation, which adds to the structural integrity of the wall unit 12 and 
reduces undesirable cracking and spalding, especially during transit and 
handling. The preferred material for the tension wires 48 is high tensile 
strength steel of approximately 5 mm (0.2 in) in diameter or otherwise 
meeting industry-accepted requirements. Despite the presence of the 
tension wires 48, and although the wall units 12 are precast at a discrete 
length, each wall unit 12 can be quickly and easily cut on-site to fit any 
length as required. Any number and type of tension wires 48 might be 
utilized according to the desired strength of the wall unit 12. Additional 
methods of imparting increased strength to the wall unit 12 include, among 
others, the casting in place of mild steel ("rebar"), and the 
post-tensioning of a cable or wire fitted into a plastic sleeve that is 
itself cast in place. 
The preferred embodiment of the construction system 10 of the present 
invention contemplates the use of a variety of mortar spacing and wall 
tensioning methods and combinations thereof. When wall bars 24 are 
employed, as shown in FIG. 1, the combination spacer/tensioning assembly 
14 and/or wall bar extension assembly 20 may be incorporated to add 
structural strength, flexibility of design, and improve the speed and ease 
with which buildings can be constructed. The spacer/tensioning assembly 14 
serves multiple functions, including providing a wall tensioning 
capability while also acting as a spacer to introduce and maintain spaces 
for mortar joints 52 between the wall unit top surface 28 of a lower wall 
unit 12 and the wall unit bottom surface 30 of a next higher wall unit 12. 
In addition to providing mortar spacing and adding structural integrity, 
the spacer/tensioning assembly 14 further allows for the wall units 12 to 
be securely attached to the foundation 22 without the need for additional 
bracing. 
The wall bar extension assembly 20 and combination spacer/tensioning 
assembly 14 are set forth in detail in FIGS. 5-7. FIG. 5 shows an exploded 
view of the wall bar extension assembly 20 and an associated wall bar 24. 
The wall bar extension assembly 20 includes an extension bar 54 and a bar 
coupler 56. Both the wall bar 24 and the extension bar 54 are threaded, 
and each includes two bar ends 58. The bar coupler 56 includes a threaded 
coupler aperture 60 for simultaneously receiving the bar ends 58 of both 
the wall bar 24 and the extension bar 54. The wall bar extension assembly 
10 provides, in essence, the capacity to vertically extend the wall bar 
24. This aspect is advantageous in the event the wall units 12 must be 
stacked higher than the vertical height of the wall bars 24. By using the 
wall bar extension assembly 20, extension bars 54 may be added to as great 
a height as is necessary for the structure under construction. 
A preferred embodiment of the spacer/tensioning assembly 14 is set forth in 
detail in FIGS. 6 and 7. As illustrated in the exploded view of FIG. 6, 
the spacer/tensioning assembly 14 of the construction system 10 includes a 
spacer/tensioning bracket 62, a tensioning washer 64, and a tensioning nut 
66. The spacer/tensioning bracket 62 is integrally formed and includes a 
bar receiving aperture 68, two upper alignment fins 70, two lower 
alignment fins 72, and two spacer fins 74. Both pairs of upper and lower 
alignment fins (70 and 72) are present in parallel opposing fashion, with 
an upper alignment fin 70 and a lower alignment fin 72 being present in an 
identical vertical plane. Each spacer fin 74 projects horizontally outward 
from an upper and lower alignment fin (70 and 72) in a plane perpendicular 
to the aforementioned vertical plane. In the construction system 10 of the 
preferred embodiment (and in applications for which wall units 12 having a 
width of approximately 20 cm (8.0 in) are utilized), the spacer/tensioning 
bracket 62 will have an overall length of approximately 15 cm (6.0 in), 
with a width of approximately 5.1 cm (2.0 in). The preferred spacer fins 
74, as will be explained below, have a thickness of approximately 0.95 cm 
(0.38 in). 
Referring now to both FIG. 6 and the cross-sectional view of FIG. 7, the 
spacer/tensioning bracket 62 fits over the wall bar 24 with the wall bar 
24 passing through the bar receiving aperture 68 and with the lower 
alignment fins 72 being inserted between the interior surfaces 76 of 
opposing wall unit side walls 36. The tensioning washer 64 and tensioning 
nut 66 are subsequently threaded onto the wall bar 24 and can be tightened 
such that the spacer/tensioning bracket 62 exerts a downward force on the 
wall unit top surface 28 to thereby tension the wall unit 12 onto the 
foundation 22 or a wall unit 12 directly below. When a second wall unit 12 
is stacked on top of the first wall unit 12, the upper alignment fins 70 
are likewise inserted between the interior surfaces 76 of opposing wall 
unit side walls 36 of the upper wall unit 12. The spacer/tensioning 
bracket 62 thus forces the wall unit side walls 36 of the two wall units 
12 to be in vertical alignment. The clearances between the upper and lower 
alignment fins (70 and 72) and the interior surfaces 76 of the wall unit 
side walls 36 are small so that precision stacking may be achieved. The 
spacer/tensioning assemblies 14 are typically incorporated at increments 
of 3.0 to 4.6 m (10 to 15 ft) along the length of a wall unit 12. 
Also shown in FIG. 7, and indicated therein by dashed lines, are variations 
on the preferred embodiment in which notches 78a or 78b are incorporated 
into the wall unit side walls 36. Notch 78a is a recess in the interior 
surface 76 of the wall unit side wall 36, while notch 78b is a vertical 
hollow in the wall unit top or bottom surfaces (28 or 30). Either of the 
recessed or hollowed notches (78a or 78b) can be precast or field-cut and 
both allow for simultaneous vertical and horizontal alignment of the wall 
units 12. (The spacer/tensioning bracket 62 would of course require a 
lengthening of the distance between opposing pairs of upper and lower 
alignment fins (70 and 72) in order to accommodate these variations so 
that those alignment fins (70 and 72) may be mateably received by the 
notches (78a or 78b.)) In addition, it is contemplated that a bracket 
similar to spacer/tensioning bracket 62 could be employed, wherein the 
upper and lower alignment fins (70 and 72) are omitted to give a bracket 
that is essentially a flat plate having only the bar receiving aperture 68 
and that functions in a spacer capacity only. This "bare" bracket could be 
used in conjunction with wall units 12 having notches similar to hollowed 
notch 78b, and into which a separate alignment fixture (e.g., a short 
metal bar) is placed, or with wall units 12 that are precast to include 
mating vertical protrusions and hollows in the wall unit top and bottom 
surfaces (28 and 30), or in some other way specifically shaped to aid in 
alignment and stacking. 
Continuing to refer to FIG. 7, the spacer fins 74 prevent the top and 
bottom surfaces (28 and 30) of stacked wall units 12 from making contact, 
thereby creating spaces for mortar joints 52. In practice, mortar 80 is 
applied during the stacking process, that is, an upper wall unit 12 is 
laid upon a fresh bed of mortar 80 covering the wall unit top surface 28 
of a lower wall unit 12. Because the spacer fins 74 do not extend 
completely to the wall unit side surfaces 32, but rather are set back by 
approximately 2.5 cm (1.0 in), the spacer/tensioning bracket 62 is hidden 
from view by the mortar joint 52. For the first course of wall units 12 
rising up from the foundation 22, standard construction shims (not shown) 
are inserted between the wall unit bottom surface 30 and the foundation 22 
to insure that the resulting wall 26 is level and aligned. In addition, 
since a mortar joint 52 is also desired between the foundation 22 and the 
first course of wall units 12, a modified spacer/tensioning bracket 62 
having no lower alignment fins 72 is employed at the base of the first 
course in order to provide spacing for the mortar joint 52. 
While the spacer/tensioning bracket 62 as depicted in the drawings is shown 
with the intermediary portion 82 of the spacer/tensioning bracket 62 lying 
between opposing pairs of upper and lower alignment fins (70 and 72) as 
being planar and plate-like, it is contemplated that this intermediary 
portion 82 may be specifically designed to assist in the flow of grout 
over and around the spacer/tensioning bracket 52 and throughout the wall 
26. Thus, this intermediary portion 82 may be preferably formed with a 
downwardly-curving or other hydraulically engineered shape. 
For the construction of structures in which the Uniform Building Code (UBC) 
is controlling, the thickness of the spacer fins 74 will generally be 0.95 
cm (0.38 in) or greater, because a mortar joint 52 of that thickness, 
under current UBC requirements, permits the thickness of the wall unit 
side walls 36 to be taken into account as part of the overall wall unit 12 
thickness for purposes of structural engineering calculations. For walls 
employing CMU's, the genre in which the wall units 12 of the preferred 
embodiment of the present invention are technically categorized, in which 
mortar 80 is not used, or in which mortar 80 is present in a thickness of 
less than 0.64 cm (0.25 in), structural wall thickness calculations must 
be limited to using the width of the (grout-filled) cavities 44 only, as 
measured between the interior surfaces 76 of opposing wall unit side walls 
36. Thus, the inclusion of a sufficiently thick mortar joint 52 allows 
wall units 12 of a smaller width to be used than would otherwise be 
possible in the construction of walls using CMU's, reducing both the 
weight of the wall units 12 and construction costs. Moreover, the presence 
of mortar joints 52 allows a wall 26 to be engineered and built as a 
conventional CMU wall. It is contemplated, however, that UBC requirements 
may be revised and modified, in part because of the introduction onto the 
market of the wall units 12 of the present invention, to make it possible 
to meet certain structural requirements with the use of an adhesive other 
than mortar 80. For example, an epoxy or similar glue might be permitted 
to be employed to make an adhesive, water-tight joint between the wall 
unit top and bottom surfaces (28 and 30). 
As noted previously, and still referring to FIG. 7, in the preferred 
embodiment of the construction system 10, the cavity wall top and bottom 
surfaces (40 and 42) are each recessed from the wall unit top and bottom 
surfaces (28 and 30). Thus, when two wall units 12 are stacked one upon 
the other, in addition to a plurality of vertical passages 85 being 
formed, the cavity wall top surfaces 40 of the lower wall unit 12 and the 
cavity wall bottom surfaces 42 of the upper wall unit 12 combine together 
with interior surfaces 76 of opposing wall unit side walls 36 to create a 
horizontally disposed passage 86 that extends the length of the stacked 
wall units 12. Referring also to FIG. 8 now, the passage 86 permits grout 
84 that is poured into the cavities 44 to flow between laterally adjacent 
cavities 44, thereby creating a wall 26 in which is contained a continuous 
cementitious skeleton 88. The passage 86 also allows for the placement of 
horizontal reinforcement rod or rebar 90 within the wall units 12. The 
cementitious skeleton 88, reinforced by rebar 90 (and wall bar 24), 
greatly increases the structural integrity of the resulting wall 24, 
although for some applications (and under certain building codes), grout 
84 and/or reinforcement with rebar 90 may be unnecessary. (Although not 
shown, even greater reinforcement is possible by wrapping containment 
rings or ties around rebar 90 of more than one level of wall units 12.) It 
is also possible to create a passage similar to passage 86, and into which 
rebar 90 may likewise be placed, by recessing only the cavity wall top 
surfaces 40. However, the additional recessing of the cavity wall bottom 
surfaces 42 enables standard rigging equipment to be employed to grab hold 
and lift wall units 12 of any length without the need for special precast 
or field-installed lifting inserts. In the preferred wall units 12, all of 
the cavity wall bottom surfaces 42 are recessed so that if it is necessary 
to cut a wall unit 12 at any particular point, a cavity wall bottom 
surface 42 will always be present so that a hook of the rigging equipment 
may be positioned thereunder for lifting. The application of mortar 80 
between the wall unit top and bottom surfaces (28 and 30), and the pouting 
of grout 84 into the cavities 44 and passages 86, provides a monolithic 
wall 26 of great structural strength. 
While in FIG. 8 a continuous cementitious skeleton 88 is shown, it is also 
contemplated that for certain applications, in which less structural 
strength is required, grout 84 might not be poured throughout the entire 
wall 26. For these lower strength applications, sleeves or similar 
partitioning devices (not shown) might be employed to prevent the grout 84 
from entering the horizontal passages 86, thereby creating single vertical 
grout voids (i.e., contained vertical passages 85) wherein discrete 
concrete pillars or columns would be formed upon the pouring of the grout 
84. These voids could similarly be permitted to remain empty, with grout 
84 poured in neighboring vertical and horizontal passages (85 and 86). 
This latter application is useful where, for example, plumbing fixtures 
need to be installed or maintained. 
As indicated previously, in the construction system 10 of the preferred 
embodiment, the foundation 22 provides a number of vertically disposed 
reinforcing wall bars 24. Referring once again to FIG. 1, it is shown that 
the wall units 12 are stacked onto the foundation 22 with the wall bars 24 
inserted through the cavities 44 within the wall units 12. While the 
incorporation of wall bars 24 provides for walls 26 of increased strength, 
it is understood that walls 26 can also be built that do not have wall 
bars 24 by simply stacking the wall units 12 and introducing a mortar 
joint 52 with a spacing device that does not utilize a wall bar 24. Spacer 
assembly 16 may be employed in this regard. Moreover, spacer assembly 16 
can also be employed in conjunction with the combination spacer/tensioning 
assembly 14 and/or the tensioning assembly 18, as shown in FIG. 1. 
Referring now to the exploded view of FIG. 9, one preferred embodiment of 
the spacer assembly 16 is shown to include an inner bracket half 92, an 
outer bracket half 94, and a bracket bolt 96. The inner bracket half 92 
includes inner bracket alignment fins 98 and an inner bracket spacer fin 
100 that is perpendicular to the inner bracket alignment fins 98. The 
outer bracket half 94 similarly includes outer bracket alignment fins 102 
and a perpendicular outer bracket spacer fin 104. The outer bracket spacer 
fin 104 is longer than the inner bracket spacer fin 100 (this is best seen 
in FIG. 10). The inner bracket spacer fin 100 is provided with a threaded, 
bolt receiving aperture 106, while the outer bracket spacer fin 104 has a 
non-threaded, bolt receiving aperture 108. Analogously to 
spacer/tensioning bracket 62, both sets of inner and outer bracket 
alignment fins (98 and 102) are present in parallel opposing fashion when 
the inner and outer bracket halves (92 and 94) are mated together with 
bracket bolt 96. The preferred inner and outer bracket spacer fins (100 
and 104) have a thickness of approximately 0.95 cm (0.38 in) to allow for 
a mortar joint 52 of at least 0.64 cm (0.25 in) thickness. 
Referring now to the cross-sectional view of FIG. 10, in which is shown 
both a complete and a partial spacer assembly 16, the inner and outer 
bracket halves (92 and 94) are assembled together with the bracket bolt 96 
and then positioned over a wall unit top surface 28 so that the inner and 
outer bracket alignment fins (98 and 102) straddle the wall unit side wall 
36, the inner bracket half 92 being on the cavity 44 side of the wall unit 
12. When a second wall unit 12 is stacked on top of the first wall unit 
12, the wall unit side wall 36 of the upper wall unit 12 is likewise 
inserted into opposing inner and outer bracket alignment fins (98 and 
102). The distance between opposing inner and outer bracket alignment fins 
(98 and 102) is just sufficient to allow insertion of the wall unit side 
walls 36, thus the wall unit side walls 36 of the two wall units 12 are 
forced into vertical alignment and precision stacking may be achieved. 
Once the wall units 12 have been stacked, mortared, and grouted, the 
bracket bolt 96 is removed together with the outer bracket half 94. The 
inner bracket half 92 is left in place (as shown at the left of the 
drawing) to maintain the desired spacing for the mortar joint 52. A simple 
patch of mortar 80 is applied to fill in the void in the mortar joint 52 
remaining from removal of the outer bracket half 94. Thus, the inner 
bracket half 92 is hidden from view. Like the combination 
spacer/tensioning assembly 14, the spacer assemblies 16 (where used alone) 
are typically incorporated at increments of 4.6 m (10 to 15 ft) along the 
length of a wall unit 12. Notches similar to recessed and hollowed notches 
(78a and 78b) may also be utilized in conjunction with the spacer assembly 
16, together with other automatic alignment methods as described 
previously for spacer/tensioning bracket 62. 
Although the spacer assembly 16 does not have the wall tensioning 
capability of the spacer/tensioning assembly 14, since it is designed to 
interact with only one of the wall unit side walls 36 at a time, the 
spacer assembly 16 is more flexible in other regards. Specifically, the 
inner and outer bracket alignment fins (98 and 102) of the mated spacer 
assembly 16 are able to straddle both a wall unit side wall 36 and a wall 
unit end wall 110. Thus, the spacer assembly 16 can be used to align not 
only the wall unit side walls 34, but also the wall unit end walls 110, 
unlike the spacer/tensioning bracket 62. 
Furthermore, as shown in FIG. 1, the outer bracket half 94 of the spacer 
assembly 16 may be modified to integrate a wall brace fin 112. In the 
modified spacer assembly, which is given the reference numeral 17 in the 
drawing, the wall brace fin 112 extends perpendicularly outward from the 
outer bracket half 94 and includes a wall brace fin aperture 114. The 
modified spacer assembly 17 may be used to assist in the bracing of a wall 
26 during its construction when the height of the wall 26, or the 
prevailing wind conditions, are such that the use of external bracing is 
mandated to prevent the wall from leaning or falling over. External 
bracing 115, such as a rod or beam, may be conveniently attached to the 
wall brace fin 112 via either bolting or tying with a cable through the 
wall brace fin aperture 114. In addition, the wall brace fin 112 may be 
further employed to assist in the alignment of consecutive lengths of 
walls 26. The situation will often exist where it will be required that 
two or more walls 26 be placed end-to-end in order to construct a 
structure having a sufficiently long overall wall length. And even where 
it is possible to pre-cast wall units 12 of sufficient length for the 
particular application at hand, building code requirements may mandate 
that vertical "breaks" or joints be incorporated at specific distances 
along the length of a wall 26 to help maintain the integrity of the wall 
26. In either event, the modified spacer assembly 17 having the wall brace 
fin 112 can be used to assist in plumbing adjacent wall 26 sections. As 
with the modified version of the spacer assembly 16, the outer bracket 
half 94 (which incorporates the wall brace fin 112) is removed after 
grouting of the wall and a simple patch of mortar 80 applied to fill the 
resulting void. The modified spacer assembly 17 may be placed anywhere 
along a horizontal mortar joint 52 to meet a wide range of job-specific 
requirements. 
It is also understood that the above-described embodiment of the spacer 
assembly 16 is only one of many possible embodiments. Another prominent 
example would be a purely internal spacer assembly of unitary construction 
essentially identical to the spacer/tensioning bracket 62, but without the 
bar receiving aperture 68. Of course, the spacer/tensioning brackets 62 
may be used as is, with the bar receiving aperture 68 simply being 
ignored. All of the various embodiments of the spacer/tensioning bracket 
62 and the spacer assembly 16 may be made of steel, plastic, or other 
structural material. 
As mentioned previously, the spacer assembly 16 may be used alone or in 
conjunction with the spacer/tensioning assembly 14. Where horizontal rebar 
90 (and wall bar 24) is employed, the spacer assembly 16 and/or 
spacer/tensioning assembly 14 may also be used, as shown in FIG. 1, in 
conjunction with tensioning assembly 18. As illustrated in the exploded 
view of FIG. 11, the tensioning assembly 18 includes a rebar bracket 116, 
a tensioning washer 64, and a tensioning nut 66. The rebar bracket 116 
includes a wall bar receiving aperture 118 and a rebar receiving notch 120 
which traverses the width or length of the rebar bracket bottom surface 
122. 
Referring to both FIG. 11 and the cross-sectional view of FIG. 10, the 
rebar bracket 116 fits over the wall bar 24 with the wall bar 24 passing 
through the wall bar receiving aperture 118 and the rebar receiving notch 
120 fitting onto the horizontal rebar 90. As indicated previously, the 
horizontal rebar 90 lies within passage 86. In the construction system 10 
of the preferred embodiment, rebar guide notches 124 are precast or 
field-cut into the cavity wall top surfaces 40 to assist in the 
positioning ("registering") of the rebar 90 and to further increase the 
structural integrity of the resulting wall 26. The tensioning washer 64 
and tensioning nut 66 are subsequently threaded onto the wall bar 24 and 
are tightened such that the rebar bracket 116 exerts a downward force on 
the wall unit 12 via the registered horizontal rebar 90, thereby 
tensioning the wall unit 12 onto the foundation 21 or a wall unit 12 
directly below. The ability to employ the various combinations of the 
different spacer and tensioning assemblies (14, 16, 17 and 18) gives the 
construction system 10 of the preferred embodiment great versatility in 
application. 
While the above disclosure describes the use of the wall units 12 only in 
terms of vertical applications (i.e., the building of walls), the "wall" 
units 12 may just as easily be used in similar fashion for horizontal 
applications such as floors and decks (in which cases the wall unit side 
surfaces 32 would face upward and downward). Moreover, the nature of the 
wall units 12 is such that an individual wall unit 12 may be employed 
singularly to function as a beam. Applications include, among others, a 
beam for spanning an opening such as a large doorway, or a grade beam for 
a pier and grade-beam foundation. To use the wall unit 12 in the capacity 
of a beam, the wall unit 12 is conveniently placed upright on a flat piece 
of wood or similar surface and concrete is poured within the cavities 44. 
Typical beam applications require a large amount of reinforcement, and the 
recessed nature of the cavity walls 38 permits a larger amount of 
reinforcing steel and concrete to be added than is possible with existing 
CMU's. 
In addition to the preceding and above mentioned examples, it is to be 
understood that various other modifications and alterations with regard to 
the types of materials used, their method of joining and attachment, and 
the shapes, dimensions and orientations of the components as described may 
be made without departing from the invention. Accordingly, the above 
disclosure is not to be considered as limiting and the appended claims are 
to be interpreted as encompassing the entire spirit and scope of the 
invention. 
INDUSTRIAL APPLICABILITY 
The modular precast construction block system 10 of the present invention 
is compatible with wall and foundation designs that would normally employ 
standard cast-in-place concrete walls. Implementation of the construction 
system 10 is simple compared to heretofore known methods capable of 
producing structures of comparable strength. Prior to delivery of the 
precast wall units 12, a layout crew sets wall lines. Using a relatively 
lightweight crane, wall units 12 are removed from the delivery truck and 
stacked over the wall bars 24, a bed of mortar 80 being laid down on the 
foundation first. Between the first course of wall units 12 and the 
foundation 22, structural shims are placed as needed, together with the 
modified spacer/tensioning brackets 62 having no lower alignment fins 72. 
In between each stacked wall unit 12, an installation crew places 
combination spacer/tensioning assemblies 14, spacer assemblies 16 and 17, 
extension assemblies 20, horizontal rebar 90, and/or tensioning assemblies 
18 as needed. A bed of mortar 80 is also laid down. The wall units 12 are 
easily positioned atop one another because of the built-in alignment 
features of the various spacer assemblies 14, 16, and 17. As the wall 26 
proceeds higher, the installation crew works atop a scissors lift, 
ladders, or scaffolding. Where necessary, external bracing 115 may be 
attached to the modified spacer assemblies 17. When stacking of the wall 
units 12 is complete, grout 84 is poured into the cavities 44 and the 
horizontal passages 86. Prior to pouring the grout 84, additional 
reinforcing steel may be placed into the vertically extending cavities 44, 
the structure of the wall units 12 allowing the resulting wall 26 to 
contain more reinforcing material than is possible with walls built using 
known CMU's. After the grout 84 has cured, any external bracing 115 and 
outer bracket halves 94 are removed and patches of mortar 80 applied. 
Unlike cast-in-place concrete methods, the construction system 10 is a very 
"clean" system. The present invention also completely eliminates the need 
to create forms on site. The inherent stability of structures created with 
the construction system 10 eliminates as well the need for a welded 
superstructure. The construction system 10 of the present invention is 
intended to be widely used in the construction industry as a quick, 
precise, cost effective and strength equivalent alternative to 
cast-in-place concrete structural elements. For these reasons and numerous 
others as set forth herein, it is expected that the industrial 
applicability and commercial utility of the present invention will be 
extensive and long lasting.