Patent Application
20220144704
This disclosure relates generally to cementitious building materials used in the design and formation of concrete structures. More specifically, this disclosure relates to a method of mixing cementitious building materials that provides the performance necessary to meet or exceed conventional linear elastic design norms associated with structural plain concrete structures.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. Structural plain concrete is described in ACI 318-14 guide, Chapter 14 (American Concrete Institute, Farmington Hills, Mich.). Similar concepts are employed in ACI 332-14 guide for residential walls. In addition, plain concrete methods are employed in slab on grade design in ACI 360-10 guide. The structural plain concrete sections allow use of plain concrete in members in buildings and non-building structures. This includes slabs, soil-supported structures, arches, walls and pedestals. Design is done elastically using a tensile and shear capacity based on conservative relationship between the compressive strength of the concrete and these properties. A conservative resistance factor derived first 1950's is applied to the designs. The American Concrete Institute in ACI 360, as well as the Portland Cement Association (Farney, J A, 2001), publish guides for slab on grade construction that rely on modulus of rupture for design on plain concrete slabs. ACI 318-14, 332-14 and ACI 360 all prescribe that modulus of rupture (MOR) be defined in terms of correlations to compressive strength. Thus, the MOR of concrete may be defined as the concrete's resistance to bending stresses.
The basic approaches as described in ACI 322 guide were developed in the 1970's to allow for design based on modulus of rupture. The provisions were later removed from the code and there has been little work in this area since. There has, however, been significant development in products that can enhance the properties of plain concrete. Thus, alternative methods of design and analysis are desired in order to provide approaches that will allow ready-mix concrete producers to develop performance mixes that can be used to reduce the requirement for traditional reinforcement in a variety of applications.
The present disclosure generally provides a process for the mixing design of a cement mixture for use in forming a concrete structure. This process comprises providing a cement paste comprising a mixture of water and cement; providing one or more aggregates having an outer surface; mixing the aggregates with the cement paste to form the cement mixture; and using the cement mixture to form the concrete structure. The flexural tensile strength measured as the Modulus of Rupture according to ASTM C78 or the associated coefficient of variation at 28 days for this concrete structure is enhanced over the flexural tensile strength or coefficient of variation measured for an identical conventional concrete structure.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is in no way intended to limit the present disclosure or its application or uses. It should be understood that throughout the description, corresponding reference numerals indicate like or corresponding parts and features.
The present disclosure generally provides a process for the mixing design of a cement mixture for use in forming a concrete structure that exhibits a flexural tensile strength measured as the Modulus of Rupture (MOR) according to ASTM C78 or the associated coefficient of variation (COV) at 28 days for this concrete structure is enhanced over the flexural tensile strength or coefficient of variation measured for an identical conventional concrete structure.
For the purpose of this disclosure the terms “about” and “substantially” are used herein with respect to measurable values and ranges due to expected variations known to those skilled in the art (e.g., limitations and variability in measurements).
Furthermore, any range in parameters that is stated herein as being “between [a 1st number] and [a 2nd number]” or “between [a 1st number] to [a 2nd number]” is intended to be inclusive of the recited numbers. In other words, the ranges are meant to be interpreted similarly as to a range that is specified as being “from [a 1st number] to [a 2nd number]”.
Increases in modulus of rupture (MOR) are possible through the use of, without limitation, chemical admixtures, fibers, engineered aggregates, and special types of cement. The process of the present disclosure provides a simple path for designers to characterize concrete performance through standard testing and modify the tensile capacity and resistance factor in order to allow the benefit in concrete structures formed therefrom while still providing the required structural reliability.
At a more fundamental level, the modulus of elasticity of the course aggregates is correlated to the MOR. The failure in plain concrete may occur at the interface between the paste and the aggregate due to the mismatch in stiffness between the paste and aggregate. If the stiffness of the aggregate is higher, it more closely approaches the stiffness of the paste, thereby delaying failure at this critical interface.
The creation of a performance based alternative approach for designing and/or forming plain concrete structures would allow engineers to use existing and new technologies to their advantage, as well as create a competitive market focused on actually improving the elastic tensile behavior of concrete. With the advent of nanotechnology, for example, it is no longer inconceivable that concrete tensile capacity could actually approach its compressive strength. The adoption of a performance-based approach may pave the way for the industry to capitalize on the economy, simplicity of construction, and the safety that such materials could offer now and in the future.
The modulus of rupture (MOR) may also be used in deflection calculations. The ACI 318-14 guide uses a higher value for deflection than for structural plain concrete. The ACI 318-14 guide provides equations for computing deflection in Chapter 22 with the Modulus or Rupture being defined according to Equation 19.2.3.1. There is potential value in computing deflection using a performance-based approach (e.g., potential to in-crease cracking moment and the effective moment of inertia using the mean values for MOR as determined in this guide).
With increasing costs of steel, tariffs and competition from non-concrete building materials such as wood and masonry block and concerns over the environment, the concrete industry must respond in a positive manner. The performance-based approach of the present disclosure allows the concrete industry to take full advantage of materials available now and would encourage the market to develop new innovative materials making concrete more competitive in the marketplace.
Referring now to
A conventional concrete structure may be defined as a structure formed from a cement mixture that comprises aggregates whose outer surface has not been modified by increasing the roughness or adding a primer or a formed from a cement mixture in which one or more reinforcing fibers incorporated into said mixture has not been pre-stressed by any means known to one skilled in the art. A conventional concrete structure may further be defined as lacking not including the addition of sand or another substitute material or a chemical admixture that is capable of increasing the interfacial bonding between the cement paste and the aggregates and/or reinforcing fibers The increased bonding may include providing elasticity in the interfacial zone between the aggregates and/or reinforcing fibers and the cement paste.
According to another aspect of the present disclosure, the process 1 may further comprise increasing 25 the roughness of the outer surface of the aggregates. Increasing the roughness of the aggregates may enhance the interfacial bond between the cement paste and the aggregates. The roughness of the outer surface of the aggregates may be increased by etching, embossing, scratching or similar method. When desirable, the process 1 may also comprise the addition 30 of an agent in the form of a primer to the outer surface of at least one aggregate in order to facilitate the bonding of the cement paste to the aggregates.
Still referring to
Referring now to
Referring once again to
According to another aspect of the present disclosure a concrete structure is provided that may be formed according to the process described above and in
Further embodiments that may be incorporated as part of the teachings of this disclosure are provided in Attachments A and B, the entire contents are included as part of this disclosure. In addition, the following bulleted listing of features further describe the disclosure:
Within this specification, embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without parting from the invention. For example, it will be appreciated that all preferred features described herein are applicable to all aspects of the invention described herein.
The foregoing description of various forms of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Numerous modifications or variations are possible in light of the above teachings. The forms discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various forms and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2020/023490 | 3/19/2020 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62822250 | Mar 2019 | US |
