Patent Application
20220234951
The present invention relates to a concrete mix design and placement method for realizing dam or other massive structure by using the concrete mix design approach.
In particular, the mix design of the present invention has been optimized for the construction of dams (or other massive structures) to be placed by no-conventional means.
For several years, the problem of the durability and cost of construction of concrete structures was a major topic of interest in particular in the construction of dams.
A dam is a huge construction that needs massive amount of concrete to build it with and that leads to high cost, so alternative methods should be considered to minimize the cost of constructing the dams with new material methods.
One known method is building the dams with Roller Compacted Concrete (RCC), which by definition is a composite construction material with no-slump consistency in its unhardened state and it has achieved its name from the construction method. The definition for a no-slump consistency is a freshly mixed concrete with a slump less than 6 mm.
The RCC is placed with the help of paving and earthmoving equipment and then it is compacted by vibrating roller equipment from the surface rather than with immersion type vibrators. The basic ingredients RCC mix designs are the same as for the conventional concrete but it has different ratios in the materials that are blended to produce concrete that yields an entirely different set of fresh properties that normal weigh concrete. It differs when it comes to aggregates because both similar aggregates used in conventional concrete or aggregates that do not fulfill the normal standards can be used in the RCC mixtures, in particular the amount of fines (% passing ASTM E11 Sieve #200, minus 75 micron) and smaller sieve sizes in the sand fraction.
The RCC dams are usually built in thin, horizontal lifts, in such a way to reduce the amount of formwork and allow for successful external consolidation by vibratory rollers.
RCC addressed two factors to lower the cost and decrease the time of concrete dam construction:
One of the key concepts in the RCC method of building dams is to place one large lift of concrete, about 300 mm in depth, in a continuous manner for the entire surface of the dam, covering each layer with another layer before the initial set of the previous layer. This results in a chemical bond between the layers and results in a more monolithic structure.
Because RCC is dryer than normal mass concrete, dozers can spread the material and double or single drum vibrating rollers compact the RCC (similar to building an asphalt road). This is opposed to immersion type vibrators used in typical mass concrete.
The method of one layer of continuous placement is opposed to the method of individual blocks used in conventional mass concrete construction.
So, the key steps in RCC Dam 100 construction are (
However, for RCC method it is necessary to use machines for spreading and compacting the lifts.
In particular, this type of construction consumes huge amount of construction material and takes long construction period which increases overhead cost and significantly affect the environment.
In this context, the technical task underlying the present invention is to propose a concrete mix design and a method of placement for realizing dam or other massive structure by using the concrete mix design that overcomes the drawbacks of the prior art mentioned above.
In particular, it is an object of the present invention to provide a structural mix design which could be used for a massive self-compacting concrete (MSCC) method for realizing a dam.
In detail, it is an object of the present invention to reduce both the equipment and machines used as well as the number of people in construction process for building dams further still from the RCC method of construction as well as traditional conventionally cast and immersion vibrated concrete.
Additional features and advantages of the present invention will become more evident from the approximate and thus non-limiting description of a preferred but non-exclusive embodiment of a concrete mix design and a method of placement for realizing dam or other massive structure by using the concrete mix design, as illustrated in the appended drawings, in which:
With reference to the drawings, they serve solely to illustrate embodiments of the invention with the aim of better clarifying, in combination with the description, the inventive principles of the invention.
The present invention refers to a concrete mix design and method for realizing dam 100 or other massive structure by using Self-compacting/Self-consolidating Concrete 101, particularly mass structural concrete.
In particular, the specific concrete below described for the present invention is a massive self levelling concrete 101 (MSCC) which is different from concrete used for an known SCC.
There have been laboratory investigations to determine the feasibility of developing a normal weight, Self-compacting/Self-consolidating, portland cement based concrete mix design. It is envisioned that the mix design of the present invention has highly modified dosages (with respect to conventional Roller Compacted Concrete) of various admixes to enable the ability to flow freely and self-compact and thought to be outside of presently known building codes and practices.
The massive self-compacting/self-leveling concrete 101 is being developed for use in mass and conventional concrete structures, both reinforced and unreinforced, to allow for little or no internal or external consolidation effort. Typical applications include, but are not limited to, gravity dams 100, arch dams 100, foundation slabs, runways, bridge abutments and other members, loch walls, ballast blocks, and other concrete structures.
The concrete mix design provide that:
In particular, the mix design depends on a “heavily” influenced mix in terms of chemical admixtures to take advantage of advances in the industry.
It is used a lower cement/fly ash content, for many reasons, some of which are heat of hydration (trying to reduce), as well as economy, as well as shrinkage.
Further, it is using a “dirty” sand. This means that there is more fine material at the bottom end of the gradation that would be normally used for traditional structural or mass concrete.
Below is described an example of realizing the concrete design mix:
Water content of the mix design is comprised between 150 l/m3 and 250 l/m3 and preferably 200 l/m3.
Regarding the chemical admixtures, they are showed and indicated in the table represented in
In detail, chemical admixtures comprising one or more components, preferably all these components, selected between the following list:
The acrylic formaldehyde-free polymer-based admixture has a density of 1.07 g/m3, a dosage comprised between 3 liter/m3 and 4 liter/m3 of cementitious content and a dosage comprised between 2% and 3% liter/m3 of the volume of the cementitious content.
The surfactant admixture has a density of 1,005 g/m3, a dosage comprised between 0.7 liter/m3 and 1 liter/m3 of cementitious content and a dosage comprised between 0.5% liter/m3 and 0.7% liter/m3 of the volume of the cementitious content.
The organic polymer admixture has a density of 1,022 g/m3, a dosage comprised between 4 liter/m3 and 5 liter/m3 of cementitious content and a dosage comprised between 2% liter/m3 and 5% liter/m3 of the volume of the cementitious content.
ASTM standards are the main referenced standards, although equivalent internationally recognized standards may be substituted.
Initial targets, fresh properties:
(no thermal properties will be tested until satisfactory fresh and hardened mechanical properties are established. However, the following are test envisioned for the thermal properties testing:
Mix proportions will be determined after initial review of proposed admixture types and dosages, as well as actual determination of:
Regarding the method for realizing dam 100 or other massive structure by using the concrete mix design, one of the key concepts in the MSCC 101 concept of building dams 100 is to borrow the RCC method of placing concrete for the entire lift surface, but using gravity to accomplish the compaction effort, thus eliminating much of the required equipment.
If the concrete can behave more closely to the properties of an ideal fluid, then it will be self-leveling, and no need for compaction effort.
Assuming that the construction process would be similar to RCC construction and be placed in one continuous lift across the entire dam 100 surface with a massive self-leveling type of concrete, precast elements 7 could be used for the US and DS facing elements.
These would be left in place after construction, and the erection process to be heavily automated. Conventional formwork 6 solutions could also be utilized.
The overall placement of the MSCC 101 for the dam 100 construction aims to be similar to 3D printing, where the user directly deposit the material at the point needed for construction, and move forward at a rapid rate until completion with the minimal amount of unit processes involved during construction.
So, the key steps in MSCC 101 Dam 100 construction are:
In particular, with reference to
This aspect is advantageous because the new concrete could be easily transported and placed at the dam 100 location.
Further, it has to be noted that the new concrete mix design avoids the external vibrating phase of concrete otherwise provided for the RCC method (
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2020/054631 | 5/15/2020 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62849389 | May 2019 | US |
