[001] The present invention relates to chemically processed mineral additive for increasing the durability of concrete and cement.
BACKGROUND OF THE INVENTION
[002] Construction is an important sector that contributes greatly in the economic growth of a nation. With continual growth in construction sector coupled with a drastic change in the conditions the concrete structures are exposed to, there is requirement of concrete with increased durability. For this purpose, a variety of cement additives have been introduced in the market, for example silica fume, metakaolin, etc. These additives improve the property of concrete such as, hardening properties, strength, durability and workability.
[003] US patent 8133317 relates to cement additive and cement composition. In this invention, the additive composition uses gypsum and blast furnace slag powder. The cement additive of the present invention enables effective use of industrial waste, and allows producing a hardened cementitious material having good durability.
[004] Additive composition disclosed in JP 2002104866 uses active silica and gypsum and relates to cement admixture having good workability and enabling to reduce cracking in early stage of drying. The admixture improves slump loss of flow reduction or concrete mortar. Furthermore, US patent 5340397 discloses ultrafine cement composition which uses Portland cement in its composition.
[005] The concrete additive formulations known in the art uses gypsum, silica, Portland cement, blast furnace slag powder and various components in different ratios. Further, the silica fume requires a high amount of water and is more prone to increase the drying shrinkage cracks which may affect the overall strength. Cost factor is also one of the disadvantages while using silica fume in cement.

[006] In light of the above described state-of-the-art, there is requirement for an additive formulation, which makes concrete and cement more durable and is economical and safe for the environment.
OBJECTIVE OF THE INVENTION
[007] The primary objective of the present invention is to propose an additive composition to increase the compressive strength of cement/concrete.
[008] Another objective of the present invention is to propose the mineral additive composition which reduces the water permeability of cement/concrete.
[009] Yet another objective of the present invention is to propose the method for making the mineral additive that will give concrete a high compressive strength and low water permeability.
[0010] Yet another objective of the present invention is to propose the mineral additive formulation which is economical and green.
[0011] These and other features and advantages of the present invention may be incorporated into certain embodiments of the invention and will become fully apparent from the following description or may be learned by the practice of the invention as set forth hereinafter. The present invention does not require that all the advantageous features and all the advantages described herein be incorporated into every embodiment of the invention.
SUMMARY OF THE INVENTION
[0012] The present invention discloses composition and method for making a mineral additive which increases the compressive strength and reduces the water permeability of concrete thereby, making the cement and concrete more durable.

DETAILED DESCRIPTION OF THE INVENTION
[0013] The following presents a simplified description of the invention in order to provide a basic understanding of some aspects of the invention. This description is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form.
[0014] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
[0015] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.
[0016] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention.
[0017] It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.
[0018] It should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. The equations used in the specification are only for computation purpose.

[0019] The present invention relates to the composition of a mineral additive to be added with concrete and cement to improve its durability. Moreover, the invention also discloses a method for making the mineral additive.
[0020] The main embodiment of the present invention is to propose the composition of the mineral additive to be added with cement to improve the durability of concrete. The mineral additives in the proposed composition consist of alkali metal carbonate, alkali metal sulfate, amine, industrial byproduct and alkali metal silicate or phosphate.
[0021] The mineral additive in proposed composition consists of 1% to 30% of an alkali metal carbonate. In an embodiment, the alkali metal carbonate may be calcium carbonate having particle size in the range of 2-20 microns. Alternatively, the alkali metal carbonates may be selected from the group of sodium carbonate, potassium carbonate, barium carbonate and lithium carbonate.
[0022] Further, the mineral additive in proposed composition consists of 0.1% to 20% of an alkali metal sulfate. In an embodiment, the alkali metal sulfate may be sodium sulfate having a solubility of more than 15%. Alternatively, the alkali metal sulfate may be selected from the group of calcium sulfate, potassium sulfate, barium sulfate and lithium sulfate.
[0023] The mineral additive in proposed composition also consists of 0.1% to 2% of a tertiary amine. Preferably, the amine may be triethanol amine or tri isopropanol amine. Alternatively, the amine may be selected from the group of primary or secondary or tertiary amines. The amines may be selected from the group of aliphatic amines like methylamine, di methylamine, diethylamine, tri ethanol amine, and tri isopropanol amine.
[0024] The mineral additive in proposed composition consists of 30% to 70% of industrial byproduct. The industrial byproduct preferably contains fly ash having retention on 45 microns between 2% to 15%.

[0025] The mineral additive in proposed composition consists of 0.1% to 0.5% of alkali metal silicate or alkali metal phosphate. Preferably, the alkali metal silicate may be potassium silicate and the alkali metal phosphate may be sodium hexa meta phosphate. Alternatively, the alkali metal silicate/phosphate may be selected from the group of 5 sodium silicate, lithium silicate and tri potassium phosphate, potassium poly phosphate etc.
[0026] Another embodiment of the present invention is a method for making the mineral additive for concrete. The method includes blending all the components in a high precision blender. Before blending, the liquid components i.e. tertiary amine, alkali 10 metal silicate and one of the solid component alkali metal sulfate are mixed separately. Then the mixed solid and liquid components are fed to blender alongwith other components. All the components are blended for around 3 to 5 minutes in the high precision blender.
[0027] After blending, the mixture was bagged and cubes were casted using the additive 15 composition mixed with cement. The additive was used at a percentage of 0.7 by weight of cementitous materials for low grade concrete (M-20) and used at a rate of 2% by weight of cementitous materials for high grade concrete (M-50). The corresponding mix designs are shared at the end. After around 24 hours, the casted cubes of mixture are demolded and immersed in water for curing. Then, the cubes are taken out of water after 20 1, 3, 7 and 28 days, dried and tested for its compressive strength and water permeability.
[0028] As per the exemplary embodiment, 50 kilograms of the proposed composition were blended in a high precision blender for about 5 minutes. Firstly, the liquid components tri iso propanol amine (TIPA) was mixed with solid component sodium sulfate separately and then fed alongwith the other components into the blender in 25 accordance with the weights depicted in Table 1 below:
6

S. No.
1 2 3 4 6 Ingredient Name Weight in Kgs Physical Form

Micro Calcium Carbonate 10 Powder

Sodium Sulfate 18 Powder

Fly ash 32 Powder

Potasium Silicate 0.250 Liquid

Tri Isopropanol amine 1.500 Liquid
Table 1
[0029] After mixing the above mentioned composition for 5 minutes in the blender the mixture was bagged and 150 mm cubes were casted using the mix. After 24 hours, the concrete cubes were demolded and immersed in water for curing. Then the cubes were 5 then taken out, dried and tested for its compressive strength at 1, 3, 7 and 28 days. Further the cubes were tested for water permeability after 28 days.
[0030] The compressive strength of concrete was tested with two formulations prepared with 2% additive and without additive as tabulated below (Table 2):

Composition Without Additive With Additive
(2% by weight of cementitious materials)
Cement (Kg/m3) 245 245
GGBFS (Kg/m3) 245 245
Sand (Kg/m3) 701.5 701.5
20 mm Coarse Aggregate (Kg/m3) 641 641
12.5 mm Coarse Aggregate (Kg/m3) 427.3 427.3
Blended Additive (Kg/m3) 0 9.8
Water (Kg/m3) 152 152
7

[0031] The measured compressive strength of concrete with and without using the additive are tabulated below (Table 3):

Compressive Strength (Mpa)
Day Without Additive With Additive
IDay 22.0 22.3
3 Days 34.6 34.9
7 Days 42.7 43.7
28 Days 61.5 67.6
Table 3
[0032] As seen above, the proposed formulation of additive shows comparable improvement in the compressive strength of concrete and cement.
[0033] The water permeability with and without using the proposed formulation on M50 grade concrete is tabulated below (Table 4):

Water permeability at 5 bar for 72 Hours With additive Without additive
Depth of Water Penetration 5 mm 15 mm
Table 4
[0034] As depicted in the table above, the proposed additive formulation reduces the water permeability by 200% in concrete.
[0035] Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the invention.

We Claim:

An additive for concrete consisting of:
1% to 30% by weight of an alkali metal carbonate;
0.1% to 20%) by weight of an alkali metal sulfate with minimum solubility of
15%;
0.01%) to 2%> by weight of a tertiary amine;
30%o to 70%) weight percent of an industrial byproduct; and
0.01%o to 0.5%) weight percent of an alkali metal silicate or alkali metal
phosphate.
The additive for concrete as claimed in claim 1, wherein the alkali metal carbonate is calcium carbonate having a particle size of 2-20 microns.
The additive for concrete as claimed in claim 1, wherein the industrial byproduct is fly ash having 90 percent particle size of 25 to 40 microns.
The additive for concrete as claimed in claim 1, wherein the alkali metal sulfate is sodium sulfate.
The additive for concrete as claimed in claim 1, wherein the tertiary amine is tri-ethanol amine or tri-isopropanol amine.
The additive for concrete as claimed in claim 1, wherein the alkali metal silicate is potassium silicate.
The additive for concrete as claimed in claim 1, wherein the alkali metal phosphate is sodium hexa-metaphosphate.

The additive for concrete as claimed in claim 1, wherein the alkali metal carbonate is selected from the group of sodium carbonate, potassium carbonate, barium carbonate and lithium carbonate.
The additive for concrete as claimed in claim 1, wherein the alkali metal sulfate is selected from the group of calcium sulfate, potassium sulfate, barium sulfate and lithium sulfate.
The additive for concrete as claimed in claim 1, wherein the amine is selected from the group of aliphatic amines like methylamine, di methylamine, diethylamine, tri ethanol amine, and tri isopropanol amine.
The additive for concrete as claimed in claim 1, wherein the alkali metal silicate is selected from the group of sodium silicate, lithium silicate.
The additive for concrete as claimed in claim 1, wherein the alkali metal phosphate is selected from the group of tri potassium phosphate, potassium poly phosphate etc.
A method of preparation of an additive for concrete, the method comprising the
steps of:
(i) mixing alkali metal carbonate and fly ash;
(ii) mixing alkali metal sulfate and tertiary amine;
(iii)blending the mixtures of steps (i) and (ii) with alkali metal silicate or phosphate
for a period of 200 - 400 seconds; and (iv) isolating the additive.
The method as claimed in claim 13, wherein the alkali metal carbonate is calcium carbonate having a particle size of 8-20 microns.

15. The method as claimed in claim 13, wherein the industrial byproduct is fly ash having a 90 percentage of particle size of between 25 to 40 microns.
16. The method as claimed in claim 13, wherein the alkali metal sulfate is sodium sulfate.
17. The method as claimed in claim 13, wherein the tertiary amine is tri-ethanol amine or tri-isopropanol amine.
18. The method as claimed in claim 13, wherein the alkali metal silicate or phosphate is potassium silicate or sodium hexa-metaphosphate
19. The method as claimed in claim 13, wherein the additive is blended in a high precision blender.
20. The method as claimed in claim 13, wherein the additive is mixed in a ratio of 0.7 to 5% by weight of cementitious materials depending on the grade of concrete.