EXPERIMENTAL INVESTIGATION FOR SUSTAINABLE MORTAR MIX CONTAINING SEWAGE SLUDGE AS RECYCLED FINES IN ORDINARY PORTLAND CEMENT

Abstract

The present disclosure relates to a process has been carried out to use sewage sludge (locally available waste material) and carbide lime sludge (CLS) in construction as recycled fines (RF) which are obtained from sewage sludge in the form of ash (SSA) after its incineration and CLS as a byproduct of acetylene industry respectively. The effects of partial replacement of OPC using RF on compressive strength and split tensile strength after the 3rd, 7th and 28th day have been evaluated. The outcome from the present disclosure shows that the elevating replacements of RF up to 70% can be used in mortar as per IS: 2250 (2000) in structural applications. Utilization of RF up to 70% would be possible with OPC as it indicates an acceptable level of compressive strength of mortar, conservation of depleting natural reserves, saving in thermal and electrical energy besides emissions reduction of carbon dioxide.

Specification

Description:The current invention intended to examine the mortar mixes that contain RF up to 90% replacement of OPC for its various usages in construction. All mortar mix samples were prepared according to IS-4031: Part 6 (2005) using the following building materials and examined in controlled laboratory conditions at 26ºC (recommended 27±2°C) and 64% relative humidity (recommended 67±5%).
In the present invention Ordinary Portland cement (OPC) was used. The clinker used in this study was collected from the Jaypee cement plant, Rewa (Madhya Pradesh), India and gypsum was collected from DCM Shri Ram Works, Kota (Rajasthan), India for the preparation of OPC. The collected clinker was ground to the achieved desired fineness in the laboratory ball mill. Then 90µm IS sieve was used to sieve the ground material. For the conversion of sieved clinker powder into OPC, it was blended with 2.5% gypsum. This process is an illustration in Figure 1. For the comparison purpose of mortar mixes Portland Pozzolana cement (PPC) was used as a control mix. The properties of the PPC are mentioned in Table 1 in accordance with the specifications provided in Indian standards. In mortar mixes, natural standard sand (NSS) conforming to IS-650 (1999) is used. It is siliceous sand with round particles and having a silica content of up to 98% that occurs naturally. Natural standard sand (Ennore sand) that is supplied in pre-packed bags for use in cement plants and research laboratories. Grade I (particle size 2mm-1mm), grade II (particle size 1mm-500µm) and grade III (particle size 500µm-90µm) are the three grades of NSS. To make a well-graded mortar mix, all three grades of NSS are used in equal proportions. The different grade of NSS is shown in Figure 2(a-c). Digested sewage sludge having 30-40% moisture content was collected from the dumping site located at Jaypee University of Engineering and Technology, Guna (Madhya Pradesh), India.
To remove the initial moisture content, the collected digested sewage sludge was sun dried for a week. After that, it was dried in an electrical oven at 105°C for 24 hours to remove residual moisture content. For removal of foreign material available as impurities, dried sewage sludge was pulverized and sieved through a 1.18 mm IS sieve. Then sewage sludge is incinerated in an electric muffle furnace at 703°C for 1 hour. The temperature for incineration is decided by thermo gravimetric (TG) analysis. HITACHI-STA7300 was used in this process using alumina pan in the nitrogen atmosphere. 13.756 mg sample weight was taken and the temperature was started from 40 to 1300ºC at the rate of 20 ºC/min for this analysis. The weight loss on ignition increased significantly with increasing temperature, as shown by the TG curve. The findings show that the significant thermal decompositions and combustion of organic materials in sewage sludge occurred at temperatures between 90 and 703°C. It was observed that the appropriate temperature for ignition of sewage sludge sample was 703ºC, decomposition of organic matter take place. A TG and derivative thermo gravimetric (DTG) analysis curve of the raw material is shown in Figure 3. Then ash obtained from the incineration of sewage sludge was ground in a laboratory ball mill and sieved through a 90µm IS sieve. This process is shown in Figure 4. The carbide lime sludge is a waste material generated from the acetylene industry in slurry form (50-60% moisture content) was collected from the acetylene industry, DCM Shri Ram Works, Kota (Rajasthan), India.
The collected carbide lime sludge was sun dried for 48 hours to remove the initial moisture content. Subsequently, it was oven dried at 105ºC for 24 hours for removal of residual moisture content. Dried lime sludge is ground in a laboratory ball mill and subsequently sieved through a 90µm IS sieve.
Mortar specimens were made according to Indian Standard specifications by taking one part of binder (cement), three parts of sand (NSS of each type in equal quantity) and water, measured as a function of normal consistency of the mix. Eqs. (1) and (2) show how much water (in ml) is required to mix 1:3 cement sand mortar for 1 cubical specimen of compressive strength testing and briquette specimens for split tensile strength testing respectively.
(P/4+3) ×W ...(1)
[2/3 (P/((n+1)))+K]×W ...(2)
P = The amount of water that is required to achieve a normal consistency.
n = Number of parts of sand to one part of cement by weight, which is 3 in this case.
K = 6.5, which is the same for natural standard sand.
W = Cement and sand combined weight.
Specifically, mortar mix preparation satisfying one cubical mortar mould with internal dimensions, 70.6 mm x 70.6 mm x 70.6 mm as shown in Figure 11, 200 gm of cement, 600 gm of NSS (200 gm of grade I, grade II and grade III each) for compressive strength test are dry mixed and gauged with water according to calculations. 300 gm cement and 900 gm NSS (300 gm each of grade I, II, and III) are dry mixed and water gauged according to calculations for the preparation of six briquettes specimens and dimension of the mould shown in Figure 12.
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof. the results of normal consistency, specific gravity, soundness, initial and final setting time, tensile strength and compressive strength of the sustainable mortar mixes containing RF as per the specifications establish in Indian standards and also determine the percentage increase or decrease in compressive strength, reliability and carbon dioxide (CO2) emission analysis of sustainable mortar mixes With reference to the Table 6, it can be seen that the percentage of OPC replaced with RF increased, the amount of water required for normal consistency of binder mix increased. The specific gravity for all the mortar mixes was determined and the reduction was observed in the specific gravity due to the lesser specific gravity of SSA with CLS. Soundness was found to be 2 mm for all mortar mix samples where CLS was used. This value is found to be within permissible limits according to Indian Standard. The setting time of the mortar mixes was determined by the needle penetration method in Vicat's apparatus. The results of the initial and final setting time are shown in Figure 13.
It can be seen that the percentage of OPC replacement using RF increases the initial and final setting time of mortar mixes. The increase in setting time of mortar mixes with increasing percentages of RF can be justified by the higher water absorption of RF. In the cement specifications, the limit for initial and final setting time is defined therefore it is necessary to test this parameter in all mortar mixes. As per the Indian Standards, all the values are within permissible limits. The mortar mixes with the compositions listed in Table 5 have been prepared in controlled laboratory conditions with special attention to water requirements. In the current study, specimens were kept immersed in potable water and cured at room temperature. On the 3, 7 and 28 days, the cubical specimens were tested for compressive strength using a Universal Testing Machine (UTM) and tensile strength using a briquette testing machine on briquette specimens. For compressive strength calculations, the load (in Newton, N) at the failure of the compressive strength specimen is divided by the area of the cube subjected to loading, which is 4984.36 mm2. The failure load (in Newton, N) of split tensile strength specimens is divided by the area of the neck of the briquette subjected to extreme tension, which is 645 mm2, to determine split tensile strength.
Because the types of loading is compressive in nature and the entire strength of a masonry structure lies in the stability of its joints, the compressive strength of mortar is important when mortar is used as a binder between the joints of brick or stone masonry. When the mortar is used for plastering the surface, however, the tensile strength of the cement mortar plays a vital role. Because it ensures resistance to cracks caused by tensile stresses followed by thermal movements and drying shrinkage.
Figs. 14 and 15 show the results of compressive strength and split tensile strength on the 3, 7 and 28 days respectively, for mortar mixes with variable OPC substitutes using RF. For all of the substituted mortar mixes, PPC use as the control mix. For the control mix sample, PPC, the compressive strength is found to be 19.44 N/mm2, 28.04 N/mm2 and 43.45 N/mm2 on the 3, 7 and 28 days of curing respectively.
Figure 14 shows that the compressive strength of the OPC70SSA20CLS10 mix with up to 30% OPC substitution is similar to the compressive strength of the control mix (PPC) with a slightly limiting variation of ±2 N/mm2, which is within reasonable limits and can be considered equivalent to the control mix (PPC). The minimum defined limit for compressive strength of cement sand mortar for structural use is 7.5 N/mm2 therefore up to 70% RF can be used for this purpose. For structures requiring greater durability, mortars with 28 days compressive strength greater than 10 N/mm2 are usually suggested.
The cement used is PPC, which is also low heat cement and hence classed as CEM.IV in ASTM specifications. On the 28 days, the minimum tensile strength of CEM.IV is 300 psi or 2.06 N/mm2 [35].
Therefore, the compressive and split tensile strengths of cement sand mortar for structural use have minimum specified limits of 7.5 N/mm2 and 2.06 N/mm2, respectively [36]. Figure 16 illustrates the compressive strengths of different mortar mixes as a percentage increase or decrease in the minimum required strengths. It is found that OPC10SSA80CLS10 mix can give negative results when compared with the minimum strength given in standard, but up to 70% OPC substitution with RF exhibits greater compressive strength when compared with minimum required strengths for mortar. Thus OPC30SSA60CLS10 mix of mortar is the best combination for compressive strength and also safe increase in compressive strength above minimum requirement is achieved. Clinker production is the most energy-intensive phase in the cement manufacturing process and generates a higher quantity of carbon dioxide (CO2). In particular, during the calcination process, CO2 is released as a by-product that occurs at higher temperatures which results in the conversion of carbonates to oxides. Approximately 90% of CO2 emissions from the cement production process are direct emissions (calcination process), whereas the remaining 10% originate from the transportation of raw materials and other production processes .
Moreover, the generation of fly ash from thermal power plants is also responsible for CO2 emission to the atmosphere. About 60% (in India) of the enhanced greenhouse effect is directly due to CO2 produced as a result of coal (fossil fuel) combustion. At least three-fourths of a ton of carbon is emitted as CO2 for every ton of fossil fuel combustion .
In the current study, industrial by-products, such as CLS and a pozzolanic material, SSA as RF are used for the production of sustainable mortar mix. To create a homogeneous product, these products are blended with the ground clinker plus gypsum.
The current study suggests the substitution of RF wherein only 10% CO2 emits during the incineration (Electricity consumption) of sewage sludge. No calcination process has occurred in sustainable mortar mixes because the proportion of CaO in SSA is 18.6% in the form of oxide. The CO2 emission in the sustainable mortar mix made using RF is less than that of PPC/OPC. For making sustainable mortar mix the digested sewage sludge is incinerated in a muffle furnace at 703ºC only for 1 hour for decomposing the organic matter in it.
Figure 18 shows the CO2 emission in sustainable mortar mixes made by using different RF%
Reference throughout this specification to "an aspect", "another aspect" or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises...a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting. Embodiments of the present disclosure will be described below in detail with reference to the accompanying drawings.
The present invention is described hereinafter by various embodiments with reference to the accompanying drawing, wherein reference numerals used in the accompanying drawing correspond to the like elements throughout the description. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiment set forth herein. Rather, the embodiment is provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. In the following detailed description, numeric values and ranges are provided for various aspects of the implementations described. These values and ranges are to be treated as examples only and are not intended to limit the scope of the claims. In addition, several materials are identified as suitable for various facets of the implementations.
While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art. Thus, the scope of the present disclosure is defined by the appended claims and includes both combinations and sub-combinations of the various features described hereinabove as well as variations and modifications thereof, which would occur to persons skilled in the art upon reading the foregoing description.
, C , Claims:1. A method of making the composition of Up to 30% substitution of RF in OPC gives comparable compressive strength to the control mix (PPC).
2. The method as claimed in claim 1 wherein Up to 50% to 70% replacement of RF in OPC exhibits reasonable compressive strength as compared to 33 to 43 Grade Ordinary Portland cement respectively and also tensile load results are significantly improved. Since it can withstand tensile stresses caused by shrinkage and thermal movements on the exterior surfaces of masonry structures, this mortar mix can be used for plastering the surfaces.
3. The method as claimed in claim 1 wherein 70% substitutions of RF in OPC mortar mixes are performing better than the minimum compressive strength requirements demanded in IS-2250(2000) for structural application.

Documents