Water Absorption and Sorptivity of Masonry Blocks using Soil, Phosphogypsum and Stabilised with Different Additives.

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 6, Issue 7, July 2016)

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Water Absorption and Sorptivity of Masonry Blocks using Soil,

Phosphogypsum and Stabilised with Different Additives.

T. H Sadashiva Murthy

1

, Achyuth R B

2

, Sujith S

3

, Manjunath S B

4

, Varadamurthy Acharya B

5

1_{Civil Engineering,}2,3,4,5_{B.E Graduate, National Institute of Engineering, Mysore, India} 2,3,4,5_{B.E Graduate, National Institute of Engineering, Mysore India}

Abstract: The world is experiencing an unprecedented transition from predominantly rural to urban living with ever increasing population. Hence leading pressurizing the agriculture industry to opt for an accelerated modern method of food production, utilizing more fertilizers, which yield by products. The disposal of solid wastes like Phosphogypsum is a subject that has led to intense research in this field. The paper explains masonry blocks production with conventional

soil cement and in addition the waste product

Phosphogypsum, The experiments conducted for its

properties, proportion of constituents, Tests, results and conclusions. Utilization of solid wastes in construction materials can reduce its adverse effects on the surroundings.

Keywords-- Masonry block, Phosphogypsum, water absorption, sorptivity, compressive strength, RBI grade-81.

I. INTRODUCTION

Phosphoric acid can be used as as rust inhibitor, food additive, electrolyte, fertiliser feedstock, component in home cleaning products and many more besides being a chemical reagent.. The production of phosphoric acid from phosphate rock yields a by-product called phosphogypsum. Phosphogypsum being a chemical by-product is non-biodegradable and is difficult to dispose large quantities of phosphogypsum. Presently, in many parts of the world, phosphogypsum is used as fertiliser, soil conditioner and stabiliser and also in glass and ceramic industry.

In our country Phosphogypsum is used mainly for agriculture purposes in very small quantities in contrast with huge quantities produced in industries. Phosphogypsum is a non-biodegradable chemical product and poses a major threat to the environment. Phosphogypsum has been dumped in large quantities nearby industries and is increasing every year and causing problem of disposal.

In this study, it is intended to use Phosphogypsum for development of soil based masonry blocks stabilised with different additives. So as to find effective means of utilization of solid wastes to cater to a better environment.

II. REVIEW OF LITERATURE

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III. MATERIAL PROPERTIES

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The major materials used for the block making are soil, phosphogypsum and cement having specific gravities 2.68, 2.8 and 3.11 respectively. Figure 1 and 2 show grain size distribution, maximum dry density and OMC of soil. From Figure 1, the soil consists of 70% sand and 12% clay, suitable for block making.

Figure 1: Grain size distribution curve

Figure 2: Water content-Density relationship of soil

[image:2.612.56.279.227.466.2]

IV. NOMENCLATURE AND BLOCK MAKING

Table 1:

Nomenclature of blocks and their composition

Block designation

Soil (%)

PG* (%)

Cement (%)

RBI GRADE

81 (%)

QUARRY DUST (%)

CO 93 0 7 - -

PG5 88 5 7 - -

PG10 83 10 7 - -

PG15 78 15 7 - -

PG20 58 20 7 - 15

R2PG5 86 5 7 2 -

R2PG10 81 10 7 2 -

Note: All values in percentage by weight of block. *PG=Phosphogypsum

Block making procedure

Required quantity of soil is sieved through 4.75 mm sieve

Phosphogypsum is fully dried and lumps are powdered so as to pass through 425 micron sieve.Depending upon the combination, constituent materials are batched into different bags.Dry mix of the ingredients depending upon the combinations as tabulated in Table 1 is prepared.Water corresponding to the OMC is added and wet mix is prepared until uniform colour is obtained. Wet mix is fed into the Mardini press of mould size 230mm x 190mm x100mm by a measuring scoop. The mix is pressed manually using the Mardini press. The compacted block is taken out and stacked. Curing is done for required period by covering them with gunny bags using potable water

V. EXPERIMENTAL STUDIES

1.COMPRESSION TEST [IS 3495(PART 1): 1992]

Specimen selected for testing is cured for14 and 28 days. The frogs on both the sides are filled with 1:3 cement mortar ten days prior to testing and cured along with the block. The blocks are then sundried. Testing is carried out as per IS 3495 (PART 1):1992.The results obtained are as shown in Figure 3.

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International Journal of Emerging Technology and Advanced Engineering

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Table 2:

Compressive strength at 14 and 28 days

The compressive strength of control block was observed to be 6.64 MPa. At 14 days, compressive strength throughout all the combinations remains fairly around 5.1 MPa (PG20) to 5.68 MPa (PG10). At 28 days, compressive strength throughout all the combinations is in the range 5.6 MPa (PG20) to 8 MPa (R2PG10). Replacement of 15% of soil by Phosphogypsum (PG15) yielded a compressive strength of 7.55 MPa which is 13.81% greater than control block owing to Phosphogypsum fineness, chemical property and stabilizing property. Addition of 2% RBI Grade-81 (R2PG10) yielded highest 28 day compressive strength of 8.01MPa which is 20.71% greater than control block. Addition of 2% RBI Grade-81 (R2PG5 and R2PG10) along with Phosphogypsum showed considerable increase in compressive strength than blocks with Phosphogypsum only (PG5 and PG10) due to its stabilizing property and fibrous content.

2. WATER ABSORPTION [ IS 3495 (PART 2):1992]

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Water absorption test helps in determining the percentage by mass of water absorbed by the blocks. The test is conducted on blocks of various proportions as per IS 3495 (PART 2):1992 and a comparative study is made.

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Figure 4: Variation of water absorption for different masonry blocks

Table 3:

Average water absorption for different masonry blocks

Block designation Average water absorption (%)

CO 4.72

PG5 9.76

PG10 9.32

PG15 6.68

PG20 13.13

R2PG5 8.06

R2PG10 8.41

From Figure 4, it can be noted that, the control (CO) has the least water absorption percentage (4.72%). Addition of 20% Phosphogypsum (PG20) has highest water absorption capacity (13.13%) which is 2.8 times greater than CO. This might be due to the fineness of Phosphogypsum. The block combination PG15 (having maximum compressive strength) shows the least percentage of water absorption (6.68%) than all other blocks with Phosphogypsum.

Block designation

14 day compressive strength (MPa)

28 day compressive strength (MPa)

CO 5.50 6.64

PG5 5.52 6.71

PG10 5.68 5.95

PG15 5.40 7.55

PG20 5.10 5.64

R2PG5 5.40 7.09

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Addition of 2% RBI Grade-81 (R2PG5 and R2PG10) along with Phosphogypsum showed slight decrease in water absorption than blocks with only Phosphogypsum (PG5 and PG10) mostly by blocking the pores due to its stabilising property. Addition of 15% quarry dust to PG20 blocks showed an elevated water absorption capacity (13.13%). This might be due to presence of quarry dust. As per IS 1077:1992, section 7.2, The bricks, when tested in accordance with the procedure laid down in IS 3495 (Part 2): 1992 after immersion in cold water for 24 hours, water absorption shall not be more than 20 % by weight up to Class 12.5 and 15 % by weight for higher classes.. All the blocks tested fall under Class 5 and have water absorption capacity within 14%, satisfying the provisions of the code IS 1077:1992, section 7.2. Hence these blocks can be used for construction purposes. In Karnataka, water absorption capacity of table moulded bricks is in the range 10.1% to 15.9% (Table 2.2, Ref 20). The results obtained in this study, show that all the block combinations (except PG20) have water absorption capacity in par with bricks available in market and can be used for construction purposes.

3. SORPTIVITY TEST

The sorptivity can be determined by the measurement of the capillary rise absorption rate on reasonably homogeneous material. Sorptivity (S) is a material property which characterizes the tendency of a porous material to absorb and transmit water by capillarity. It gains importance knowing the amount of water lost from the mortar.

The masonry blocks are cured for 28 days after casting. After drying in an oven at a temperature of 100+10 °C, the specimens of size 230mm x 190mm x 100 mm are immersed in water with the water level not higher than 5 mm above the base of the specimen. The flow from the peripheral surface is prevent by sealing it properly with non-absorbent coating. The quality of water absorbed in time period of 150 minutes at an interval of 15 minutes, is measured by weighting the specimen on a top pan balance weighting up to 0.1mg. The weighting operation is done after the surface water on the specimen is wiped off with a damp cloth and each weighting operation is completed within 30 seconds. The cumulative water absorption (Δw), (per unit area of the inflow surface) increases simultaneously in accordance with the square root of elapsed time (t) in minutes.

Where, S = Sorptivity in mm/min0.5 t = Elapsed time in minutes I = Δw/AD

Δw = Change in weight = W2-W1 W1= Initial weight of block in grams

W2= Weight of block after 15 minutes capillary suction of water in grams

A = Surface area of the specimen through which water has penetrated

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D = Density of water

Figure 5: Comparison of sorptivity for different masonry blocks

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It was observed from the graph that, there was a linear increase in sorptivity up to 15 minutes and then graph had a gradual decreasing trend with time up to 150 minutes.

VI. CONCLUSIONS

The blocks obtained from Phosphogypsum, soil, quarry dust, and cement showed maximum compressive strength of 7.5 MPa (PG15). The average dry compressive strength was about 6.96 MPa, whereas the control blocks possessed dry compressive strength of 6.6 MPa. Addition of RBI Grade-81 aided in increasing the strength. The maximum compressive strength obtained was 8 MPa (R2PG10). The average strength obtained with the addition of 2% RBI Grade-81 was about 7.5 MPa. Hence all blocks can be classified as Class 5 bricks as per IS 1077:1992 and are having better compressive strength than the locally available bricks in the Karnataka market whose compressive strength ranges from 4.8 MPa to 5.7 MPa.

The water absorption capacity of control blocks was about 4.72%. The water absorption capacity for blocks with Phosphogypsum was in the range 6.68% to 13.13%. The average water absorption capacity of blocks with Phosphogypsum and RBI Grade-81 was 8.23%. However, all the blocks are within the permissible limits (20%) as per IS 1077:1992, Section 7.2.

Control Block shows least peak sorptivity (0.149 mm/min0.5).Addition of phosphogypsum shows increase in peak sorptivity (1.26 mm/min0.5) on an average of about ten times w.r.t CO (.1063 mm/min0.5). The sudden increase in sorptivity due to addition of phosphogypsum might due to the fineness of phosphogypsum. Addition of RBI Grade-81 shows considerable decrease in peak sorptivity (0.74 mm/min0.5) on an average of about six times w.r.t CO (.1063 mm/min0.5). This might be due to chemical action of RBI grade 81 to react reduce permeability of the block.

In all the cases, sorptivity decreased with time beyond 20 minutes. It was observed from the graph that, there was a linear increase in sorptivity up to 15 minutes and then graph had a gradual decreasing trend with time up to 150 minutes.

Hence by all these observations, Stabilized mud Blocks prepared using Phosphogypsum can be used as an efficient construction material.

REFERENCES

[1] S. R. Satone, D. K. Parbat, D. P. Singh (2013) “Experimental Investigation on Feasibility of Phosphogypsum in M25 Grade Cement Concrete” International Journal of Research in Civil Engineering, Architecture & Design Volume 1, Issue 2, October-December, pp. 28-32.

[2] S. S. Bhadauria, Rajesh B. Thakare (2006), “Utilization of phosphogypsum in cement mortar and concrete”, 31st Conference on our world in concrete & structures: 16 - 17 August 2006, Singapore Article Online Id: 100031016.

[3] Harsha H. N., Radhakrsihna and Devanand R (2015). “Utilization of coal ash in stabilized mud blocks”, Journal of Environmental Research and Development Vol. 9 No. 3A, January-March. [4] M. Lyssandroua, A. Charalambides, K. Kehagia, V. Koukouliou, K.

Poteriades, M. Konstantinou, K. Kolokassidou and I. Pashalidis “Characteristics of phosphogypsum disposed on a coastal area in Cyprus”.

[5] Anitha K. R., et al. (2009) “Effect of RBI Grade 81 on different types of subgrade soil”,10th

National Conference on Technological Trends (NCTT09) 6-7 Nov.

[6] IS: 2720-Part 3/Sec-1 (1980), Indian standard methods of test for soils: Determination of Specific gravity, Bureau of Indian Standards, New Delhi.

[7] IS: 2720-Part 4 (1985), Indian standard methods of test for soils: Grain size analysis, Bureau of Indian Standards, New Delhi. [8] IS: 2720-Part 7 (1974), Indian standard methods of test for

soils: Determination of water content-Dry density relation using light compaction, Bureau of Indian Standards, New Delhi.