An Experimental Investigation of Self Curing Concrete Incorporated with Light Weight fine Aggregate

IJIRST –International Journal for Innovative Research in Science & Technology| Volume 3 | Issue 04 | September 2016 ISSN (online): 2349-6010

An Experimental Investigation of Self-Curing Concrete Incorporated with Light Weight Fine Aggregate and Polyethylene Glycol Vishnu T M. Tech. Student Department of Civil Engineering FISAT, Kerala, India-683577.

Beena B R Assistant Professor Department of Civil Engineering FISAT, Kerala, India-683577.

Abstract Curing of concrete is defined as providing satisfactory moisture content in concrete during its early ages in order to develop the desired properties of concrete. In conventional curing this is achieved by external supply of water after mixing, placing and finishing of concrete. In practice conventional type of curing is difficult to perform as it shall need a large amount of water, meanwhile scarcity of potable water increases day by day. In order to save water as well as achieve curing several researchers started thinking about developing self-curing agents. Self-curing or internal curing is a technique that can be used to provide additional moisture in concrete for more effective hydration of cement and reduced self-desiccation. Internal curing can be achieved by using saturated light weight aggregate and polyethylene glycol. They provide sufficient moisture to the hydrating cement throughout the cross section of the concrete. This study deals with objective of gaining knowledge in the field of concrete technology which includes the study of self-curing of concrete. The aim of the investigation is to evaluate the use of poly ethylene glycol and light weight fine aggregate as self-curing agent. Self-cured specimens were developed and kept as such without the application of any external curing. In this study compressive strength, flexural strength, split tensile strength of concrete containing self-curing agent is investigated and compared to conventional concrete.

Keywords: Curing, Light Weight Fine Aggregate, Light Weight Expanded Clay Aggregate, Polyethylene Glycol, Self Curing Concrete _______________________________________________________________________________________________________ I.

INTRODUCTION

Curing of concrete plays a major role in developing the strength and hardness of concrete, which leads to its improvement in durability and performance. The concrete achieves its strength through a series of chemical reactions, known as hydration. The rate of the reactions influences the properties of the hardened concrete. As long as water is present, the hydration will continue for many years. The final strength of the concrete formed in the process will depend on the constituents in the original mixture, and the environment under which the reactions take place. In conventional curing this is achieved by external supply of water.

Practically good curing is not at all achievable in many cases due to the non-availability of good quality water and also due to practical difficulties. For a normal concrete each 1m³ of concrete requires about 3m³ of water for construction, were most of which is used for curing and a good quantity of it is wasted due to evaporation and runoff. Water is a valuable resource and its usage and wastage should be minimized in the construction industry. In order to tackle the present scenario many researches are concerned to identify effective self-curing agent and it leads to the development of self-curing concrete.

Self-curing refers to the process by which the hydration of cement occurs because of availability of additional internal water that is not a part of mixing water, that is curing is taken to happen from inside to outside. Internal curing distributes extra water throughout the entire microstructure, thus maintaining saturation of the cement paste during hydration. There are two major methods available for internal curing of concrete. The first method uses saturated porous lightweight aggregate in order to supply an internal source of water which can replace the water consumed by chemical shrinkage during cement hydration. These saturated porous lightweight aggregate stores water in it and act as reservoirs which will be able to release the water whenever the concrete requires. The second method uses poly-ethylene glycol which reduces the evaporation of water from the surface of concrete and also helps in water retention. The polymers added in the mix mainly form hydrogen bonds with water molecules and reduce the chemical potential of the molecules which in turn reduces the vapour pressure, thus reducing the rate of evaporation from the surface.

II. LITERATURE REVIEW El-Dieb A.S et al. described about water retention of concrete using polyethylene-glycol. He evaluated that self-curing concrete suffered less self-desiccation and water retention of self-curing concrete is higher when compared to conventional concrete.

Water sorptivity and water permeability values for self-curing concrete decreased with age indicating lower permeable pores

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An Experimental Investigation of Self-Curing Concrete Incorporated with Light Weight Fine Aggregate and Polyethylene Glycol (IJIRST/ Volume 3 / Issue 04/ 022)

percentage. Daniel Cussonandet al. stated that the use of saturated light weight aggregate as curing agent in concrete effectively improved the mechanical properties and reduces autogeneous shrinkage. Magda I. Mousa et al. had studied that the substitution of light weight aggregate, polyethylene glycol and silica fume influenced the mechanical properties of concrete. The concrete with polyethylene-glycol as self-curing agent attained higher values of mechanical properties than concrete with saturated lightweight aggregate. The study indicated that in all cases, 2% polyethylene-glycol and 20% saturated lightweight aggregate was the optimum ratio. It is noted that incorporation of silica fume in self-curing concrete with 2% polyethylene-glycol causes higher improvement in the mechanical properties of concrete. Alvaro Paul et al. analyzed the performance of light weight aggregates for internal curing, including artificial and natural light weight aggregates. The study showed that the natural light weight aggregates presented higher water storage capacity and higher rates of water uptake than the artificial light weight aggregates. Cusson D et al. evaluated the life cycle cost of high performance concrete bridge decks by using analytical model.

The study showed that compared to normal concrete decks, high performance concrete bridge decks provide additional 23 years of service and internal cured high performance concrete bridge decks provides additional 41 years of service life .When using high performance concrete over normal concrete, especially with internal curing the life-cycle cost of a bridge deck can be considerably reduced by about 38%.

III. MATERIALS Cement The Ordinary Portland Cement of 53 grade conforming to IS: 12269-1987 is used. Various tests were performed to find the properties of cement. The specific gravity of cement was found to be 3.15. The standard consistency of cement was obtained to be 35 % .The initial and final setting times for cements are found to be 80 minutes and 364 minutes.

Coarse Aggregate The fractions from 20 mm to 4.75 mm are used as coarse aggregate, conforming to IS: 383 is use. The properties of coarse aggregates such as specific gravity were found to be 2.64.

Fine Aggregate The fine aggregate type used in the study was manufactured sand. The manufactured sand is screened to eliminate over size particles. According to IS: 383 the fine aggregate conforming to zone I was used. The properties of sand such as specific gravity was found to be 2.76 and fineness modulus obtained is 2.927 Light Weight Fine Aggregate For the present work lightweight aggregate used was light weight expanded clay aggregate. The light weight aggregate of the fraction between 0.3 and 4.75 mm has a specific gravity of 2.54.The light weight expanded clay aggregate was submerged in boiled water for 24 hours and air dried before mixing. According to IS: 383 the fine aggregate conforming to zone II was used.

Polyethylene Glycol (PEG)-600 Polyethylene glycols (PEGs) are family of water-soluble linear polymers formed by the additional reaction of Ethylene oxide (EO) with Mono ethylene glycol (MEG) or Diethylene glycol. The generalized formula for polyethylene glycol is H(OCH2CH2) n OH. Polyethylene glycols are available in average molecular weight ranging from 200 to 8000, For the experimental programme PEG 600 was used. PEG 600 consists of a distribution of polymers of varying molecular weights with an average of 600 and it has specific gravity of 1.13.The appearance of PEG 600 is clear liquid. One common feature of PEG appears to be the water-soluble nature.

IV. CASTING PROGRAMME Casting programme consists of  Preparation of moulds as per IS 10086:1982, preparation of materials, weighing of materials and casting of cubes, beams and cylinders.  Mixing, compacting and curing of concrete done according to IS 516:1959.  Concrete mix is were prepared as per design mix and for each mix following specimens of both conventional and selfcuring concretes were casted.  Cubes of size 150mm X 150mm X150mm  Cylinder of size 150mm diameter and 300mm height  Beam of size 100 mm X100 mm X500 mm  Self-cured specimens were developed using self-curing agents like light weight expanded clay aggregate and polyethylene glycol.

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An Experimental Investigation of Self-Curing Concrete Incorporated with Light Weight Fine Aggregate and Polyethylene Glycol (IJIRST/ Volume 3 / Issue 04/ 022)

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Initially the mix was prepared using light weight expanded clay aggregate alone. Then the specimens were tested and optimum percentage of light weight expanded clay aggregate is obtained. To that optimum mix polyethylene glycol is added in various proportions to find the optimum percentage.

Self-cured specimens were kept as such without the application of any external curing after their removal from moulds.

The cubes which are intended for self-curing are kept in indoor/shade at room temperature. The mix design and material required for mix are shown in Table 1

No

Mix

1 2 3 4 5 6 7 8

M1 (M40) M2 (10% LECA) M3 (20%LECA) M4 (30%LECA) M5 (20%LECA+1% PEG) M6 (20%LECA+2% PEG) M7 (20%LECA+3% PEG) M8(20%LECA +4% PEG)

Table - 1 Mix proportion of materials per mÂł Cement Coarse Natural Fine (Kg) Aggregate (Kg) Aggregate (Kg) 350 1140 896 350 1140 806.4 350 1140 716.8 350 1140 627.2 350 1140 716.8 350 1140 716.8 350 1140 716.8 350 1140 716.8

Light Weight Fine Aggregate (Kg) 0 89.6 179.2 268.8 179.2 179.2 179.2 179.2

Water (Lit) 140 140 140 140 140 140 140 140

PEG (lit) 0 0 0 0 3.5 7 10.5 14

V. TESTING PROGRAMME In order to find the properties of self-curing concrete the following test were conducted on both self-cured concrete and conventional concrete.

Slump Test Slump test is the most commonly used method of measuring consistency of concrete which can be employed either in laboratory or at site of work. The concrete was tested for workability by slump Cone test by varying the percentage of light weight fine aggregate in fine aggregates and by adding polyethylene glycol. Slump test as per IS: 1199-1959 is followed.

Compressive Strength Test The cube specimens of size 150mm X 150 mm X 150 mm were tested on compression testing machine.The bearing surface of machine was wiped off clean and sand or other material removed from the surface of the specimen. The specimen was placed in machine in such a manner that the load was applied to opposite sides of the cubes as casted that is, not top and bottom. The load applied was increased continuously at a constant rate until the resistance of the specimen to the increasing load breaks down and no longer can be sustained. The maximum load applied on specimen was recorded.

Compressive strength is calculated using the formulae fc = p/A, Where, p is the maximum load A is the cross-sectional area Split Tensile Strength Test The cylinder specimens of size 150 mm diameter and 300 mm height were tested on universal testing machine and the load is applied until the failure of cylinder along the vertical diameter. When the load is applied along the generatrixan element on the vertical diameter of the cylinder subjected to a horizontal stress and found the split tensile strength using subsequent formulae.

Split tensile strength is calculated using the formulae đ?‘“đ?‘?đ?‘Ą=2đ?‘ƒ/đ?œ‹đ?‘‘đ?‘™ Where P= maximum load in Newton applied to the specimen l = length of the specimen (in mm), d = cross sectional dimension of the specimen (in mm) Flexural Strength Test Flexural strength is the ability of beam or slab to resist failure in bending. The beam specimens of size 100 mm X 100 mm X 500 mm were tested on compression testing machine. The flexural strength is expressed as modulus of rupture in N/mm². The load applied was increased continuously at a constant rate until the resistance of the specimen to the increasing load breaks down and no longer can be sustained. The maximum load applied on specimen was recorded.

Flexural strength is calculated using the formulae đ?‘“đ?‘?= đ?‘?đ?‘™/đ?‘?d² Where p = maximum load l= length of the specimen b= breadth

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d=depth VI. RESULTS AND DISCUSSIONS Slump The results of workability test were represented in Table 2. The results showed that as the percentage of self curing agent is increased the workability is found to increase due to the availability of additional moisture.

No 1 2 3 4 5 6 7 8

Table -2 Slump value of mixes Mix Slump value(mm) M1 (M40) 93 M2 (10% LECA) 95 M3 (20%LECA) 95 M4 (30%LECA) 97 M5 (20%LECA+1% PEG) 99 M6 (20%LECA+2% PEG) 101 M7 (20%LECA+3% PEG) 103 M8(20%LECA +4% PEG) 106

Compressive Strength Table 3 shows the compressive strengths of all mixes. From the Fig 1, shows that the use of self curing agents in concrete mixes improves the compressive strength of concrete under self-curing. Among the values examined the replacement of 20% lightweight expanded clay aggregate and 2 % polyethylene glycol represent the optimum doses. When compared to conventional concrete the replacement of fine aggregate with fine light weight expanded clay aggregate doesn’t improves the compressive strength of concrete. Incorporation of polyethylene glycol with expanded clay aggregate causes additional improvement in the compressive strength of concrete by about 2%.

No 1 2 3 4 5 6 7 8

Mix M1 (M40) M2 (10% LECA) M3 (20%LECA) M4 (30%LECA) M5 (20%LECA+1% PEG) M6 (20%LECA+2% PEG) M7 (20%LECA+3% PEG) M8(20%LECA +4% PEG)

Table - 3 7th and 28th day compressive strength 7th day compressive strength N/mm² 28th day compressive strength N/mm² 36.81 48.28 31.06 41.9 32.04 44.1 31.74 43.4 32.9 48.12 34.1 49.1 32.3 47.8 32 47.14

Fig. 1: 28th day compressive strength of concrete with light weight fine aggregate and polyethylene glycol

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An Experimental Investigation of Self-Curing Concrete Incorporated with Light Weight Fine Aggregate and Polyethylene Glycol (IJIRST/ Volume 3 / Issue 04/ 022)

Split Tensile Strength The results of the split tensile strength are represented in Table 4 and the graphical representation is shown in the Fig 2. The use of saturated light weight expanded clay aggregate and poly ethylene glycol leads to improvement of the tensile strength of the concrete. Compared to conventional concrete the incorporation of 20% saturated lightweight fine aggregate into concrete mixtures with 2% polyethylene glycol resulted strength increase by about 2.2 %.

No 1 2 3 4 5 6 7 8

Mix M1 (M40) M2 (10% LECA) M3 (20%LECA) M4 (30%LECA) M5 (20%LECA+1% PEG) M6 (20%LECA+2% PEG) M7 (20%LECA+3% PEG) M8(20%LECA +4% PEG)

Table - 4 7th and 28th day split tensile strength 7th Day Split Tensile Strength N/mm² 28th Day Split Tensile Strength N/mm² 2.63 3.3 2.55 2.89 2.56 3.24 2.58 3.2 2.64 3.32 2.7 3.371 2.62 3.3 2.57 3.25

Fig. 2: 28th day split tensile strength of concrete with light weight fine aggregate and polyethylene glycol

Flexural Strength The results of the flexural strength are represented in Table 5. It shows that, conventional concrete exhibited a higher flexural strength compared with concretes containing light weight expanded clay aggregate. Beyond that, Incorporation of polyethylene glycol with expanded clay aggregate increases the strength of self-cured concretes gradually and becomes higher than conventional concrete. Among the values examined the replacement of 20% lightweight expanded clay aggregate and 2 % polyethylene glycol represent the optimum doses. When compared to conventional concrete the concrete containing 20% lightweight expanded clay aggregate gave a lesser 28 days strength by about 3% and concrete with light weight expanded clay aggregate and poly ethylene glycol resulted strength increase by about 7%.

No 1 2 3 4 5 6 7 8

Mix M1 (M40) M2 (10% LECA) M3 (20%LECA) M4 (30%LECA) M5 (20%LECA+1% PEG) M6 (20%LECA+2% PEG) M7 (20%LECA+3% PEG) M8(20%LECA +4% PEG)

Table - 5 7th and 28th day flexural strength 7thday Flexural Tensile Strength N/Mm² 3.35 3.37 3.44 3.42 3.68 3.79 3.63 3.58

28thday Flexural Tensile Strength N/Mm² 4.45 4.27 4.36 4.3 4.69 4.784 4.6 4.576

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Fig. 3: 28th day flexural strength of concrete with light weight fine aggregate and polyethylene glycol

VII. COST ANALYSIS OF CONCRETE MIXES In construction, cost is a prime factor for determining the budget of a project and concrete shows a major role in it. A costbenefit analysis is used to evaluate the risks and rewards of projects under consideration. So concrete cost analysis is very effective in analyzing the overall budget of a construction work. The cost analysis of normal conventional concrete and optimum self-curing concrete are shown below. The total cost of normal conventional concrete (M40 mix)is rupees 7424.5/-. The total cost of Self curing concrete with 20% light weight fine aggregate 2% ploy ethylene glycol is rupees 11596.5/-. When compared to normal conventional concrete, the cost of optimum self-curing concrete is increased by about 56%.

Table - 6 Cost analysis of normal conventional concrete Material

Standard Market Rate Per Kg(In Rs)

Cement Coarse aggregate Fine aggregate Super plasticizers Water Total cost

9.8 .925 .625 100 12

Material Cement Coarse aggregate Fine aggregate Light weight expanded clay aggregate Polyethylene glycol Super plasticizers Water Total cost

M1 (M40) Weight (in kg for 1 m³ of concrete) 350 1140 896 7 140

Cost (in Rs) 3430 1054.5 560 700 1680 7424.5

Table - 7 Cost analysis of optimum self-curing concrete Standard Market Rate Per Kg(In Rs) M5 (20%LECA+2% PEG) Weight (in kg for 1 m³ of concrete) Cost (in Rs) 9.8 350 3430 .925 1140 1054.5 .625 716.8 448 20 179.2 3584 100 7 700 100 7 700 12 140 1680 11596.5

VIII. CONCLUSION  

An experimental investigation is carried out to study the influence of polyethylene glycol and light weight fine aggregate on self curing concrete A control mix of M40 was developed as per IS 10262 .2009 which is kept for normal curing. Self cured specimens were developed using self curing agents like light weight expanded clay aggregate and polyethylene glycol.Self-cured specimens were kept as such without the application of any external curing after their removal from moulds. The strength related tests

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An Experimental Investigation of Self-Curing Concrete Incorporated with Light Weight Fine Aggregate and Polyethylene Glycol (IJIRST/ Volume 3 / Issue 04/ 022)

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were carried out for hardened conventional concrete and self-cured concrete at the age of 7 days and 28 days to ascertain the strength related properties.

Based on the experimental studies conducted , following conclusions were arrived Workability

1) As the percentage of self curing agent increased ,the workability of concrete increased due to the availability of additional moisture Compressive Strength 1) It is observed that there is an increase in compressive strength by using light weight fine aggregate and poly ethylene glycol 2) The results shows an increase of 6.3% in 28days strength in mix3 (with 20% light weight aggregate) as compared to mix 6 (with 2% poly ethylene glycol and 20% light weight aggregate) 3) When compared to conventional concrete , compressive strength of self curing concrete increased by about 2% Split Tensile Strength and Flexural Strength 1) Split tensile strength and flexural strength both shows a slight increase when light weight fine aggregate and polyethylene glycol is added to it 2) When compared to conventional concrete the replacement of fine aggregate with poly ethylene glycol resulted split tensile strength increase by about 2.2 %.

3) When compared to conventional concrete the concrete containing 20% lightweight expanded clay aggregate only gave a lesser 28 days strength by about 3% and concrete with light weight expanded clay aggregate and poly ethylene glycol resulted flexural strength increase by about 7%.  Self curing concrete using lightweight aggregate and polyethylene glycol seems to be suitable for preparing concrete with good mechanical behavior.  By experimental program the optimum ratio of light weight fine aggregate and poly ethylene glycol for maximum strength was found to be 20% and 2%.

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