Variation of Flexural strength and water absorption in concrete made by Two-stage mixing approach(TS

IJSTE窶的nternational Journal of Science Technology & Engineering| Vol. 1, Issue 1, July 2014| ISSN(online): 2349-784X

Variation of Flexural Strength and Water Absorption in Concrete Made by Two-Stage Mixing Approach(TSMA) using Fly Ash and Nominal Concrete Made by Normal Mixing Approach(NMA) Sandeep Uniyal Final year M.Tech Student Department of Civil Engineering MMEC Ambala, Haryana, India

Dr. Vanita Aggarwal Professor Department of Civil Engineering MMEC Ambala, Haryana, India

Abstract Since sources of good quality aggregates are fast depleting, the concrete industry in India needs to prepare itself to use locally available aggregates. The use of local materials helps to reduce the efforts to transport material from far away places to site. Thus, from sustainability point of view, the emphasis should be placed on using locally-available aggregates, even if there are small deficiencies in their quality. It has been demonstrated manier times that desired properties of concrete can be obtained by intelligent blending of available aggregates with crushed sand, inert fillers, supplementary cementitious materials and chemical admixtures. The concrete in this paper is produced by utilizing alternative and recycled waste materials such as fly ash and recycled concrete aggregates to reduce energy consumption, environmental impact, and usage of natural resources. In the current papper we will discuss two parameters on which the concrete made by the two-stage mixing approach(TSMA) has been tested and those parameters are flexural stremgth and water absorption. These parametric properties are compared with the conventional concrete with the variation of percentage of recycled coarse aggregates(RCA) and fly ash.

Keywords: concrete, recycled aggregates, cement, flexural strength, Water absorption, RCA, fly ash, Two-stage mixing approach(TSMA), Normal mixing approach(NMA) _________________________________________________________________________________________________________ I.

INTRODUCTION

Concrete is a crucially important construction material, vital to every economy in the world. Much of the economic development of the last fifteen years or so has been seen by increases in the use of concrete, particularly in countries like China and India.

Sustainability is accounted for in concrete in terms of emissions of greenhouse gases from cement works and other key parts of the industry, as well as local air pollution, waste, and health and safety issues. M C Limbachiya [6], indicating the inferiority of recycled aggregate concrete, reported that often this concrete is used in as road construction, backfill for retaining walls, low grade concrete production, drainage and brick work and block work for low cost housing. Concrete is a building material that is not only strong and durable but can also be produced in ways that are easily moulded and environmentally friendly. With sustainable concrete infrastructure and structures, the concrete industry can develop a sustainable future for generations yet to come. Buildings that are constructed to be both environmentally friendly and durable have higher productivity because the buildings generally lead to better air quality and therefore higher productivity. Advantage of sustainable concrete is buildings constructed with concrete that have reduced energy costs and maintenance. Concrete highways reduce the fuel needed for heavily loaded trucks. The cement and concrete industries can make substantial contributions to sustainable development by creating and adopting technologies that can reduce the emissions of greenhouse gases. The production of Portland cement, an essential constituent of concrete, leads to the release of significant amount of a greenhouse gas, CO 2. The production of one tonne of Portland cement produces about one tonne of CO2 and other green house gases. The environmental issues associated with green house gases and natural resources issues will play a leading role in the sustainable development of the concrete and cement industry during this century. For example, as the supply of limestone decreases it will become more difficult to produce adequate amounts of Portland cement for construction. Once there is no more limestone, and thus no Portland cement. Therefore, it is necessary to find sustainable solutions for concrete construction in future.

II. LITERATURE REVIEW Tam V.W.Y et al(2005)[11], proposed a modified mixing technique of concrete. The scientists concluded that the poor quality of RAC was a result of higher porosity and higher water absorption. Weaker interfacial transition zone (ITZ) between Recycled Aggregates(RA) and cement mortar hampers the application of RAC in higher grade applications. In this study, the TSMA proposes All rights reserved by www.ijste.org

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Variation of Flexural Strength and Water Absorption in Concrete Made by Two-Stage Mixing Approach(TSMA) using Fly Ash and Nominal Concrete Made by Normal Mixing Approach(NMA) (IJSTE/ Volume 01/ Issue 01 / 003)

to strengthen the weakness of RAC, which is located at the (ITZ) of the RA. The TSMA gives a way for the cement slurry to gel up with RA, providing a stronger ITZ by filling up the cracks and pores within RA. From the laboratory experiments, it can be seen that the compressive strength is improved. This TSMA can provide an effective method for enhancing the compressive strength and other properties of RAC, and thus, this approach creates a wider scope of RAC applications.

According to Yong P.C and Teo D.C.L(2009)[14], the Recycled Aggregate Concrete(RAC) can achieve high compressive strength, split tensile strength as well as flexural strength. RAC has higher 28-day compressive strength and higher 28-day split tensile strength compared to natural concrete whereas the 28-day flexural strength of RAC is lower than that of natural concrete.

Recycled Coarse Aggregate(RCA) shows good potential as coarse aggregate for the production of new concrete.

Patil S.P et al(2013)[8], have concluded in their paper on Recycled Coarse Aggregates that the compressive strength of concrete containing 50% RCA has strength in close proximity to that of normal concrete. Tensile splitting test shows that concrete has good tensile strength when replace upto 25-50%. The strength of concrete is high during initial stages but gradually reduces during later stages. Water absorption of RCA is higher than that of natural aggregate. Thus the usage of RCA in concrete mixture is found to have strength in close proximity to that of natural aggregate and can be used effectively as a full value component of new concrete.

Vyas C.M and Pitroda J.K(2013)[12], have worked on the combination of RCA and Fly Ash and have concluded that the applications of recycled coarse aggregate in the construction area are very wide. The main aim of using recycled coarse aggregate is to reduce the use of natural resources. Another improving method is using the Fly ash in the recycled coarse aggregate mixing.

Application of fly ash in the recycled coarse aggregate concrete can improve the durability of the recycled coarse aggregate concrete.

The use of fly ash could improve the strength characteristic of recycled coarse aggregate concrete.

According to Kamala R. and Rao B. K(2012)[3], the results obtain shows that there is decrement in the Flexural strength of beams for 56 days. The maximum 28 days tensile strength was obtained with 40% replacement of crushed tile aggregates and the strength is more at 28 days of curing compared to the NCC mix.

Katz A.(2003)[4], by experimental analysis on the Properties of concrete made with recycled aggregate from partially hydrated old concrete and two different types of cements showed that the difference in the quality of the two types of cement was clearly seen and the ratios of the flexural and the splitting strengths to the compressive strength values were within a reasonable range. The higher values of the flexural and splitting strengths relative to the predicted ones were clearly seen especially for the OPC recycled concrete.

Smaller values than the predicted ones are expected for lightweight aggregate concrete.

The analysis done by Puri N., Kumar B. and Tyagi H.(2013)[9], shows a significant increase in flexural strength was observed when natural aggregates were replaced with recycled concrete aggregates. However a decrease in flexural strength was observed when natural aggregates were replaced with PVC aggregates. Very low flexural strength has been shown by concrete in which fine aggregates were replaced by pulverized leather waste.

As per the experimental work done by Deshpande N.K, Kulkarni S.S and Pachpande H.(2012)[2], For M25 grade concrete the flexural strength of nominal M25 grade concrete is 3.5N/mm2. Conventional materials satisfies the requirement with 3.76N/mm2.

Split tensile test and Flexural strength both are tests for tensile strength of concrete. Concrete made by using recycled aggregates showed slightly lower values of tensile strength as well as flexural strength, hence the loss in tensile strength should be considered while designing members using recycled aggregate concrete.

According to Yadav S R and Pathak S R(2009)[13], Aggregate in the size of 4 to 8mm is found to have the highest amount of adhered mortar, thus implying that the size of aggregates will have tremendous effect on the water absorption and strength of concrete. The changes in mechanical properties of recycled concrete aggregateare attributed to the patches of cement mortar present after crushing which increases the water absorption. depending upon the size of the aggregates and the water absorption lies between 3–10 percent while for natural aggregates the value is less than 5 percent.

According to Kenai S., Debieb F. and Azzouz L.(2005)[5],The results of their experiments indicate that it is possible to produce good quality concrete using recycled aggregates. Recycled aggregates have higher water absorption and a lower density because of the adhering old mortar. water absorption and water permeability are increased for recycled aggregate concrete, and hence the level of substitution has to be limited and precautions should be taken to avoid durability problems in some structural elements in practice.

Sharma S, Sharma S K and Chakraborty K.(2014)[10], elaborated that with increasing percentage of waste concrete aggregates, water absorption increases. This can be seen in their experimental analysis.

According to Malešev M., Radonjanin V. and Marinković S.(2010)[7], the water absorption of concrete depends on the quantity of recycled aggregate. The amount of absorbed water is proportionally increased with increasing recycled aggregate content. Water absorption depends on the porosity of cement matrix in the new concrete and porosity of cement matrix of the recycled concrete: if recycled aggregate is produced from low porosity waste concrete, water absorption of the new concrete depends on the achieved structure of the new cement matrix.

III. MATERIALS USED A. Cement Ordinary Portland cement of 43 grade satisfying the requirements of IS: 8112-1989[12]. The specific gravity of cement was found to be 3.005.

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Variation of Flexural Strength and Water Absorption in Concrete Made by Two-Stage Mixing Approach(TSMA) using Fly Ash and Nominal Concrete Made by Normal Mixing Approach(NMA) (IJSTE/ Volume 01/ Issue 01 / 003)

B. Fine aggregates The sand generally collected from haryana. Sand is the main component grading zone-I of IS: 383-1978[11] was used with specific gravity of 2.62 and water absorption of 1 % at 24 hours.

C. Coarse aggregates Mechanically crushed stone from a quarry situated in haryana with 20 mm maximum size, satisfying to IS: 383-1978[11] was used.

The specific gravity was found to be 2.63 and water absorption is 0.5 % at 24 hours.

D. Recycled coarse aggregates Aggregates obtained by the processing of construction and demolition waste are known as recycled aggregates.

RCA for the experimental analysis was procured from the C & D waste plant in Delhi which is in collaboration with Municipal Corporation Of Delhi.

E. Fly Ash Fly ash is used as partial replacement of cement which replaces 10% of total cementitious material in all the cases of the experiments.

Class F fly ash is used from haryana having specific gravity as 2.4 and satisfying IS 3812-1999[13].

1) Methodology NMA follows the following steps:  First, coarse and fine aggregate are mixed.  Second, water and cementitious materials are added and mixed.

However, TSMA follows different steps:  First, coarse and fine aggregates are mixed for 60 seconds and then half of water for the specimen is added and mixed for another 60 seconds.  Second, cementitious material is added and mixed for 30 seconds.  Thirdly, the rest of water is added and mixed for 120 seconds.

The specific procedure of TSMA creates a thin layer of cement slurry on the surface of RA which is expected to get into the porous old mortar and fill the old cracks and voids.

Using recycled concrete as the base material for roadways reduces the pollution involved in trucking material.

IV. EXPERIMENTAL OBSERVATIONS Following table shows the experimental observations of the test samples made from TSMA and nominal mix by NMA. (1) M-25(10-25) signifies the specimen mix having 10% fly ash and 25% RCA content.

(2) M-25(10-50) signifies the specimen mix having 10% fly ash and 50% RCA content.

(3) M-25(10-25) signifies the specimen mix having 10% fly ash and 75% RCA content.

(4) M-25(10-25) signifies the specimen mix having 10% fly ash and 100% RCA content.

S. No. 1 2 3 4 5

Table – 1 Compressive strength COMPRESSIVE STRENGTH 28th day Specimen 7th day (MPa) (MPa) Nominal M-25 17.84 31.7 M-25(10-25) 18.81 33.77 M-25(10-50) 20.21 32.88 M-25(10-75) 22.51 32.88 M-25(10-100) 15.10 27.99

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Variation of Flexural Strength and Water Absorption in Concrete Made by Two-Stage Mixing Approach(TSMA) using Fly Ash and Nominal Concrete Made by Normal Mixing Approach(NMA) (IJSTE/ Volume 01/ Issue 01 / 003)

Chart - 1 7th day Flexural Strength

7th Day Strength (in MPa)

7th day strength 6.5 6 5.5 5 4.5

7th day strength Specimen Mix Chart - 2 28th day Flexural strength

28th day strength

M-25…

M-25…

M-25…

M-25…

7 6.5 6 5.5 5

Nomin…

28th Day Strength(in MPa)

28th day strength

Specimen Mix

Strength (in MPa)

Graph Flexural strength(both 7 and 28 day)

8 6 4 2 0

7th day strength 28th day strength Specimen Mix Table – 2

S. No.

Specimen

1 Nominal M-25 2 M-25 (10-25) 3 M-25 (10-50) 4 M-25 (10-75) 5 M-25 (10-100) These observations can be depicted in graphical form as follows:

Water Absorption (in %) 2.82 3.01 3.41 3.89 4.81

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Variation of Flexural Strength and Water Absorption in Concrete Made by Two-Stage Mixing Approach(TSMA) using Fly Ash and Nominal Concrete Made by Normal Mixing Approach(NMA) (IJSTE/ Volume 01/ Issue 01 / 003)

Chart – 3 Water Absorption

M-25…

M-25…

M-25…

M-25…

6 4 2 0

Nomin…

Water Absorption (in %)

Water Absorpton(%)

Water Absorpton( %)

Specimen Mix

V. RESULTS AND DISCUSSIONS A. Results The above experimental analysis provides us with the following results: (1) The compressive strength of M-25 grade nominal concrete made by NMA gives 7 day and 28 day strengths as 17.84 MPa and 31.7 MPa respectively. The same mix shows flexural strength at 7 day and 28 day as 6.25 MPa and 6.375 MPa respectively.

(2) Using TSMA, addition of 10% fly ash, the specimen made by 25% RCA gives compressive strength at 7 day and 28 day as 18.81 MPa and 33.77 MPa respectively The same mix shows flexural strength at 7 day and 28 day as 6.375 MPa and 6.75 MPa respectively (3) Using TSMA, addition of 10% fly ash, the specimen made by 50% RCA gives 7 day and 28 day strengths as 20.21 MPa and 32.88 MPa respectively. The same mix shows flexural strength at 7 day and 28 day as 6.375 MPa and 6.50 MPa respectively (4) Using TSMA, addition of 10% fly ash, the specimen made by 75% RCA gives 7 day and 28 day strengths as 22.51 MPa and 32.88 MPa respectively. The same mix shows flexural strength at 7 day and 28 day as 6.0 MPa and 6.125 MPa respectively (5) Using TSMA, addition of 10% fly ash, the specimen made by 100% RCA gives 7 day and 28 day strengths as 17.10 MPa and 27.99 MPa respectively. The same mix shows flexural strength at 7 day and 28 day as 5.375 MPa and 5.75 MPa respectively.

B. Discussion The specimen mix M-25(10-25) shows an increase of 5.46% in 7 day and 6.52% in 28 day compressive strength and shows an increase of 2% in 7 day and 5.8% in 28 day flexural strength, however, specimen mix M-25(10-50) shows an increase of 13.32% in 7 day compressive strength and 3.72% in 28 day strength and shows an increase of 2% in 7 day and 4.3% in 28 day flexural strength with respect to nominal mix specimen.

The specimen mix M-25(10-75) shows an increase of 26.17% in 7 day and 3.72% in 28 day compressive strength and shows a decrease of 4% in 7 day and 3.9% in 28 day flexural strength, whereas, specimen mix M-25(10-100) shows decrease of 15.10% in 7 day and 11.70% in 28 day compressive strength and shows a decrease of 14% in 7 day and 9.8% in 28 day flexural strength with respect to nominal mix specimen.

From 28 day strength point of view, specimen M-25(10-25) shows optimum increase in compressive strength i.e 6.52% and flexural strength i.e 5.8% with respect to nominal mix specimen.

VI. CONCLUSIONS Samples after casting were tested and gave the above results depicted by chart 1,2,3 and 4. The outcome of this work reveals that concrete made by replacement of 25% and 50% RCA and addition of 10% fly ash using TSMA gives more compressive as well as flexural strength for both 7 day and 28 day strength than the referred nominal concrete specimen made by NMA however on using 75% RCA the concrete shows increase in compressive strength but a decrease in flexyral strength. On using 100% RCA, the concrete shows decrease in compressive as well as flexural strength strength than the Nominal concrete.

Maximum 28 day compressive and flexural strength is obtained by concrete made by using TSMA involving replacement of 25% RCA and addition of 10% fly ash. This concrete so made will be strong as well as cost effective and can be used in any constructional works in place of normal concrete.

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Variation of Flexural Strength and Water Absorption in Concrete Made by Two-Stage Mixing Approach(TSMA) using Fly Ash and Nominal Concrete Made by Normal Mixing Approach(NMA) (IJSTE/ Volume 01/ Issue 01 / 003)

ACKNOWLEDGEMENT I want to express my gratitude towards the people who have helped me in various ways to perform this piece of research paper. First of all I would like to express my gratitude to my guide Dr. Vanita Aggarwal, who graciously gave me the opportunity to work under her supervision. I sincerely thank her, as working under her was a memorable experience.. Her perfect guidance and immense faith in my capabilities made me face difficulties during the progress of this paper. My whole hearted thanks to my Lovely parents and and my friends for their constatnt love and support throughout. And above all I thank the Almighty for showering all His grace upon me all these days, without which this paper and my project would not be in existence.

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Kamala R. and Rao B. K(2012). ‘Reuse of Solid Waste from Building Demolition for the Replacement of Natural Aggregates’, International Journal of Engineering and Advanced Technology (IJEAT), Vol. 2(1),74-76.

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IS CODES: IS : 383-1978 Specification for coarse and fine aggregate from natural sources of concrete.

IS: 8112-1989 43 grade Ordinary Portland Cement- Specifications.

IS: 3812-1999 Specification for Fly ash to use as pozzolana and admixture.

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