EFFECTS OF HIGH WATER REDUCING ADMIXTURES ON CONCRETE CONTAINING QUARRY DUST AS THE SOLE FINE AGGREGATE
This work investigated the effects of high water reducing admixtures on some properties of concrete made with quarry dust as the sole fine aggregate. The properties of interest are the compressive strength, workability and the water absorption properties, while the high water reducing admixture used is the Conplast SP430. A total of 144 concrete cubes were cast using the standard 150mm moulds. With a common mix ratio of 1:2:3 (cement: fine aggregate: coarse aggregate), four unique Mixes (A, B, C and D) were produced. Crushed granite rock was employed as the coarse aggregate for Mixes A and B while gravel was used for C and D. Quarry dust with fineness modulus of 2.52 was used as the fine aggregate for all the mixes while river sand of fineness modulus of 2.93 was used for the control mix. Also, the water-cement ratio of mixes A and C was 0.45 while that of B and D was
0.5. For each mix, the percentage of superplasticiser (by mass of cement) was gradually increased from 0.8% to 3.0% (by weight of cement). The cubes were cured and tested for their 28 day compressive strength and water absorption. Test results show that addition of the superplasticiser increases the compressive strengths of mixes A, B and C up until about 1.4% admixture beyond which increasing superplasticiser content causes a decrease in compressive strength. However, for mix D, addition of the superplasticiser causes an initial decrease in compressive strength until 1.0% admixture beyond which a marginal increase in compressive strength is recorded. A maximum compressive strength of 30.07 N/mm2 was attained from mix A at 1.4% admixture while the least (15.57 N/mm2) was attained using mix D at 1.0% admixture. Water absorption of Quarry Dust Concrete (QDC) was found to increase with addition of superplasticisers up to 1.0% admixture for all mix types. However, there is drastic decline in water absorption between 1.0% - 2.0% admixture for Mixes A and B, and 1.0% - 1.5% admixtures for Mixes C and D. On the other hand, Workability, as given by slump tests, was found to be directly proportional to the amount of admixture added in all mixes. It is therefore recommended to include superplasticisers in QDC at percentages greater than 1.4% (by weight of cement) but less than 2% using granite as the preferred coarse aggregate to obtain optimum compressive strength, workability and durability properties.
TABLE OF CONTENTS
Cover page i
Table of contents vii
List of Figures xi
List of Tables xii
CHAPTER ONE: INTRODUCTION
Background of study 1
Statement of problem 2
Objectives of study 4
Significance of study 4
Scope of study 5
CHAPTER TWO: LITERATURE REVIEW
2.1 Concrete 6
2.1.1 Definition of concrete 6
2.1.2 Concrete as a building material 7
2.1.3 Advantages of using concrete 8
2.1.4 Limitations of using concrete 10
2.1.5 Materials used in making concrete 11
184.108.40.206 Cement 11
220.127.116.11 Aggregates 15
18.104.22.168 Water 21
22.214.171.124 Admixtures 23
2.2 Quarry dust 25
2.2.1 Physical properties of quarry dust 26
2.2.2 Chemical properties of quarry dust 26
2.2.3 Uses of quarry dust 27
2.2.4 Quarry dust as a fine aggregate in concrete 27
126.96.36.199 Quarry dust as a partial replacement for sand in concrete 28
188.8.131.52 Quarry dust as a substitute for sand in concrete 30
2.3 Structural properties of concrete 32
2.3.1 Workability, Consistency and Cohesiveness 32
2.3.2 Strength: Compressive and Flexural 33
2.3.3 Durability 35
CHAPTER THREE: MATERIALS AND METHODS
3.1 Materials 38
3.1.2 Quarry dust 38
3.1.3 Water 38
3.1.5 Coarse aggregates 39
3.1.5 Superplasticiser 39
3.2.1 Trial mix 39
3.2.2 Laboratory tests 40
184.108.40.206 Sieve analysis test 40
Specific gravity test
220.127.116.11 Bulk density test 41
18.104.22.168 Moisture content test 41
22.214.171.124 Compressive strength test 41
126.96.36.199 Water absorption test 41
Preparation of specimens
CHAPTER FOUR: RESULTS AND ANALYSIS
4.1 Results 43
4.1.1 Sieve analysis result 43
4.1.2 Specific gravity and Bulk density test results 47
4.1.3 Compressive strength test results 48
4.1.4 Water absorption test results 52
4.2 Analysis of results 55
4.2.1 Sieve analysis results 55
4.2.2 Specific gravity, Bulk density and Moisture content tests 55
4.2.3 Slump test results 56
4.2.4 Compressive strength results 56
4.2.4 Water absorption test results 57
CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions 58
5.2 Recommendations 59
LIST OF FIGURES
Fig 2.1: Different sizes of coarse aggregates 17
Fig 2.2: Profile of sand 17
Fig 4.1: Gradation curve for Quarry dust and River sand 45
Fig 4.2: Gradation curve for Granite and Gravel 46
Fig 4.3: Compressive strength of mixes A, B, C and D 51
Fig 4.4: Compressive strengths of conventional QDC and RSC at 0.5 w/c 52
Fig 4.5: Water absorption for Mixes A, B, C and D 54
Fig 4.6: Water absorption for control mixes with no admixture 54
LIST OF TABLES
Table 2.1: Typical constituents of Portland cement clinker 14
Table 2.2: Chemical constituents of Quarry Rock Dust 26
Table 4.1: Grain size distribution of quarry dust 43
Table 4.2: Grain size distribution of river sand 44
Table 4.3: Grain size distribution of crushed granite 44
Table 4.4: Grain size distribution of gravel 45
Table 4.5: Coefficients of uniformity and gradation for quarry dust and river sand 47 Table 4.6: Summary of specific gravity and bulk density of all aggregates 48
Table 4.7: Compressive strength test results for mixes A and B 49
Table 4.8: Compressive strength test results for mixes C and D 50
Table 4.9: Water absorption test results for Mixes A and B 53
Table 4.10: Water absorption test results for Mixes C and D 53
1 Background of study
Concrete is an artificial composite material that consists essentially of a binding medium within which are embedded particles or fragments of aggregates. It is basically a product of water, cement and aggregates, which when sufficiently hardened is used in carrying various loads (Neville and Brook, 1990). In hydraulic cement concrete, the binder is formed from a mixture of hydraulic cement and water. Aggregates on the other hand, are the granular materials, such as sand, gravel, crushed stone, crushed blast furnace slag, etc. More so, admixtures can be added to the concrete mix to enhance the properties of the fresh and/or hardened concrete. They are materials other than aggregates, cement, and water which are added to the concrete batch immediately before or during mixing.
Concrete, as a basic Civil Engineering material, is employed in virtually all types of construction work globally. The ability of concrete to withstand the action of water without serious deterioration makes it an ideal material for building structures to control, store, and transport water. According to Monteiro (2012), it is estimated that the present consumption of concrete in the world is of the order of 12 billion tons per year. Humans consume no material except water in such tremendous quantities.
As a result of the relevance and applications of concrete, a lot of research are been carried out to investigate means of improving the properties of concrete while making the material as economical as possible. Some of the properties of interest include: strength (compressive and flexural), workability, durability, consolidation, creep resistance, fire resistance etc. The outcome of previous researches with respect to
the above reason has always led to altering the concrete constituents, addition of several admixtures, full/partial replacement of cement and/or sand from the concrete mix, to achieve certain desired properties.
This piece of work is aimed at investigating the effects of adding high water reducing admixture to a concrete mix with which quarry dust is used instead of the conventional river sand as the fine aggregate.
1 Statement of problem
The demand for natural sand is quite high in developing countries owing to rapid infrastructural growth, thereby leading to supply scarcity. Therefore, construction industries of developing countries are under pressure to identify alternative materials to the conventional natural sand as the fine aggregate in concrete (Lohani et al, 2012). Consequently, common river sand is expensive due to excessive cost of transportation from natural sources (Ilangovana, 2008 and Chandana, 2013).
Again, large scale depletion of river sand sources creates environmental problems (Anupama et al, 2010). According to Subramanian and Kannan (2013), sand mining on either side of the rivers is one of the causes for environmental degradation and also a threat to biodiversity.
With the increased shortage of natural river sand for construction due to overexploitation from sources and the inability of the nature to replace it as well as increasing pressures from local bodies, to protect the environment, either replacement or substitution for sand is warranted during this decade and for future (Appukutty and Murugesan, 2009). Hence, there arises the need for engineering consideration of the
use of cheaper and locally available materials to meet desired need, enhance self efficiency, and lead to an overall reduction in construction cost for sustainable development (Onwuka et al, 2013). In such a situation, attempts have been made to replace river sand with quarry dust.
Works by Ilangovana (2008) and Sivakumar (2011), have shown that the quarry dust can be an economic alternative for river sand in concrete production. Findings by Sivakumar (2011), shows that quarry dust concrete (QDC) has a compressive strength 11.8% higher than the conventional river sand concrete (RSC) while Ilangovana concluded that QDC has a compressive strength 10-12% higher than that of RSC. Chandana (2013) also noted that quarry dust is known to increase the strength of concrete over concrete made with equal quantities of river sand, but, it causes a reduction in the workability of concrete. Thus, works by Anitha et al (2013) as well as Priyadharshini and Krishnamoorth (2014) recommended use of high water reducing admixtures to ameliorate the decline in workability of fresh concrete due to full replacement of river sand with quarry dust.
However, existing literatures by these researchers have failed to establish a relationship between the variations of compressive strength of QDC with the dosage of water reducing admixtures. Also, specifications on these admixtures by the manufacturers are solely based on the conventional RSC with no information whatsoever on the allowable dosage of superplasticisers to be used on QDC. Finally, not much work has been done to determine the effects of addition of high water reducing admixtures on the durability of QDC.
1 Objectives of study
The objectives of this study are:
I. To investigate the compressive strength, durability and workability properties of concrete made with quarry dust
II. To determine the effects of addition of high water reducing admixture on the workability, durability and compressive strength properties of Quarry Dust Concrete (QDC) made with crushed granite or gravel as coarse aggregate.
III. To compare the compressive strengths of super plasticised quarry dust concrete with that of conventional River Sand Concrete (RSC).
IV. To determine the allowable dosage of superplasticiser to be used in Quarry Dust Concrete considering compressive strength and durability requirements.
1 Significance of study
This study is significant/important for the following reasons:
I It will help civil engineers as well as every other person involved in the execution of any civil engineering job requiring the use of concrete, to have a better understanding of the engineering properties of concrete made with quarry dust and/or super-plasticisers.
II This work will also help to determine the extent to which a virtually waste material (quarry rock dust), can be utilised as a useful construction material.
III The recommendations of this research can go a long way to ease off the pressure on natural sand, whose increasing demand has led to acute shortage of the material as well as environmental degradation due to its extraction.
I The findings of this work will highly contribute to the already existing knowledge as well as enlighten researchers/engineers more on the benefits of integrating quarry dust and high water reducing admixtures in concrete mixes.
II The results of this work can encourage civil engineers and builders to consider replacing sand with quarry dust as fine aggregate for concrete production in sites close to quarry dust sources thereby reducing the overall cost of housing, as well as execution of civil engineering projects in such locations.
III The recommendations of this research will help further explain ways in which a highly workable concrete can be achieved without tampering with its desired compressive strength.
1 Scope of study
This project will be streamlined to the study of the effects of high water reducing admixtures on the workability, compressive strength and durability of quarry dust concrete made with granite and that made with gravel as coarse aggregate, using a single mix ratio of 1:2:3. Also, comparisons will be made to concrete made with river sand as the control..