PRODUCE CONCRETE STRENGTH

Transcription

1 OPTIMUM FINE AND COARSE AGGREGATES PROPORTION TO PRODUCE CONCRETE STRENGTH GOKOJOHIN Tesis Dikemukakan Kepada Fakulti Kejuruteraan, Uiversiti Malaysia Sarawak Sebagai Memenuhi Sebahagian Daripada Syarat Penganugerahan Sarjana Muda Kejuruteraan Dengan Kepujian (Kejuruteraan Awam) 2000

2 To my beloved father and mother. 1l

3 ACKNOWLEDGEMENTS First of all, I would like to thank God for giving me the strength to finish my study successfully. Thanks also goes to my supervisor, Haji Mohammad Ibrahim Safawi bin Haji Zain, for the useful guidance and supervision offered to me throughout the period of this study. A very special thanks to my family, especially to my father, Johin Gidob, my mother, Noip Rieh, and to my brothers and sister, for their love, patience, guidance and inspiration. Thanks also to all my friends, who has supported, inspired and guided me over the past five years of my study in UNIMAS. 111

4 ABSTRACT Nowadays, concrete has becoming more and more important in any construction works. There will be no progress in development without concrete. Almost all mega projects in this country involve the using of large amount of concrete. As demand for concrete increases, thus the price of cement (main component in concrete production) also increases. Because of this, more money need to be spent on concrete. Because of that, something needs to be done in order to cut down the expenditure on this material. In this final year project, quarry chip will be introduced as a new ingredient in making concrete. Quarry chip can be collected for free from a quarry since it is a waste product of rock crushing. Thus, there will be no problems arise due to shortage of this material. The project will be mainly based on experimental works. These experimental works were done in a laboratory where all the equipment and materials were kept. The purpose of this study is to have a look on the influence of quarry chip on concrete strength. Beside that, there will also test conducted on the fresh concrete such as slump test and flow table test. From observation, it is found that concrete mixed with quarry chip is more dry and stiff, compare to normal concrete Vvith the same design. By using different amount of quarry chip for each batch of concrete mixed, the concrete strength produced will vary. As the amount of quarry chip is increased, the concrete strength will also increase. Thus, this proves that quarry chip affects concrete strength in a good manner. The findings are really reliable, as there is no admixtures used in the mixing. Ifthis result is accepted by all, then it is said that a more economical way of producing concrete with high strength has been found. IV

5 ABSTRAK Kini, konkrit menjadi semakin penting di dalam kelja-kelja pembinaan untuk pembangunan. Hampir semua projek- projek mega eli negara ini melibatkan penggunaan konkrit yang banyak. Apabila perrnintaan terhadap konkrit meningkat, maka harga untuk bahan asas konkrit terutamanya simen pun turut meningkat. Oleh itu, sesuatu perlu dilakukan untuk menurunkan perbelanjaan penghasilan konkrit. Untuk projek tahun akhir, penggunaan butiran kuari sebagai satu bahan baru di dalam penghasilan konkrit akan diperkenalkan. Butiran kuari merupakan serpihan batu yang terhasil daripada proses pemecahan batu eli kuari. Ia biasanya diambil secara percuma dari kuari. Maka, ini dapat menjamin kelancaran projek kerana tidak akan timbul masalah kekurangan bahan tersebut. Projek ini lebih berasaskan kepada kelja-kelja amali yang dilakukan di dalam makmal, di mana semua bahan serta radas boleh didapati. Tujuan kajian ini adalah untuk melihat pengaruh butiran kuari terhadap kekuatan konkrit. Selain itu, beberapa ujian ke atas konkrit basah (baru dibancuh) akan turut dijalankan seperti ujian penurunan dan ujian aliran. Daripada pemerhatian kami, elidapati konkrit yang menggunakan butiran kuari adalah lebih kering serta likat. Ini adalah kerana butiran kuari menyerap banyak air. Dengan menggunakan jumlah butiran kuari yang berlainan bagi setiap bancuhan, didapati ada perubahan dari segi kekuatan konkrit yang terhasil. Semakin banyak butiran kuari digunakan, semakin tinggi kekuatan konkrit yang terhasil. Seandainya keputusan ini diterima umum, maka ini menunjukkan bahawa satu penemuan barn telah dicapai di dalam penghasijan konkrit yang mempunyai kekuatan yang tinggi secara lebih ekonomi. v

6 TABLE OF CONTENTS Page BORANG PENYERABAN TESIS UNIMAS PERAKUAN PENYELIA TITLE DEDICATION ACKNOWLEDGEMENTS ABSTRACT ABSTRAK TABLE OF CONTENT LIST OF FIGURES LIST OF TABLES LIST OF APPENDIX II III IV V VI x XII XlV CHAPTER 1 INTRODUCTION Introduction Objective Review of Chapters 2 vi

7 CHAPTER 2 LITERATURE REVIEW Concrete Aggregates 7 2.l.2 Cement Voids in Concrete Structure ofconcrete Transition Zone Transition Zone Strength Concrete Strength Shrinkage ofconcrete Compressive and Tensile Strength Factors Affecting Strength 13 a) Water/Cement Ratio 13 b) Aggregate 14 c) Type ofcement 19 d) Curing Conclusion 20 CHAPTER 3 METHODOLOGY Introduction Reading Materials Sieve Analysis Workability Test 26 vii

8 Slump Test Flow Table Test Compacting Factor Test Vebe Test Concrete Cube Test Trial Test Experimental Works Conclusion 46 CHAPTER 4 RESULTS AND ANALYSIS Introduction Trial Test Experimental Works Control Batch Second Batch Third Batch Fourth Batch Fineness Modulus Analysis Workability Analysis Compressive Strength Analysis Optimum Proportion 81 VUl

9 CHAPTER 5 CONCLUSION AND RECOMMENDATION 83 REFERENCES 85 APPENDIX 87 ix

10 LIST OF FIGURES Figure Page 2.1 Process ofconcrete mixing Concrete components by volume Cross section ofhardened concrete where cement 8 and water paste completely coats each aggregate particle and fills all spaces between them 2.4 Effect of water/cement ratio and age on concrete strength The influence ofcuring conditions on concrete strength Sieves stacked together according to their size Standard cone and funnel for slump test Measuring slump Types ofslump Typical flow table Typical compacting factor apparatus Typical vebe test apparatus N ewl y casted concrete cubes Concrete cubes under curing process Cracking patterns ofconcrete cube and cylinder Concrete cube ready for compression test Graph of sieve analysis (sand) for trial test 50 x

11 4.2 Graph of sieve analysis (quarry chip) for trial test Concrete in mixer machine Concrete poured into sampling tray Graph of sieve analysis (sand) for control batch (a) Graph ofsieve analysis (sand) for second batch 4.6(b) Graph of sieve analysis (quarry chip) for second batch Slump for second batch Graph ofcompressive strength with age for second batch (a) Graph ofsieve analysis (sand) for third batch. 4.9(b) Graph ofsieve analysis (quarry chip) for third batch Zero slump obtained Graph ofcompressive strength test with for third batch Graph ofsieve analysis (quarry chip) for fourth batch ( a) Graph ofworkability tests results (b) Graph ofresults for compacting factor test Compression test results 81 Xl

12 LIST OF TABLES Table Page 2.1 Various shapes for aggregate Typical surface textures of a selected group ofaggregates Standard Portland cements Sieve analysis ofa concrete fine aggregate Typical slump and compacting factor values for different 30 workability degree 3.3 The mix proportion for the trial mix Mix design ofconcrete for experimental works Amount of materials for each batch Sieve analysis on sand for trial test Sieve analysis on quarry chip for trial test Results ofcompressive strength test for trial test Workability tests results for control batch Results ofcompression test for control batch Sieve analysis on sand for control batch (a) Sieve analysis on sand for second batch (b) Sieve analysis on quarry chip for second batch Workability tests results for second batch Results of compression test for second batch 64 Xll

13 4.1O(a) Sieve analysis on sand for third batch O(b) Sieve analysis on quarry chip for third batch Workability tests results for third batch Results ofcompression test for third batch Sieve analysis on quarry chip for fourth batch Workability tests results for fourth batch Results ofcompression test for fourth batch Values offineness modulus for comparison 77 Xlll

14 LIST OF APPENDIX Appendix Page A Project planning 87 XIV

15 CHAPTER 1 INTRODUCTION 1.1 Introduction Concrete is one of the most important construction materials other than steel. There are many types of structures that requires concrete in order to construct it, such as multistory building, railroad, warehouses and darns. It is very dominant in a developing country such as our country, Malaysia. Examples of big project in Malaysia that requires large amount of concrete are Bakun Hydroelectric Dam and Petronas Twin Towers. Concrete can be divided into several types, such as self-compacted concrete, high strength concrete (HSC) and normal strength concrete (NSC). The first two examples mentioned are under high-performance concrete (HPC). High performance concrete is a type of concrete that has special features. It can do works that can't be achieved by using conventional concrete. Beside that, its application can contribute in reducing construction period as it saves time. Normal strength concrete is the type of concrete that has 28-day compressive strength below than the one that could be achieved by high strength concrete, which is below 50 Mpa. Examples ofnsc are concrete of Grade 30 and Grade 40. NSC is usually produced in a normal way without addition of admixtures such as silica fume and superplasticizers.

16 In this project, a study on how to increase concrete strength is going to be conducted by introducing quarry chip in the concrete mixture. This study is made possible due to the availability of quarry chip, which can be collected from a nearby quarry without any payment. 1.2 Objective The objectives of this project are shown below: 1) To introduce quarry chip, a waste product in a quarry, as a new ingredient in concrete preparation. 2) To study the effects of using quarry chip in concrete production on the strength and workability of concrete. This quarry chip is combined together with sand to produce fine aggregates. 3) To find relationship between coarse to powder ratio and strength ofconcrete. 4) To give better understanding on concrete production process, such as selection of materials, producing mix design for concrete, tests on fresh and hardened concrete. 1.3 Review of Chapters In order to have a more organized way to represent the data and information gathered throughout the study, they were divided into several chapters. Each chapter contains different information and data. For the purpose ofthis study, there will be 5 chapters overall 2

17 The first chapter, which is the introduction chapter, provides brief idea to the readers on the type of study that is going to be conducted and also to explain the objective of the project. In Chapter 2, there will be information gathered based on the previous studies that were done by other people. This information is very useful throughout the study, especially the one on concrete strength. Most of the content in this chapter is based on books and journals. The methodology of the study will be discussed more in Chapter 3. Here, details on types of test and material used will be shown. The details will give brief idea on how the study is conducted in order to get results. In Chapter 4, the results of the tests conducted are shown here. The analysis for the data gathered would also be part of this chapter. For the final chapter, which is Chapter 5, conclusions on the achievement of the project will be featured here. This will include the recommendations, which is important for future studies. 3

18 CHAPTER 2 LITERATURE REVIEW 2.1 Concrete Concrete is mainly a mixture of two main components that are aggregates and paste. Here, aggregates consist of coarse aggregate and fine aggregate while paste is a combination of cement and water. In concrete, paste plays a major role in binding aggregates into rocklike mass as the paste hardens. The hardening is due to the chemical reaction between cement and water. The process of concrete mixing is easy to understand in the form of diagram, as shown in Figure 2.1. The cement paste component functions in the first instance to coat and "lubricate" the individual grains of sand, thereby imparting "workability" to the mortar phase. In turn, the mortar serves to lubricate the coarse aggregate particles and so give workability to the fresh concrete. The quantities of cement paste and mortar necessary to achieve appropriate levels of workability will depend on the amounts of sand and coarse aggregate present in the concrete, on the associated "gradinglf of constituent particle sizes, and on the actual level of workability required for the job. If there is insufficient mortar or cement paste the mix will tend to be "harsh H and unworkable. Conversely, too much mortar or cement paste will promote the likelihood of Hsegregation" effects whereby the coarser aggregate fractions tend to separate out from the remainder of the mix. 4

19 Portland Cement I + I B I." Cement Paste + Fine Aggregate (Sand) l I ~r I Mortar I + I I Coarse Aggregate I." Concrete! I Fig. 2.1 Process ofconcrete mixing. Concrete does not set and harden through a physical drying-out process. Setting and hardening is due instead to a series of chemical reactions between the Portland cement and water present in the mix. This is due to a process called hydration where the original cement paste phase is transformed into a sort of "mineral glue" which acts to bind the sand and coarse aggregate fractions together. 5

20 In concrete, aggregates make up 60% to 75% of total volume of concrete. About 25% to 40% of concrete volume consists of cement paste. Voids make up about 2% to 8% of total volume. The above information can be summarized in Figure 2.2 below voids (2% - 8%) ~~----~~----~ : -: -:. :- :- :- : -: :- :- :-...t-.-.~.-:+--- Cement Paste (23% - 40%) Aggregates (60% - 75%) Fig. 2.2 Concrete components by volume. From the total volume of cement paste above, about 25% to 40% of its volume consists of cement while water represents about 60% to 75%. For aggregates, about 30% to 45% of its volume are fine aggregate while coarse aggregate represents about 55% to 70%. The above information is based on conventional concrete. 6

21 2.1.1 Aggregates Aggregates are considered as major component in concrete. It is usually divided into two types, which are fine aggregate and coarse aggregate. Coarse aggregate is usually defined as materials or aggregates that pass a 100 mm square opening sieve and are retained on the NO.4 (4.75 mm) sieve. Types of aggregates are usually gravel or crushed stone. Gravel is produced due to natural disintegration and rock abrasion while crushed stone is the product of rocks, boulders or large cobblestones crushed using artificial way. Fine aggregate is the materials that pass the No.4 (4.75 mm) sieve. It is predominantly retained on the No. 200 (75 J.1m) sieve. Sand is the most commonly used fine aggregate in mixing concrete. Sand is the product of natural disintegration of rock Cement Cement is the most important material in concrete production. Without it,. aggregates would not bind together to produce a hard mass. Portland cement is the most widely used cement. It is also known as hydraulic cement. This means that Portland cement will harden when it is mixed with water in a proper proportion. The term "cement" used throughout this text refers to Portland cement unless otherwise stated. 7

22 2.1.3 Voids In Con.crete Voids in aggregates, represent amount of air space between aggregates or space between particles. It is generally expressed as a percent of gross volume that is solid volume plus voids volume. For example, 40% void means 40% of aggregate volume are filled with air while solids (aggregates) occupy the remaining 60%. This is done by assuming that the aggregates are in a dry condition. In concrete mixes, voids content in the mix should be low as possible. This is because voids can decrease strength. If concrete has high content of voids, this will cause concrete to crack easily when load is applied. When concrete is made, cement paste will fill voids in fine aggregate, thus producing mortar. The mortar produced win then fins the voids in coarse aggregate, thus producing concrete. To have a good mixture of concrete, about 75% of concrete volume should be occupied by mixed aggregates. The remaining volume should consists of cement paste and air voids. Fig. 2.3 Cross section of hardened concrete where cement and water paste completely coats each aggregate particle and fills all spaces between them. s

23 2.2 Structure of Concrete Concrete structure can be divided into three phases. They are the hydrated cement paste, transition zone and coarse aggregate. Transition zone and hydrated cement paste are the nvo components that are influenced by environment humidity, time and temperature. Transition zone is the weakest compare to the other two components, as it exists as thin shell. Thus, more attention should be put on this part in order to improve strength Transition Zone Transition zone is a small area surrounding coarse aggregate (typically 10 to 50 J..Ull wide around the particles of coarse aggregate). In freshly compacted concrete, it consists of water film. Then, it will form ettringite and calcium hydroxide. For concrete with high water/cement ratio, these nvo crystalline products consist of relatively larger crystals. The transition zone between hydrated cement paste and coarse aggregate influence more on the behavior of concrete. This transition zone is formed due to water content. For an ordinary concrete mixture (without admixtures present), the water content is quite enough to cause 'bleeding', which is a form of segregation. For this situation, water in the concrete mixture tends to move upwards, as water is the lightest component in fresh concrete mixture. For the heavier solids, it tends to settle down. Only part of the bleed-water reaches the concrete surface where it may be lost by eva}x)ration. Owing to the wall effect, a large amount of bleed water gets blocked at the aggregate surfaces, especially at the underside ofcoarse aggregate particles. 9

24 2.2.2 Transition Zone Strength The attraction caused by van der Waals force plays a main role in the adhesion of hydration product and the aggregate particle. Thus, the transition zone strength depends on volume and size of voids present. The larger the size of calcium hydroxide crystals, the less it posses adhesion capacity. This is due to lower surface area and weak van der Waals attraction forces. For ordinary concrete, the transition zone at early ages is very weak. It microcracks even under the influence of stresses induced by environmental temperature and humidity changes. The presence of microcracks contributes mainly to its poor strength. The amount of microcracks depends on various parameters, which are aggregate size and grading, cement content, humidity, curing condition and also water/cement ratio. Segregation proneness in compacting will increase as the aggregate is poorly graded. Thus. causing thick water films to form below it. The thickness ofthis water film depends on the aggregate size. The larger the size, the thicker the water film. This will cause the transition zone to be susceptible to cracking when subjected to the influence of tensile stresses induced by movements between the aggregate and the hydrated cement paste which may arise from the drying or the cooling of concrete. This means that concrete already have microcracks even before a structure is subjected to load. 10