The Effect of Some Admixtures on Structural Behavior

Republic of Iraq Ministry of Higher Education &Scientific Research AL- Mustansiriya University College of Engineering Department of Civil Engineering

The Effect of Some Admixtures on Structural Behavior of Self-Compacting Recycled Aggregates A THESIS SUBMITTED TO THE CIVIL ENGINEERING DEPARTMENT COLLEGE OF ENGINEERING AL-MUSTANSIRIYA UNIVERSITY IN PARTIAL FULFILIMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCINCE IN CIVIL ENGINEERING

BY Lubna Mohammed Abd

Supervised by Prof. Dr. Mohammed Mosleh

Asst. Prof. Jamal Saeed

June 2015

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‫بسم اهلل الرحمن الرحيم‬

‫ٍ‬ ‫ل‬ ‫ك‬ ‫ق‬ ‫و‬ ‫ف‬ ‫و‬ ‫اء‬ ‫ش‬ ‫ن‬ ‫ن‬ ‫م‬ ‫ات‬ ‫ُ‬ ‫نَ ْرفَ ُع دَ َرَج َ ْ َ َ ُ َ َ ْ َ ِّ‬ ‫ِ‬ ‫ذي ِعْلٍم عَلِيم‬ ‫صدق اهلل العظيم‬

‫‪2‬‬

‫( سورة يوسف ‪)67:‬‬

Abstract Concrete wastes are generally delivered to the landfill sites for disposal. Due to increase charges of landfill and shortage of natural coarse aggregate (NA), recycled coarse aggregate (RA) (resulting from concrete wastes) is growing interest in Building Engineering. It is sustainable to use recycled construction materials to preserve the natural resources. In the present study, RA was used as full replacement of NA in some specimens of beams to produce normal concrete (NC) and self-leveling concrete (SCC). SCC(s) are highly fluid concrete that spread throughout congested reinforcement, fill each bend of the formwork and get consolidated under their weight. This thesis presents experimental and analytical investigation of both flexural and shears behavior (strength and deformation characteristics) of NC and SCC rectangular beams with constant longitudinal reinforcement ratio (ρ=0.008). The experimental work consists of casting and testing sixteen rectangular simply supported reinforced concrete beams as well as a series of tests carried out on construction materials, tests of fresh state for SCC and tests for control specimens to determine the mechanical properties of NC and SCC. Eight of the tested beams are made with NC and the others made from SCC. Four of each eight beams for flexural and the other four beams for shear behavior. The present research also includes studying the effect of the following main variables: transverse reinforcement (stirrups spacing, 50 mm and 100 mm), coarse aggregate (RA and NA) and steel fibers of (Vf = 0.5%) on the ultimate loads, cracking loads, deflection at mid span and quadrant of beams and mid span strain distribution of all NC and SCC beams. The crack patterns and modes of failure of all tested beams are presented and discussed.

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Experimental results have generally showed that ultimate loads (Pu) of beams mad with RA are approximately close to the results of beams made with NA and the percentages of this slight increase are: For NC the percentages of slight increase are (6.2% and 10.1%) for flexural and shear behavior respectively. For SCC the percentages of increase are (7.5% and 11.2%) for flexural and shear respectively. It can be used RA as full replacement in the future construction industry. While the increase in Pu values for specimens with steel fibers are: For NC (7.6% and 11.4%) for flexural and shear behavior respectively. For SCC (10.8% and 12.3%) for flexural and shear respectively. The results also show the following conclusions: 1. For NC and SCC: the maximum deflection of mixes made with RA is greater than the deflection of mixes with NA by 26.78% for flexural behavior. 2. For NC and SCC: the maximum deflection of mixes made with NA is greater than the deflection of mixes with RA by 39.59% for shear behavior. 3. The maximum deflection of mixes with steel fiber is greater than the mixes without steel fiber by the percentages below:  For NC the percentages are 38.55% for flexural and 31.70% for shear.  For SCC the percentages are 43.58% for flexural and 22.48% for shear.

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Chapter One Introduction

1.1 Recycled aggregate: Concretes are commonly using by way of an essential material in place of structure and substructure. It is an important versatile construction material, used in wide variety of situations. In Japan around 1990, about (500) milion tons from concrete are created, and about (35) milion tons from damaged concrete that presence produced each year. Essentially, the figure (1-1) may be an undervalue partially cause various concrete are unlawfully discarded and mixed with structure soil that is not preserved as unwanted. 95% of concrete are reused using force reprocessing and later recycled as low/quality way subbase. First-class level reusing, in which recycled coarse aggregate (RA) is prepared as of concrete, is not supported at current time. In forthcoming, a generous quantity of concrete for the building started throughout the cost-effective development of the 1960 and 1970 will influence its life end, and the generation from damaged concrete is projected to rapidly increase (Hirokazu, et al., 2005).

Fig. (1-1) Flow chart of concrete recycling system (Hirokazu, et al., 2005)

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A sustainable construction development has become a great concern and challenge faced by construction industry due to depleting natural resources and

increasing

construction

and

demolition waste

(Wai, et al., 2012).

Sustainable development was defined as “an cost-effective activity that is in agreement with the earth‟s eco-system”. In other words it characterizes the opportunity of conference the present requirements without stopping the future generations from conference their requirements (Valeria, et al., 2009). In the recent time due to significant increase in population and urbanization large amount of waste from construction and demolition are generated. Therefore majority of the developed/ developing countries are facing the problem of handling and disposal of such construction and demolition wastes. Considering this aspect, there has been a growing emphasis on the utilization of waste materials and byproducts in construction activities. Use of waste materials not only helps in getting them utilized but also has numerous indirect benefits such as savings in energy and protection of environment. Figure (1-2) shows recycled coarse aggregate (RA) used in this study which is highly angular and irregular in shape.

Fig.(1-2) Recycled Concrete Aggregate (Valeria, et al., 2009)

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1.2 Self-leveling concrete (SLC): Improvements of self/leveling concrete (SLC) are desired attainment in the building engineering to overawed difficulties related with cast and place concrete. Self/leveling concretes are not pretentious through the abilities of labors, profile and quantity of bars reinforcement or prearrangement of a construction, and refer to its great –flexibility and segregation resistance, it could be pumped elongated spaces (Bartos, 2000). The idea of self/leveling concrete is suggested in (1986) (Okamura, 1997), on the other hand the model is first established in (1988)-Japan. The developing of Self/leveling concrete in that period was to increase the permanency for construction (Ozawa et al., 1989). Self-leveling concretes are casting therefore no extra internal and external shaking is required for compaction. It is flowing similar to (honey) besides having a highly flat surface when placing. With respect to the configuration, self/leveling concrete contains the similar compounds like traditionally concrete, which were cement, aggregate, and water, with adding of different proportions of mineral and chemical additions. Generally, the chemical additions used are High Range Water Reducer (super-plasticizers) and the Viscosity Modifying Agents, while mineral additions that used as finer materials, in addition to cement. Self-leveling concrete is not a new concrete. Special uses such as under-water concreting has concrete needed which can be located without necessity for compaction (Bartos, 2000). In these conditions, shaking was simply difficult. Primary self/leveling concretes depend on higher fillings of mortar and the super-plasticizers became available for adding to the mixes of concrete. The mixes need specified and well controlled casting procedures to prevent segregation. The motive for development of self/leveling concrete was the problems of concrete structure durability that get up nearby (1983) in Japan. Because a regular decrease in numbers of labors in Japan's- construction industry, a

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alike decrease in the feature of construction industry took place. For example, the solution for the attainment of durability concrete constructions was the developing of self/leveling concrete, which can be compressed into each corner of the mold under its own weight.

1.3 Steel fibers: Fibers were used by Babylonians, who lived in ancient Iraq to reinforce brittle materials since ancient ages. It was realized that the addition of fiber vegetable matter to mud walls or bricks improves their strength, ductility and durability (Ali, et al, 1975). At present, many types of discrete fibers are available in various sizes, shapes and metal types depending on the manufacturing process. Mild steel, high tensile steel and stainless steel wires are produced by a series of hot and cold working methods. Circular steel fibers are made by cutting or chipping the chains, typically they are having diameter of 0.25 to 0.75mm. Rectangular steel fibers, having thickness of 0.15 to 0.41mm and width of 0.25 to 0.9mm. They are made by trimming sheets or flatting wires. Sickle shaped fibers are produced by means of melt extract process. Furthermore, to improve anchorage efficiency and bond strength with cement matrix (concrete), mechanical devices such as bends, crimps or flattened ends are used (Hannant, 1978). Due to variation in diameters and lengths of circular steel fibers, the "aspect ratio" of a fiber (i.e., fiber length divided by an equivalent fiber diameter) is the most convenient parameter by which a steel fiber can be described (Aliewi, 2006).

Steel fibers can: (ASTM A820, 2006)    

Increase strength of structures. Decrease requirements of steel reinforcement. Increase ductility. Decrease crack width, thus increase durability.

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 

Increase abrasion resistance. Increase freeze and thaw resistance.

1.3.1The influence of fibers on workability: In the fresh state, fibers affect the features of Self leveling concrete. They are needle in shape like particles which increase flow resistance and contribute for interior structure in fresh state. Reinforced concrete with steel fibers is stiffer than traditional concrete. Fibers need to be regularly distributed; crowding of fibers has to be avoided in order to optimize the performance of the single fibers. The influence of fibers on concrete workability is generally due to four causes: 1- Fibers shape is more extended than the aggregate which leads to the higher surface area at the same volume. 2- The structure of the granular skeleton is changed by stiff fibers while the space between concrete components is filled by flexible fibers. 3- The surface properties of fibers change from that of cement and aggregates, e.g. plastic fibers might be hydrophilic or hydrophobic. 4- Steel fibers often are deformed either with hooked ends or be wave-shaped to increase the anchorage between concrete components. There is a relation between fiber size and the aggregate which determines there distribution. It is recommended to choose fibers not shorter than the maximum size of aggregate in order to be effective in the hardened state of concrete, i.e usually, the used fiber length is (2-4) times that of the maximum size of aggregate(Johnston, 1996; Vandewalle, 1993).

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1.4 Objective of the study: The main objective of the present study is to investigate both flexural and shear behavior of recycled reinforced normal and self-leveling concrete beams with variables including steel fiber of Vf (0.5%), stirrups spacing of (50 and 100)mm, and finally using new type of coarse aggregate which is recycled from an old concrete barrier of maximum size (10mm).

1.5 Layout of the thesis: The thesis has been divided into five chapters and the brief description about each chapter is shown below:  Chapter One: is an introductory.  Chapter Two: gives a review of some researches of the recycled coarse aggregate (RA) besides the behavior and properties of Self-leveling concrete and Normal concrete.  Chapter Three: includes the properties of materials used and the experimental program.  Chapter Four: demonstrates the obtained results and presents the discussion of the experimental work.  Chapter Five: the conclusions and recommendations are presented.

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Chapter Two Literature Review 2.1 Introduction:Concrete is the principal building material that is widely used in all kinds of engineering civil workings like substructure, short and tall buildings, and installations of defense work, environs defense and local-domestic improvements. Concrete is a product that is manufactured, basically made of cement, aggregate, water and additions. Surrounded by these, aggregates such as coarse materials which are crushed stone or gravel form the major part and sand. Conventionally aggregates are readily available at cost-effective prices and of good qualities to costume all determinations. However, recently the perception of the continued extensive abstraction and use of natural resources aggregates is questioned at a worldwide level. This is chiefly because of natural aggregates quality depletion and the greater awareness of protection of environmental. Considering this, the obtainability of natural resources to the future had also been recognized (CSIR, 2000). Aggregate is the essential basic construction material affecting the properties of concrete and taking approximately 70% of volume of Portland cement concrete and over 90% of asphalt concrete, respectively. Such aggregate performs an important function when it is mixed with relatively expensive binders such as cement or bituminous materials, and enables economical construction. It also takes a role of maintaining the structure‟s stability against physical and chemical effects of cement ( Metha and Monterio, 2006). Today, there are severe lacks of natural resources in current situation. Concrete production and use are rapidly increased, which result in increased natural aggregate consumption as they are the largest component of concrete. Building materials are progressively featured by their sustainable features; a solution of these problems is recycling damaged concrete and producing a substitute aggregate for concrete structures. Recycled coarse aggregate (RA) lessens impact on landfills, reduces energy

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depletion and provides cost reserves. On the other hand, there is the beneficial use of RA in concrete building. Recycled aggregate is made of crumpled, arranged, inorganic subdivisions treated from material that is used in structure and destruction rubbles (Ravi, et. al, 2013). In fact, several governments through the world have recently introduced many processes directed at reducing the usage of chief aggregate and growing reuse and recycling, where it is technically, carefully, or ecologically suitable (D.N.Parekh and C.D. Modhera, 2011). Recycled aggregate (RA) is defined in (BS 8500-1, 2006) as the general word for aggregate result from the reusing of inorganic material before used in building. In adding to the natural aggregates significant quantities, recycled aggregate may contain contaminations such as wood, metal, asphalt and plastic. This need to be measured to suitable stages depending on the suggested recycled aggregate use. (The Concrete Society, BRE. 2005) recycled aggregates may be subdivided into three classes, depending on the brick content as shown in table (2-1): RCA (I) expresses the lowest class material. It can have rather little strength and great intensities of contaminations. It may contain up to 100% brick or block stone, and include concrete with high levels of contaminations. RCA (II) expresses a high quality material including crumpled concrete with up to 10% brick by weight but little levels of contaminations, less than 1.5% by weight of metals, wood, asphalt, plastics, and glass. In these cases, it can contain a quantity of natural aggregates.

RCA (III) expresses a material mixed with up to 50% brick and great heights of contaminations. This Instruction Note denotes only to type material RCA (II), and materials compatible to RCA (I) and (III) are not allowable.

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Table (2-1) Acceptable RCA Quality* Contaminant % by mass

BS 8500

The Concrete Society, BRE. 2005 (II)

*

Masonry

< 5%