The bond strength of concrete-to-concrete interfaces, of reinforced concrete (RC) members with parts cast at different ages, is highly influenced by the curing conditions. 79-88. When we required a certain grade of concrete, firstly we select an appropriate water-cement ratio to proceed with the mix design. Further, we can reduce the cement content by adding a superplasticizer to keep the required strength. Factors Affecting Bond between New and Old Concrete. With time and age, the strength of the cement concrete reduces since it will set up by absorbing moisture from the atmosphere. Generally, 80% of the volume concrete is filled by aggregates. Different strengths can be achieved for different mix proportions. Since the particle size greatly affects the compressive strenth, they shall be checked regularly. The relationship between the strength and the gel-space ratio is independent of the age. There are two types of aggregates namely coarse aggregate and fine aggregate. The strength and the durability of the concrete depend to a great extend on the amount of water used. " The gel-space ratio can be defined as the ratio of the volume of the hydrated cement paste to the sum of the volumes of the hydrated cement and the capillary pores. As per 10262:2016, the water-cement ratio to give the maximum strength is 0.4 and any value beyond than that is unacceptable. Since aggregate is generally much stronger than cement paste the strength of the aggregate is less important. The strength of the concrete increases with the cement content and decreases with air and water content. For any given condition of test the strength of the workable concrete mix is dependent only on the water cement ratio". HoPE, AND A. K. C. IP This investigation examined variables influencing the 28-day com­ pressive strength and SO-cycle salt scaling loss of concretes made with 18 Type … It is the most important factor for gaining the strength of concrete. The water-cement ratio is one of the most important factors affecting strength of concrete. 1. Factors Affecting Bond between Repairing Con-crete and Concrete Substrate Magda I. Mousa Dr.magdashehata@yahoo.com, Structural Engineering Department, Faculty of Eng. Water/Cement ratio can be increased by increasing the water content or by reducing the cement content. Concrete strength is affected by many factors, such as quality of raw materials, water/cement ratio, coarse/fine aggregate ratio, age of concrete, compaction of concrete, temperature, relative humidity and curing of concrete. It adds more advantages. The factors affecting the strength of concrete are must known to develop the required strength. The lower w/c ratio leads the higher strength of concrete. The maturity is measured in degree centigrade hours or degree centigrade days. Similarly, there are several aspects that should be looking into when considering the quality of the cement. Most of the factors are interrelated in certain means. Aggregates are the key factors that will affect the impact strength of the concrete under aggressive load condition. Concrete with lower water cement ratio gains strength, more rapidly than the mix with high w/c. Generally, 150mm cubes are specified irrespective of the size of the aggregates. When the mix designs are done, mix proportion of the aggregates are considered as one of the most important factors. Good quality aggregates will absorb less water content that is meant for hydration of cement. When the water cement ratio is less than 0.4, there is improper consistency and workability of the cement and honeycombed structure. Generally, the water/cement ratio of 0.45 to 0.60 is used. These factors can be either dependent or independent of each other when comes to the concrete strength. However, internally entrained air voids improve the resistance of concrete to damage from cycles of freezing and thawing. In 1918, Abrams presented his classic law in the form. ISSN 0024-9831 | E-ISSN 1751-763X. Magazine of Concrete Research . Larger the aggregate size, smaller will be the surface area for developing the gel bonds that will lead to lower strength of concrete. Structural Guide © 2021. Abrams's law of compressive strength versus water/cement ratio is well known and many investigators have studied the possible effects of other factors, such as cement content and sand concentration, upon concrete strength. The water-cement ratio is the ratio of volume of water mixed in concrete to volume of the cement used. Factors Affecting Bond between New and Old Concrete by Pedro Miguel Duarte Santos and Eduardo Nuno Brito Santos Júlio. The following factors are considered to maintain the quality of the aggregates. There are key factors as discussed in the article Compressive Strength of Concrete and Testing of Concrete that affect the strength of the concrete. have discussed in addition to other aspects. B. The strength of the cement depends on the date of the manufacture. The use of quality cement improves the bond and strength. However, the dosage of the admixtures shall be as specified by the manufacturer. cement is the material that creates the bond between aggregate after reaction with the addition of the water. Fiber reinforced polymer (FRP) sheet is one of the most popular method used that externally bonded for flexural retrofit of concrete member. The strength of the concrete at a lower age and 28 days depends upon the cement composition, fineness of the cement and the curing temperature. By that, we can save some money. These admixtures are categorized under chemical admixtures. The evidence for the theory that the failure occurs at limiting values of strain rather than the stress. Mainly there are four materials used to make the concrete. The article on key factors affecting the compressive strength of concrete could be read for more information on factors related to the strength development of concrete. El-Mansoura University, Egypt Abstract. Sand and the quarry dust is used as fine aggregate. The age of the concrete is an indication of the strength development of concrete. affect the bond between the steel bars used and concrete and consequently the strength of reinforced concrete members will decrease. Dry cubes of concrete may have drying shrinkage and bond failure that will lead to smaller strength. The strength of the concrete can be more correctly related to this ratio. Some of the critical variables are identical to those that affect bond strength, including bar size, concrete compressive and tensile strength, concrete cover, type of aggregate, bar spacing and coating (if used). The majority of the volume of concrete is represented by the aggregates; fine aggregates and coarse aggregates. Hence a lower water cement ratio can be used which will result in higher strength. An insufficient bond will compromise pavement performance. We at engineeringcivil.com are thankful to Sir Kaushal Kishore for submitting this research paper and helping all civil engineers understand the concept of Concrete Strength and factors affecting it. Larger aggregates will also bring a heterogeneous structure for the concrete thus making the non - uniform distribution of the loads when it is stressed. As we know, superplasticizers are widely used as admixture due to its advantages. https://www.prodyogi.com › 2017 › 09 › top-15-factors-affecting-strength-of.html Cube test of concrete and factors affecting concrete compressive strength. In addition, there are other cement tests to be carried out to find the quality of the cement. This paper describes how the bond strength of concrete-to-concrete interfaces, of reinforced concrete (RC) members with parts cast at different ages, is highly influenced by the curing conditions. Volume 32 Issue 111, June 1980, pp. The effect of each of the materials can be discussed separately. It was found that increasing the substrate concrete surface roughness by hand-chiseling considerably improved the bond strength compared with grinding. When the concrete getting older, its strength increases. In present investigation, the bond strength of the oil polluted steel bars with concrete was studied. As described above, the critical factor for good performance of the BCO is the bond between existing concrete and overlaid concrete. Further, it improves the workability of the concrete. x. Seyit Ali … Cement content and aggregate volume ratio is related to the strength of the as shown in the following figure extracted from a technical paper. The strength of concrete increase with the increase in the rate of loading. The concrete compacted by the vibrator displays higher strength even up to a water cement ratio of 0.3. With the current developments in this industry, there are admixtures that can provide multiple functions such as retarding and water reducing actions. The results of this paper are being summarized in a series of articles categorized into the principal properties of the mortars, for example compression strength, admixtures, air-content and water cement ratio, and the impact of those properties on bond strength were analyzed. 11 Factors that can Affect the Strength of Concrete Concrete is widely used building material in the construction world. The factors affecting the strength of concrete are: For concrete that has to be compacted by a vibrator, a lower water cement ratio may be used. Test procedure and for concrete compressive strength. An increase in the volume of air voids by 1% reduces the strength by 5%. The following figure extracted from the web site clearly indicates the effect of the curing period on strength development. El-Mansoura University, Egypt Abstract. It is quite clear that compaction directly affects strength. All those will be discussed in the latter part of this article. No Fine Concrete [application and advantages]. Compressive strength of concrete for different grades of concrete @ 3 Days, 7 days, 14 days, 21 days & 28 days with video explanation. The use of larger size aggregates leads to higher strength i.e larger the size, lower will be the surface area and the water requirement is lower. The lower w/c ratio leads the higher strength of concrete. All Rights Reserved. With an increase in the cement to aggregate ratio, the ultimate strength will increase to some extent. Strength of concrete or in other words, the compressive strength of the concrete, dominant factor considered in the structural design in addition to the strength of the reinforcements. The bond strength between precast concrete and cast in place ultra high performance concrete (UHPC) plays a significant role in the application of UHPC as a filling material for bridge connections or an overlay in the rehabilitation of bridges. Concrete cure time and environmental factors also affect bond strength; in some cases, the bond between the type of bar and the cement may take varying amounts of time to form. Structural loads, structural analysis and structural design are simply explained with the worked example for easiness of understanding. Cement after reacting with water create the bond with the aggregates to create the concrete. The resistance offered to slipping of bars is due to three factors: The chemical adhesion between the two materials The friction due to natural roughness of bars The strength of the concrete will depend on the moisture content at the time of loading. In addition, like development length, bond strength has a direct connection to the required length for reinforcement splices. Also, the specimen should be tested immediately after taking it out of the curing tank in order to give uniformity to the results as compared to the testing of samples which may have dried at different degrees. Water Cement Ratio – Water and cement are to be selected in such a way that it gives higher strength. Therefore, the monolithic behavior is dependent on these conditions. FACTORS AFFECTING STRENGTH. Each factors affecting strength of concrete are discussed as follows. In engineering practice, the strength of the concrete at a given age and cured in water at a specified temperature is mainly dependent on two main factors. The rate of gain of strength will depend on the age. Therefore, the rounded spherical aggregates give higher strength. This study examined several factors that affect the interfacial bond strength in order to cover wide range of conditions in the field. Ten hours curing at a temperature of about 90 degree Celsius will make attain 70% of its 28 days of strength. Whenever there is a change in the source of the material, verification shall be done. Therefore, it is very important to compact concrete adequately. The following figure also indicates the variation of the compressive strength of concrete with the water-cement ration based on the entrainment of air. The maximum strength is derived at w/c = 0.4. The hydration process can be represented by the following equation. Overdosage could reduce compressive strength also. The most important properties of aggregate are shape and texture and the maximum aggregate size. When large size aggregates is used due to the internal bleeding, the transition zone becomes weaker and will lead to lower strength. A., & Rajaie, H. (2004). Using the test data, the variation in the average bond strength with respect to each of the stated parameters is formu-lated. Note: Compressive Strength (CS) of cement given are average values. Therefore, the quality of the aggregate effect on the strength of concrete. Factors affecting the relationship between rate of loading and measured compressive strength of concrete Open PDF. However, the problem of dismantling of … Usually, we have a fine and coarse aggregate. Aggregate is the material bond with the cement paste after reacting with water. The pulling out of steel bars from concrete is resisted by the gripping action of concrete known as bond and the resulting stress is called bond stress. This strength increase will be for the same cement content with the reduction of the amount of water. The cement requires about 1/5 to 1/4 of its weight of water to become completely hydrated. Factors Affecting Strength and Durability of Concrete Made with Various Cements K. RosE, B. What is PERT?? The increase in the strength beyond 28days is taken in into consideration in the design of structures. Poorly compacted concrete has more voids and as a result, it reduces the bond between the aggregates. Get all latest content delivered straight to your inbox. Factors affecting concrete strength Concrete porosity: voids in concrete can be filled with air or with water. The above mention characteristic influences workability, finishability, bleeding, and segregation of fresh concrete effects the strength, shrinkage, density, and durability of hardened concrete. All of these aggregates, their properties shall be checked according to the standards and the gradation of the materials shall also be within the acceptable range. The use of new admixtures has brought more advantages to the industry and also the risk. Increasing fly ash content increases the bond strength of the geopolymer concrete. However, for aggregates that are less than 25mm in size, 100mm cube is allowed. At present, almost all the time, admixtures are used for all the concreting work. reinforcing bars associated with bond characteristics is one of the main factors affecting the ultimate behaviour and failure of reinforced concrete members. Aggregate proportions are greatly affecting the strength. In the case of lean mixes, the larger aggregates will give higher strength. A rounded spherical shaped aggregate when compacted contains fewer voids than an irregular and flaky aggregate of the same nominal size. Tests were conducted on 72 cylindrical concrete specimens with compressive strength of 24 MPa at age of 28 days. Factors Affecting Strength of Concrete. According to Power's equation, the strength of the concrete can be expressed as. 1- Water – Cement Ratio (W/C Ratio) The ratio of the weight of water to the weight of cement is called Water/Cement ratio. In a concrete, mix proportions of cement, water, coarse and fine aggregates decides the strength of the concrete. In particular, the British and American literature is often at variance concerning these secondary effects so that a primary aim of the present paper is to reconcile … The primary factor that has a higher influence on the strength of the concrete is the mix design factors. Superplasticizers reduce the water requirement by 15 to 20% without affecting the workability leading to high strength and dense concrete. For Abram's law, it follows that provided the concrete is fully compacted, the strength is not affected by the aggregate shape, type, texture or the grading, workability and the richness of the mix. With time concrete strength increases but it does not increase proportionately. Th e adopted geometry for the slant shear specimens was a 150 x 150 x 450 mm 3 (5.91 x 5.91 x 17.72 in.3) prism with the shear plane at 30 degrees to the vertical. However, beyond a certain period, the increase of the strength is minimal. As indicated in the above figure, the increase of the water/cement ration reduces the compressive strength of the concrete. The period of curing of concrete is directly affecting the strength development of the concrete. Water/Cement ratio is inversely proportional to … The relationship between 7 days strength and the 28 days strength is: The strength at 28 days = (28); The strength at 7 days = (7). There are many control factors that influence the bond strength, such as the compressive strength of the weakest material, roughness of the substrate concrete, cleanliness and moisture content of the substrate concrete and curing conditions of the substrate concrete and of the cladding layer (Momayer & Ehsani, 2004 Momayez, A., Ehsani, M. R., Ramezanianpour, A. As indicated in the figure, and due to the importance of curing of concrete to gain its strength, curing shall not be avoided. Aggregate-- Second to w/c ratio, aggregate is an important factor affecting concrete strength. factors that influences the shear bond strength of orthodontic brackets. Depending on the water-cement ratio, the compressive strength is defined in the mix designs. Here, x = water cement ratio by volume; A & B are the constants; S = Strength; Top 15 Factors Affecting Strength of Concrete. Prev Next > Factors affecting the relationship between rate of loading and measured compressive strength of concrete Authors: Seyit Ali Kaplan, PhD. 450 ACI Materials Journal/July-August 2011 tension, respectively (Fig. Factors Affecting Strength. The article published in this website Factors affecting Curing Time of Concrete provides detailed information on the curing period of concrete. The results indicated that the bond strength between reinforcement and concrete increased with increasing concrete strength, cover thick-ness, and amount of web reinforcement, while it decreased with increasing bar size. This verification is recommended for all new concrete at the beginning of the project as compressive strength is within the major factors affecting the concrete mix design. In general, air entrainment in the concrete reduces its strength. Air voids are an obvious and easily-visible example of pores in concrete. The moisture content in concrete provides lubrication effect and will reduce the strength. - Advantages & Disadvantages, Working Stress Method (WSM) and Limit State Method (LSM), Types of Plumbing System in Building Construction. Among the three group of aggregates we have:- Gap Graded, Poorly graded and Well-graded aggregates, the use of well-graded aggregates imparts higher strength to the concrete. In general, cement is considered one of the highly influential factors affecting strength of concrete. In this website factors affecting the strength and the durability of the material bond with mix. Time of concrete is the rate of gain of strength will increase to extent... Concrete can be either dependent or independent of the strength of the same nominal size of days! Weaker and will lead to smaller strength be increased by increasing the substrate concrete roughness. Only on the strength of concrete Authors: Seyit Ali Kaplan, PhD lower... 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