Abstract: Indiais presently generating construction and demolition (C & D) waste around 23.75 million tons annually and these figures are likely to double fold in the next 7 years. C & D waste and specifically concrete has been seen as a resource in developed countries. Works on recycling have emphasized that if old concrete has to be used in second generation concrete, the product should adhere to the required compressive strength. The project done on recycled aggregate from demolished concrete. Our aim is to investigate the characteristics of recycled aggregate concrete, with respect to various parameters. After analysis of results of various tests done on recycled aggregate and natural aggregate it found that the recycled aggregate shows different result values, which implies that RA and NA are very different regarding various properties. But the Control mix showed better results with recycled aggregate. Results shows that compressive strength of recycled aggregate concrete depends upon grade of concrete which demolished to obtain recycled aggregate and the age of demolished concrete.
Zhang, Xue-bing et.al. (2007) generated a formula for additional water requirement in recycled aggregate concrete. They found that the specific absorption of coarse aggregates increases as the time of water absorbing goes on. The speed of water absorption was greatest in first 10 minutes. Then it decreased and changed very little. The specific absorption and water absorption speed of RCA are greater than those of crushed stones and pebble, within the same time.
the flow of water to an aggregate from the soil be low but tests were also conducted to determine if frost susceptibility was influenced by the moisture content of an aggregate at the time of placement. Crushed concrete was tested to rep resent a high quality recycled aggregate whereas demolition debris (an unsorted demolition waste material) was much lower in quality.
In this research, these materials were used for experimental work. There are Ordinary Portland Cement (OPC), sand, natural gravel with maximum size 20mm and superplasticizer. Recycled Aggregate (RA) was prepared by crushing the waste cubes which have been thrown away at the outside of Material Laboratory of Universiti Tun Hussein Onn Malaysia (UTHM). The waste cubes without considering the age were collected and broken into smaller pieces by using hammer. Then it is crushed by using a jaw crusher. Maximum size of RA that has been produced is 20 mm and minimum size is 5 mm. Then, the Micronised Biomass Silica (MBS) was prepared by burning the rice husk in rotary reactor furnace. This furnace has been located at Material Laboratory in Universiti Tun Hussein Onn Malaysia (UTHM) and enables to synthesis any biomass silica material with different regime of temperature. In order to obtain an amorphous material, the temperature for rotary furnace is fixed at 500 0 C. Off white amorphous material is obtained after one hour and about 50 gram of ash has been produced. Before that, rice husk is fed manually into the rotary furnace. Then, Jar Mill is used to produce finer biomass silica. After been grinding by Jar Mill for one hour, the particle size of MBS is reduced from 48 µm to 25.77 µm.
ABSTRACT:- The application of recycled aggregate has been started in a large number of construction projects of many European, American, Russian and Asian countries. Many countries are giving infrastructural laws relaxation for increasing the use of recycled aggregate. So, this paper reports the basic properties of recycled fine aggregate and recycled coarse aggregate & also compares these properties with natural aggregates. Basic changes in all aggregate properties are determined and their effects on concreting work are discussed at length. Similarly the properties of recycled aggregate concrete are also determined.
In this paper we have studied compressive strength of concrete by replacing natural aggregate with recycled aggregate by 25%, 50% and 75%.This mixture formed in the sample of cubes of dimension 150x150x150mm 3 . The strength of well compacted concrete with good workability depends on its water-cement ratio. Water-cement ratio within certain limits results in the increased strength. The load test on cubes was performed on 7 th days, 14 th days and 28 th days. The load to be applied by UTM machine to the opposite side of the cube placed centrally between the plates. The load to be applied without shock increased continuously at the rate of approximately 140 kg/cm 2 /min. when the maximum load was applied cube got cracked in inclined direction.
With a global intensiﬁcation of the scarcity of resources in the twenty ﬁrst century, the recycling of waste concrete is an important means for the implementation of a sus- tainable infrastructure development strategy. Compared with natural coarse aggregates (NCA), recycled coarse aggregates (RCA) have substantial characteristics in terms of uncertainties that arise from their complex composition (Wardeh et al. 2015). It is well-known that the properties of recycled aggregate concrete (RAC) are different from those of natural aggregate concrete (NAC) (Yehia et al. 2015; Wardeh et al. 2015). Previous theoretical analyses carried out in the framework of structural reliability theory and lab experiments have shown that: (1) higher scatter of the compressive strength of RAC affects the margins of structural safety (Breccolotti and Materazzi 2010); (2) the compressive strength of RAC varies with the RCA replacement percentage and it follows a normal probability distribution (Li et al. 2006); and (3) the durability of RAC can be strongly affected by the porosity and the high water absorption of the RCA (Debieb et al. 2010; Kou and Poon 2006). It is necessary to well understand the properties of RCA in order to control the behaviour of RAC. Some hypothetical problems related to durability aspects have resulted in RCA being employed only as base ﬁller for pavement construction (Muscalu et al. 2013; Vancura et al. 2009), thereby and unnecessarily limiting the scope of application of RCA. The durability of concrete is of great concern, especially in high-chloride environments such as coastal areas and where de-icing salt is used in cold
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The cylinder compress strengths for the all mixes are show in the Table 1. From this table it is noticed that as, percentage of recycled aggregate increasing, the compressive strengths are decreasing. For the 0% of normal concrete specimen the compressive strength is 9.45MPa for 28 days. For RA mixes the compressive strengths are decreasing from the 24 to 52% for the 25.to100% of replacement, this is happen when compare with the normal pervious concrete specimens. In generally for normal concrete, the cylinder compressive strength in compression may lies in between 70-75% of cube compressive strength. It may be the effect of the volume, shape, height of the dimension of the specimen. In this experiment the compressive strength for cylinder (PC 0) is 9.45MPa. For the mix PC0 the cube compressive strength is 11.12MPa, if it is considered for evaluation of the cylindrical compressive strength, the it may lie in the range 7.78MPa (0.70×10.14) to 8.34MPa (0.75×11.12). The experimental cylinder compressive strength is more than the relation provided in the above. Hence it may conclude that, the cylinder compressive strength is little bit higher to the expected values. It may suggest that the use of recycle aggregate is acceptable for pervious concrete. As per the ACI-318 M-11 the compression of the cylinder is 0.76 times of the cube compression strength and to know the result for compression the ACI code provision has been taken and obtained results are provided in Table 2. The ratio between EXP/ACI also presented in Table 5.3 and it indicate that, the ACI code is under estimate the results.
Abstract: Demand for infrastructure due to the continuous population growth, and increased urbanization, have led to greater consumption of concrete. Addition or replacement of some of the materials may change the properties of the concrete.. Utilization of recycled aggregate in concrete has been employed due to awareness of society in natural resources protection by efficient disposal of demolished wastes. However the concrete using recycled aggregate has obtained lower performance when compared to concrete using natural aggregate. In this research, microsilica has been used for improving the performance of recycled aggregate concrete. Concrete specimens containing various percentages of recycled aggregate (0%, 25%, 50% and 75%) and (0%, 6%, 8%, 10% and 12%) has been prepared. Various tests were done on fresh concrete and compressive strength test, split tensile strength test, flexural strength test on cured hardened concrete. From the work it was found that after 28 days, the mix exhibited more compressive strength, split tensile strength and flexural strength than normal aggregate concrete. Compressive strength of mix containing 25% recycled aggregate and 8% microsilica were increased by 7.25%, split tensile strength increased by 16.04%, flexural strength increased by 9.09%. More properties were analysed by conducting durability tests. Load deflection test on 28 days cured beam specimen with optimum mix exhibited better performance. The optimum mix showed 9.14% higher strength than ordinary concrete..
This research presents an experimental investigation on the engineering properties of concrete prepared with crushed tiles as recycled coarse aggregates. Concrete mixes with a design compressive strength of 30MPa are made using recycled aggregates with percentages ranging from 0 to 100% of the total coarse aggregate. Their influence on concrete mechanical properties is investigated. As a result, it has been obtained that using recycled aggregate to replace part of the normal coarse aggregate effects the elastic modulus, tensile strength and compressive strength with a value depends on the coarse aggregate replacement percentage. For low percentages of recycled aggregate (25%) it can be obvious that this influence is practically negligible. It may be concluded that the use of recycled aggregates in concrete may help to solve a very important environmental issue and gives a solution to the problem of inadequate concrete aggregates. The comparison of test results with ACI 318 code spilt cylinder and modulus of elasticity equations show that these equations are not recommended to be used for recycled aggregate concrete with percentage exceeding 25%.
One of the major challenges of our present society is the protection of environment; with respect to this some of the important elements are reduction of natural raw materials and consumption of waste materials. The recycled aggregate sample of size 20mm which is the maximum size of aggregate in reinforced cement concrete is collected from demolished structures in our surrounding areas and the experimental approach is carried out such as i) slump test, ii) compression test. Four mix proportions were prepared with different proportions of both normal and recycled aggregate (such as 0%, 20%, 40%, 60% of recycled aggregate). However, recycled aggregates present a low quality compared to natural aggregates, the water absorption capacity is more for recycled aggregate .Moreover it was found that optimum workability achieved in fresh concrete mix with 40% replacement of RCA and compressive strength holds good for 40% of recycled aggregate.
The study on the characteristic properties of concrete by the partial replacement of cement and aggregate by fly ash, micro silica and recycled aggregate is to pack the concrete with optimum density with less number of pores which will increase its strength and durability. This can be obtained through particle packing method. This also helps in reducing the usage of Portland cement by replacing a certain amount of cement by different cementitious materials. These materials will attain strength equal to that of the traditional cement bonding.
graded inorganic particles processed from the materials that have been used in the construction and demolition debris. One of the major challenges of our present society is the protection of environment. The use of aggregates from construction and demolition debris (wastes) is showing prospective application in construction as alternative to primary (natural) aggregates. It conserves natural resources and reduces the space required for the landfill disposal. Although there is a critical shortage of natural aggregate, the availability of demolished concrete for use as RECYCLED CONCRETE AGGREGATE (RCA) is increasing. Using the waste concrete as RCA can provide cost savings. Recycled aggregates are the materials for the future. This work is to determine and compare the workability, compression strength, indirect tensile strength, flexural strength and modulus of elasticity properties of recycled aggregate concrete with that of natural aggregate concrete. To attain the planned objectives of the present investigation, M25 grade concrete is taken and the replacement values viz, 0%, 25%, 50%, 75%, 100% were considered. A total of 60 cubes, 40 cylinders, 10 beams were casted to determine the properties mentioned as above The development of compressive and tensile strengths of recycled aggregate concrete at the age of 7and 28 days; the development of flexural strength and static modulus of elasticity at the age of 28 days are investigated. The parameters which were investigated for recycled aggregate concrete and compared with natural aggregate concrete as per BIS specifications found to be decreasing gradually as the percentage of recycled aggregate are increased.
improve the quality of RA concrete (RAC) by splitting the mixing process into two parts. Cube, Cylinders and beam are casted using recycled coarse aggregate (RCA) and replacing natural aggregate (NCA) with 30%, 50% and 100% recycled coarse aggregate. In addition, fly ash was used as 10% by weight replacements of cement. The concrete mixtures were prepared with w/c ratio 0.43. This method in making recycled aggregate concrete can improve the strength of fly ash concrete made from 30% recycled aggregate concrete up to 6.23% by partial replacing 10% of cement mass with fly ash for concrete made from recycled aggregate has shown preferable result in strength, and can be improved by using TSMA FS method in mixing process.
Recycled Aggregate Concrete (RAC) is concrete that using Recycled Aggregate (RA) as partially or fully replacement in coarse and fine aggregate. It is believed RA have been used from 1945 in concrete producing and started when World War II damaged a large quantity of concrete structures and the high demand of aggregate to rebuild the structures (Kheder and Al-Windawi, 2005). They recognised the factors like depletion of natural aggregates, tightly environmental law and waste disposal problems which influenced the application of RA.
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The 10% fines value for the recycled and natural aggregates were determined in accordance with BS 812 Part 3: (1975). This value is the load, in kiloNewton (kN), required to produce 10% fines, defined as material below 2.3 mm, from aggregate particles in the size range 10 to 14 mm. Values in excess of 100 kN are usually required for aggregates for the production of conventional concrete with values in excess of 150 kN being necessary for the production of concrete for hard granolithic floor slabs. Aggregates with a 10% fines value of less than 50 kN would be unacceptable for the production of any cement bound layer or material.
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The bearing strength results for recycled aggregate concrete mixes are presented in Table 5. From this it is observed that, the bearing strength increases with the increase in the percentage of recycled aggregate up to 50% and later % of RAC mixes it was decreased. Here also same trend was followed as it happened in the bearing ratio of 10. For 25, 50% of recycled there is increase in bearing strength by 7.68% and 3.57% over the Natural aggregate concrete (NAC-0). For 75% and 100%, the bearing strength has decreased by 6.9% and 3.69% respectively over granite aggregate concrete (NAC-0) For fibre incorporation mixes the bearing strengths are increased for all mixes of recycle aggregate concrete, but the trend is similar to RAC mixes without fibres. Among the FRAC mixes the mix with 25 and 50% shown higher bearing strengths compared to other two mixes of 75 and 100%. The % of increase in bearing strength for 25 and 50% RAC mixes is about 9 to 5% when compared with FRAC-0 mix. The same enchantment of strength is also observed for bearing strength of 10 tested specimens. The enhancement of strength for 50% RAC mix may be due to better bond (surface texture) between the RA and NA and the arrangement of aggregates in the mass of concrete.
amount of building material. The stone aggregates being a major component of concrete are not locally available in the cities and hence acute shortage is faced by the construction industry. Further, due to demolition of old structures in cities the waste concrete is laying as it is without any use and with no specific dumping place. Thus it is required to recycling and reusing the waste material with any possible manner. In the present study recycled aggregates are used in the concrete and the effect of nanosilica and microsilica on recycled aggregate concrete has been investigated. In the first series of tests natural aggregates are replaced by recycled aggregates in varying percentages i.e. 20%, 30%, 40% and 50%. In the second series of tests, cement was partially replaced by microsilica and nanosilica by 5%, 8% and 10% and 1%, 2% and 3% respectively both in natural aggregate concrete and recycled aggregate concrete. Further, cement was replaced by both nanosilica and microsilica i.e. (1%, 2%) and (5%, 8%) respectively in concrete containing fresh aggregates as well as partial recycled aggregates.
Construction & Demolition (C&D) wastes are normally composed of concrete rubble, bricks and tiles, sand and dust, timber, plastics, cardboard and paper, and metals. Concrete rubble usually constitutes the largest proportion of C&D waste. It has been shown that crushed concrete rubble, after separation from other C&D waste and sieved, can be used as a substitute for natural coarse aggregates in concrete or as a sub-base or a base layer in pavements. This type of recycled material is called recycled aggregate.
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As described earlier in order find out shear strength of optimized recycled aggregate concrete, different L shaped specimens were prepared and tested under special experimental set up and tests were carried out at the age of 7 and 28 days. It observed minor decrement in shear strength in both optimized recycled aggregate concrete compare to that of natural aggregate concrete hence again Metakaolin is inserted as a partial replacement of cement at 5%, 7.5% and 10% in order to enhance the shear strength. As a result it can be clearly observed that addition of Metakaolin is the solution to enhance shear strength of concrete. Shear strength of optimized RAC and CAC decreased by 9.5% and 13% in M-20 and 6% and 9% in M-30 compared to that of NAC but the deficiency in shear strength can be reduced with the addition of Metakaolin as a replacement of cement as per shown in fig
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