Figure 1. Methodology Adopted for the Study
The Lightweight Aggregate Concrete is usually produced by using natural and artificial lightweight aggregate together with mineral and chemical admixtures. In this study, artificially occurring lightweight expanded clay aggregate was used for the development of structural lightweight concrete to reduce both the high self weight and the negative environmental effects that are typically associated with the production of normal Lightweight Aggregate Concrete. The main purpose of this study is to investigate and compare the behavior of lightweight aggregate concrete and normal weight aggregate concrete and also the study focused on influence of the physical properties of the aggregates on strength development. In this research, the investigation done about the use of lightweight expanded clay aggregate as coarse aggregate in concrete by replacing normal weight aggregate up to 60% by volume along with the steel fibers to 3 produce a Lightweight Expanded Clay Aggregate Concrete (LECAC) and the unit weight in the range of 1600 kg/m to 1800 3 kg/m . The primary aim of the investigation was to reduce both the economic costs and the negative environmental effects that are typically associated with production of lightweight concrete containing artificially produced aggregates by taking advantage of India abundant expanded clay resources. LECA is a lighter aggregate with a higher strength when compared to other artificial lightweight aggregates, it allows producing high strength, lightweight concrete that can be used in structural systems of buildings. This study also includes the properties of lightweight expanded clay aggregate concrete, such as workability of fresh concrete, compressive strength of cubes at 28 days and 90 days, compressive strength of cylinders, split tensile strength of cylinders, and flexural strength of prisms at 28 days.
The concrete is an important material made from a mixture of Ordinary Portland Cement, water, fine and coarse aggregates, and with some amount voids. It is the most widely used construction material in the world. The concrete is a material, which can be moulded into any shape when it is in the fresh liquid state and hardens into a rock-like material later on. At present, the normal weight aggregate concrete increases the dead load on the structure in order to reduce the dead load on the structure and to overcome the problem producing the lightweight expanded clay aggregate concrete (Sellakkannu & Tamilarasan, 2016). The lightweight aggregate concrete gives low density (Nemes & Jozsa, 2006; Bajare, Kazjonovs, & Korjakins, 2013) and better thermal insulation (Bodnárová, Hela, Hubertová, & Nováková, 2014). The use of lightweight expanded clay aggregate concrete in structures offer many advantages over the conventional concrete (Sellakkannu & Tamilarasan, 2016). The steel fibers can be used as an additional part of concrete to increase the strength by using desired shape and cross section in the concrete, which are available in the market. The fibers which act as reinforcement in concrete interlocks the coarse aggregate particles and considerably reduce the workability, while the mix becomes more harsh and less prone to segregation. The fibers when distributed uniformly in the concrete mix will increase the properties of the concrete. Fibers help to improve the compressive strength (Subasi, 2009), tensile strength, flexural strength, ductility performance, pre-crack tensile strength, fatigue strength, impact strength, and eliminate temperature and shrinkage cracks. The main objective of this study is to compare the lightweight concrete strength parameters like compressive strength, split tensile strength, flexural strength with normal weight aggregate concrete (Kumar & Prakash, 2015a; Hyeok, Mun, Sim, & Song, 2011) and also workability properties (Parmar, Patel, Vaghashiya, Parmar, & Parmar, 2016). The lightweight expanded clay aggregate is available in Denmark, Middle East, Holland, and Germany.
There were many researchers, who have done investigations on the strength parameters of Lightweight Expanded Clay Aggegate Concrete. Many of them showed that there was an increase in the compressive, flexural, and split tensile strength of the Lightweight Expanded Clay Aggegate Concrete (Paul & Babu, 2014). The following were some of the literature showing the same. Mahdy (2016) has presented an experimental investigation on workability, mechanical, and durability. The study mainly focuses on the density and strength properties of lightweight concrete using LECA as a coarse aggregate and the silica fume in the concrete mixes to improve the strength properties of lightweight concrete. The lightweight aggregate concrete was compared with conventional concrete properties like strength and density (Mahdy, 2016).
Sellakkannu and Tamilarasan (2016) have focussed on the strength properties of lightweight concrete. The lightweight concrete and conventional concrete can be compared by non-destructive test methods. The lightweight aggregates like expanded clay aggregate are replaced in the natural coarse aggregate and the non-destructive tests are performed and the use of waste aggregates reduces the cost thus developing new technology for the development of light weight concrete (Sellakkannu & Tamilarasan, 2016).
The experimental investigation done by (Shebannavar, Maneeth, & Brijbhushan, 2015) involved artificially occurring lightweight expanded clay aggregate for the development of structural lightweight concrete (Shebannavar et al., 2015). The primary aim of the investigation was to reduce both the economic costs and the negative environmental effects that are typically associated with the production of conventional lightweight concrete containing artificially produced aggregates by taking advantage of India abundant expanded clay resources. The study mainly focussed on the density and strength properties of lightweight aggregate concrete (Shebannavar et al., 2015).
Kumar and Prakash (2015a) have done an experimental investigation about lightweight coarse aggregate from available sources found in different countries. The present study focused on the strength properties of lightweight concrete using expanded clay aggregate and cinder for M20 grade of concrete for various proportions in the volume of concrete (Kumar & Prakash, 2015a). To increase the strength of the lightweight concrete, Ground Granulated Blast Furnace Slag (GGBFS) is used by replacing 20% of cement to achieve more strength. The comparison of lightweight concrete with conventional concrete for the properties like strength and density was done (Kumar & Prakash, 2015a).
Kumar and Prakash (2015b) have also performed an experimental investigation about the behaviour of LECA and cinder for the replacement of coarse aggregate. The experimental work was carried out on the lightweight concrete by using natural aggregates cinder and LECA in various proportions by volume of concrete. The normal coarse aggregate can be replaced by using cinder and LECA. Increasing the percentage of lightweight aggregate decreases the cubes weight from 8.9 kg to 6.45 kg (Kumar & Prakash, 2015b), but simultaneously there was decreasing strength. Blending of lightweight aggregates showed better performance in this case. The concrete mixes are blended in various proportions like (50:50, 60:40, 70:30, 80:20, 90:10, fully 100%) and vice versa in LECA and cinder. The 60% of cinder and 40% of LECA with 20% of GGBS replaced for cement gave a good low weight structural concrete. Cinder and LECA can be used as lightweight aggregate in replacement of normal coarse aggregate. The M30 grade lightweight concrete had an average compressive strength of 39.20 N/mm2, which was almost nearer to the compressive strength of normal aggregate concrete, which was 43.40 N/mm2. The density of lightweight aggregate concrete varied from 1800 to 1950 kg/m3, which were lesser than that of normal weight concrete having a density of 2637 kg/m3. There was significant cost reduction when compared to normal concrete. The batching of concrete work is done volume wise, where 1 kg of LECA is replaced by 3.5 kg of normal aggregate by mass.
In the present investigation, a methodology is proposed to compare conventional and lightweight expanded clay aggregate concrete. The Lightweight Aggregate Concrete (LWC) has been used as a construction material for many decades. The main objective for using LWAC is normally to reduce the dead load of structures with less weight. The dimensions of the foundations of buildings can be reduced in areas with low bearing capacities, even with the major advantage of reduced weight and the higher strength-to-weight ratio of the material compared to conventional concrete. Other advantages of LWC compared to normal weight concrete are the improved durability properties (Khaiat & Haque, 1999).
The use of lightweight aggregates concrete in structures offers many advantages over the conventional normal weight concrete, including an increased, strength weight ratio and improved thermal and sound insulation and fire resistances properties. In the concrete construction field, the concrete represents a very large proportion of the total load on the structure and there are clearly considerable advantages in reducing its density (Mahdy, 2016).
One of the ways to reduce the weight of a structure is the use of lightweight aggregate concrete. Lightweight Aggregate Concrete (LWAC) has been used successfully for structural purposes for many years because of their improved properties, such as the strength and resistance to freezing and thawing of lightweight concrete (Mandlik, Sood, Karade, Naik, & Amrutakulkarni, 2015). The advancement in the new construction materials has lead to develop high strength, which are generally selected to reduce the weight of the construction. Also the developments in the stress analysis methods enable a more reliable determination of local stresses in the materials. It has been widely used following advances in production technology for lightweight aggregates.
The advantage of lightweight concrete is to reduce dead load for structures. The aim of the experiment is to develop the lightweight concrete for the mix design of conventional concrete such as the M40 by partial replacement of the portion of coarse aggregates (granite) by LECA with percentage and thereby achieving the target strength with low density of concrete (Mahdy, 2016). The concrete, which is thus developed is compared with the conventional M40 grade concrete and further the graphs are obtained for the above comparison.
The present investigation is on Lightweight Expanded Clay Aggregate Concrete by using Lightweight Expanded Clay Aggregate of varying percentages to the total volume fraction of coarse aggregate. A mix design was conducted as per IS 10262-1982 to arrive at M40 mix concrete.
Figure 1 shows the research methodology with the collection of literature review, materials, specimen preparation, testing, and the result analysis.
Figure 1. Methodology Adopted for the Study
To perform the experimental investigation on the Lightweight Expanded Clay Aggregate Concrete specimens, initially, the materials (ingredients of the mix, for Ratio C:FA:CA:w/c=1:1.49:2.49:0.45), were tested for characterization of its physical properties and the same is verified for its suitability to use it in the mix design. The laboratory tests, were performed on mixes for evaluation of performance characteristics.
The various raw materials used are:
Aggregates. It is the special type of aggregate, which are formed by a pyroclastic process in a rotary kiln at very high temperature. Since it is exposed to high temperature, the organic compounds burn, as a result the pellets expand and form a honeycombed structure, whereas the outside surface of each granule melts and is sintered. The resulting ceramic pellets are lightweight, porous, and have a high crushing resistance. It is environmental friendly, which is entirely a natural product incorporating same benefits as tile in brick form. LECA is non-destructible, noncombustible, and impervious to attack by dry-rot, wet-rot, and insects. Figure 2 shows the LECA used in the study. Based on the standard tests, the results conducted on LECA were specific gravity = 0.81, Water absorption = 16.42%, and Fineness modulus = 5.84.
Figure 2. (a) Steel Fibers (b) LECA (c) Micro Silica
The raw materials used are tested for various characteristics. Cement is tested for standard consistency, initial setting time, fineness, specific gravity, and soundness. Coarse aggregates are tested for specific gravity, abrasion resistance, and impact value and water absorption. Fine aggregate is tested for specific gravity and sieve analysis.
Design mix proportion for M40 grade of concrete:
191.58 : 425.73 : 635.83 : 1060.6
0.45 : 1 : 1.49 : 2.49
Figure 2 represents the materials used in the present work, i.e., Micro silica, LECA and steel fibers.
The quantities of materials in the concrete design mix in kg/m3
Water – 191.58 kg/m3
Cement – 425.73 kg/m3
Fine aggregate – 635.83 kg/m3
Coarse aggregate – 1060.6 kg/m3
The Unit weight values for NWAC and LECAC 60 with 0%, 0.5%, 1% steel fibers concrete mixes are 2380 kg/m3, 1720 kg/m3, 1756 kg/m3, and 1786 kg/m3, respectively.
The compressive strength of cubes for NWAC and LECAC 60 with 0 %, 0.5%, 1% steel fibers concrete mixes are 47.29 MPa, 24.6 MPa, 30.73 Mpa, and 33.23 MPa at age of 28 days, respectively and the cylinders’ compressive strength of mixes NWAC and LECAC 60 with 0 %, 0.5%, 1% steel fibers at 28 days are 36.8 MPa,19.3 Mpa, 23.6 MPa, and 25.7 Mpa, respectively.
The cylinders’ split tensile strength of mixes NWAC and LECAC 60 with 0 %, 0.5%, 1% steel fibers at 28 days are, 10.25 MPa, 9.65 MPa, 11.25 MPa, and 13.25 Mpa, respectively and flexural strength of mixes NWAC and LECAC 60 with 0%, 0.5%, 1% steel fibers at 28 days are 5.41 MPa, 4.46 MPa, 5.56 MPa, and 6.71 Mpa, respectively.
The compressive strength values for NWAC and LECAC 60 with 0 %, 0.5%, 1% steel fibers concrete mixes are 47.29 MPa, 24.6 MPa, 30.73 MPa, and 33.23 MPa at age of 28 days, respectively and also the compressive strength values of NWAC and LECAC 60 with 0 %, 0.5%, 1% steel fibers concrete mixes are 54.43 MPa, 28.92 MPa, 36.24 MPa, and 39.29 MPa at age of 90 days, respectively.
It was observed that the development of compressive strength of mixes NWAC and LECAC 60 with 0%, 0.5%, 1% steel fibers at 90 days increased by 13.11%, 17.55%, 17.95%, and 18.24% compared to 28 days respectively and also it is observed that LECAC 60 with 0%, 0.5%, 1% steel fibers mixes have got the strength 47.9%, 35%, and 29.7% less than the strength for NWAC mix at 28 days, respectively.
Table 1 gives the Unit weight values for NWAC and LECAC 60 with 0 %, 0.5%, 1% steel fibers concrete mixes 2380 kg/m3, 1720 kg/m3, 1756 kg/m3, and 1786 kg/m3, respectively. Table 1shows the percentage decrease in unit weight of concrete with 60 % replacement of Lightweight Expanded Clay Aggregate Concrete LECAC 60 and steel fibers 0.5% and 1% with Normal Weight Aggregate Concrete (gravel) of 27.73%, 26.2%, and 24.9%, respectively. Table 4 gives the compressive strength values for NWAC and LECAC 60 with 0 %, 0.5%, 1% steel fibers concrete mixes of 47.29 MPa, 24.6 MPa, 30.73 MPa, and 33.23 MPa at age of 28 days, respectively and also the compressive strength values of NWAC and LECAC 60 with 0%, 0.5%, 1% steel fibers concrete mixes are 54.43 MPa, 28.92 MPa, 36.24 MPa, and 39.29 MPa at age of 90 days, respectively.
Table 1. The Unit Weight of Concrete for NWAC and LECAC 60 with 0%, 0.5%, and 1% Steel Fibers
Table 2. The 28 days Cubes and Cylinders Compressive Strength of Concrete for NWAC and LECAC 60 with 0%, 0.5%, and 1% Steel Fibers
Table 3. The 28 days Split Tensile and Flexural Strength of Concrete for NWAC and LECAC 60 with 0%, 0.5% and 1% Steel Fibers
Figure 3 represents the variation of unit weight compared with normal weight concrete to lightweight concrete with various percentages of micro silica and steel fibers.
Figure 3. Comparison of Unit Weight Variation for the Normal Weight Aggregate Concrete (NWAC) and Lightweight Expanded Clay Aggregate Concrete (LECAC 60) Mixes with and without Steel Fibers
From Table 4, it was observed that the development of compressive strength of mixes NWAC and LECAC 60 with 0%, 0.5%, 1% steel fibers at 90 days increased by 13.11%, 17.55%, 17.95%, and 18.24% compared to 28 days respectively and it is also observed that LECAC 60 with 0%, 0.5%, 1% steel fibers mixes obtained the strength 47.9%, 35%, and 29.7% less than the strength for NWAC mix at 28 days respectively. Table 4 shows the % loss of compressive strength of mixes LECAC 60 with 0%, 0.5%, 1% steel fibers with respect to NWAC at 28 days by 47.9%, 35%, and 29.7%, respectively. Figure 4 represents the variation of compressive strength compared with normal weight concrete to lightweight concrete with various percentages of micro silica and steel fibers at 28 days.
Table 4. The 28 and 90 days Cubes Compressive Strength of Concrete for NWAC and LECAC 60 with 0%, 0.5%, and 1% Steel Fibers
Figure 4. Compressive Strength at 28 days for the Normal Weight Aggregate (NWAC) and Lightweight Expanded Clay Aggregate Concrete (LECAC 60) Mixes with and without Steel Fibers
Figure 5 represents the variation of split tensile strength and flexural strength compared with normal weight concrete to lightweight concrete with various percentages of micro silica and steel fibers at 28 days.
Figure 5. Split Textile Strength and Flexural Strength at 28 days for the Normal Weight Aggregate (NWAC) and Lightweight expanded Clay Aggregate Concrete (LECAC 60) Mixes with and without Steel Fibers
From Table 4, it was observed that there is % loss of compressive strength of mixes LECAC 60 with 0%, 0.5%, 1% steel fibers with respect to NWAC at 90 days by 46.8%, 33.4%, and 27.8%, respectively. Table 2 shows the cylinders’ compressive strength of mixes NWAC and LECAC 60 with 0%, 0.5%, 1% steel fibers at 28 days are 36.8 MPa, 19.3 MPa, 23.6 MPa, and 25.7 MPa and the % decrease of cylinders’ compressive strength of the mixes LECAC 60 with 0%, 0.5%, 1% are 47.5%, 35.8%, 30.1% with respect to NWAC. Table 3 shows the cylinders’ split tensile strength of mixes NWAC and LECAC 60 with 0%, 0.5%, 1% steel fibers at 28 days are 10.25 MPa, 9.65 MPa, 11.25 MPa, and 13.25 MPa. Table 3 also shows the flexural strength of mixes NWAC and LECAC 60 with 0%, 0.5%, 1% steel fibers at 28 days are 5.41 MPa, 4.46 MPa, 5.56 MPa, and 6.71 Mpa. Figure 6 represents the variation of % increase of compressive strength of cubes compared with normal weight concrete to lightweight concrete with various percentages of micro silica and steel fibers at 28 and 90 days.
Figure 6. Percentage Increase of Compressive Strength with Age of Curing for the Normal Weight Aggregate (NWAC) and Lightweight expanded Clay Aggregate Concrete (LECAC 60) Mixes with and without Steel Fibers
The following conclusions are drawn from the experimental investigation in present research work.