An Experimental Study on FaL-G Mortar and Concrete

Transcription

1 Proceedings of International Conference on Advances in Architecture and Civil Engineering (AARCV 01), 1 st rd June An Experimental Study on FaL-G Mortar and Concrete RadhaKrishna, P.S. Niranjan, P. Prithvi Raj and Vitta Sanket Kumar Abstract--- FaL-G is the product name given to a cementitious mixture composed of Fly ash (Fa), Lime (L) and Gypsum (G). It is low-cost and environmental-friendly material very useful even in rural housing industry. FaL-G in certain proportions, as a building material, is an outcome of innovation to promote large-scale utilization of fly ash. It gains strength like any other hydraulic cement, in the presence of water, and is water resistant when hardened. Large amounts of gypsum and fly ash are available at phosphoric acid manufacturing plants and thermal power plants, respectively. These materials can be used to source sulphate and silica alumina. Gypsum contains impurities of phosphate, fluoride, organic matter and alkalies which prevent its direct use as building material. It is one of the calcium sulphate s rich residues. FaL-G technology contributes to the conservation of energy and reduces environmental degradation. Since it is manufactured using industrial wastes and by-products, the environmental impacts are mitigated. This paper addresses the technology of making compressed FaL-G mortar blocks with low-calcium (Class F) dry fly ash procured from Raichur Thermal Power Plant, Karnataka as the base material. he cardinal aim is to optimize the combinations of the ingredients to produce FaL-G compressed block sand concrete to meet the strength development desired at the specified age. The FaL-G compressed blocks and concrete were prepared without the use of conventional cement. Rock dust was used as fine aggregate for sustainability. The compressive strength of FaL-G concrete was tested for different parameters. It was concluded that FaL-G masonry blocks can be produced using FaL-G as binder and quarry dust as aggregate The experimental results reveal that the blocks are suitable to be used as masonry blocks. The properties of the blocks can be compared to the available masonry blocks in the market. FaL-G concrete is suitable for making roller compacted concrete. Keywords--- Fly Ash, Lime, Gypsum, Mortar, Concrete, Compressive Strength RadhaKrishna, Associate Professor and Dean-Civil Engineering, R.V. College of Engineering, Bangalore, India chakavelu_rk@yahoo.com P.S. Niranjan, Professor and Head, Dept of Civil Engineering, MVJ College of Engineering, Bangalore. P. Prithvi Raj, Former UG Student, R.V. College of Engineering, Bangalore. Vitta Sanket Kumar, UG Student, R.V. College of Engineering, Bangalore. I I. INTRODUCTION N recent times the emission of carbon dioxide into the air is being increased day by day. Considerable amount of fossil fuel, coal and oil are burnt for different reasons. This weakens the heat trapping blanket that surrounds the planet, causing global warming. Various alternatives can be considered to protect the planet. The rapid increase in the capacity of thermal power generation has resulted in the production of a huge quantity of fly ash. The prevailing disposal methods are not free from environmental pollution and ecological imbalance. On the other hand, the production of each ton of cement releases equal amount of carbon dioxide to the atmosphere. The usage of cement can be reduced by using the other possible cementing materials without compromising the strength and durability The most basic building material for construction of houses is the usual burnt clay brick. A significant quantity of fuel is utilized in making these bricks. Also, continuous removal of topsoil, in producing conventional bricks creates environmental problems. There is strong need to adopt cost effective sustainable technologies using local materials and appropriate/intermediate technologies using materials with efficient and effective technology inputs. Different methods are adopted to produce the building blocks using cement, lime-fly ash, lime-slag bindings etc. There is a need to develop simple and highly effective technologies for producing the building blocks. The imperative need to produce more building materials for various elements of construction and the role of alternative options would be in sharp focus. This is in considering the short supply, increasing cost, energy and environment considerations for traditional and conventional materials. The possibility of using innovative building materials and technologies, using waste material like fly ash has been considered. There is a strong need to adopt cost-effective and environmentally appropriate technologies by upgrading of traditional technologies, as also using local materials as well as appropriate and intermediate technologies employing modern construction materials with efficient, effective technology inputs. Building materials is an area where enormous amount of innovation for cost reduction can be achieved. FaL-G is the product name given to a cementitious mixture composed of Fly ash (Fa), Lime (L) and Gypsum (G). It is low-cost and environmental-friendly material very useful even in rural housing industry. FaL-G in certain proportions, as a building material, is an outcome of innovation to promote

2 Proceedings of International Conference on Advances in Architecture and Civil Engineering (AARCV 01), 1 st rd June large-scale utilization of fly ash by Bhanumathidas and Kalidas [1]. It gains strength like any other hydraulic cement, in the presence of water, and is water resistant when hardened. Large amounts of gypsum and fly ash are available at phosphoric acid manufacturing plants and thermal power plants, respectively. These materials can be used to source sulphate and silica alumina. Gypsum contains impurities of phosphate, fluoride, organic matter and alkalies which prevent its direct use as building material. It is one of the calcium sulphate s rich residues. Phosphogypsum is an important byproduct of phosphoric acid fertilizer industry. It consists of CaSO.H O and contains some impurities such as phosphate, fluoride, organic matter and alkalies. Approximately 5 million tons of phosphogypsum is produced each year in India []. Cementitious binder, FaL-G, finds extensive application in the manufacturing of building components and materials such as bricks, hollow bricks and structural concretes. FaL-G technology enables production of bricks with a simple process of mixing and water curing. Due to such appropriate technology apart from economy, conservation of energy and pollution control are also achieved []. Good quality masonry blocks can be prepared by using FaL-G as cementitious material[6]. FaL-G technology contributes to the conservation of energy and reduces environmental degradation. Since it is manufactured using industrial wastes and by-products, the environmental impacts are mitigated. FaL-G plants have the advantage of continuous year-wide operation and hence provide year-long employment opportunity to skilled artisans. It creates self-help livelihood opportunities for the people. In certain cases, where by-product lime is not available in adequate quantity, ordinary Portland cement is used as the source of lime, producing the same quality of bricks and blocks. II. SCOPE OF RESEARCH FaL-G is relatively economical material derived from base materials like fly ash, lime and gypsum. The research reported till date speaks about the random use of the material without any rational approach. The report on proportioning, strength development in FaL-G is very less. Also there is large scope for the development of FaL-G compressed blocks made from mortar.. In this research both FaL-G concrete and mortar are prepared and the development of compressive strength is analysed. III. MATERIALS AND METHODS A. Casting and Testing of the Blocks FaL-G mortar was prepared using FaL-G as binder and sand/rock dust as fine aggregate. Tap water was used to mix the ingredients. The procedure adopted is same as that of cement mortar. FaL-G mortar is a dry frictional material at w/b ratio of the range FaL-G compressed blocks were prepared using FaL-G mortar at various w/b ratios. The static compaction device was used to cast the compressed blocks. The process compressed the wet mix into a specified size and to the required densities. The diameter and height (length) of the specimen were 8 mm and 76 mm, respectively (volume = cm ). The blocks were cured by keeping in humidity chamber at a humidity of 98% or by covering with wet jute bags. The details of mixes used for preparing FaL-G compressed blocks are shown in Table 1. The blocks were tested for unconfined compression at various ages as indicated. Series ID Table 1: Mix Proportions for FaL-G Blocks Proportion of binder Type constituents of fly ash Fly ash Lime Gypsum Fine Binder-toaggregate aggregate ratio Degree of saturation FBS S* 10 FA1 Sand 1:1 0 FBS 50 0-S 10 FA1 Sand 1: 0 FBS 50 0-S 10 FA1 Sand 1: 50 FBS 50 0-S 10 FA1 Sand 1: 0 FBS S 10 FA1 Sand 1: 0 FBS S 0 FA1 Sand 1: 0 FBS S 15 FA1 Sand 1: 0 FBS S 10 FA1 Sand 1: 0 FBS S 10 FA1 Sand 1: 0 FBS S 10 FA1 Sand 1: 0 FBS S 10 FA1 Sand 1: 0 FBS S 10 FA1 Sand 1: 0 FBS S 10 FA1 Quarry dust 1: 0 0- FBS1 50 US** 10 FA Sand 1: 0 FBS S 10 FA Sand 1: 0 FBS US 10 FA1 Sand 1: 0 FBS S 5 FA1 Sand 1: 0 *S Slaked lime **US Unslaked lime During the preparation of FaL-G composites it was noticed that the mix attains saturation at w/b ratio of 0. and more. The static compaction was not required to make cubes as the mix attains the shape of the mould. To begin with, ACI method [] was used to proportion the FaL-G concrete. The range of w/b ratios for the concrete was The FaL-G concrete was used to cast cubes of size 150 mm side. The procedure to cast the cubes was the same as that of geopolymer concrete with the change of ingredients. The cubes were cured in humidity chamber at a humidity of 98% or covered with wet jute bags till the age of 8 days or till the date of testing whichever was earlier. The FaL-G concrete was prepared with and without the use of OPC as binder. The mix without OPC was termed as lime route FaL-G, and with FaL-G + OPC was termed as OPC route - FaL-G. The cubes were tested for compression at different ages. Different proportions used to prepare FaL-G concrete are given in Tables

3 Proceedings of International Conference on Advances in Architecture and Civil Engineering (AARCV 01), 1 st rd June Table : Mix Details of FSC1 Lime Route FaL-G Concrete Ingredients (kg/m ) Water- to-binder ratio (w/b) Water Fly ash FA Slaked Lime Gypsum Coarse aggregate w/b = 0.00 w/b = 0.5 w/b = 0.50 Fine aggregate Table : Mix Details of FSC Lime Route FaL-G Concrete Ingredients (kg/m ) Water- to-binder ratio (w/b) Age (Days) Figure 1: Strength of FaL-G Blocks with Age Series FBS Water Fly ash FA Slaked lime Gypsum Coarse aggregate Fine aggregate Binder:Agg = 1:1 Binder: Agg = 1: Binder:Agg = 1: Binder:Agg = 1: Table : Mix Details of FSC Lime Route FaL-G Concrete Ingredients (kg/m ) Water Water- to-binder ratio (w/b) Fly ash FA Slaked lime Gypsum Coarse aggregate Fine aggregate B. Strength Development The compressive strength of FaL-G compressed blocks depends on many factors and was studied with parameters as listed below. Age: 7, 1, 8, 56, 90 and 10 days Binder-to-aggregate ratio: 1:1, 1:, 1: and 1: Degree of saturation: 0, 0 and 50% Fineness of fly ash: FA1, FA and FA Type of lime: Slaked and unslaked Quantity of fly ash: 0, 0, 50, 60 and 70% Quantity of lime: 0, 0, 50 and 60% Quantity of gypsum: 10, 15 and 0% C. Compressive Strength with Age The strength development in FaL-G compressed blocks was studied with age, retaining all other parameters the same. The variation of strength with age for the series FBS is shown in Fig Figure : Strength with Binder-to-Aggregate Ratio It was observed from Fig. 1 that the strength of FaL-G compressed blocks increases with age with all w/b ratios. It was slow till the age of 1 days compared to the later period. This is due to the slow rate of hydration in the early period compared to the later period. This trend was different in geopolymer blocks. D. Strength Development with Binder-to-Aggregate Ratio The strength depends on the quantity of binder in the block. The series considered to study the effect of binder-toaggregate was FBS1, FBS, FBS5 and FBS1 at the age of 90 days. From Fig. it is noticed that the strength of FaL-G blocks increases with increase in the ratio of binder-toaggregate. The trend is the same in all the cases. E. Strength Development with Degree of Saturation The degree of saturation affects the strength in partially saturated FaL-G compressed blocks. FaL-G mortar is suitable for casting compressed blocks for the degree of saturation of 0 50%. All the blocks were cast at constant degree of saturation unless specified. However strength development with different degrees of saturation is studied. The series considered for this purpose are FBS, FBS and FBS at the age of 90 days (Fig. ).

4 Compressive strength (MPa) Proceedings of International Conference on Advances in Architecture and Civil Engineering (AARCV 01), 1 st rd June Degree of saturation = 0% Degree of saturation = 0% Degree of saturation = 50%..1 Slaked lime Un-slaked lime Figure : Strength Development with Degree of Saturation FA1 Figure 6: Optimum Quantity of Fly Ash FA.00 FA Figure : Variation of Strength with Fineness of the Fly Ash It was observed that as the degree of saturation increases the strength decreases. If the degree of saturation was less, then the effort required to cast the specimens was more and vice versa. Depending on the availability of manual labour and equipment, the degree of saturation can be fixed for a particular batch. F. Strength Development with Fineness of Fly Ash The variation of strength was studied using three fly ash samples FA1, FA and FA for the series FBS, FBS1 and FBS15 at the age of 90 days. The results are shown in Fig.. It was observed that the strength development in FaL-G compressed blocks depends on the fineness of the ash used. As the fineness of the ash increases the strength development also increases due to the increased surface area of the ash sample. As the surface area increases hydration also increases resulting in greater strength. This is also true of geopolymers and fly ash concrete. The strength development of the blocks using fly FA is not reported as it was less than 1 MPa even at 90 days. G. Strength Development with Type of Lime Slaked or unslaked (raw lime) lime can be used to make FaL-G blocks. The series considered for the comparison were FBS10 and FBS16 at 90 days age. The strength development of the blocks with slaked and unslaked is depicted in Fig Fly ash Figure 5: Strength Development with the Type of Lime It can be observed that strength would be marginally higher if slaked lime is used for the preparation of the blocks. During the casting of the blocks it was observed that unslaked lime caused harshness in the mix after a few minutes. It hindered the process of the casting of the blocks. It is advantageous to use slaked lime. Un-slaked lime is not recommended. H. Strength Development with the Percentage of Fly Ash In the preparation of FaL-G blocks, it is important to estimate the optimum quantity of ingredients used like fly ash. The series considered for this study was FBS, FBS68, FBS9 FBS10 and FBS11 (Fig. 6). For 50% fly ash content the strength developed would be the maximum for both the water-to-binder ratios as shown in Fig. 6. It is true in all the cases. A fly- ash content of 50% (in the total binder) can be recommended to get optimum strength for the materials considered. I. Strength Development with Lime Content Figure 7 shows the strength development with different contents of lime. The series considered for this study was FBS, FBS6, FBS8 and FBS9 at the age of 90 days for two different water-to-binder ratios. It was noticed that for 0% of lime content in total binder the strength developed would be maximum. It is true for all the cases considered.

5 Compressive strength (MPa) Compressive strength (MPa) Compressive strength (MPa) Proceedings of International Conference on Advances in Architecture and Civil Engineering (AARCV 01), 1 st rd June maximum strength. The strength development in FaL-G blocks for all the series considered is shown in Fig.9. It is interesting to observe that at constant degree of saturation, the compressive strength development decreases as the water-to-binder ratio increases. It is in accordance with Abrams law [5] which is well established in cement composites Lime Figure 7: Optimum Quantity of Lime FBS1-90Days FBS-10Days FBS-90Days FBS-8Days FBS5-56Days FBS6-90Days FBS7-8Days FBS8-90Days FBS9-56Days FBS10-8Days 1 FBS11-8Days FBS1-56Days 0.5 FBS1-90Days 0 FBS1-8Days FBS15-56Days (w/b) FBS16-90Days Figure 9: Compressive Strength with Water-to-Binder Ratio Gypsum Figure 8: Optimum Quantity of Gypsum J. Strength Development with Gypsum After determining that optimum quantity of fly ash and lime, the quantity of third ingredient gypsum can be estimated in FaL-G with simple calculations. Optimum percentage quantity of gypsum = 100 (optimum quantity of fly ash + optimum quantity of lime) = = 10. This is verified with the experimental available data. The series considered for this study was FBS, FBS6 FBS7and FBS17 (Fig. 8). As expected, the optimum quantity of gypsum found experimentally was 10%, which is the same as estimated. From the present study, it is inferred that the optimum quantities of fly ash, lime and gypsum for the compressed blocks are 50, 0 and 10% to get maximum strength at the age of 90 days. These quantities are the most optimal for the materials considered. However, it may change with the properties of different materials used. In the series FBS1 FBS5, the ratio of fly ash: lime: gypsum is 50:0:10. For further investigations, the blocks were considered from this series. The strength developed was marginally higher with curing temperature. Thermally cured blocks possess marginally higher strength other parameters being the same. But this may not be economical or feasible always. The above parameters in the strength development in FaL- G compressed blocks would be helpful in making the blocks in the field. Optimum values can be considered to get the Figure10: Strength Development with Water-to-Binder Ratio for Fal-G Concrete IV. FSC- FaL-G Concrete in lime Route FCC- FaL-G Concrete in OPC Route (w/b) FAL-G CONCRETE FSC1-8Days FSC1-56Days FSC1-90Days FSC-8Days FSC-56Days FSC-90Days FSC-8Days FSC-56Days FSC-90Days FCC1-Days FCC1-7Days FCC1-8Days FCC-Days FCC-7Days FCC-8Days When the w/b ratio was increased to 0. and more, the consistency of the FaL-G mix makes it flowable and does not require any external effort to transform it into a shape as the mix is fully saturated. It was possible to mould the material just by manual compaction like OPC concrete. At this consistency, it is easy to make concrete using FaL-G as binder. Six series of FaL-G concrete were considered for the study. The source of lime for FSC series was slaked lime and for FCC series, it was OPC. Fig. 10 shows the strength development with w/b ratio for the FaL-G concrete in lime and OPC routes. It is observed that the strength decreases with increase in w/b ratio. It is in accordance with Abrams law [5] which is applicable to OPC and geopolymer concrete. The strength of OPC-route FaL-G concrete was higher compared to lime-route FaL-G concrete.

6 Proceedings of International Conference on Advances in Architecture and Civil Engineering (AARCV 01), 1 st rd June V. CONCLUSIONS The strength development of FaL-G compressed blocks was studied at constant degrees of saturation varying different parameters. It was found that the trend of strength development is unique for various parameters at constant degree of saturation. Masonry compressed blocks can be prepares using FaL-G economically. By using the marginal materials, sustainability can be achieved in the process. The compressive strength in case of FaL-G concrete is comparatively less even after considerable age. Hence this concrete can be used base concrete and roller compacted concrete. The strength development in FaL-G concrete is as per Abrams law. REFERENCES [1] Bhanumathidas, N and Kalidas, N. (00) FaL-G: Hydraulic cement, Proc. Of National workshop on Alternative Building Methods. Department of Civil Engg. Indian Institute of Science. Bangalore: 00, pp.17-. [] Singh.M. and M. Garg, (1997), Durability of cementitious binder derived from industrial wastes, Mater Struct 0, pp [] Sunil Kumar., (00), A perspective study on fly ash lime gypsum bricks and hollow blocks for low cost housing development, Construction and Building Materials, Volume 16, Issue 8, December 00, [] ACI committee , (199) Standard practice for practice for selecting proportions for normal, heavy weight, and mass concrete, American Concrete Institute manual of concrete practice, part 1: Materials and General properties of concrete, pp8 ( Detroit, Michigan, 199) [5] Abrams D. (198), Design of concrete mixtures, Bulletin No.1, Structural Materials Research Laboratory, Lewis Institute Chicago, p [6] Radhakrishna, Analysis and Assessment of Compressive Strength in FaL-G Composites, The Journal of Solid Waste Technology and Management, Volume 6, No., May 010, pp