Sustainable Construction—High Performance Concrete Containing Limestone Dust as Filler

Massive amounts of limestone waste are produced by the stone processing industry worldwide. Generally, it is believed that 60% to 70% of the stone is wasted in processing in the form of fragments, powder and slurry out of which around 30% is in the form of fine powder [1]. This waste has no beneficial usage and poses environmental hazards. Use of this waste product in the construction industry can largely reduce the amount of waste to be disposed off by the local municipalities in addition to reducing large burden on the environment. Some basic research on use of limestone dust as cement/ concrete filler has been carried out in the recent past but high strength/ high performance concretes have not been investigated yet [2] [3]. The concrete industry is among the largest consumer of raw materials worldwide and has been investigated for use of various types of waste materials like crushed brick, rice husk and straw ash as either aggregates for concrete or as partial cement substitutes. Use of limestone dust as filler material in concrete can consume a huge amount of this waste material which has to be disposed off otherwise, creating large burden on the environment. This experimental study aimed at evaluating the properties of high performance concretes made from Portland cement, natural aggregates and sand. Limestone dust was added by replacing sand in the percentages of 10% and 20%. Wide ranging investigations covering most aspects of mechanical behavior and permeability were carried out for various mixes for compressive strengths of 60 N/mm, 80 N/mm and 100 N/mm. Compressive strengths of concrete specimen with partial replacement of sand with 10% and 20% limestone dust as filler material for 60 N/mm, 80 N/mm and 100 N/mm were observed to be higher by about 4% to 12% than the control specimen. Flexural strengths were also observed to be higher by 12% 13%. Higher elastic moduli and reduced permeability were observed along with better sulphate and acid resistance. Better strengths and improved durability of such high-performance concretes make it a more acceptable material How to cite this paper: Kibriya, T. and Tahir, L. (2017) Sustainable Construction— High Performance Concrete Containing Limestone Dust as Filler. World Journal of Engineering and Technology, 5, 404-411. https://doi.org/10.4236/wjet.2017.53034 Received: May 15, 2017 Accepted: July 14, 2017 Published: July 17, 2017 Copyright © 2017 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Open Access T. Kibriya, L. Tahir 405 for major construction projects.


Introduction
The quality of concrete has improved tremendously over the recent years due to ongoing research on newer materials and chemicals. High performance concretes with improved strengths and durability are readily available in the markets. Scarcity of natural aggregates and cement manufacturing raw materials has led to exploration of cheaper alternatives worldwide. Furthermore, sustainable and emerging green practices leading to environmentally friendly materials have led to use of many waste materials in manufacturing of cement and concrete.
These have led to newer avenues especially in the developing/under developed countries where resource crunch is a major hurdle towards development. A number of studies have been carried out to find better/cheaper aggregates and cements along with better usage of waste materials in construction [4]- [11].
Massive amounts of limestone and marble are quarried and used worldwide for various purposes. Marble is a refined form of limestone and dolomite formed by their metamorphism. During cutting and sawing process of limestone, huge amounts of fragments, fine powder and slurry are generated as waste product.
Generally, it is believed that 60% to 70% of the stone is wasted in this process in the form of fragments, powder and slurry out of which around 30% is in the form of fine powder [1]. Large quantities of limestone processing waste worldwide poses disposal problems since it has no beneficial usage. Use of limestone dust waste in production of concretes for major construction projects will certainly reduce the costs and will hence result into cheaper construction and improved durability. Bulk use of this waste material can consume large quantities in construction industry, thereby reducing the burden on the environment in addition to producing environment friendly concrete. In the absence of any worthwhile research in this field, this study was undertaken to assess the properties of concretes produced by using limestone dust as partial fines replacement.

Research Significance
The significance of this research is to investigate the possible use of an abundantly available waste product in construction industry thereby solving its disposal problems along with possibility of obtaining a better product i.e. high performance concrete with improved characteristics. Environment is benefitted as a consequence.  All specimens were cured in water at 20˚C for 28 days before testing.

Discussion of Test Results
The properties of the high-performance concretes produced are summarized in Table 2 and Table 3.

Compressive Strength
Compressive strength tests on cubes at 7 & 28 days showed that the rate of   Table 2 gives the compressive strengths of the samples as well as the control specimen.

Flexural Strength
The flexural strength of high performance concrete with 10% sand replaced with limestone dust as well as specimen containing 20% sand replaced with limestone dust both were observed to be higher by 12% to 13% as compared to control specimen. Higher flexural strengths are certainly a consequence of higher compressive strength and increased density of concrete with 10% and 20% sand replaced with limestone dust as compared to the control mixes as shown in Table 2.

Stress/Strain Behavior
It was observed that the general slope of the stress/strain curve for high performance concrete with 10% sand replaced with limestone dust as well as specimen containing 20% sand replaced with limestone dust both were similar to the curve for control specimen. All the curves were observed to be virtually linear up to the point of failure which is typical of high strength concretes. Higher static and dynamic moduli of elasticity were observed for high strength concretes with 10% sand replaced with limestone dust as well as specimen containing 20% sand replaced with limestone dust both. Values for static and dynamic moduli are given in Table 3 while idealized stress/strain relationships for all samples are shown in     Table 3.

Dynamic Modulus of Elasticity
Dynamic Modulus of Elasticity for concrete with 20% sand replaced with limestone dust was observed to be 4% higher than the control as compared to concrete with 10% sand replaced with limestone dust which was observed to be about 2% higher than the control specimen. Table 3 gives the values of Dynamic Moduli of Elasticity of various specimen.

Ultrasonic Pulse Velocity
Average pulse velocity across concrete with specimen containing 10% and 20% sand replaced with limestone dust was observed to be 5.2 and 5.4 km/s respectively as compared to an average velocity of around 4.8 km/s for control mixes.
Hence ultrasonic pulse velocity in the case of concrete with 10% and 20% sand replaced with limestone dust was observed to be 10% to 12% higher than the control mixes. Higher pulse velocities are certainly due to better quality, higher density and reduced voids in the high strength concretes containing partial replacement of limestone dust with sand, as compared to the control mixes. The ultrasonic pulse velocities observed for different concretes are given in Table 3.

Density of Hardened Concrete
The average saturated and oven-dried densities for high strength concrete with 10% and 20% sand replaced with limestone dust were 2580 and 2490 kg/m 3 respectively, as compared to control mixes which were 2488 and 2461 kg/m 3 , respectively. Hence the saturated and dry densities of concrete with 10% and 20% sand replaced with limestone dust are about 4% & 2% higher respectively than the control mixes. Higher densities for concrete with 10% and 20% sand replaced with limestone dust are due to better packing of materials in concrete with sand replaced with fine limestone dust. In the presence of higher content of fines and cementitious material and low w/c ratios, most of the unhydrated cementitious material too acts as filler to densify the concrete, whilst the hydration process continues over longer duration.

Initial Surface Absorption (ISAT)
Initial surface absorption for concrete with 20% sand replaced with limestone dust was observed to be lowest with around 22% lower whilst for concrete with 10% sand replaced with limestone dust it was around 19% low as compared to the control. The values are compared with the guidelines given by the Concrete Society Technical Report # 31 [14]. Results of ISAT are given in Table 3.

Sulphate and Chloride Resistance
For chloride resistance, submersion of specimen in HCL solution resulted in average weight loss of 7% for control specimen as compared to 3.6% and 3.2% for concrete with 10% and 20% sand replaced with limestone dust respectively. For sulphate resistance, submersion of specimen in H 2 SO 4 solution resulted in average weight loss for control specimen as 6% as compared to 2.7% and 2% for specimen containing 10% and 20% sand replaced with limestone dust respectively.
Hence, the performance of concrete with partial replacement of sand with limestone dust was almost twice better in acidic environment and slightly over twice better in sulphate environment as compared to concrete with ordinary Portland cement control mixes. Better chloride and sulphate resistance for concrete with 10% and 20% sand replaced with limestone dust is mainly due to the reduced permeability and higher densities of concrete with partial replacement of sand with limestone dust.

Shrinkage
Shrinkage of all specimen was observed to be similar. No appreciable difference in shrinkage of specimen cast from concrete with partial replacement of sand with limestone dust and control mixes were observed for 90 days.

Conclusion
The performance of concrete with partial replacement of sand with limestone dust proved to be satisfactory with improved performance. Compressive strengths of 60/80/100 N/mm 2 can be attained with up to 20% sand replaced with limestone dust in normal concrete mixes. Better packing, reduced voids, improved workability and better hydration due to fines dispersal in the mix resulted into better performance. 4% to 12% higher compressive strengths could be achieved with 10% and 20% sand replaced with limestone dust in normal concrete with higher range for 20% sand replacement with limestone dust. Flexural strength of high performance concrete with 10% and 20% sand replaced with limestone dust is observed to be higher by 12% to 13% as compared to control specimen. The average static modulus of elasticity for concrete specimen containing 20% sand replaced with limestone dust was observed to be about 4% to 5% higher than the control specimen while for concrete with 10% sand replaced with limestone dust, it was observed to be 2% to 3% higher than the control. The average dynamic modulus of elasticity for concrete with 20% sand replaced with limestone dust was observed to be 4% higher than the control as compared to concrete with 10% sand replaced with limestone dust which was observed to be about 2% higher. Ultrasonic pulse velocity in the case of concrete with 10% & 20% sand replaced with limestone dust was observed to be 10% to 12% higher than the control mixes. Saturated and dry densities of concrete respectively than the control mixes. The performance of concrete with partial replacement of sand with limestone dust was almost twice better in acidic environment and slightly over twice better in sulphate environment as compared to concrete with ordinary Portland cement control mixes. There is no appreciable difference in shrinkage of specimen cast from concrete with partial replacement of sand with limestone dust and control mixes were observed for 90 days.