Use of classified rice husk ash for high strength concrete

Salim Ahmed Barbhuiya, Pichai Nimityongskul and Junlatep Chitasombuti

This study was conducted to investigate the feasibility of using classified rice husk ash (RHA) to replace some part of cement in high strength concrete. The research involved partial replacement of cement by different fineness of RHA. The percentage replacements of cement by each type of RHA were 0 percent, 15 percent and 30 percent by mass of cementitious material. The total cementitious material content, water-binder ratio, fine-to-total aggregate ratio and aggregate-to-cementitious material ratio were kept constant. The properties studied include compressive, flexural and splitting tensile strengths of concrete. Test results reveal that it is possible to replace a part of cement by classified RHA while making high strength concrete.

Effects of addition of more than two chemical admixtures on concrete properties

K.B. Prakash and D.K. Kulkarni

Durability aspects of steel fibre-reinforced SCC

N. Ganesan, P.V. Indira and P.T. Santhosh Kumar

Experiments were conducted to study the effect of steel fibres on the durability parameters of self compacting concrete (SCC) such as permeability, water absorption, abrasion resistance, resistance to marine as well as sulphate attack. The variables considered were aspect ratio (0, 15, 25 and 35) and volume fraction (0, 0.25 , 0.5 and 0.75 percent) of steel fibres. The water-cement ratio of 0.36 by weight and a trinary blend of cement, fly ash and silica fume were used. A total of 244 specimens were cast and tested for this study. It was observed that the coefficient of permeability and wear of SFRSCC were lower than the corresponding moderate strength concrete. Under the marine and sulphate attack, the losses in mass of concrete and compressive strength of cubes were found to be negligible. It was observed that SFRSCC resists these attacks within tolerable limits and the optimum dosage of fibres for better performance was found to be 0.5 percent.

Mechanical properties of lightweight expanded polystyrene concrete containing fly ash

Daneti Saradhi Babu, K. Ganesh Babu and Wee Tiong Huan

Each year more than 90 million tonnes of fly ash is generated in India; however, the use of fly ash in cement and concrete production is less than 15 percent. With a view to increase its utilisation further in concrete industry, lightweight expanded polystyrene (EPS) concretes were developed using high volumes of fly ash (30 and 50 percent). The present study covers mechanical properties of these lightweight concretes designed for a wide range of concrete densities ranging from 550 to 2200 kg/m3. The results indicate that the compressive strengths of lightweight EPS concretes containing fly ash show a better strength gain rate even after 28 days, unlike that reported for EPS containing ordinary Portland cement and silica fume in literature. It was also found that the failure of these concretes both in compression and splitting tensile strength tests and stress-strain tests was gradual as was observed earlier for the concretes containing plastic shredded aggregates. EPS concretes exhibited only local failure and the structural integrity of the concrete also was not affected much.

Reliability of RC slab culverts

Praveen Nagarajan and Devdas Menon

This paper presents a reliability-based analysis of reinforced concrete slab culverts constructed as per the design recommendation of the Ministry of Road Transport and Highways (MORTH) at the flexural limit states. Hasofer and Lind's technique is employed to evaluate reliability index, , which is a measure of probability of failure. The results indicate that the nominal probability of failure of slab culverts designed as per MORTH's recommendations at the limit state of collapse in flexure lies in the order of 10^-5 to 10^-8, which reveal that the designs are conservative (in comparison with AASHTO's recommendations), and the degree of conservatism is not uniform for all spans.

PACs : An effective tool for transfer of new and innovative technologies to field

J.K. Prasad and R.K. Celly

Since the beginning of civilisation, human beings have utilised locally available resources with necessary changes for constructing shelter and for satisfying other infrastructural needs. A variety of materials and techniques have been used over the ages. The materials/techniques are required not only to fulfill the functional needs for the intended purpose but also to meet durability and safety requirements. A proper code of practice is also required to use such materials/techniques. The user and all others concerned require to know whether the materials/techniques being used would serve the above requirements and whether proper guidelines for their use exist. Standardisation has played an important role in achieving these objectives. A number of materials and techniques has been standardised at corporate, association, national/international levels and documented as standards. However, for effective use of materials and systems, national standards are referred. Compliance with a national standards, preferably by a third party/independent agencies brings confidence in the user's mind about the suitability of any materials/systems. The process of formulation of a standard at national level requires necessary authentic data regarding the performance including its testing, durability, usability and a general acceptance of the materials/techniques by all those involved in the formulation of standards. Due to a variety of reasons such as lack of technical data, product being a proprietary item, absence of code of practice, lack of acceptance at national level etc., there remains a time gap between the introduction of new/innovative material/system and availability of a national standard on the subject. Many such technologies/materials therefore, do not easily get translated to field use, though they have potential to replace conventional materials.