Mix Design For Concrete Roads As Per IRC:15-2011

By
Kaushal Kishore, Materials Engineer, Roorkee

ABSTRACT:
The stresses induced in concrete pavements are mainly flexural. Therefore flexural strength is more often specified than compressive strength in the design of concrete mixes for pavement construction. A simple method of concrete mix design based on flexural strength for normal weight concrete mixes is described in the paper.

INTRODUCTION:
Usual criterion for the strength of concrete in the building industry is the compressive strength, which is considered as a measure of quality concrete. However, in pavement constructions, such as highway and airport runway, the flexural strength of concrete is considered more important, as the stresses induced in concrete pavements are mainly flexural. Therefore, flexural strength is more often specified than compressive strength in the design of concrete mixes for pavement construction. It is not perfectly reliable to predict flexural strength from compressive strength. Further, various codes of the world specified that the paving concrete mixes should preferably be designed in the laboratory and controlled in the field on the basis of its flexural strength. Therefore, there is a need to design concrete mixes based on flexural strength.
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Given a 1m high staircase resting on solid concrete, would it be adequate to design nominal reinforcement for the staircase?

For the design of staircase, there are three main scenarios:

(i) Stairs spans longitudinally
This kind of stairs refers to stairs spanning between landings only without any side supports. In this case, the staircase should be designed as a beam between two end supports (i.e. landing) and the main reinforcement is provided at the bottom of staircase slabs.

(ii) Stairs spanning transversely
This kind of staircase is supported by sidewalls only and it may also be supported by stringer beams. For the case of sidewalls, it acts as a cantilever beam and the main reinforcement are provided the top surface of slab. For the case of staircase supported sideways by both sidewall and stringer beam, it should be designed transversely with end supports as sidewall and stringer beam and reinforcement is provided at the bottom of the staircase.

(iii) Stairs resting on solid support
For stairs resting on solid supports, only nominal steel reinforcement is provided to control thermal and shrinkage cracking.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

Study Of Crack Pattern And Strength With Replacement Of Natural With Artificial Fine Aggregate In Concrete

Submitted By
Vinayak Ravindra Supekar.
(National Institute Of Construction Management And Research Center, (Nicmar))

ABSTRACT:
Now days the construction industry in the India is facing one of the major problem that is natural fine aggregate. And court awarded that totally band on excavation of fine aggregate from river because they affect on environment and changing the river direction. (fig.5). Thus the more natural fine aggregate are highly needed to replace with artificial fine aggregate. This paper presentation the study of crack pattern of concrete slab, each size is (500*300*50) mm and replacement of natural fine aggregate with artificial fine aggregate by 20%,40% 60% 100% and also finding the compressive Strength of that concrete cube. And these experiment is carried out maintain temperature 32 0cAnd the according to experimental result show that the replacement of natural sand by artificial sand up to 60% and gives best result that is maximum strength and minimum area of crack.

Key words: – Concrete slab, natural fine aggregate, artificial fine aggregate (grit), crack pattern.
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Assessment of the properties of Self-Cured Concrete.

By
Nagesh Tatoba Suryawanshi
Asst.Professor in Civil Engg. dept
S. B. Patil, College of Engineering, Indapur,(Pune).

Abstract

This Paper reports an experimental study carried out to investigate the use of water-soluble polyvinyl alcohol as self-curing agent. In this study Compressive and tensile strength of self-curing concrete for 7 and 28 days is found out and compared with conventional concrete of similar mix design. The durability of self curing concrete is found out by exposing concrete cubes to chloride environment and effect of the same on strength of cubes is determined by finding out compressive strength of cubes. The results indicated that Water retention for the concrete mixes incorporating self-curing agent is higher compared to conventional concrete mixes, as found by the weight loss with time. The result also showed that compressive, tensile and flexural strength of self curing concrete is found to be higher than conventional concrete.

Key words: Self curing agent, polyvinyl acetate, polyvinyl alcohol, water Retentivity. etc.

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An Experimental Study on Synergic Effect of Sugar Cane Bagasse Ash with Rice Husk Ash on Self Compaction Concrete

By
Amir Juma
(Amir Juma is in his final semester of Bachelor of Science in Civil Engineering in Koneru Lakshmaiah University-India. His research interests lie in the field of Self Compaction Concrete.)

E.Rama Sai
(E.Rama Sai is in his final semester of Bachelor of Science in Civil Engineering in Koneru Lakshmaiah University-India. His research interests lie in the field of Self Compaction Concrete.)

D.V.A.K.Prakash
(D.V.A.K.Prakash is in his final semester of Bachelor of Science in Civil Engineering in Koneru Lakshmaiah University-India. His research interests lie in the field of Self Compaction Concrete.)

Md. Shahbaz Haider
(Md.Shahbaz Haider is in his final semester of Bachelor of Science in Civil Engineering in Koneru Lakshmaiah University-India. His research interests lie in the field of Self Compaction Concrete.)

S.Kanakambara Rao
(Associate Professor in Department of Civil Engineering in Koneru Lakshmaiah University-India. He specialized in structural Engineering and research interests lie in the field of Self Compaction Concrete.)

Abstract
Self-compacting concrete, also referred to as self-consolidating concrete, is able to flow and consolidate under its own weight and is de-aerated almost completely while flowing in the formwork. It is cohesive enough to fill the spaces of almost any size and shape without segregation or bleeding. This makes SCC particularly useful wherever placing is difficult, such as in heavily-reinforced concrete members or in complicated work forms.

The objectives of this research were to make a synergic effect of Rice husk Ash (RHA) and Sugar cane bagasse ash(SCBA) incorporated in self compaction concrete in order to increase in strength and a better bonding between aggregate and cement paste, . The mix design used for making the concrete specimens was based on previous research work from literature. The water – cement ratios varied from 0.3 to 0.75 while the rest of the components were kept the same, except the chemical admixtures, which were adjusted for obtaining the self-compactability of the concrete.

All SCC mixtures exhibited greater vaules in compressive strength after being tested, the compressive strength was around 40% greater. In addition, the SCC had a good rheological properties as per the requirements from European standards from economical point of view the pozzolanic replacements were cheap and sustainable.
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