Concrete Engineering

By
Shubham Sunil Malu

1.0 INTRODUCTION:
Cracking is one of the major issues in concrete. Since concrete has various physical and chemical properties it is prone to cracking. Its elimination is not possible totally but it can be restricted or reduced to a certain extent. Mostly, cracking goes on a microscopic scale and does not appear visibly as a fault. If the cracking goes on a macroscopic scale it can result in loss of strength, stability and durability. It can also cause decrease in sound insulation and overall efficiency besides affects aesthetics to a greater extent.

The main causes of cracking are as follows:

• Ageing – Carbonation
• Foundation problems
• Weathering Actions
• Improper or modified use of the structure
• Poor maintenance
• Progressive loading
• Deficiencies in design
• Poor quality of concrete material
• Improper concrete mix
• Movement of concrete arising from physical properties
• Poor workmanship and negligence
• Over trowelling and impermeable formwork
• Reduced continuity of the structural member
• Defects and errors in construction practices
• Improper structural repairs or modification
• Chemical attacks by Chlorides and Sulphates
• Differential thermal stress – Heat of hydration of cement

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By
Shubham Sunil Malu

ABSTRACT:
A concrete plant, also known as batch plant is device that combines various ingredients to form concrete. In general, it is a process of combining all ingredients of concrete as per the mix design. Batching and mixing are extremely important parts of mortar and concrete manufactures they influence properties of concrete both in plastic as well as in hardened stages. Also, it is one of the important processes, which is to be done to obtain a quality concrete. Many processes are carried out in various parts of the world with many changes and different equipment. There are various types of batching and mixing equipment and methods that is to say from manual to most sophisticated computerized batching and mixing. Mechanization improves quality of batching and mixing, its speed and thereby can most often result in economy.There are number of factors which are to be considered while doing the process which are discussed in this paper. Moreover, the machinery, which is to be required while making concrete or for batching process and discharging and unloading of the mixture, are also discussed in brief.
1.0 INTRODUCTION:

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By:
Shubham Sunil Malu.

ABSTRACT:
With the growth of construction industry there is need to give quality in it. Many of the projects fail in construction field because of improper results and improper testing on site. One of the basic and important test is compressive test which should be done carefully since it is taken as the backbone of all tests of civil engineering related to concrete. Compression test is required almost in every project since it gives us a brief idea of the grade and type of concrete. Many of them do small mistakes in these which includes the different exclusion of different parameters of concrete, improper procedure for filling and compacting concrete, wrong methods of testing of concrete and many more. This paper contains all the necessary parameters, equipment and the acceptance criteria of the test. It also includes procedure for filling and compacting concrete as well as methods of testing of concrete.

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By
Sourav Dutta
Manager-Civil

What is slab?
A RCC (Reinforced Cement Concrete) slab is the most common structural element of any type of building. Horizontal slabs, typically between 4 and 20 inches (100 and 500 millimeters) thick, are most often used to construct floors and ceilings.Here discussion on “flat slab” has not been considered.

Typical loads to be considered for slab design
(i) Dead load: Any permanent load acting on the slab e.g. self-weight of slab, weight of floor finish & plaster

(ii) Live Load: Any non-permanent or moving load e.g. weight of occupants, furniture, and partitionon the slab

(iii) Snow load (if any)

Note: Earthquake and Wind loads are not considered in the design of slabs.

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By
KAUSHAL KISHORE
Materials Engineer, Roorkee

While carrying out Concrete Mix Design, there are chances that we do not consider some technical points resulting the production of poor quality concrete. This is best illustrated by the following two examples. The I^st mix design is carried out carelessly, where as the 2^nd mix design is worked out taking into consideration all technical points. In both mix design examples the materials and requirements are same as given below:

1. Cement, PPC, 7-days strength 36.5 N/mm² and 28-days strength 46.8 N/mm². Specific gravity 3.0
2. Aggregates grading are as given below:

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By
Sourav Dutta
Manager-Civil

Introduction
There are a number of ways in which the superstructure can be built. In areas where average to good quality bricks are available, the walls of houses for two to three storeyed constructions can be built out of bricks with the slabs, lintels, chajja etc. in reinforced concrete. Such construction is termed as load bearing construction (Fig 1). This is essentially because the entire load coming from the slabs, beams, walls etc is transmitted to the foundation through the brick walls.

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By
Priyanka Gupta

1.0 Introduction

In small residential buildings the quality of construction is seldom questionable. The reason varies from poor building material quality to lack of knowledge of good construction practices. Most of the times, engineers are ignored by individual house owners and masons are given sole responsibility of both design and construction. Almost all structural engineers practicing in India will agree that 99% of the failures of structures in India are not due to design failure.

Explaining the different aspect of construction that a normal home builder, engineer or contractor needs to remember.

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BY
ANBARASAN.R, MANIKANDAN.P AND SURESH.S,
Department of civil engineering,
IFET College of Engineering. Tamil Nadu, India.

Abstract
Steel gets oxidise (corrosion) in the present of oxygen and water. Even present of oxygen in the concrete pore will not cause a corrosion at high alkaline environment. Concrete contains microscopic pores which contain high concentrations of soluble calcium, sodium and potassium oxides, this creates alkaline condition of pH 12–13. The alkaline condition leads to a ‘passive’ layer forming on the steel surface. The dense passive layer over the reinforcement prevents the alkalinity. This paper involves in the prevention of corrosion by maintaining alkalinity in concrete by using bacteria.

Key words: Reinforced concrete, corrosion, passive layer, alkaline, bacteria.

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BY
E.Divya¹ , R.Shanthini², S.Arulkumaran³
Student, Dept. of civil engg., IFET college of engg., India^{1, 2}
Asst. professor, Dept. of civil engg., IFET college of engg., India³

ABSTRACT
The use of quartz sand as replacement for sand is an economical solution for making the concrete resistant to weathering. The paper presents a concrete mix design procedure for partial replacement of sand with quartz sand. Present method was performed to evaluate the additional compressive, flexural strength with higher slump over conventional concrete in which sand is replaced with 0%, 25%, 50% and 100% of quartz sand by weight with 1% super plasticizers. The research also revealed that there is possibility of replacing fine aggregate with quartz sand in the production of structural concrete. The mix proportion adopted was 1:1.7:3 as per 10262:2009. Compressive and flexural strength tests were carried out to evaluate the strength properties of concrete at the age of 7 and 28 days. Modulus of elasticity tests were carried out at the age of 28 days.

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By
1) KAUSHAL KISHORE
Materials Engineer
Roorkee
Kaushal Kishore is retired from IIT, Roorkee and now a Consulting Materials Engineer. He has over 50 years of experience in all types of Concrete Mix Design.

2) RAKESH SHARMA
Vice President Project
Supertech Limited
Rakesh Sharma is Vice President Project of M/s Supertech Limited. He has 28 years of experience in Construction.

I.T. Park, Doon Square Mall at Dehradun, Uttarakhand is being constructed by M/s Supertech Ltd. For this site M-30 grade of concrete suitable for pumped concrete is required. Aggregates for construction was stored at site. Its analysis report is given in Table 2.

For laboratory trial 5 brands of PPC cement bags were taken from local market. They were identified as cement brand, 1, 2, 3, 4 and 5. Two reputed brands of normal superplasticizers based on sulphonated naphthalene formaldehyde (SNF) were taken for trials. They were identified as SP (A) and SP (B) to find their compatibility with the given 5 brands of PPC cement identified as cement brand 1, 2, 3, 4 and 5.

COMPATIBILITY
The behavior of concrete in the presence of superplasticizers is related to the amount and type of sulfate added to the clinker. The rheological and setting Behavior are changed depending on whether the sulfate is added as anhydrite, hemihydrates, or gypsum. The difference are explained by the different rates of dissolution of these sulfates.
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