Polymer-Modified Mortars And Concrete Mix Design

Kaushal Kishore
Materials Engineer, Roorkee

Polymer-modified Concrete (PMC) has also been called polymer-Portland cement-concrete (PPCC) and latex-modified concrete (LMC). It is defined as Portland cement and aggregate combined at the time of mixing with organic polymers that are dispersed or redispersed in water. This dispersion is called latex; the organic polymer is a substance composed of thousands of simple molecules combined into large molecules. The simple molecules are known as monomers, and the reaction that combine them is called polymerization. The polymer may be a homopolymer if it is made by the polymerization of one monomer, or a copolymer when two or more monomers are polymerized.

Of various polymer-modified mortar and concrete, latex-modified mortar and concrete have superior properties, such as high tensile and flexural strength, excellent adhesion, high waterproofness, high abrasion resistance and good chemical resistance, to ordinary cement mortar and concrete. Accordingly they are widely used in many specialized applications in which ordinary cement mortar and concrete have been employed to a lesser extent till now. In these applications, the latex-modified mortars are widely used rather than the latex-modified concrete from the viewpoint of a balance between their performance and cost.
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Quality Control Of Construction Testing Of Concrete Cubes

By Kaushal Kishore
Materials Engineer, Roorkee

The acceptance criteria of quality of concrete is laid down in IS:456-2000. The criteria is mandatory and various provisions of the code have to be complied before the quality of concrete is accepted. In all the cases, the 28-days compressive strength shall alone be the criterion for acceptance or rejection of the concrete. In order to get a relatively quicker idea of the quality of concrete, optional test for 7 days compressive strength of concrete be carried out.

6 Cubes of 150 x 150 x 150 mm size (the nominal size of aggregate does not exceed 38 mm) shall be cast, 3 for 7-days testing and 3 for 28-days testing. A set of
3 cubes (specimen) average strength will be a sample. The individual variation of a set of 3 cubes should not be more than ± 15% of the average. If more, the test result of the sample is invalid.

Note:- For aggregates larger than 38 mm, bigger than 150 mm moulds are to be used. See IS:10086-1982
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Development Of Light Weight Concrete

Dhawal Desai
IIT Bombay

This paper deals with the development of two types of lightweight concrete the one using lightweight aggregate (Pumice stone) and the other water floating type using Aluminium powder as an air entraining agent. This also shows the importance of water/cement ratio as in first type of concrete it relates to the smoothness of the surface and in second one it is a major factor which controls the expansion of concrete.

Lightweight concrete can be defined as a type of concrete which includes an expanding agent in it that increases the volume of the mixture while reducing the dead weight. It is lighter than the conventional concrete with a dry density of 300 kg/m3 up to 1840 kg/m3. The main specialties of lightweight concrete are its low density and low thermal conductivity.
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Pervious Concrete – Effect of Material Proportions on Porosity

Dhawal Desai

This paper describes the effect of size of aggregates and proportions of cement, aggregates, admixture and water on porosity of Pervious concrete which is the main feature of pervious concrete. Different sample blocks were made in lab with variations in mixture to see the porosity for final conclusion

Pervious concrete is a type of concrete with high porosity. It is used for concrete flatwork applications that allow water to pass directly through it, thereby reducing the runoff from a site and allowing groundwater recharge. The high porosity is attained by a highly interconnected void content. Typically pervious concrete has water to cementitious materials ratio (w/cm) of 0.28 to 0.40 with a void content of 18 to 35%.
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Behavior of Concrete in Shear and Torsion with Different Types of Steel Fiber Using Constant Volume Fractions and Different Aspect Ratio

Kishor Sambhaji Sable (Faculty, Civil Engineering Department, Amrutvahini College of Engineering, Sangamner, Ahmednagar, Maharashtra, India)

Yogesh Ravindra Suryawanshi (M.E Civil (Structures), Amrutvahini College of Engineering, Sangamner, Ahmednagar, Maharashtra, India)

Mehetre Amol Jagganath (Faculty, Civil Engineering Department, Amrutvahini College of Engineering, Sangamner, Ahmednagar, Maharashtra, India)

In this modern age, civil engineering constructions have their own structural and durability requirements. Fiber Reinforced Concrete (FRC) is a composite material made primarily from hydraulic cements, aggregates and discrete reinforcing fibers. Fiber incorporation in concrete, mortar and cement paste enhances many of the engineering properties of these materials such as fracture toughness, flexural strength, resistance to fatigue, impact, thermal shock and spalling.

The SFRC is a composite material made of cement, fine and coarse aggregates and discontinuous discrete steel fibers. Recently developed an analytical model to predict the shear, torsional strength and bending torsion behavior of fiber reinforced concrete beam with experimental substantiation. However, very little work has been reported in combined torsion and shear. Similarly to beam with conversional reinforcement, the presence of shear may significance influence on torsional strength of fiber concrete beams. Present paper investigates the mechanical properties like as shear strength, and torsion strength of concrete with different types of steel fiber with constant volume fractions and different aspect ratio.

Key words: Aspect ratio, Fatigue, Flexural strength, Fracture toughness, Mechanical properties, Spalling, Volume fraction.
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