Development and characterization of al sic composites

Dissertant

Tawfiq, Sinan Samir

University

University of Technology

Faculty

-

Department

Department of Chemical Engineering

University Country

Iraq

Degree

Master

Degree Date

2004

English Abstract

Considerable researches and studies have been conducted to investigate various properties of lightweight concrete and no-fines concrete.

However, very limited amount of work have been reported concerning these types of concrete incorporating lightweight aggregate and air entraining agent.

In this thesis local porcilinite lightweight aggregate is used and air entraining agent is added to form large quantity of air bubbles within the concrete mass in an easy and economical way without the need for air bubble generator.

The aim is to reduce the density of concrete and then to increase the thermal and electrical insulation and to attain better sound absorption.

The experimental work includes the preparation of three types of mixes.

The first mix is no-fines concrete with mix proportions (1 : 1, 1 : 1.5, 1 : 2, 1 : 3, 1 : 4, 1 : 5, 1 : 6) by weight using single size aggregate.

The second mix is lightweight aggregate concrete with mix proportion 1 : 2 : 2.2 and the third mix is lightweight porcelanite mortar with mix proportions 1:2 and 1:3 by weight.

The percentage of flow is maintained between (45-55) % for the first and second type of mixes to prevent segregation and to maintain uniformity of the mix.

For mortar mix, the W / C ratio is adjusted to attain a flow of (90-100) %.

Various tests are conducted; 28 days air dry density, compressive strength and drying shrinkage at various ages up to 90 days, thermal conductivity, ultrasonic pulse velocity and electrical resistance at 60 days.

Relationships between these properties are clearly established.

The values of 28 days air dry density for no-fines porcelanite aggregate concrete lies between 845-1450 kg / mj and their compressive strength falls in the range of 1.2-22.5 MPa based on the mix proportion.

The use of air entraining agent lead to reduction in density lies between 1.2-13.25 % and reduction in compressive strength ranged between 6.1-30.6 %.

The values of thermal conductivity for this type of concrete with air entraining agent are within the range of 0.309-0.402 Watt / m.

Kelvin.

Thereby this concrete is suitable for thermal insulation purposes at low cement content whereas it is suitable for structural purposes at high cement content.

The value of 28 days air dry density for lightweight porcelanite aggregate concrete is 1245 Kg / m5 and its compressive strength is 10.07 MPa.

The use of air entraining agent lead to 10 % reduction in density and 56% reduction in strength.

The thermal conductivity for this concrete with air entraining agent is 0.493 Watt / m.

Kelvin.

Accordingly this concrete is also suitable for insulation purposes.

The values of 28 days air dry density for lightweight porcelanite mortar falls between 1346-1694 Kg / m3 and their compressive strength between 10.6-16.44 MPa depending on mix proportion.

The use of air entraining agent lead to reduction in the values of densities to between 764-951 Kg/mj and reduction in the values of strength to between 0.24-0.8 MPa.

The significant reduction in density is of vital importance for thermal insulation purposes.

Results indicated that the pulse velocity values are between 1.93-3.13 Km / sec and the electrical resistance lies between 840-6460 Ohm for no-fines porcelanite aggregate concrete.

The use of air entraining agent lead to reduction in pulse velocity values to between 1.87-2.86 Km / sec and in electrical resistance to between 813-4236 Ohm.

On the other hand, the pulse velocity and the electrical resistance values for lightweight porcelanite aggregate concrete are 2.59 Km / sec and 2979 Ohm for the adopted mix respectively.

The use of air entraining agent lead to a reduction in pulse velocity to 2.28 Km / sec and to increase in electrical resistance to 4236 Ohm The maximum value of drying shrinkage for no-fines porcelanite lightweight aggregate concrete is 0.130 x l0 6 and for lightweight porcelanite aggregate concrete is 0.492 x 106.

The use Of air entraining agent lead to a reduction in the latter value to 0.435 x 10.

But the rate of drying shrinkage for these types of cone is considered high since 80 % of shrinkage occurs in 40 days.

Main Subjects

Chemistry

Topics

• Concrete
• Mechanical properties

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-305596