Date of Award

12-1988

Degree Type

Master's Essay - Restricted

Degree Name

Master of Science (MS)

First Advisor

S.H. Wenzel

Second Advisor

Richard Cluft

Abstract

In concrete structures, admixtures are used to impart special properties to the mix. Admixtures can be broadly classified as: (1) air-entraining admixtures, (2) water-reducing admixtures, (3) retarding admixtures, ( 4) accelerating admixtures (5) pozzolan admixtures, (6) workability agnts and (7) dampproofing and permeability reducing agents. DELVO is the commercial name of one of the newest admixtures that is available. It could be classified as a retarding admixture.

There are two main reasons why retarding admixtures are used. First, a retard­ing admixture can be used to produce a concrete with a high degree of workability and second, retarding admixtures can be used to produce high strength concrete with normal workability and a lower water content. Because of this, retarded concrete can be placed in very congested areas as well as in special shapes where vibration or compaction is difficult or impossible. Easy and quick placement is necessary for concrete that is used in bay areas, floor systems, foundation slabs, bridges, pavements,...etc. [1]. Retarded concrete can be pumped and placed by tremie pipe which is particularly useful in underwater locations. It is used by the precast industry since strengths of the order of 40 Mpa can be achieved in 8 to 18 hrs. [2]. Retarded concrete has also been used to produce concrete with a strength of more than 100 Mpa. In addition to producing high strength concrete with a high degree of workability, retarders can be used advantageously in the production of fly ash concrete, blast furnace slag cement concrete, lightweight concrete,. and concrete composites with various types of fibers.

There are limitations associated with the use of retarders. Retarded concrete shows a high rate of slump loss and investigations must be carried out on the compatibility between the retarders and other admixtures such as accelerators and air-entraining agents.

Recently, a new admixture has been introduced in the market. The new admixture as stated earlier is called DELVO. Because of its ability to delay the setting time of concrete, it can be broadly classified as a. retarder. DELVO stops the cement hydration by forming a protective barrier around cementitious particles. This barrier prevents portland cement, fly ash, and granulated slag from achieving initial set.

The objective of this paper is to examine the strength properties of concrete made with varying amounts of the admixture DELVO. An experimental study was conducted on a number of specimens with different amounts of the material. Results were compared with those of a plain mix without the DELVO additive. The compressive strength was determined for standard cylinders when the concrete was 28 days old.

A review of the literature is presented in chapter 2. This includes general information on admixtures as well as detailed information on retarders. In addition, a brief description of the material DELVO is given.

In chapter 3, a discussion of the testing program is presented. This includes a discussion of the specifications for properties of the constituents, mixes, mix production and preparation of the specimens.

In chapter 4, the results from the study are discussed. Finally, a summary of the results obtained from the tests as well as the conclusions and recommendations are presented in chapter 5.

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