Test Method for Effectiveness of Pozzolans or Ground Blast-Furnace Slag in Preventing Excessive Expansion of Concrete Due to the Alkali-Silica Reaction

Alkali substances are present in cements used as a binder in concrete only in a minimum content. The most known process that alkali causes is the alkali-silica reaction. In this reaction, the alkali contained in the cement or supplied from the outside with an inappropriately selected aggregate containing amorphous SiO2. This reaction results in the development of hydration products, resulting in an increase in the volume of the original components, which can cause a breakage of the concrete structure and subsequent disintegration. The range of alkali-silica reaction can be reduced by the use of a suitable aggregate or the use of Type II admixtures which are characterized by pozzolanic or latently hydraulic activity. These admixtures react with alkali and then no longer react with the amorphous SiO2 contained in the aggregate. Alkalis also affect other properties of concrete such as basic physical-mechanical properties, frost resistance and pH.In the experimental part the pH values were compared between mixtures of Portland cement and alkaline activated blast furnace slag using slag aggregate from the heap Koněv.

Download Full-text

Early Age Cracking Characteristic of Concrete with Compound Admixtures

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.325-326.71 ◽

2013 ◽

Vol 325-326 ◽

pp. 71-74

Author(s):

Yun Feng Li ◽

Dong Sheng Zhang ◽

Li Xu

Keyword(s):

Blast Furnace ◽

Fly Ash ◽

Blast Furnace Slag ◽

High Performance ◽

High Performance Concrete ◽

Steel Slag ◽

Test Method ◽

Mineral Admixture ◽

Early Age ◽

Furnace Slag

The shrinkage cracking of concrete plays an important role to the accelerated deterioration and shortening the service life of concrete structures. The mineral admixture will be a perfect component of high performance concrete and its utilization will be a valuable resource for recycling. Early age cracking characteristics of concrete with compound admixtures, such as steel slag, blast furnace slag, fly ash, are studied in this paper using plate test method. The better anti-cracking performance of concrete will be realized when blast furnace slag replacing cement at 30%, steel slag and fly ash as the equal mixture components replacing cement at 30%, three kinds of admixtures replacing cement at 30% under the proper proportion.

Download Full-text