Which supplementary cementitious material increases water demand in the concrete?

silica fume
High-range water-reducing admixtures are often used to offset increased water demand and improve particle dispersion for concretes containing silica fume. Other pozzolanic SCMs include Class F fly ash and raw or processed natural pozzolans such as shale, clay, metakaolin and rice husk ash (RHA).

How do fly ash slag and silica fume affect the following properties of cement paste mortar or concrete?

Fly ash, slag, and calcined clay and shale generally improve the workability of concretes of equal slump. Silica fume may contribute to stickiness of a concrete mixture; adjustments, including the use of high-range water reducers, may be re- quired to maintain workability and permit proper compaction and finishing.

What are the benefits of using supplementary cementitious materials in concrete?

Supplementary Cementitious Materials (SCM’s) are added to concrete mixtures for various reasons including improving durability, decreasing permeability, aiding in pumpability and finishability, mitigating alkali reactivity and improving the overall hardened properties of concrete through hydraulic or pozzolanic …

What is the effect of supplementary cementitious materials on hydration process of Portland cement?

SCMs of this form typically will contain both calcium and reactive silicates. Pozzolanic Reactivity: The SCMs will react chemically with water and the hydrated cement paste to form additional strength-bearing phases and cause a densification of the microstructure.

Does fly ash contain silica?

Fly ash contains crystalline silica which is known to cause lung disease, in particular silicosis, if inhaled.

What is silica fume concrete?

9 – Use of silica fume in concrete Condensed silica fume is a very fine, amorphous, and reactive mineral admixture. It reacts readily with the calcium hydroxide, which is produced during Portland cement hydration. Silica addition refines pore structure and produces concrete of improved mechanical strength.

What is the effect of fly ash in concrete?

The use of fly ash in portland cement concrete (PCC) has many benefits and improves concrete performance in both the fresh and hardened state. Fly ash use in concrete improves the workability of plastic concrete, and the strength and durability of hardened concrete. Fly ash use is also cost effective.

What is cementitious material used for?

SCMs are used in conjunction with portland cement in concrete mixtures to improve the workability of fresh concrete and reduce thermal cracking in massive structures by reducing heat of hydration.

What is a supplementary cementitious material?

Supplementary Cementitious Materials (SCMs) are materials that, when used in conjunction with portland cement, portland limestone cement or blended cements, contribute to the properties of hardened concrete through hydraulic and/or pozzolanic activity.

How does supplementary cementing material affect the strength of concrete?

Supplementary cementing materials (SCMs) contribute to the properties of hardened concrete through hydraulic or pozzolanic activity. Supplementary cementing materials are often added to concrete to make concrete mixtures more economical, reduce permeability, increase strength, or influence other concrete properties.

What are the effects of supplementary cementitious materials on workability of concrete?

Abstract: In view of the global sustainable development, it is imperative that supplementary cementing materials (SCM) be used for replacing cement in the concrete industry and several researchers have shown that mineral admixtures can enhance the workability of lightweight aggregate concrete (LWAC) mixture and its …

What is silica fume fly ash?

Definition: Silica Fume: Very fine non-crystalline silica produced in electric arc furnaces as a by product of the production of elemental silicon or alloys containing silicon-ACI 116R-Grey colored powder similar to Portland cement or some fly ash.

What are the most commonly used supplementary cementitious materials?

Slag cement (Ground Granulated Blast Furnace Slag) and fly ash (Coal Combustion Product) are the most commonly used supplementary cementitious materials in construction today.

What is Class F fly ash in concrete?

Class F materials are generally low-calcium (less than 10\% CaO) fly ashes with common. Supplementary cementitious materials are used in at least 60\% of ready mixed concrete (2000PCA). ASTMC 311 provides test methods for fly ash and natural pozzolans for use as supplementary cementitious material in concrete.

What are the materials used in concrete construction?

Traditionally, fly ash, slag, calcined clay, calcined shale, and silica fume were used in concrete individually. Today, due to improved access to these materials, concrete produc- ers can combine two or more of these materials to optimize concrete properties.

What is the best type of cement for low W/cm applications?

In low W/CM applications such as paving, mixtures with 15 percent fly ash and 30 percent slag cement component have been used successfully. The spirit of St. Louis Airport in Chesterfield, MO placed airport paving with blended cement (Type I (SM)) and Class C Fly Ash for a more durable and resilient concrete. (photo credit 5)