Concrete Technology Overview

The type of cement affects the rate of hardening and overall durability by determining the chemical composition and hydration properties that influence strength.

In the fresh state, water impacts workability and cohesion, while in the hardened state, it is involved in hydration, contributing to dimensional changes like shrinkage and creep.

The grading, shape, texture, type, and quality of aggregate affect the elastic properties of both fresh and hardened concrete, impacting strength and durability.

<p>Porosity in both fresh and hardened states influences workability, cohesion, as well as strength, stiffness, and density, particularly affecting resistance to freeze-thaw cycling.</p> Signup and view all the answers

<p>Admixtures are small quantities added to cement to alter the properties of fresh and hardened concrete, improving workability, strength, or durability.</p> Signup and view all the answers

<p>It reduces heat of hydration, lessens restrained thermal stress, and improves sulphate resistance.</p> Signup and view all the answers

<p>Microsilica increases workability for the same water content and enhances mobility for a given slump.</p> Signup and view all the answers

<p>They increase setting times by 1 to 4 hours compared to standard blends.</p> Signup and view all the answers

<p>Microsilica increases the tendency to develop plastic shrinkage cracks due to reduced bleed.</p> Signup and view all the answers

<p>It is typically higher in price compared to standard cement.</p> Signup and view all the answers

<p>Microsilica may have questionable resistance to chloride ion diffusion, requiring increased cover depth.</p> Signup and view all the answers

<p>It defines and specifies 27 distinct common cement products and their constituents.</p> Signup and view all the answers

<p>It leads to improved durability by minimizing expansive reactions.</p> Signup and view all the answers

<p>He added clay to limestone before heating, creating a hydraulic cement.</p> Signup and view all the answers

<p>It consists of at least two-thirds calcium silicates with the remainder being aluminum and iron clinker phases and other compounds.</p> Signup and view all the answers

<p>They were introduced to reduce the self-weight of arch and dome constructions.</p> Signup and view all the answers

<p>William Wilkinson patented reinforced concrete, which was initially used for manufacturing boats and plant tubs.</p> Signup and view all the answers

<p>It involves the reaction of Portland cement with reactive silica materials for improved properties.</p> Signup and view all the answers

<p>Concrete is a composite of coarse aggregate bound by cement-based mortar made of fine aggregate and cement paste.</p> Signup and view all the answers

<p>It marked a significant application of the 'new' cements in large-scale civil engineering projects.</p> Signup and view all the answers

<p>Asbestos-cement provided increased resistance to environmental factors and structural durability.</p> Signup and view all the answers

<p>GGBS is a semi-cementitious material that can set on its own, unlike PFA which is not cementitious on its own.</p> Signup and view all the answers

<p>The typical blending percentage of GGBS with Portland cement is between 10-90%. This blending releases hydroxide and sulfate ions that accelerate strength gain.</p> Signup and view all the answers

<p>The initial set time should be greater than 60 minutes for strength class 42.5 and greater than 45 minutes for strength class 52.5.</p> Signup and view all the answers

<p>Microsilica is a by-product from the reduction of high purity quartz in submerged electric arc furnaces and has a very small particle size of 0.1 micron.</p> Signup and view all the answers

<p>The relative density of microsilica is 2.2, whereas Portland cement has a relative density of 3.1.</p> Signup and view all the answers

<p>The ultra-fine particle size of microsilica provides nucleation sites for Ca(OH)2 and CSH hydrates, enhancing the reactivity.</p> Signup and view all the answers

<p>The addition of PFA and GGBS can increase the volume of fine powder, leading to greater cohesiveness and reduced bleeding.</p> Signup and view all the answers

<p>The high proportion of amorphous silicon in microsilica enhances its reactivity and ability to react with Ca(OH)2 to form additional CSH.</p> Signup and view all the answers

<p>The average production cost range of aggregates is £5-10 per tonne.</p> Signup and view all the answers

<p>The approximate range for land-based sand and gravel is 68-80 x 10^6 tonnes per annum.</p> Signup and view all the answers

<p>The standard that covers aggregates for concrete in the UK is BS EN 12620: 2002.</p> Signup and view all the answers

<p>Admixtures are added to modify one or more properties of the fresh or hardened concrete.</p> Signup and view all the answers

<p>Workability aids, also known as water-reducing admixtures, are used to improve the workability of concrete.</p> Signup and view all the answers

<p>Transportation costs can significantly increase the final price of aggregates, affecting overall supply.</p> Signup and view all the answers

<p>Durability (thermal and weathering) characteristics and chemical requirements are two of the requirements.</p> Signup and view all the answers

<p>Trial mixes are used to evaluate admixtures with similar cements and aggregates to ensure compatibility.</p> Signup and view all the answers

<p>A low workability mix requires a large amount of external work or vibration to achieve full compaction.</p> Signup and view all the answers

<p>The presence of macro-voids significantly reduces the compressive strength of hardened concrete.</p> Signup and view all the answers

<p>Workability generally increases with an increase in water content in the concrete mix.</p> Signup and view all the answers

<p>Achieving full compaction is important to ensure maximum potential strength and reduce voids in the hardened concrete.</p> Signup and view all the answers

<p>For a given W/C ratio, an increase in cement content results in increased workability.</p> Signup and view all the answers

<p>The trade-off involves balancing the time and effort required to vibrate the concrete against the need for full compaction.</p> Signup and view all the answers

<p>Increased internal friction between individual particles reduces workability, making compaction more difficult.</p> Signup and view all the answers

<p>There is no single measurement technique because workability is influenced by various factors that cannot easily be quantified.</p> Signup and view all the answers