Setting Of Mixture of Cement with Sand, Time and Fly Ash
Published on Dec 13, 2018
To study the setting of mixture of cement with sand, time and fly ash with respect to time and strength.
In the most general sense of the word, CEMENT is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder. The volcanic ash and a pulverized brick additive that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum, cimentum, cament and cement. The most important use of cement is the production of mortar and concrete. The bonding of natural or artificial aggregates to form a strong building materials that is durable n the face of normal environment effects.
Cement is made by heating limestone (calcium cabonate), with small quantities of other materials (such as clay) to 1450ͦC in a kiln, in aprocess known as calcination, whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide,or quicklime,which is then blended with the other materials that have been included ih the mix. The resulting hard substance, called ‘clinker’, is then ground with a small amount of gypsum into a powder to make ‘Ordinary Portland Cement’, the most commonly used type of cement(often referred to as OPC).Portland cement is a basic ingredient of concrete, mortar and non speciality grout. The most common use for portland cement is in the production of concrete. Concrete is a composite material consisting of aggregate (gravel and sand), cement and water. As a construction material, concrete can be cast in almost any shape desired and once hardened, can become a structural (load baering) element. Portland cement may be gray or white.
Construction of buildings using cement
Cement used in construction is characterised as hydraulic or non-hydraulic. Hydraulic cements (eg. Portland cement) harden because of hydration chemical reactions that occurs independently Of the mixture’s water content; they can harden even underwater or when constantly exposed to wet weather. The chemical reaction that results when the anhydrous cement powder is mixed with water produces hydrates that are not water-soluble. Non-hydraulic cements (eg. Lime and gypsum plaster) must be kept dry in order to retain their strength.
Effect of Quality of Sand on Setting of Cement Mortar
Sand obtained from different sources has different qualities. For example, Sea sand obtained from sea contains unwanted salts and retards setting of cement and is not suitable for making mortar. On the other hand, Pit sand is obtained from pits in the soil and the River sand obtained from riverbed is considered excellent for preparing mortar and concrete.
Effect Of Time On Setting Of Cement Mortar
Time has an important role on strength of developed cement mortar. When a cement paste in the ratio 1:3 in water is allowed to dry, the strength of solid mass keeps on increasing with increase in time given for setting. It acquires a nearly full strength in 28 days.
1. Beakers, glass rods, weight box, matchboxes
2. Limestone, river sand, cement and fly ash
1. Prepare mixtures of various compositions as given in Observation table.
2. Take each of the given mixtures in different beakers and prepare their pastes by adding minimum amount of water
3. Take nine cases of empty match boxes and mark them from 1 to 9.
4. Fill the three cases with the paste of each composition.
5. Spray water from time to time over the paste ,so that they remain moist all the time.
6. After three days, take out one slab of each composition and test their strengths.
7. Similarly, take out a set of three slabs after 7 days after 30 days respectively and test their strengths
By seeing the observation we can estimate the hardness of the slab.
The strength of the slab increases with the increase in setting time allowed.