Tubular Calcrete This Calcrete forms tube shaped carbonate concretions from indurated to soft and powdery. The conglutination may be separate or connected by size and content of carbonated by size and content of carbonate. Some are hallowed but other is solid or filled with materials other than carbonates. This Calcrete can be classified (Klappa 1980) and the common type is carbonated Rhizoliths or tubules. (Lintern, Roach, and Chen, 2002) 1.4.3.
CHAPTER 1 – INTRODUCTION 1.1 GENERAL Now a day, the most widely used construction material is concrete, commonly made by mixing cement with sand, crushed rocks and water. Last year only in US 63 billion tons of Portland cement were converted into 500 billion tons of concrete, which is five times the consumption by weight of steel. In most of the countries the ratio of concrete consumption to steel consumption exceeds about ten to one. The total consumption of concrete is in the world is estimated at 11billion metric tons every year. Man consumes no material except water in such tremendous quantity.
Concrete of higher strength and better quality can, therefore, be made with the given cement by using less but sufficient water. 3. Curing of the concrete is paramount in achieving its strength. To get high quality concrete, the curing must be given higher importance. It is very essential to keep the concrete moist and warm enough.
However, most countries as of now do not recycle a large percentage of the concrete; with the leaders being Netherlands and UK both countries which have a consumption of recycled aggregate above 20% (Jahren, 2013). This is not all, according to Jahren, other materials such as used tires and glass can be used as aggregate in concrete for both functional and aesthetically pleasing results. Researchers have presented preliminary results of using different materials from wasted plastic as light weight aggregate in concrete to hemp and even slag from lead production. (Jahren, 2013).
The strength of concrete varies according to the proportions of its constituents. Concrete gains its strength over time as it hardens by means of setting, where by cement undergoes a chemical reaction known as hydration. It can set and harden underwater hence it can be used as foundation material. Its hardening process can be enhanced by curing. Due to its workability it can be formed into different
Concrete is the primary material in construction industry. It consists of cement, coarse aggregate, fine aggregate, water and other admixtures. Generally Ordinary Portland cement is used in concreting but the production of OPC causes a huge amount of carbon emission and also it uses a huge amount of non-renewable natural resources. The concrete construction practice in use is considered as unsustainable because it consumes a huge quantity of sand, stone and water and 2.5 billion tons of OPC per year. A major component of concrete is cement, which has its own environmental and social impacts and contributes largely to those of concrete.
Concrete is the composite mix of cement, aggregates, sand and water. Concrete gets hardened like stone on mixing water with cement and aggregates. Concrete have two type ingredients namely active and inactive. The active group consists of water and cement. The inactive part consists of sand and coarse aggregates.
Until 1992, the government’s active control over the cement sector through State Cement company had dept private speculation in the sector to a minimum. This sale of state-owned units to private sector in 1992 led to price deregulation. The increasing limits attracted fresh private savings, which resulted in an exorbitant increase in ability from 8.2 million tonnes in 1992 to 17 million tonnes in 1998. The huge addition in the capacity of the cement industry is heavily in charge for the current strife in the cement sector of Pakistan. This increase in capacity increased the opposition between the producers, but with the rising cost of production they couldn’t keep themselves ready for action.
These results do not necessarily relate to the compressive strength of concrete made with that aggregate (Afrisam, 2016). Once the crushing has taken place the material is placed into a sieve and the final material is the material that passes through a 2,8mm sieve. If the final material is not exactly 10% of the original mass of material then the test has to be redone until exactly 10% is reached. All the groups’ results were put into a table and with these results a graph plotting a trend line could be produced. Using this trend line, the FACT results were calculated by solving for x in the trend line equation.
CHAPTER 1 INTRODUCTION 1.1 GENERAL Concrete is an extraordinary and key structural material in human history. Concrete holds the credit of being the most widely utilized tailored or man- made material in the construction industry and will hold good for the years to come. This credit goes to the properties of concrete like excellent strength, durability, less maintenance costs and use in many structural applications. But in the recent years the concrete industry is facing a big challenge mainly due the cement which is a vital component. International Energy Agency states that cement production accounts for 7% of total global CO2 emissions.