How The Concrete Formed After Hydration Essay

In the hydration reaction of Portland cement, the absolute volume of hydration products formed is less than the combined volume of the reacted cement and water. This volume reduction is called the chemical shrinkage. After setting of the cement paste, microstructure of the paste is developed as a result that the paste is not able to change its bulk volume freely; therefore, only a fraction of total chemical shrinkage results in a decrease of its external volume which is known as autogenous shrinkage. While, the rest of total shrinkage presents as an increase of the internal porosity. [Ivan Odler. Special inorganic cements. 1st ed. London: E & FN. Spon; 2000.] Another kind of bulk shrinkage of cement is called drying shrinkage. Drying shrinkage is caused due to the loss of moisture from cement paste to environment. To prevent these shrinkages, moist curing may be used. But, upon subsequent exposure to an atmosphere of normal humidity, the material slowly loses water and exhibits a shrinkage finally. In addition, during

For those used to concreting on dry condition, concreting under water presents various challenges. Transporting, compacting, quality control, finishing and accuracy must all be carried out successfully in this different, and often difficult, environmental conditions. There are, however, many common aspects, chief of which is that air is not required for the setting and hardening of concrete – it sets and hardens just as well, and often even better, under water. Moreover, it must be fluid enough to flow into position and be self-compacting as conventional vibration is not practicable under water. During transporting and placing, conventional concrete and water must be kept apart and, when they inevitably do come into contact, rapid interface flow must be minimized or cement may be washed out to form a weak layer. Washout can be avoided by the use of an admixture to make the concrete non-dispersible but this comes at a cost and contractors unwilling to pay the additional expense involved often adhere to the more traditional methods of placing under water.

Assortment of NDT systems have been produced and are accessible for examination and assessment of diverse parameters identified with quality, toughness and general nature of cement. Every system has some quality and some shortcoming. In this manner reasonable methodology would be to utilize more than one strategy in mix so that the quality of one remunerates the shortcoming of the other. The different NDT techniques for testing solid are recorded underneath –

* Verma Ajay et al.., Investigated in ‘Effect of Micro Silica on The Strength of Concrete with Ordinary Portland cement’. The author has observed that the addition of micro silica in concrete reduces the capillary action, absorption and porosity because of fine particles of silica fume. It also decreases the voids in concrete (1).

In general, the durability of concrete covers directly on the ease or difficulty of fluid transport within the concrete, and classified as a concrete or too little permeable. The main transport agent fluid is water in the concrete, which may be pure or contain aggressive agents, such as dioxide carbon and oxygen. The displacement of these elements will depend on the concrete structure hydrated cement paste (Neville, 1997). THE Concrete durability of recycled aggregates also it depends on the ease or otherwise of transport these fluids. Olorunsogo and Padayachee (2002) studied properties related to the durability of concrete as the conductivity of chloride ions, sortividade permeability to oxygen and water, containing percentages of 0%, 50% and 100% replacement of natural aggregates by recycled. The results showed that the durability decreases increases in proportion as the percentage of replacement for all properties evaluated. However, these properties improve with increasing age and with percentages of 50% recycled aggregates in the

The properties of the concrete develop as a result of hydration: the exothermic reactions between water and cement and the interaction with the pozzoloniccementitious components in the mixture (Nawy, 2001). Also the properties of the concrete depend on the mix proportions and the placing and

Successful design of underwater concrete mixtures must fulfill two basic requirements: adequate flowability to spread into the placing forms without consolidation, and viscosity in order to resist the washing out. In this paper an investigation was carried out to determine the effect of the dosage of antiwashout admixture (AWA), watercementitious materials ratio (w/cm),sand to total aggregate ratio(s/a), and the supplementary cementitious materials on the washout resistance, fresh properties and the relative compressive strength of self compacting underwater concrete (SCUWC). Therefore five groups were prepared for this study.First group studied the effect of the supplementary cementitious materials, second group dealt with the effect of the AWA ratios, third group is concerning with the effect of w/cm ratio, fourth group take into account the effect of s/a ratio and finally fifth group included the effect of cementitious materials. Test results indicate that the concentrations of

This experiment was therefore aimed at determining the ultimate compressive strength of different concrete samples after 14 days. Additionally, other properties of the concrete such as modulus of elasticity and Poisson ratio were also determined.

SCC mainly used in highly congested reinforced concrete structure in seismic region and to overcome the problem of storage of skilled labours for the efficient compaction of concrete. Review of literature indicates that durability of SCC largely depends on the type of mineral admixtures.

Ghosh, P., S. Mandal, B. Chattopadhyay and S. Pal, Use of microorganism to improve the strength of cement mortar. Cement and Concrete Research, 2005. 35(10): p. 1980-1983.

The manufacturing process of cement consists of mixing, drying and grinding of limestone, clay and silica into composite mass. The

Abstract-Concrete is the most widely used construction material in civil engineering industry because of its high structural strength and stability. Cement and sand is a major constituent material of the concrete which produced by natural raw material like lime and silica and natural sand respectively. Once situation may occurs there will be no lime on earth production of cement also natural sand. This situation leads to think all people working in construction industry to do research work on cement replacing material and natural sand for use of it. The construction industry is constantly looking for supplementary cement and natural sand material with the objective of reducing the solid waste disposal problem. Ground granulated blast furnace slag (GGBS), quarry sand are the solid wastes generated by Industry. To overcome from this crisis, partial replacement of Cement with GGBS, natural sand with quarry sand (QS) can be an economic Alternative. The cubes are tested for compressive strengths. Ordinary Portland cement was partially replaced by GGBS of 0%, 30%, 40%,50% and natural

This paper presents the results of an experimental investigation on the properties of concrete using copper slag as partial replacement of fine aggregate. In the present study the experimental investigations are carried out to evaluate the strength and durability characteristics of concrete by replacing the cement with Silica fume and fine aggregate with copper slag of various proportions. Silica fume and Copper slag are the materials that is considered as a industrial waste which can be used in construction Industry. It could have a promising future in construction industry as partial substitute of either cement or aggregate. Many researchers have already found that it is possible to use silica fume and copper slag as a concrete aggregate. But not much research has been carried out concerning durability and corrosion studies. Based on the properties of material used in concrete, mix design (M30) was done and the proportions of the mix was presented. Based on the mix proportion, trial mix was prepared and cube compressive strength at 7 days was found out. This result showed that about 60% of the 28 days cube compressive strength was attained during seven days of curing.

In the most general sense of the word, a concrete is a substance that solidifies to act as glue. Romans were the first to use “modern cement “for purposes of masonry made of crushed stone with vivid lime as binder. They named this substance “caementicium opus “which was later referred to as cement, cimentim , cäment and cement.

According to ASTM and ACI committee, concrete is defined as a composite material that consists essentially of a binding medium within which are embedded particles or fragments of aggregate. But Hansen suggested that a composite material can have two fundamentally different structures. The first one is an ideal composite hard material, which has a continuous lattice of an elastic phase with a high modulus of elasticity, with embedded particles of a lower modulus of elasticity. The second type of structure is that of an ideal composite soft material, which has elastic particles with a high modulus of elasticity embedded in a continuous matrix phase with a lower modulus of elasticity. (Neville, et al., 1983). Concrete being a composite material can thus be considered as consisting of two phases: hydrated cement paste and aggregates, and the properties