Under fire conditions tensile strength of concrete can be even more crucial in cases where fire induced spalling occurs in a concrete structural member. Another property that influences fire resistance is the modulus of elasticity of concrete which decreases with temperature. At high temperature, disintegration of hydrated cement products and breakage of bonds in the microstructure of cement paste reduce elastic modulus and the extent of reduction depends on moisture loss, high temperature creep, and type of
That is why steel bars are embedded in the concrete for the structures to carry tensile loads. The steel reinforced bars take the tensile load when the concrete cracks in tension. On another hand, the concrete protects the steel reinforced bars from the environment and prevents corrosion. However, the cracks in the concrete form a major problem which affects the durability
Desciription Durability of concrete can be defined to mean ‘its resistance to deteriorating influences, which may reside inside the concrete itself, or which are present in the environment to which the concrete is exposed’. As it defined what is durability it brings us to Durability Cracking which also called “D” cracking is stated by sequence of crescent-shaped closely spaced hairline cracking pattern. Fig.1 Durability cracking is mostly seen in joints or free edges and also , it usualy begins from slab corners. Cracking pattern is looked dark color place on the pavements and its surrunded area. Causes Aggregates is most important materials to understand durability cracikngs structure.
Portland cement mixed with sand, gravel and water, a process called hydration, is how concrete is created. Crushed stone aggregate fine and coarse aggregates make up the bulk of a concrete mixture. Durability of concrete may be defined as the ability of concrete to resist weathering action, chemical attack, and abrasion while maintaining its desired engi-neering properties. Different concretes require different degrees of durability de-pending on the exposure environment and properties desired. For example, concrete exposed to tidal seawater will have different requirements than an indoor concrete floor.
This additive has low water content as well as a different particle seize that varies from group to group. Heavy weight additives are chemically inactive and can react with other chemicals (additives) (Joel, 2010). Viscosity Control Additives and Dispersants: This additive is introduced to viscosify the cement slurry while Dispersants, are introduced to help in reducing the viscosity of the cement slurry or the slurry consistency. These additives are used when designing high density slurry and also to improve fluids lose control (Joel, 2010). Fluid Loss Control Additives: Fluid-Loss or Permeability Plugging additive are added to reduce the rate at which water from the cement slurry enters the permeable formations when positive differential pressures exist in the permeable formation.
This test primarily measures the mobility of the mix. Effect of Polypropylene Fibers on Plastic and Drying Shrinkage Cracking is one of the major problems this is faced during concrete construction. Shrinkage is one of the primary reasons for cracking shrinkage is caused by loss of water. There can be two types of shrinkage, hardened and plastic. The effects on both are defined below PLASTIC
This is caused by chloride and chlorine found in the supply water. The chloride and chlorine have acid (Hydrochloric acid) forming tendancies. One method of reducing risk of failure from pitting is to increase pipe wall thickness. This, however, serves only to delay the potential breach. Studies have shown that three factors lead to the haviest corrosion attack on steel fire sprinkler pipes.
This problem along with scarcity of cement, and its increased cost can be solved to some extent by partial replacing the cement in concrete with phosphogypsum. Due to its pozzolonic properties it can be used for partial replacement of cement. The present paper deals with the experimental investigation on compressive strength, tensile strength, impact strength and durability characteristics of hardened concrete. The study aims
In particular, the seismic rehabilitation of older concrete structures in high seismicity areas is a matter of growing concern, since structures vulnerable to damage must be identified and an acceptable level of safety must be determined. To make such assessment, simplified linear-elastic methods are not adequate. Thus, the structural engineering community has developed a new generation of design and seismic procedure that incorporates performance based design of structures and is moving away from simplified linear elastic methods and towards a more non linear technique. Recent interests in the development of performance based codes for the design or rehabilitation of buildings in seismic active areas show that an inelastic procedure commonly referred to as the pushover analysis is a viable method to assess damage vulnerability of buildings. Basically, a pushover analysis is a series of incremental static analysis carried out to develop a capacity curve for the building with increasing lateral load or displacement.
Chapter 6 : Literature Reviews Wen-Chen Jau gives statement that self-curing concrete will be provided to absorb water from moisture from air to attain better hydration of cement in concrete. It resolves the difficulty occurred when the degree of cement hydration is lowered due to improper curing by using a self- curing agent like poly-acrylic acid, which has strong capability of absorbing moisture from the atmosphere and providing water required for curing concrete. M.V.Jagannadha Kumar,M.Srikanth, Dr.K.JagannadhaRao in their research studied that the optimum dosage of PEG400 for maximum strengths such as compressive, tensile and modulus of rupture was found to be 1% for M20 and 0.5% for M40 grades of concrete. As percentage of PEG400 increased, slump will also increased for both M20 and M40 grades of concrete. Strength of self-curing concrete will be on par with conventional concrete.