are formed in concrete due to many reasons but when these cracks are very deep, it is unsafe to use that concrete structure. Various reasons for cracking and improper mix design, insufficient curing. omission of expansion and contraction joints, use of high slump concrete mix, unsuitable sub-grade etc.

also called as pattern cracking or map cracking is the formation of closely spaced shallow cracks in an uneven manner. ______ occurs due to rapid hardening of top surface of concrete due to high temperatures or if the mix contains excess water content or due to insufficient curing.

is the formation of hollow bumps of different sizes on concrete surface due to entrapped air under the finished concrete surface. It may cause due to excessive vibration of concrete mix or presence of excess entrapped air in mix or due to improper finishing.

is also similar to blistering. In this case also, top surface of concrete gets separated from underlying concrete. Hardening of top layer of concrete before the hardening of underlying concrete will lead to ________. It is because the water and air bleeding from underlying concrete are struck between these two surfaces, hence space will be formed.

also called as chalking, is the formation of fine and loose powdered concrete on the hardened concrete by disintegration. This happens due to the presence of excess amount of water in concrete. It causes bleeding of water from concrete, with this fine particles like cement or sand will rise to the top and consequent wear causes dust at the top surface.

When a concrete slab is distorted into curved shape by upward or downward movement of edges or corners, it is called ______. It occurs mainly due to the differences in moisture content or temperature between slab surface (top) and slab base (bottom).

is the formation of deposits of salts on the concrete surface. Formed salts generally white in color. It is due to the presence of soluble salts in the water which is used in making concrete mix.

in both the cases, concrete surface gets deteriorated and flaking of concrete occurs. The main cause for this type of cases is penetration of water through concrete surface. This makes steel gets corroded and _______ or _______ may occur.

is caused by the setting of solids and the loss of free water from the plastic concrete (plastic ______), by the chemical combination of cement with water (autogenous ________) and by the drying concrete (drying _________).

1. Alkali-aggregate reactions 2. Volume change due to difference in thermal properties of the aggregate and cement paste. 3. Permeability of concrete.

1. Leaching out of Cement 2. Actions of sulphates, seawater and natural slightly acidic water. 3. Occurrence of extreme temperatures, abrasion and electrostatic action.

Besides its ability to sustain loads, concrete is also required to be durable. The _______ of concrete can be defined as its resistance to deterioration resulting from external and internal causes. The external causes include the effects of environmental and service conditions to which concrete is subjected such as weathering, chemical actions and wear. The internal causes are the effects of interaction between the constituent material such as alkali-aggregate reaction, volume changes, absorption and permeability.

______is a loading in which a part of a member attempts to slide or shear along another part. _______ which is a twisting, is also complex and difficult to evaluate. When concrete fails, a combination of stresses causes the failure.

There is no field test for direct determination of tension under axial loading. An indirect method called the splitting tensile test, in which a standard test cylinder is loaded in compression on its side.

is one measure of the tensile strength of concrete. It is a measure of an unreinforced concrete beam or slab to resist failure in bending

The compression strength of concrete is a measure of the concrete's ability to resist loads which tend to compress it. It is measured by crushing cylindrical concrete specimens in compression

is product of binding and hardening of the concrete mixture which contains ingredients quantified in the appropriate proportions: binder (cement) coarse aggregate (gravel) fine aggregate (sand, fraction <2mm) water and optional additives (> 5% by weight of binder) admixtures (<5% by weight of the binder).

A special technique used to make concreting in water (Tremie Method)

A type of concrete which is designed to be pump able with relatively high slump (6-8")

Suitability of water for mixing and curing processes should be considered, quality of water is covered by saying water must be fit for drinking.

The creation of an environment for a period of time (suitable temperature, prevention of loss of moisture or providing moisture)

Consists essentially of the elimination of entrapped air in concrete (ramming/vibration)

a weak, friable layer on the surface of concrete and sand cement screeds which appears after curing.

Water from the mix tends to rise to the surface of freshly placed concrete. _____ can be expressed as the total settlement per unit height of concrete.(water gain)

Separation of the constituents of a heterogeneous mixture so that the distribution is no longer uniform.

Measures the depth of penetration

Measures the diameter of the spread after vibration (Self ConsolidationConcrete/Self CompactingConcrete)

Measurement of the density ratio(actual recorded density to the density of the same concrete that is fully compacted)

Used in detecting variations in the uniformity of a mix of given nominal proportions

zero slump

slump varies but satisfactory

shear or collapse slump

Used to describe the ease with which concrete mixes can be compacted (completely compacted using the lowest possible w/c)

The strength of concrete is affected by the degree of its compaction. It is vital, therefore, that the consistency (ability to flow) of the mix be such that, the concrete can be transported, placed and finished sufficiently, easily and without segregation