Showing posts from January 6, 2018

How to test Hardened Concrete for Quality of Construction

Hardened concrete gains strength with time and testing these hardened concrete for quality check is important for structures. Different types of tests are available to check different properties of hardened concrete which are discussed. Properties of Hardened Concrete Early volume change Creep Properties Permeability Stress-Strain Relation Early Volume Change (Shrinkage) may result in cracking. Plastic Shrinkage occurs due to water loss from fresh paste by evaporation or from suction by dry surface. Volume decreases up to 1% when the paste is still plastic. Controlling water loss may help to prevent plastic shrinkage of concrete. Drying Shrinkage occurs due to loss of water and/or cooling. 15-30% of dry shrinkage occurs in the first 2 weeks, 65-85% in first year. Drying shrinkage can be induced by lack of curing, high water-cement ratio, high cement content, low coarse aggregate content and existence of steel reinforcement. It depends on size and shape of concrete structu

Ho to determine Compressive Strength of Mortar -Mix Ratio and Cube Test

Compressive strength of mortar is determined by using 2 inch or 50mm cubes as per ASTM C109 / C109M – Standard Test Method for Compressive Strength of Hydraulic Cement Mortars. Mortar is a combination of cement, sand mixed with water. It is used for masonry works such as brick masonry and stone masonry and for plastering walls, columns etc. Common mix ratio of mortar used in masonry works are  1:3, 1:4 and 1:6 of cement to sand ratio. For important masonry structures such as brick walls, 1:3 ratio is used. Why Compressive Strength Test of Mortar is Important? Generally masonry structures are constructed as load bearing. For example, load bearing walls, load bearing masonry columns etc. are constructed for residential and other masonry buildings. For a masonry buildings, foundations are also constructed with brick masonry. For a load bearing masonry construction, it is important to know the compressive strength requirement of masonry to withstand the load subjected on it. A m

Compaction Factor Test for Concrete Workability – Method and Procedure

Compaction Factor Test for Concrete Workability Compaction factor test is the workability test for concrete conducted in laboratory. The compaction factor is the ratio of weights of partially compacted to fully compacted concrete. It was developed by Road Research Laboratory in United Kingdom and is used to determine the workability of concrete. The compaction factor test is used for concrete which have low workability for which slump test is not suitable. Apparatus Compaction factor apparatus consists of trowels, hand scoop (15.2 cm long), a rod of steel or other suitable material (1.6 cm diameter, 61 cm long rounded at one end ) and a balance. Sampling Concrete mix is prepared as per mix design in the laboratory. Procedure of Compaction Factor Test on Concrete Place the concrete sample gently in the upper hopper to its brim using the hand scoop and level it. Cover the cylinder. Open the trapdoor at the bottom of the upper hopper so that concrete fall into the lo

How to determine the Penetration Value of Bitumen -Determination for Road Construction

Penetration value test on bitumen is a measure of hardness or consistency of bituminous material. A 80/100 grade bitumen indicates that its penetration value lies between 80 & 100. Penetration value is the vertical distance traversed or penetrated by the point of a standard needle into the bituminous material under specific conditions of load, time and temperature. This distance is measured in one tenths of a millimeter. Penetration test is used for evaluating consistency of bitumen. It is not regarded as suitable for use in connection with the testing of road tar because of the high surface tension exhibited by these materials. Penetration test on bitumen is carried to determine: Consistency of bituminous material Suitability of bitumen for use under different climatic conditions and various types of construction. Table of Contents  [ show ] Determination of Penetration Value of Bitumen Apparatus for Penetration Test Container A flat bottomed cylindrical m