What is Crazing on Concrete Surface? Crazing is the development of fine shallow hair cracks on create surface. Due to crazing the surface appearance of concrete looks not so pleasing. This may appear within few day after curing or sometimes after a longer periods. These cracks do not penetrate deep onto the concrete and do … Read more
What is Slump Loss in Concrete? Slump value is of great importance when concrete is in its fresh state. Slump value represents the workability property of concrete. Due to its importance, the value of slump is generally specified by the designer. And while working on site, the engineer’s responsibility is to make sure that the … Read more
Sulphates present in soil or water can cause serious damages to concrete. The methods given below can be adopted to protect concrete from sulphate attack. Use of Sulphate Resisting Cement The most efficient method of resisting the sulphate attack is to use cement with the low C3A content. It has been found that a C3A … Read more
Factors Affecting Strength Test Results of Concrete Compressive strength is the most important property of concrete. The compressive strength of concrete is determined in the laboratory in controlled conditions. On the basis of this test result we judge the quality of concrete. But sometimes the strength test results vary so widely that it becomes difficult … Read more
Capping of Concrete Cylinders Capping is required to give a smooth surface for applying compressive load to concrete cylinders. Only cylindrical concrete test specimens are capped using appropriate method. When the ends of cylindrical test specimens are not plane within 0.05 mm, it is required to cap those test specimens. The capped surfaces should be … Read more
Aim To determine volume of concrete per batch, where nominal maximum size of aggregate does not exceed 38 mm. Apparatus Balance – Sensitive to 0.01 kg Tamping bar – Length 38 cm, Weight 1.8 kg Cylindrical mould – Dia = 250 mm, Height = 280 mm, Capacity = 0.01m3 Step by Step Procedure to Calculate … Read more
Sampling of Fresh Concrete To ensure it is representative of the whole truck load, a standard sample consists of scoopfuls taken from different parts of the batch and collected in bucket. Scoopfuls must be taken through the moving stream, as the load is discharged, sampling the whole width and depth (not just the top part). … Read more
Effects of Hot Weather on Concrete Any operation of concreting done at atmospheric temperature above 400C may be put under hot weather concreting. The effect of hot weather may be as follows: Accelerated setting: A higher temperature of fresh concrete results in a more rapid hydration and leads to reduced workability/ accelerated setting. This reduces … Read more
Objective Determination of unit weight or bulk density and void of aggregates. Equipments Name Capacity 1. Balance Sensitive to 0.5% of weight of material 2. Cylindrical metal measure Of 3 litre capacity (for fine aggregate) Of 15 litre capacity (for aggregate upto 40mm) 3. Tamping rod 16 mm dia. and 60 cm long Sample Preparation … Read more
Miniature Stockpile Method The miniature stockpile method is used for reducing all samples of fine aggregates when the material is in damp or moist condition. If the sample to be split is dry, the material is required to be moistened before using this method. Procedure Place the original sample on a clean, dry plate or … Read more