When concrete is compacted with vibrators the following precautions may be taken to produce a concrete of good quality. The formwork should be strong and tight so that there is no leakage of mortar. The leakage of mortar results in honey combing. A lining of plywood may be provided to prevent the leakage if the … Read more
What is Standard Deviation? When repeated measurements give different results, we want to know how widely spread the readings are. The spread of values tells us something about the uncertainty of a measurement. By knowing how large this spread is, we can begin to judge the quality of the measurement or set of measurements. The … Read more
Output of a Concrete Mixer The output of a mixer essentially depends upon the capacity of a mixer. In addition, it depends upon the duration of mixing, supply of materials to the mixer and the speed at which charging and discharging operations are carried out. Sometimes the speed of transporting concrete from mixer to the … Read more
What is Curing? Curing is a procedure of promoting the hydration of cement for development of concrete strength and controlling the temperature. As a result of curing, we can achieve higher strength and reduced permeability which is very vital for long term strength or durability. The effect of curing has been shown in the following … Read more
What is Compaction? Compaction is a process of expelling the entrapped air. If we don’t expel this air, it will result into honeycombing and reduced strength. It has been found from the experimental studies that 1% air in the concrete approximately reduces the strength by 6%. Different Methods Of Concrete Compaction There are two methods … Read more
Methods of Concrete Transportation Transportation of concrete is an important activity in the production of concrete. The time taken in transit should be a design parameter as it depends on the initial setting time as well as the requirement of workability at the destination. The method of transportation adopted at site should be decided in … Read more
What is Admixture? It is an optional ingredient of concrete which is added to modify the properties of fresh and hard concrete and grout materials as per some specific requirements. Addition of admixture may alter workability, pumping qualities, strength development, appearance etc in fresh concrete and permeability, strength, durability etc in hardened concrete. But use … Read more
The followings are general recommendations or considerations for hot weather concreting. Guidelines to Follow 1. Do not exceed the maximum allowable water-cementious materials ratio or the manufacturer’s maximum recommended dosage of any admixture. 2. Consider retarding admixtures if their performance has been verified during trial batches. 3. Substitute ground, granulated blast furnace slag for part … Read more
During hot weather, problems that may occur in concrete include the following. Rapid slump loss Reduced air content Premature stiffening Plastic shrinkage cracks Thermal cracking Therefore it is necessary to keep concrete temperature down. The most effective way to keep concrete temperature down is by controlling the temperature of its ingredients. Among all ingredients of … Read more
Effects of hot weather on concrete, in the absence of special precautions can be as follows. Accelerated setting of concrete Reduction in strength of concrete Increased tendency to crack Rapid evaporation of water during curing period Difficulty in control of air in air-entrained concrete Accelerated Setting The rate of setting time of the concrete increases … Read more
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