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Mixing of Concrete The mixing operation consists of rotation or stirring, the objective being to coat the surface the all aggregate particles with cement paste, and to blind all the ingredients of the concrete into a uniform mass; this uniformity must not be disturbed by the process of discharging from the mixer. Batch mixer The usual type of mixer is a batch mixer, which means that one batch of concrete is mixed and discharged before any more materials are put into the mixer. There are four types of batch mixer. Tilting drum mixer: A tilting drum mixer is one whose drum in which mixing take place is tilted for discharging. The drum is conical or bowl shaped with internal vanes, and the discharge is rapid and unsegregated so that these mixers are suitable for mixes of low workability and for those containing large size aggregate. Non tilting drum mixer: A non tilting drum is one in which the axis of the mixer is always horizontal, and discharge take place by inse

A Project quality plan is a document, or several documents, that together specify quality standards, practices, resources, specifications, and the sequence of activities relevant to a particular project, or contract. It acts as the quality bible for the project. It contains a set of activities planned at the beginning of the project that helps achieve Quality in the Project being executed. The Purpose of the Project Quality Plan is to define these activities or tasks that intend to deliver products while focusing on achieving customer’s quality expectations. These activities or tasks are defined on the basis of the quality standards set by the organization delivering the product. Project Quality Plan identifies which Quality Standards are relevant to the project and determines how they can be satisfied. It includes the implementation of Quality Events by using various Quality Materials (templates, standards, checklists) available within the organization. The holding of the Qualit

EFFECTS OF HOT WEATHER ON CONCRETE Any operation of concreting done at atmospheric temperature above  40 0 C 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 the handling time of concrete. REDUCTION IN STRENGTH: Concrete mixed, placed and cured at higher temperature normally develops higher early strength than concrete produced and cured at normal temperature but at 28 days or later the strength are generally lower. INCREASED TENDENCY TO CRACK: Rapid evaporation may cause plastic shrinkage and cracking and subsequent cooling of hardened concrete would introduce tensile stresses. EFFECTS OF COLD WEATHER ON CONCRETE Any concreting operation done at a temperature below 5 0 C is termed as cold weather concreting. In the absence of special precautions, the effect of cold wea

HOW TO CHARGE CONCRETE INGREDIENTS IN A CONCRETE MIXER? To get better efficiency, the sequence of charging the loading skip is as under 1. First place half the quantity of coarse aggregate in the skip. 2. Place half the quantity of fine aggregate over the previously placed coarse aggregate. 3. Then pour full quantity of cement (i.e. one bag of cement) over it. 4. Then deposit the remaining portion of coarse aggregate and fine aggregate over it. This prevents spilling of cement, while discharging into the drum and also this prevents the blowing away of cement in windy weather. 5. Before the loaded skip is discharged to drum, about 25 percent of the total quantity of water is introduced into the mixer drum to wet the drum and to prevent any cement sticking to the blades or at the bottom of the drum. 6. Then discharge the dry material into the drum. 7. Immediately, on discharging the dry material into the drum, the remaining 75 percent of water is added to the drum. NOTES TO REMEMB