Raw materials for fair faced concre

Raw materials for fair faced concrete shall meet the following requirements:(1) cement. Portland cement produced by cement plant with certain scale and stable quality shall be selected.Admixture. Multifunctional admixtures have become one of the cores of modern high performance concrete technology. Only by using high-performance admixture and giving full play to its efficient water reducing, enhancing and decelerating effect, can the cement dosage and hydration speed be effectively controlled. The mixture with compensating shrinkage and chemical shrinkage can reduce the shrinkage of concrete and play an important role in improving the volume stability of concrete. The new high-performance admixture can make the prepared concrete have better construction operability and is beneficial to the concrete. The material distribution of each component is more uniform, at the same time, it can reduce the generation of large bubbles, improve the visible large holes on the external surface of concrete, and improve the appearance quality.The foam content of concrete is greatly reduced.(4) commercial concrete. The production of fair faced concrete should be controlled by electronic automatic measurement of commercial concrete. Before each construction, the statistics and verification of materials shall be carried out to ensure the continuous supply of concrete. The moisture content of aggregate shall be measured for each work shift and the construction mix ratio shall be adjusted.For the selected test materials, the test shall be carried out in accordance with the provisions of "code for design of mix proportion of ordinary concrete (JGJ55-2000)." After the initial determination of the mix ratio, the simulation construction can be carried out, and the key point of the test detailed design should be in the simulation structure. Fully reflected to identify defects and improve. There are four kinds of fair faced concrete for the exterior wall of the project: C50, C45, C40 and C35. According to the construction progress, determine the construction season of each concrete, check the weather records of the past few years, and determine the construction conditions (temperature and humidity) of each concrete. In the laboratory, simulate the actual construction conditions of different grades of concrete, carry out simulation construction, use color difference to adjust the mixing ratio of test wall, so as to ensure the same construction conditions.The biggest feature of the project is the application of facing as cast finish concrete construction technology. The main construction difficulties and technical measures are summarized as follows:(1) the depth of the foundation pit reaches 13.5m, which is less than 2m from the nearest urban main road. The pipeline is dense, so it is difficult to support the foundation pit. Adopting soil nailing wall support and anchor spray technology, 26 monitoring points are set at the top of the slope around the foundation pit to monitor the barium regularly. The maximum horizontal displacement of the slope is 4mm, which is less than 0.3H% (33mm) of the allowable limit value of class II foundation pit. It has no adverse impact on the surrounding roads and buildings, and ensures the stability of the foundation pit slope.