For a long time, the amount of construction waste in China has been on the rise, and at the same time, due to the continuous production of waste, there is more demand for new building environmental protection materials in the construction process, resulting in the uselessness of construction waste. However, with the large demand of commercial concrete and the continuous development of building environmental protection industry, urban construction waste has been transformed from a large amount of transportation to coarse aggregate material of commercial concrete for burial and corresponding preparation. This paper mainly studies the optimum dosage range of construction waste under tensile strength test conditions.
Relevant measures for preparing concrete with 1 construction waste as coarse aggregate
For concrete preparation in engineering construction areas, due to the shortage of raw materials such as coarse aggregate, the amount of construction waste is increasing. In order to save resources and reflect the environmental protection characteristics of buildings, construction waste is often used as coarse aggregate to prepare concrete. Therefore, in order to improve the quality and quantity of raw materials, we must speed up the operation efficiency, and then sell the concrete made of construction waste as coarse aggregate in time. In view of this, as a supplier of concrete with construction waste as coarse aggregate, in order to obtain greater benefits, crushing is often used in the preparation process, which seriously affects the efficiency of concrete preparation and limits the corresponding quality of concrete preparation. Therefore, it is necessary to adopt additional production technology to improve its quality before use.
1. 1 mixed with fly ash
In order to effectively improve the preparation efficiency and accelerate the utilization efficiency of the whole construction waste materials, it is necessary to add corresponding cementing materials at a certain time to improve the utilization degree of construction waste, enhance the activity of concrete preparation, reduce the consumption of cement, and reasonably control the cost and performance. As an admixture of pumping concrete, fly ash will have a certain influence on the fluidity of cement composite slurry. The greater the dosage, the greater the fluidity of cement composite slurry, but there is a certain limit. As long as the dosage exceeds 30%, the fluidity will gradually decrease, even less than that of the composite slurry without admixture. This is because after adding too much fly ash, in addition to 60% glass body, there are about 40% crystalline compounds and unburned carbon. In addition, for fly ash, it can depress the strength of concrete, and the content of fly ash is inversely proportional to the strength of concrete, so the fluidity of fly ash determines the compressive performance of concrete.
1.2 control water
One of the characteristics of using construction waste as coarse aggregate is that it needs a lot of water to control the water consumption and ensure the fluidity of the whole construction waste. However, in the process of water control, although the fluidity of construction waste increases, its viscosity gradually decreases. Due to the occurrence of this principle, construction waste concrete will be applied to construction projects in the process of reducing water consumption, resulting in landslides and structural variability. Therefore, as a manufacturer of construction waste concrete, we should pay attention to this problem and raise the corresponding understanding, and don't increase the use of corresponding additives because of the reduction of water consumption, thus increasing the cost. Therefore, increasing water consumption as much as possible is the key link to ensure compressive strength.
1.3 Reasonable collocation of coarse aggregate
Coarse aggregate, namely construction waste, plays an important role in the preparation of concrete. Therefore, it is the key factor to improve the fluidity of coarse aggregate to adopt effective means to reasonably match the preparation technology of concrete, and to select the appropriate preparation ratio through multi-stage preparation to improve the preparation capacity of the whole construction waste concrete.
2. Manufacture of test blocks
2. 1 Test raw materials
The construction waste is selected from the remaining waste during the construction of a project, and the quality index is GB/T 18046—2008 Granulated Blast Furnace Construction Waste for Cement Concrete, with the grade of S95. Water glass is produced by Chongqing Jingkou Chemical Plant, with density 1.305g/ml, silica content of 25.72%, sodium oxide content of 8.48% and modulus of 3. 13. Sodium hydroxide is industrial sodium hydroxide with a purity of 98%; After sodium hydroxide is added to sodium silicate, the modulus modulation is 1.5. Fine aggregate adopts China ISO standard sand; The mixed water is ordinary tap water. The strength grades of experimental building waste concrete are C40, C50 and C60, which are the most commonly used in engineering. See table 1 for the concrete mixture ratio with three kinds of construction waste as coarse aggregate. From the comparative analysis of concrete mix proportion data in table 1, it can be concluded that among C30, C40 and C50 concrete grades, the concrete mix proportion of crushed stone is the largest, which has the greatest influence on the whole concrete mix proportion and accounts for the largest proportion. The smallest concrete mixture ratio is water, and the data value is 89.7kg/m3, which plays a small role in the concrete mixture ratio of the whole specimen, but it is essential.
2.2 Specimen making
In this experiment, according to the mix proportion of construction waste concrete with three strengths, standard specimens of 150mm, 150mm and 150mm were poured in three batches, and a unified test mold was adopted in the process of making the specimens, and the shape of the test mold was selected as a cube. According to the requirements of Standard for Test Methods of Mechanical Properties of Ordinary Concrete (GB5008 1, 2002), it is manufactured and maintained, mechanically stirred, vibrated and compacted by vibrating table, and finally the surface is smoothed. After the specimen is dismantled, all specimens are subject to standard curing, and after 28d of standard curing, the next test is conducted. The making process of specimens is strict, and the loopholes in the making process will affect the comparison of the whole test results. Therefore, in the process of specimen manufacture, especially during the curing period, the relevant test data should be strictly controlled, and the curing effect should be compared, and the problems found should be recorded in time and effectively to ensure the integrity and accuracy of the whole specimen manufacture process and meet the test requirements.
3 external load application
3. 1 test operation
The test loading operation is to choose to apply external load to the specimen to realize the failure of the specimen under a certain bearing capacity, record the pressure of the external load when the specimen is damaged, and then calculate the rebound modulus of the corresponding specimen. Before test loading, conduct rebound test on the test block. The concrete operation is to put the pouring surface of the test block between the upper and lower bearing plates of the press (as shown in figure 1), press it with a pressure of 40° 50kN, and rebound on the two opposite surfaces. Test rebound test adopts horizontal test without angle correction. Because the test block adopts standard curing method, the influence of concrete carbonization is not considered in the test. After the rebound, the compressive strength of the test block was tested, and the loading speed was controlled at 0.3 0.5N/mm2 until the test block was destroyed. Through the above analysis of the test loading operation steps, it can be concluded that the basic factors affecting data measurement in the whole test process are: the pressure value of external load, horizontal test method, loading speed and so on. Therefore, effective control of these test factors can ensure the smooth progress of the whole test process. The pressure equipment during the test is shown in the following figure 1.
3.2 Test phenomena and characteristics of specimen failure
In the process of observing the whole experimental phenomenon, recycled concrete mixed with construction waste has greater strength and is more valuable than ordinary concrete. For concrete specimens mixed with construction waste, the quantity and quality of mixed construction waste are uncertain, so it will also affect the strength of the specimens. After the mixed construction waste is mixed, the construction waste is arranged in disorder in concrete because of its dense distribution and inconsistent distribution direction. For the small pieces of construction waste chopped in concrete, there is a certain cohesive force inside the construction waste. This leads to the phenomenon that concrete is subjected to external load in the whole test process, especially in the process of applying external load, thus causing damage and cracks. However, due to the mixing of construction waste in concrete, the development of concrete cracks is limited to a certain extent, and the causes and extent of cracks have become more important test data in the whole test process. The cracking degree of concrete specimens mixed with construction waste is slow, and the concrete peeling process and specimen failure process have certain regularity.
3.3 Data analysis
For concrete with the same strength grade, the rebound value of construction waste concrete is obviously lower than that of ordinary retarded soil, which shows that the whole construction waste concrete has high strength and toughness. In the actual measurement process, the rebound value of construction waste concrete is obviously lower than that of ordinary concrete, and there is a certain gap between the concrete quality and the measured data, but the measured data has not been significantly reduced. It can be seen that the addition of the whole construction waste and recycled aggregate will directly affect the hardness and strength of the whole concrete surface. Therefore, the rebound value of construction waste concrete is lower than that of ordinary concrete. Even if the whole rebound value is effectively converted into strength and measured strength, the concrete made of its raw materials can be used to estimate the measured strength by effective data conversion. Therefore, it is necessary to establish a practical strength curve of construction waste concrete to improve the utilization efficiency of the whole construction waste concrete.
4 conclusion
According to the relevant test data and practical engineering application analysis, through the engineering application performance of construction waste inorganic polymer concrete and the rebound test of concrete compressive strength, the differences between construction waste inorganic polymer concrete and ordinary concrete are compared and analyzed. Through the analysis of the data, the following conclusions are drawn: (1) The rebound value of inorganic polymer concrete of construction waste is less than that of ordinary concrete. (2) Adding construction waste as external aggregate can improve the compressive strength of inorganic polymer concrete.
The detailed information of "Application of Construction Waste in Commercial Concrete" can be found in Zhong Da Consulting & Construction Link, and all the relevant construction information you want is available.
For more information about project/service/procurement bidding, and to improve the winning rate, please click on the bottom of official website Customer Service for free consultation:/#/? source=bdzd