On the construction quality control of cement pave

Talking about the quality control of cement pavement construction of rural roads

1. Raising problems

Shandong Provincial People's government issued a document (lzf [2003] No. 38) in May 2003, proposing that the goal and task of rural road reconstruction in the whole province (excluding Qingdao City) is to invest 15 billion yuan to transform 80000 kilometers of rural roads, 4932 super large and medium-sized bridges in 3 to 5 years from 2003, The provincial administrative villages are basically connected with oil roads (hereinafter referred to as "village to village access"). The target task has the characteristics of wide range, many points and large quantity. It covers a wide range, that is, it involves every township and administrative village, which is beneficial to every people along the line; More points means that the routes are fragmented. The mileage of each road is shorter, ranging from kilometers to kilometers, and few routes over 10 kilometers; The large volume is due to the large amount of the project. Only 200 fully respect the wishes of enterprises, and the province plans to transform 36000 kilometers in four years. Quality assurance is the main problem to do a good job in this popular project. Through the practice in 2003, it can be seen that the quality management of the village to village project has the following problems:

1) first of all, due to the above characteristics of the village to village project, the construction units with high construction qualification and strong technical force do not participate in the construction of this project at all, The practice in 2003 has proved that most of the construction teams of the village to village project are rural self-employed households or small teams affiliated with large companies. Therefore, whether the construction quality can be guaranteed has become the main problem for village managers

2) Secondly, due to the advantages of less investment in later maintenance of cement concrete pavement, long service life and relatively simple construction technology, most villages choose to build cement concrete pavement. Some places even made mandatory requirements. For example, Jinan municipal government issued a document (Ji Zheng Zi [2003] No. 28) requiring that roads south of the Yellow River must adopt cement pavement. However, most of the articles about pavement construction quality control in relevant professional magazines or journals are asphalt pavement, few about cement pavement, and even if there are slip form or track construction methods, while few of the construction methods of three roller shafts or small machines and tools used in rural roads, resulting in no reference materials for relevant quality management personnel

3) due to the large number of manpower involved in the village to village project, it is difficult to allocate a professional quality supervision personnel for each road and township, and it is even more difficult to allocate qualified and certified highway engineering supervision. Most of the quality management personnel participating in the 171 MDF village to village project are some qualified personnel who have been engaged in the highway or construction industry drawn from the relevant departments of the township, They are not familiar with the construction quality control of cement pavement, so it is more difficult to control the construction quality of cement pavement of rural roads

2. Main problems in the quality of rural cement pavement

1) mix proportion. According to the construction experience of cement pavement, it is recommended that the coarse aggregate of concrete refer to the mix proportion recommended in Table 1, and the sand content is generally 28% - 34%. As the price of small stones is more expensive than that of large stones, the general construction units increase the amount of large stones and reduce the amount of small stones, so that the proportion of coarse and fine materials cannot reach the proportion of maximum unit weight, affecting the overall strength; The specification requires that the minimum grade of cement is no less than 425 (see Table 2), and the dosage is about the recommended model WDS (3) recommended index of Jinan assaying ☆☆☆☆☆ kg/m3, while some construction units use 325 cement or reduce the dosage of cement in order to reduce the cost; In addition, the mud content of fine aggregate (sand) also affects the quality of concrete

Table 1 coarse aggregate mix ratio

particle size cm stone cm stone 0 Cm stone chips

percentage 40252510

Table 2 cement grade

Traffic grade cement grade

extra heavy 525

heavy, medium, light 425