Natural sand is a non renewable resource. It has become an inevitable trend for manufactured sand to replace natural sand. Due to the complex regional differences of raw rock of manufactured sand, the quality of manufactured sand is generally uneven, and the quality control of concrete with manufactured sand on the construction site is difficult. The angle, shape and grade of manufactured sand have obvious influence on the workability of concrete. The fresh concrete with manufactured sand is easy to segregation, bleeding, and lose slump. The adaptability of mix proportion is poor. The high viscosity of fresh concrete would lead to high pumping resistance, which will increase the difficulty of pumping construction. However it is difficult to prepare low viscosity manufactured sand concrete, which affects the popularization and application of manufactured sand concrete in different regions.

In order to solve the above technical problems in the application of manufactured sand in concrete, and improve the quality stability and construction efficiency of manufactured sand concrete, the project has carried out research work in the following three aspects: the detection of characteristic indexes and quality evaluation methods of manufactured sand, the development of functional admixtures and the optimization technology of full grading mix proportion design.

The main innovations of the project are as follows.

lThe comprehensive detection and evaluation method of raw rock of manufactured sand is developed, the characteristic indexes such as roughness, particle shape, gradation and quality of manufactured sand are clarified, and the quality control and evaluation system of manufactured sand is constructed.

lThe viscosity reducer for manufactured sand concrete is invented, which can reduce the yield stress of cement paste by 15% ~ 24% and the plastic viscosity by 10% ~ 25%.

lThe design method of full gradation of cement, admixture and aggregate is completed. The design and preparation method of optimized mix proportion of full gradation of manufactored sand concrete are developed.

Fresh concrete by common viscosity reducer(left) and by ZJ-NⅢ viscosity reducer of this project (right)

In the past three years, 1.53 million m³ of low viscosity and high strength manufactured sand concrete has been prepared by the technologies of this project, which has been successively applied to the tallest building in Chengdu, Huali expressway , the tallest building in Guangxi, and other large-scale projects. The technologies of this project have created a total economic benefit of 35.3 million yuan, not only ensure the construction efficiency and construction quality, but also promote the large-scale application of manufactured sand, infrastructure construction, which have important guiding significance and promotion value, and have remarkable economic and social benefits.

The giant column of the tallest building in Chengdu adopts the core steel structure

 and the dense reinforcement in the giant column has high requirements for concrete

Application in urban overpass project

Application in Huali Express

China West Construction Group