Production and Tensile Strength Determination of Alkali-activated Sea Sand Recycled Aggregate Concrete
YANG Shutong1,2, LI Linzhen1, YU Miao1
1 College of Engineering, Ocean University of China, Qingdao 266100, China 2 Cooperative Innovation Center of Engineering Construction and Safety in Shandong Blue Economic Zone, Qingdao University of Technology, Qingdao 266033, China
Abstract: Much CO2 emission during the cement production pollutes the environment significantly. The resource of natural sands and stones becomes scarcer. Large amounts of industrial waste (slag and fly ash) and construction and demolition waste give huge pressure on environment. Thus, the intention of this paper is to produce a new type of concrete, i.e., alkali-activated sea sand recycled aggregate concrete (AASRAC), by using seawater, sea sand, alkali-activated ground granulated blast furnace slag and fly ash instead of cement, and crushed demolition waste instead of natural stones. It is then essential to evaluate the tensile resistance of the new concrete considering its future application in ocean engineering. But it is too difficult to obtain the true tensile strength based on the conventional method due to the non-uniformity and micro-defects in the materials. Based on the boundary effect model in non-linear fracture mechanics, a linear equation of peak load with respected to the true tensile strength is then derived by incorporating the parameters reflecting the material heterogeneity and discontinuity. The size-independent tensile strength and fracture toughness can be predicted by using the linear equation only if the peak load is determined from the test. Subsequently, the means, upper and lower limits of two fracture parameters with 95% reliability are determined based on the normal distribution analysis. Moreover, different from ordinary concrete, the failure mode of AASRAC is more than 80% of the recycled coarse aggregates fractured. Thus, the tensile resistance of the new concrete depends on the tensile strength of alkali-activated mortar and recycled coarse aggregates.
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2021, Vol. 35 
