Research On Preparation Of Recycled Aggregate And Recycled High-strength Concrete

In this paper, the materials have been choice from the waste concrete of Yunnan Road in Qingdao City. After manual handling, the waste concrete that the size is 4.75mm～31.5mm were used for the recycled aggregate. The new craft of recycled aggregate was proposed. The Los Angeles abrasion machine was used as the reshaping equipment. This craft characteristic is:①It saved the clean water and the clean time by first cleans and then broken way.②the craft is simpler, the cost is lower, the useful life of equipment is longer, and the promotion is advantageous.③after the reshaping processing, the recycled aggregate surface is smooth, the mortar is removed basically.④the reshaping machine volume is smaller, the abrasion is sealer, the noise is lower, and it does not produce the dust and non-dust pollution.⑤the recycled aggregate is mutual abrasion, the vulnerable and the power consumption is lower.⑥after the reshaping, the recycled aggregate performance improvement is obvious.The best process quantity is 15kg and the best process time is 90s According to the abrasion machine operating efficiency.After the reshaping of recycle aggregate, the apparent density enhances from 2420kg/m~3 to 2600kg/m~3 and achieves 96% of the natural aggregate apparent density 2708kg/m~3; The stack density changed from 1230kg/m~3 to 1441kg/m~3 close to the natural aggregate stack density 1467kg/m~3, the void percentage reduced to 45% close to the void percentage of natural aggregate 45.8%; The water-absorptivity reduces above 50% from 4.8% to 2.3%; The crushes percentage decrease from 16% to 8.5% close to the natural aggregate 8.1%; After the reshaping, the gradation conforms to the standard gradation scope and the aggregate surface is improved.The recycled high-strength concrete was produced by the recycled aggregate according the C60 design. Some experiment were done such as the slum, the 30 minute slum lost, the compressive strength, the bending strength, the impervious performance and so on. The conclusion is as follow:The 30 minute slump lost of recycled high-strength concrete is between 4mm to 12mm, the slump lost will increase with the quantity of recycled aggregate or the quantity of cement; The 28d compressive strength is lower from 11% to 18%, the recycled high-strength concrete produced 100% recycled aggregate achieve 62.2MPa that could satisfies the C60 concrete request; The lowest bending strength is 7.21MPa. The bending strength of recycled high-strength concrete is lower from 13% to 19% than the natural aggregate high-strength concrete; The impervious performance of recycled high-strength concrete satisfies the p12 request, the impermeability of recycled high-strength concrete is close correlation with the amount of the mixes material and the impermeability is enhanced by the pulverized coal ash and the silica ash.