| As the most widely used construction materials, the cement and concrete consume lots of resources, and destroy the ecological environment. The use of the construction waste and industrial waste are generally under-utilization at present. There are still many problems, such as: destruction of ecological environment, construction waste and industrial waste. Furthermore, it will not only pollute the cultivated land area but also the air, and the heavy metal ions always pollute soil and water resources. To solve the above problem, this research used the processing steel slag, coal gangue, slag and other industrial waste residue as raw materials to prepare high performance of artificial aggregate, which was used to replace natural sand and gravel aggregate mixture to fabricate recycling concrete. The waste recycling concrete can be directly prepared by adding some crushing correction and grinding processing of raw materials. According to the cement ratio value it can be regenerated after high temperature calcining cement clinker with raw materials configuration to get the recycling of concrete. This proces is not only greatly reduce the dosage of limestone and prevent scraping resources problems, but also effectively utilize the industrial waste and reduce the emissions of CO2.In order to generalize the application of recycling concrete, the laboratory conduct research on thedurability of recycling concrete. The thesis mainly deals with the potential activity of the high performance artificial aggregate, to study the influence of volume stability and self-healing of recycling concrete. By taking use of the analysis of lithofacies, X-ray diffraction, to test the performance of the artificial aggregate. By using instruments such as the length comparator, to study the volume stability of recycling concrete, at the same time with the aid of crack width measuring instrument, ultrasonic nondestructive testing and other testing means the research of the recycling concrete crack self-healing ability, the main conclusion is as follows:(1)The basic properties of the artificial aggregate and alkali-aggregate reaction testThe main mineral compositions of artificial aggregates are C2 S, C3 S, C3 A and C4 AF, whose compositions are similar to cement clinker, and the mineral compositions of waste-based artificial aggregates are C2 S, CS, CA2 and CF2 and Ca3Al10O18, and their water absorption rates are 1.38%, 1.89%, crush index are 11.20%, 10.60%, apparent density are 2623kg/m3, 2605 kg/m3, respectively. They can meet the national standard requirements. Artificial aggregate hydration after their internal pore size smaller, its hydration products can have the effect of pore filling. Alkali-aggregate reaction test confirmed there is no potential alkali-aggregate reaction in the recycling concrete, and of alkaline artificial aggregate does not cause the destruction of recycling concrete volume under the condition.(2)The studyon artificial aggregate of recycling concrete strengthUnder the condition of same water-cement ratio, the recycling concrete has higher compressive strength than ordinary concrete. When water cement ratio is 0.47, the 28 days’ compressive strength of recycling concrete prepared with similar clinker composition of with artificial aggregates and waste-based artificial aggregates are 62.4MPa and 57.4MPa, respectively, which increase by 28.1% and 17.9% compared with the ordinary concrete(48.7MPa) respectively. Microhardness testing concrete interface transition zone, type of clinker composition of recycling concrete, waste-based recycling concrete and ordinary concrete interface transition zone hardness 80kg·mm-2 and 70kg·mm-2, respectively 40kg·mm-2, can recycling concrete interface transition zone, higher hardness, high compressive strength of recycling concrete.(3)The influence of temperature,water cement ratio and sand percentage on drying shrinkage of recycling concreteWhen the water-cement ratio are 0.42, 0.52, 0.62, maintaining at 180 days’ age, compared with ordinary concrete, the percent of volume drying shrinkage rate of recycle concrete with similar cliker composition artificial agreegates decreases to 19.2%, 16.4% and 15.7% respectively, and the percent of volume drying shrinkage rate of waste-based recycling concrete decreases to 16.1%, 18.2% and 16.1% respectively. When the sand ratio are 35%, 40% and 45% respectively, compared with ordinary concrete, the percent of volume drying shrinkage rate of recycle concrete with similar cliker composition artificial agreegates decreases to 16.0%, 16.4% and 14.1% respectively, and the percent of volume drying shrinkage rate of waste-based recycling concrete fell by 18.3%, 18.2% and 16.6% respectively. The pore size distribution shows that the concrete internal possesses much harmful holes and more harmful holes with the increasing of water cement ratio and sand ratio.(4)The influence of mineral admixture on volume drying shrinkage of the recycling concreteWith the increase of dosage of mineral admixtures, recycling concrete volume and dry shrinkage are varying degrees of decline. When the curing age was 180 d, compared with blank sample(0%) dosage of mineral admixtures of 10%, 20%, 30%, 40% of fly ash clinker composition of recycling concrete volume and dry shrinkage rate decreases to 5.2%, 15.2%, 28.5% and 42.7%, respectively, and waste material base of recycling concrete volume and dry shrinkage rate decreases to 6.3%, 11.0%, 22.9%, 38.5%. Adding 10%, 20%, 30%, 40%, slag similar to clinker composition of recycling concrete volume and dry shrinkage rate decreases to-1.0%, 7.7%, 15.2%, 20.4%, respectively. Drying shrinkage rate, and waste recycling concrete volume decreases to 1.4%, 5.5%, 10.1% and 16.0% respectively; adding 5% silica fume, the recycling concrete specimen had little influence upon the volume of drying shrinkage, after adding 10% silica fume, dry charge thumbnail of recycling concrete is less than the blank sample, decline in value is less than 5%, the volume has a little influence on drying shrinkage. Fly ash of recycling concrete volume of drying shrinkage, can effectively reduce the volume of the recycling concrete specimen dry shrinkage, mineral powders effect on early-age shrinkage of the recycling concrete is larger, but the late dry shrinkage volume decline is not obvious, low content of silica fume on the effects of a recycling concrete volume stability.(5)The research of recycling concrete crack self-healing propertiesWith the increase of water cement ratio, the self-healing performance of recycling concrete becomes less. When the water cement ratio is 0.5, the similar to clinker of mortar specimen, waste based mortar specimens and the normal mortar specimens after repair strength growth rate was 30.44%, 28.0% and 24.96%, respectively, the ultrasonic wave velocity growth rate of 13.06%, 15.83% and 12.23% respectively, the prefabricated crack healing rate of 100%, 79.6% and 55.0% respectively, namely after the repair, the strength of the artificial fine aggregate sample rate, growth rate of ultrasonic wave velocity and crack healing rate is significantly higher than ordinary mortar specimen. When the water cement ratio is 0.47, the kind of clinker composition of recycling concrete with waste recycling concrete specimens after repair strength growth rate were 22.57%, 23.13%, significantly higher than that of ordinary concrete strength growth rate 11.76%, ultrasonic wave velocity rate were 4.54%, 4.94%, 2.91% higher than that of ordinary concrete wave speed growth, the fracture healing rate were 61.9%, 53.8%, 46.5% higher than that of ordinary concrete fracture healing rate;Artificial fine aggregate on the properties of specimen self-healing effect more apparent, and self-healing properties of clinker composition of recycling concrete were more obvious. |
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