Research On Building Demolition Waste Used As Cement Mixtures

This divide building demolition waste into waste concrete (FL) and waste clay brick (FZ) of basic building materials waste, marble mixture waste (FD) and ceramic tile mixture waste (FC) of building decorative materias waste. By means of chemical composition analysis, cement performance index analysis, the methods of XRD and SEM, research the effect of construction waste single or compoundly mixed as cement mixed material,and sthdy the related mechanism. Get the following conclusion:1. In the program of the different construction waste separately mixed as cement mixed material, Standard consistency water consumption, setting time and stability performance of the cement sample is basiciy meet the standard requirements. Preparation of P·C42.5 R grade strength of cement, it can doped the waste pebble concrete with 20%, ceramic tile mixture waste with 5%, waste clay brick with 10%. Different construction waste’s active size comparison for FL> FD> FC> FZ. Due to the lack of calcium content, the activity of the construction waste is limited. At the same time, the low dosage of construction waste is good for the cement’s early strength, less than 20% content of the waste pebble concrete or less than 10% content of waste clay brick can partly and effectively improve the early strength of the cement, and high content of construction waste samples of cement’s early hydration strength decreased obviously.2. When construction waste additivly composite as cement mixing materials, compared with cement sample which only mixed construction waste, the 28 d strength of compound cement decreased, but its early strength relatively improved. For waste pebble concrete (FL) and waste clay brick (FZ) composited mixed material, low FZ is beneficial to improve the early strength of compound cement mixing materials, the optimal proportion for FL:FZ= 5:1, activity of compound mixed material was 66%, which can replace 30% cement clinker to manufacture P·C grade 42.5 cement; To the pebble (FL) and fly ash concrete (FM) as compound mixing materials,the optimal proportion for FL:FM= 2:1,the activity of composited mixed material was 64.15%,7d early compressive strength reached 31.01 MPa. Different construction waste composited each other and its effect is general,but composite effect of construction waste and other mature application of mixed material is ideal.3. trying different methods to stimulate ctivity of construction waste. It partly improved the ash activity of the construction waste by high temperature calcination, but it’s not obvious for the significant effect of excitation. When used different kinds of alkaline and calcium to stimulate the activity of construction waste, only CaO has obvious excitation effects on construction waste and the CaO content is 4%, the activity of pebble concrete waste increased from 68% to 81%, and waste clay brick’s activity increased from 48% to 69%, that the results is the best. Other exciting agent failed to inspire.4.Crystal growth of cement hydration products is closely related to the pH of cement slurry. cement slurry pH swings big is not beneficial to increase the strength of the cement system. volatility is one of the, volatility of NaOH is 0.43 and it’s the biggest excitation of the cement sample and tensity is low; while the volatility of CaO is 0.29 and the smallest inspired, but high strength.Exciting agent CaO supplied the calcium content in the pebble concrete cement waste, promoted the system to be more stable and orderly hydration, enhanced the strength of the cement system. Construction waste concrete has a large number of acicular ettringite flocculent (AFt) and C-S-H gel. Crystal growth of hydration products is more cluttered than the cement clinker and the hydration granular fills between construction waste particles, we can see a part of secondary hydration products on the surface of particles of construction waste. Construction waste playes a role on filling effect and auxiliary cement hydration and cement hydration crystal nucleus effectn in cement system, which keeps the performance of the cement products.