Development And Performance Analysis Of Waste - Fabric Reinforced Cement - Based Composite Permeable Brick

Permeable pavement helps for the circulation of urban air and water, elimination of heat island effects, absorbing noise. Cement based permeable brick is inexpensive and its making is simple, but because of its low strength, permeable bricks have not been widely popularized and applied. Polyester as the largest synthetic fiber, because of lack of natural degradation, its waste disposal is a challenge. For the above problem, this article selects polyester/cotton blend fabric and polyester plain as a reinforcement to manufacture the cement-based composite porous brick, with a view to develop the effective recovery of waste PET products, at the same time, improve the performance of cement-based permeable brick.Firstly, the scrap fabric is pre-treatment, including cutting to fragment, tearing and opening to recycled fibers, and hydrophilic treatment. The fabric fragment or fibers mix with a certain size of aggregate, cement, water, water reducer, use static compaction pressing and seal conservation to get cement-based compound permeable brick reinforced with waste fabric. The effects of parameters including aggregate particle size, aggregate-cement ratio, water-cement ratio, fabric volume and shape, and curing conditions on the compressive strength and permeable indexes of permeable brick are studied, and the best process parameters are determined.The compression damage mechanism of composite permeable brick reinforced with fabric is analyzed with composites theory, and fiber spacing theory, and theory related concrete structure. The effect of volume fraction, dimension and shape of fabric on the compression characteristics of permeable brick are researched, which includes the damage state, load-displacement curve features, compressive strength, and fracture energy. According to the compression characteristics of permeable brick, the compression toughness index I2,I3.5 and Is are defined to investigate the effect of fabric mixed on the compression toughness of composite permeable brick. The compress stress-strain curves of permeable bricks is fitted in nonlinear, fitting equation is acquired, and its parameters are analyzed by fuzzy cluster method to evaluate the differences between the stress-strain curves of composite permeable bricks prepared at different conditions.A new instrument is developed to test the water-permeability coefficient of composite permeable brick. The effect of volume fraction, dimension and shape of fabric on permeability coefficient, water-retention coefficient and evaporation capacity of composite permeable brick are researched. The evaporation intensity curve is nonlinear fitting, the parameters of fitting equation are analyzed by fuzzy cluster method. In addition, to study the environmental protection function of permeable bricks, the temperature change of common brick, permeable bricks, composite permeable bricks in a simulated solar irradiation conditions and their sound-absorbing effect are studied.Results show that:(1) Compared to the tearing and opening, the cutting is less harmful to fabric. The surface of recycled fiber which gets from tearing and opening fabric appears nicks. And the length of recycled fiber reduces from 28 ～33mm to 13～18mm. The tensile strength of cotton recycled fiber from polyester/cotton blend fabric had dropped significantly (>60%)and its elongation increased significantly (70%).The tensile strength of polyester recycled fiber from blend fabric decreased about 10% and its elongation dropped significantly. At the same time the polyester recycled fiber from pure polyester fabric damaged significantly, and its strength and elongation decreased more than 50%. The recycled fiber is curling and intertwined with each other, it is difficult to isolate it into a single independent state. TFF-5 fiber modifier can improve the hydrophilic of specimens; the moisture absorption of P/C blend samples is greater than polyester samples.(2)The structure of composite permeable bricks (CPB) like honeycomb, inside contains more and large pores to permeate water through the pore through inside and outside. The right amount of fabric can ensure internal pores of CPB by reducing the bleeding of cement paste and supporting aggregate to avoid going down, on the other hand the fabrics can stop cracks further expansion into aggregates and increase the strength, toughness and ductility of CPB.(3) As the aggregate particle size increasing, CPB compressive strength decreases, and its permeability coefficient first increases and then decreases. As the water-cement ratio increasing, CPB compressive strength first increases and then decreases, and its permeability coefficient decrease. As the aggregate-cement ratio increasing, the slurry on the surface of aggregate reduces, and its porosity increases, permeability coefficient increases but compressive strength decreases.(4)As fabric volume fraction increasing, the compressive strength of CPB first increases then reduces, and get maximum value 35.96MPa in fabric volume fraction of 2%; The declined paragraph of CPB load-displacement curves (L-D curves) gradually tends to flat, and curve length increases, residual stress increase, and the toughness index and fracture energy tend to increase; the permeability coefficient and water-retention coefficient of CPB increase.(5) As fabric volume fraction is less than 2%, the compressive strength of CPB reinforced with polyester/cotton blend fabric is greater than one of CPB reinforced with pure polyester fabric, but the porosity, permeable coefficient and water-retention coefficient is reverse, and the difference is inconspicuous. As fabric volume fraction is more than 2%, the compressive strength of CPB reinforced with polyester/cotton blend fabric is less than one of CPB reinforced with pure polyester fabric, but the porosity, permeable coefficient and water-retention coefficient is reverse. When fabric volume fraction is small, the difference between the evaporation capacity changes of two kinds of CPB with evaporation time and volume fraction is not obvious, till the volume fraction is 6%, the evaporation capacity of CPB with polyester-cotton fabric is significantly less than one of CPB with polyester fabric.(6)As fabric size increases, the compressive strength of CPB tends to decline, toughness index and fracture energy tend to increase, and permeable coefficient and water-retention coefficient tend to decline, but the differences are not obvious.(7) Respectively adding equal mass of fabric (volume fraction 0.5%) and recycled fiber to prepare composite permeable brick, the compressive strength of CPB with fabric is better than one of CPB with fiber, and toughness index, fracture energy and permeable coefficient of CPB with fabric are below CPB with fiber.(8)The compression stress-strain curves and evaporation capacity curves of different types of composite permeable brick reinforced with fabric are fitting in nonlinear. The correlation coefficient is greater than 0.90, greater than 0.97, respectively. It illuminates the effect of nonlinear fitting is better. The parameters of fitting equation are analyzed by FKCM Fuzzy cluster method. The compression stress-strain curves and evaporation capacity curves is divided into 2 categories, respectively. The classification results consistent with the result of test data analysis.(9) Due to the pore through inside and outside, the permeable brick can make the internal temperature fast reach balance state, and is a kind of fast endothermic and exothermic material. Compared to the general brick and General permeable brick, the fabric mixed in permeable brick can increase the porosity in a certain extent, therefore composite permeable brick has higher endothermic and exothermic rate.(10) Internal porosity of concrete makes sound energy decay to reduce the acoustic noise. Permeable concrete brick with intensive "honeycomb" shaped structure help absorb noise, and the fabric mixed in permeable brick can increase the porosity in a certain extent, therefore composite permeable brick has better absorption ability for noise.(11)The optimum preparation technology conditions for composite permeable brick reinforced with fabric is:using 42.5 level Portland cement, and using gravel with 5-10 mm grain diameter as aggregate, and water-cement ratio 0.3, aggregate-cement ratio 4.0, water reducer 2% and volume fraction of 3mm×3mm square shaped fabric 2%, mixing with cement pre-mix method, static pressure forming, and curing 28 day. The compressive strength of obtain composite permeable brick can reach to 35.96MPa and is higher 21.9% than one of ordinary permeable brick, its permeable coefficient can reach to 0.267mm/s and is 1.15 times larger than the ordinary permeable brick.