Properties Of Concrete With Recycled Clay-Brick-Powder

Along with the wide application of concrete, cement has become the most widely used construction material, which also leads to serious environmental issues and energy consumption. Meanwhile, waste clay-brick is continually increasing as more old building demolished, and has been recognized as a major pollutant. The disposals of clay-brick not only occupy the valuable space but also cause environmental pollution. If cement is replaced with waste clay brick, the pollution from both cement production and clay-brick disposal could be reduced, and coincidentally natural resources could be conserved with the considerably decreasing project cost.In this thesis, new research about concrete with cement partially replaced by clay-brick-powder (CBP) was proposed. This paper designed a set of techniques of producing CBP and researched the basic properties of CBP, such as water absorption and activity index. XRD test indicated that the main crystalline phases of CBP were quartz, rutile, and hematite. The size distribution of CBP was performed with the equipment of XA.L-201Laser Diffraction Particle Size Analyzer. SEM test provides the microscopic structure of CBP.The study on CBP concrete included both experimental and theoretical analysis. The orthogonal experimental design method was adopted to study the significance sequence of all influencing factors, while full factorial experimental method was used to study specific properties analysis of the CBP concrete. Statistics analysis method was adopted to analyze the experimental results. This research studied the effect of average particle size and replacement ratio of CBP on concrete mechanical properties and durability, including compressive strength, flexural strength, splitting tensile strength, static elastic modulus, and water absorption, chlorine ion electric flux, freezing-thawing. This research also studied the self shrinkage and long-term shrinkage. The hydration heat analysis provides CBP effect in cement hydration processes. The objective of this paper was to study the optimal mix design of CBP concrete, and produce high-performance recycled CBP concrete. Total13mixes, including354cement mortar specimens, were tested. Total27mixes, including1185cement concrete specimens, were tested. The following findings and conclusions can be drawn from this study:(1) As normal concrete, water/cementitious material ratio was the most significant factor on properties of concrete containing CBP. Generally, the strength decreased as the water/cementitious material ratio increased.(2) Addition of CBP could reduce concrete compressive strength. However, with proper mix design, concrete containing CBP could reach50MPa at28days. As the curing time increased, the compressive strength of CBP concrete increased quickly. Moreover, compared with the pure cement sample, samples with10%or20%brick-powder had similar or even higher compressive strength. The90-day compressive strength of some samples was higher than55MPa. The splitting tensile strength of CBP concrete ranged from2to4MPa. The flexural strength of CBP concrete ranged from10to12MPa. Compared to the normal concrete, a reduction of elasticity modulus was observed for brick samples.(3) After300times freezing-thawing resisting cycle, the flexural strength of CBP concrete was not reduced. The average water absorption of CBP concrete was2%, namely, it was similar or slightly higher than the pure-cement-concrete’s water absorption. Compared with the chlorine ion electric flux of normal concrete (1300C), the average electric flux of samples with10%or20%CBP was1400C, and with30%CBP replacement ratio, it was1600C.(4) Generally, the pure-cement-concrete had the largest constriction value (0.1mm). A significantly reduction of constriction value was observed for CBP samples.(5) Brick powder could promote the cement hydration to some extent. In fact, there exists a positive corrrelation between the hydration degree and the replacement ratio of CBP, curing time. The average particle size of CBP has little effect on cement hydration.Experiment showed that recycled clay-brick-powder could be used as a partial replacement of cement in concrete without reducing its properties.