Abstract
Traditional PHC pipe pile in foundation engineering consumes high energy and has insufficient durability. A magnesium oxide carbonization test block is a new type of environmental protection block which bases on activated magnesium oxide cementation technology. The use of CO2 carbonation technology allows reactive magnesia to react to form basic magnesium carbonate to increase the compressive strength and durability of the block. Three kinds of different magnesium oxide powders were subjected to pressure test and determined the key technical parameters, such as optimal raw materials, sample preparation methods, carbonization environment and technology, and optimized design of pipe pile concrete material system.
Highlights
Prestressed high-strength concrete pipe piles (PHC pipe piles) are widely used in industrial and civil construction, roads and railway bridges, ports, and other engineering structures
Australian researcher Harrison (2001) [2, 3] developed a new type of cement mixed with activated magnesia and ordinary Portland cement, which is based on environmental protection to design. e hydration rate of active magnesium oxide is fast, and magnesium hydroxide can react with carbon dioxide to form magnesium carbonate compound which has strong cement strength, and this is an environmentally friendly, sustainable, and efficient new material
Magnesium carbonate can regenerate magnesium oxide after calcination [4], and it means that the process is reversible and active magnesium oxide products have recyclability and recycling characteristics
Summary
Prestressed high-strength concrete pipe piles (PHC pipe piles) are widely used in industrial and civil construction, roads and railway bridges, ports, and other engineering structures. Yi et al [7, 8] used a modified three-axis device to carbonize and cure the sand; they found that blending 5% of active MgO can complete carbonization during 3∼6 hours, and its strength can reach 2 to 3 times the strength of curing 28 d cement stabilized soil This technology is still in the preliminary development stage; Formosaa et al [9] indicated that MPC formulated with a low-cost MgO by-product could be an interesting alternative to other repair mortars; Zhang et al [10] concluded that the carbonization blocks could have a higher strength; laboratory tests were performed to investigate the influence of the mixing amount of reactive MgO on compressive strength, microcharacteristics, and durability of the block, and they indicated that the carbonized products of reactive MgO are mainly hydromagnesite and nesquehonite/dypingite, with the higher amount of reactive MgO, the more carbonized products. In order to reduce environmental pollution caused by Portland cement as a solidifying agent, mainly from the following three aspects to optimize the improvement (1) replacement of Portland cement as a curing agent for blocks with new materials, (2) research low emission, low energy, and recyclable recycling block preparation method, and (3) development of the best material mix ratio and preparation method were done in the previous research
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