จำนวน Repository ( 60 )
สมบัติทางวิศวกรรมของบล็อคปูพื้นคอนกรีตพรุนจากผิวทางแอสฟัลต์เก่านำมาใช้ใหม่โดยการแทนที่มวลรวมหยาบ
This research aimed to study the use of coarse aggregate obtained from removing old recycled asphalt pavement (RAP) in the production of the porous concrete paving block. Crushing and size separation of the coarse aggregate by using standard sieve size by selected the gradation size of the coarse aggregate that passed to sieve size 1/2” and retained on sieve size 3/8” and other that passed to sieve size 3/8” and retained on sieve size No.4 by mixing ratio 50 : 50 of the mass as replaced natural coarse aggregate. Portland cement quantity about 18% and 20% by weight of the aggregate. The water to cement ratio was 0.30 and 0.35 respectively. Compressive strength flexural strength and water permeability were investigated. The results showed that the cement content and water to cement ratio was influenced the strength properties and water permeability rate of the porous concrete paving block. The porous concrete paving block mixed with higher cement content (20%) had the compressive strength at the age of 28 days increased by 16-24% when compared with lower cement content (18%). On the other hand the water permeability rate decreased by 5.1-8.1%.
กำลังอัดความสามารถเก็บกักคลอไรด์และสัมประสิทธ์การแพร่คลอไรด์ของคอนกรีตผสมเถ้าก้นเตาบดละเอียดและผงหินปูน
This research was aimed to study the compressive strength chloride binding capacity and chloride diffusion coefficient of concrete replaced by ground bottom ash (GBA) and limestone powder in ordinary Portland cement (OPC). The water to binder ratios were 0.55. The results showed that the compressive strength of concrete with GBA was lesser than that of OPC concrete at 28 days. Also the compressive strength of concrete with limestone powder was close to that of OPC concrete and compressive strength could develop of concrete with GBA 20% and 30% higher than that of OPC concrete at 56 days. Moreover the total chloride of the concrete containing GBA and limestone powder was less than that of OPC concrete. The chloride penetration of the concrete containing GBA and limestone powder was less than that of OPC concrete. The chloride binding capacity of the concrete made with ground bottom ash and limestone powder were higher than that of OPC concrete. Finally the chloride diffusion coefficient of the concrete containing GBA and limestone powder was less than that of OPC concrete.
Flexural performance of corroded reinforced concrete beams repaired with CFRP sheets
Corrosion of steel reinforcements in concrete is one of the main causes of early deterioration and reduction of service loads of reinforced concrete (RC) structures. This paper reports the results of an experimental program that was carried out to evaluate the effect of reinforcement corrosion on the flexural performance of RC beams and to investigate the efficiency of externally bonded carbon fiber reinforced polymer (CFRP) sheets to repair the corrosion-damaged RC beams. Seven RC beams with the same cross section and reinforcement details were prepared including the control beam (B0). First tension reinforcements of six RC beams were corroded by using an accelerated impress-current process to obtain corrosion levels of 15% 30% and 50% of weight loss according to Faraday’s law. Then three beams were repaired using CFRP sheets attached to the bottom surface leaving the other three unrepaired. All beams were subjected to the four-point bending load test. The experimental results show that the corrosion specimens demonstrated a significant deterioration on the structural performance and the integrity by decreasing in their ultimate load capacity stiffness and ductility. The deterioration by corrosion of tension reinforcements can be successfully overcome using CFRP sheets as the repair material. The technique can restore the beam strength to its original design strength except specimen B50F2 having severe steel-corrosion damage of 50%. A conservative value of the ultimate bending capacity of the beams with low corrosions (15%-30%) can be predicted by using RC conventional models as suggested in ACI 318. However the opposite trend is obtained for the high corrosion beam (50%). Appling ACI 440.2R provision to predict the ultimate flexural capacity of corroded beams repaired with CFRP sheets shows rather fair values for low corrosions (15%-30%) but significantly overestimates the strength of the high corrosion beam (50%).
การเสริมกำลังคานลึกคอนกรีตเสริมเหล็กที่เสื่อมสภาพเนื่องจากคลอไรด์ด้วยแผ่นคาร์บอนไฟเบอร์
Deterioration of reinforced concrete deep beam structure caused by chloride is severe andtakes up wide area even though the structure is not exposed to sea water or brackish water. Even the structure which is far from sea water or brackish water is affected by this problem.When the reinforced concreate deep beam structure is affected by chloride steel reinforced inside the structure is corroded resulting in reducing the cross-sectional area of the reinforced steel affecting load capacity deflection and beam failure. If there is no repair or strengthening such capabilities are continuously reduced until it is no longer safe to use the beam. Therefore it is necessary to repair or strengthening the deteriorated structure to be safely used. This research investigated strengthening of deteriorated reinforced concrete deep beam caused by chloride with 4 formats of carbon Fiber sheets to seek guidelines for the most efficient strengthening. The resultshowed that the strengthening by the 4 format of carbon fiber sheet could increase ultimate loadcapability yet could not improve ductility of the deteriorated beam to become close to the beamthat is not deteriorated. The strengthening that could increase the maximum ultimate load capability was the table format strengthening. In addition the strengthening that the carbon fiber making 45 degrees with the length of the beam could best prevent diagonal cracks.
คุณสมบัติเชิงกลของคอนกรีตมวลเบาผสมวัสดุปอซโซลาน
This research study the effect of pozzolanic materials on light weight concrete by replacement cement with fly ash and Meta kaolin which affect the properties of concrete by using pumics aggregate. Coarse in aerated concrete and consider mechanical properties. Aerated concrete replacement cement by fly ash 20% 35% and 50% respectively and meta-kaolin is replaced. From the results it was found that the compressive strength of light weight concrete at 28 days w/b = 0.55 was higher than that of every 14 days of cement and cement cement replacement by fly ash 50% highest value compressive strength. More than all the ingredients replaced with fly ash and Meta kaolin. When considering the flexural strength of replacement cement with 10% by Meta kaolin the maximum flexural strength of 80 ksc was higher than that of control concrete and all other ingradient. Experimental tensile strength at 28 days result found that replacement cement by fly ash at 35% gave the highest tensile strength of 28 ksc and gave higher tensile strength than all other ingradient. From the impact strength test at age 28 days it was found that the replacement cement 35% by fly ash gave the highest impact strength of 92.00 joule than the 20% and 50% respectively and higher impact strength than that of all kaolin. Except for control concrete.