Geopolymer is a new sustainable binding material. It was developed to reduce CO2 footprint of existing Portland cement concrete. One ton of Geopolymeric cement generates 0.18 ton of CO2 from combustion carbon-fuel. This figure is 6 times less than the emission of Portland cement manufacture. The relationship between the compressive strength of Geopolymer concrete and the percentage of amorphous silica in the source material has been studied in the present work. Six mixes with different source materials were investigated to verify this relationship. The used Pozzolanic materials were three types of Fly ash, two types of Metakaolin and one type of ground granulated blast furnace slag. Geopolymer concrete samples were cured by heating for 72 hours. The testing ages for compressive strength were 7, 14, 28, and 60 days. The results showed that a noticeable relationship between compressive strength and amorphous silica was observed. The microstructure of the six mixes was studied in detail through the SEM and XRD analysis.
In this study, different percentages (2, 4, 6, 8, and 10% by weight of the soil) of chopped polymeric (plastic bottles with maximum particle size 2.36 mm and 1.18 mm in addition to rubber tires of 0.6 mm max particle size) wastes are incorporated with soil to produce lightweight clay bricks, to find the optimum percentage satisfying the requirements of bricks grade C using for non-structural walls (partitions).The effects of different types and percentages of the polymeric wastes on firing shrinkage, density, water absorption, compressive strength and thermal conductivity of the fired bricks were studied. Results indicate that it is possible to incorporate not more than 8% of chopped rubber tires or not more than 6% of chopped bottles to the clay soil to produce lightweight fired clay bricks satisfying the compressive strength and water absorption requirements for grade C of bricks (used for partitions) according to the Iraqi specification IQS 25/1988, in addition to reducing the thermal conductivity by 13-17% which is desirable as it will reduce the energy required for heating and cooling. Also, found that the size of the incorporated particles of plastic wastes in clay, used for bricks manufacturing, did not have a significant effect on the different studied properties of bricks. In addition to, the incorporation of chopped rubber tires, having smaller particles size and more sphere particles shape, produce fired clay bricks with more homogeneous pores distribution and smaller size compared with clay brick incorporating chopped plastic wastes having flaky shape and larger particles size, leading to produce clay brick with higher density and strength, with lower water absorption. As a total results, the incorporation different types of polymeric wastes (chopped plastic bottles with 2.36 and 1.18 max size and chopped rubber tires) with percentages (2, 4, 6, 8, and 10% by weight of soil) , cause the firing shrinkage a nd water absorption to increase by (0.6-20.2%) and (3-43.5%) respectively, while the density, compressive strength, and thermal conductivity decrease by (3.5-25.1%), (0.4-2.3%), and (2.1-31.9%) respectively with respect to the reference fired clay bricks, depending on the percentage, particles size, and type of the polymeric wastes addition.
Decreasing the emissions of CO2 that come from vehicle exhaust, especially in car parking and tunnels, is so vital. CO2 emissions cause corrosion to a reinforcement of concrete. Thus, there is a need to provide a layer that protects the reinforcement from the reach of this harmful gas. This work goals to investigate the efficiency of using board units from Pozzolime concrete and pervious concrete to sequestrate CO2 from the environment and then to convert it into calcium carbonate inside the concrete. The units have dimensions of (200×400×40±5). All specimens were cured in a water tank after about 48 hours after casting. Then paint the sample from all surfaces (three layers) excluding the top surface. The pervious concrete and Pozzolime specimens, at age of 28 days, were put in the chamber, then the gas was supplied to the chamber with concentrations of 15%, 25%, and 50 %, for 24 hours. The efficiency was evaluated through carbonation depth, CO2-uptake, and weight change. The results showed that the maximum CO2 uptake was recorded at the age of 28 days for Pozzolime concrete when exposed to 50% of CO2 concentration.
The ambient temperature records in Iraq show a large variation between day and night reaching 20 C, depending on the season, whether it is summer or winter. For this reason, the aim of this research is to study the effect of these conditions on the drying shrinkage of self-compacting concrete produced by using Portland-Limestone cement (ASTM C595 - Type IL). SCC mixes were designed to attain compressive strengths of 40 and 60MPa at 28days with and without silica fume respectively. Same mixes were reproduced with ordinary Portland cement (ASTM C150 - Type I) for comparisons. Two maximum sizes of aggregate 10 and 20 mm were incorporated in this work. The drying shrinkage was measured for 180 days after 7 days of water curing. The range of ambient (outdoor) temperature variation was from - 4 to + 39°C and the relative humidity ranged from 15 to 60 %. The results of this exposure were compared to that of specimens kept in the shrinkage chamber, with a temperature of 21°C and relative humidity 35%. The current results showed that due to the irreversible nature of shrinkage strain, the drop of ambient temperature and the rise of atmosphere moisture or relative humidity would not reverse the shrinkage strain. It is important to figure the final total accumulated strain when dealing with ambient temperature variation. The drying shrinkage characteristics for concrete made with Type IL cement, are found similar to that for concrete produced with Type I cement.
High-volume fly ash concrete, HVFALC, may acquire popularity as durable, resource-efficient, and option of sustainability for different applications of concrete. The Pozzolanic reaction between fly ash, Ca(OH)2 and water is the cause of making high-volume fly ash concrete a promising sustainable material. The aim of this study is to enhance the rate of the Pozzolanic reaction by incorporating external source of hydrated lime in the mix by two approaches. The first is to replace 10% by weight of the cementitious materials with hydrated lime and second is to use a lime-saturated water, with a concentration of 3g/L, for mixing. Two high-volume fly ash concrete mixes, with 50 and 60 % replacement by weight of cement, were included in this study. The testing program included water absorption, dry density, compressive and splitting tensile strengths. The testing program was extended to the age of 120 days. The present results showed that both approaches have caused an increase, ranging between 10 and 24 %, in absorption values and a slight reduction, less than 3 %, in dry density values. Both approaches have caused a significant gain in compressive and splitting tensile strengths. Replacing 10 % by weight of the cementitious materials with hydrated lime caused better enhancement in compressive and splitting tensile strengths for all curing ages than using lime-saturated water in mixing. The former approach was more effective for mix FA60 than for FA50 and the higher fly ash content in the FA60 mixes could be the reason.
This research aims to study the influence of using Carbon Fiber Reinforced Polymer (CFRP) strips as an external strengthened and repairing material on the behavior of self-compacting concrete (SCC) Corbels. The experimental work involved testing twenty self-compacting concrete corbels specimens. The experimental work is divided into two parts; the first part consists of three groups to investigate the most effective direction, position, bonding type and amount of CFRP strips on the behavior of corbels and utilized it in practice, also to strengthen new variables that are investigated in the second part. Two groups in part one are strengthened with different numbers of inclined and horizontal direction of CFRP strips, while in the third group the specimens were strengthened with strips of CFRP having different directions and bond types to improve the strength capacity and behavior of corbels. This improvement is represented by increase cracking load by about (94)% and increase in their ultimate load capacity of strengthening corbels which varies from about (19 to 88)%. While the second part of experimental work included the following variables: shear span to effective depth ratio (a/d), amount of horizontal steel reinforcement stirrups and repaired damaged corbels. The reinforced concrete corbels in this part were strengthened and repaired by CFRP strips depending on optimum result that is produced from part one wherefrom position, direction and amount are considered. It was found for unstrengthened and strengthened corbels having same horizontal secondary reinforcement stirrups that when (a/d) ratio decreases from 0.65 to 0.4 causes increase in cracking and ultimate loads reach (55)% and (35.41)% respectively. For un-strengthened and strengthened corbels having same (a/d) ratio, it was found an increase in cracking load which varies from (6.66 to 34.78)% and from (18.18 to 52.63) % in ultimate load when horizontal secondary reinforcement stirrups are increased. It was also found repairing SCC corbels with CFRP strips causes an increase in ultimate load reaching up to (50)% with respect to un-strengthened specimens. From results it is concluded that strengthened or repaired corbels present stiffer load deflection response than corresponding unstrengthened corbel (control corbel).
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