Al-Qadisiyah Journal for Engineering Sciences

Abstract Some oxides in cement such as MgO, free CaO and SO3 may cause expansive reactions with time that lead to a decrease in concrete compressive strength. If such oxides were presented in high percentages, they may cause ultimate destruction of concrete. The present study was carried out to investigate the combined effect of MgO and SO3 contents in cement on compressive strength of concrete. Concrete mixes, with different MgO and SO3 percentages in type I and V cements, were cast. The results showed that there is a considerable effect of MgO content on concrete strength and on the optimum gypsum content in cement. The increase in MgO content results in a decrease in the compressive strength and a reduction in the optimum gypsum content. Type V cement appears to be more sensitive to the increase in MgO and SO3 contents than Type I.

Abstract ABSTRACT One of environmental pollution and global warming sources is cement industrials. In line to diminish the effects of cement industrial activities on environment, wastes are used in cement mortar as a partial replacement of cement weight throughout the present study. These wastes comprise poultry egg shell which is wealthy in calcium and glass of bottles of juices and soft drink which has high content of silica. Both types of wastes were grinded carefully and passed sieve No. 200 ( 75μm opening size) to produce egg shell powder (ESP) and milled glass (MG). Cement was substituted by (5%, 7.5%, and 10% ESP), and (10% MG). These ratios of replacement was evaluated individually and in groups by compressive strength test at age of 28 days and drying shrinkage test at ages of 4, 11, 18, 25, and 60 days of drying. Results of tests indicated that compressive strength and drying shrinkage have the same trend when the replacement ratios of ESP used individually in mortar mixes. The higher results were recorded with ratios of 5% and 7.5%. While, compressive strength increased when 10% of MG was used as a partial replacement of cement, and drying shrinkage decreased at ages 11, 18, and 25 days of drying. The combination of MG and ESP in one mix, decrease compressive strength in all percent of addition. However the gathering of MG to 5% of ESP, and MG to 7.5% of ESP decrease drying shrinkage at all age of testing when compared it with the reference mix.

Abstract Abstract This paper presents an analytical calculation and experimental investigation to evaluate the American and British methods usually used for mix design of normal concrete. Six concrete mixes with different target of mean strength were design using crushed and uncrushed aggregates. A reliable approach has been suggested to calculate the mix proportions. In order to validate the former approach, an experimental programme was running to measure the workability aspect and compressive strength of three selected concrete mixes designed for strength levels of 21.5 MPa, 27.5 MPa and 36.5 MPa at different sample ages using 108 cubes. The results obtained showed notable differences between the approaches of American and British methods adopted to calculate the mix proportions. There was no indication have found in the American method to distinct between design the concrete mix containing crushed aggregate and that of uncrushed aggregate. The procedure followed in British method produced concrete mix with higher strength than that designed according to American method. The experimental results of compressive strength and workability showed close agreement with the suggested approach for calculation the mix proportions.

Abstract In the present paper, experimental investigations were conducted to improve the properties of concrete by using conductive screws as a fibre. Screws of two different lengths were used (1/2 inch and 1 inch). These screws were made of iron coated with Zinc-Aluminium alloy (called Al-Clad), which is resistant to corrosion and rust. This coating gives the screw strength and flexibility. The water/cement ratio used was w/c = 0.55 and the volume fractions of the conductive screw were 0%, 0.5%, 1%, and 1.5% by volume of concrete mix. The results show that the use of the conductive screw enhanced the mechanical properties of concrete. The compressive strength increases with increasing the volume fraction of the screw with a length of 1 inch. For 1.5% fibre content, the strength was increased by 24.28%, 23.66%, and 20.91% for 7, 28, and 90 curing days respectively compared to the reference mix. The same trend was observed with the modulus of rupture results. For the same length and with the 1.5% volume fraction of fibre, the modulus of rupture increased by 19.44% and 32.26% for 7 and 28 days of curing respectively. The splitting tensile strength also increased by 27.05% and 33.17% for 7 and 28 curing days respectively for 1.0% fibre content

Abstract The aim of this study is to investigate the effect of two of oil products (kerosene and fuel oil which is locally called as black oil) on compressive strength of reactive powder concrete (RPC). RPC was prepared using cement, silica fume, fine sand, steel fibers and superplasticizer to cast and test 63 specimens of cubes with various steel fibers ratios of 0%, 1% and 2% at different exposure times in oil products (0, 30, 90 and 180) days. In general the results showed that RPC has good resistance to the effect of kerosene and fuel oil. A slight decrease in compressive strength occurred as the time of exposure to the oil products increases. The RPC specimens of 2% steel fibers content had the lower decrease in compressive strength as a result of the denser microstructure. The decreasing ratio of RPC compressive strength exposed to fuel oil (1.33%) was lower than that of kerosene (2.91%). This may be attributed to the lower viscosity of kerosene than fuel oil.

Abstract Fine aggregate contaminated with interior sulfates is an important problem of concrete manufacture in Iraq. It is difficult to obtain well graded fine aggregate with sulfates content within standard specifications. The main objective of this study is to investigate the effect of internal sulfates in sand on some properties of self compacting concrete (SCC) by adding natural gypsum to fine aggregate as a partial replacement by weight. In this work, two basic categories of selfcompacting concrete are used: (SCC) incorporating limestone powder (LSP) and SCC incorporating 10% high reactivity metakaolin (HRM) Class N plus limestone powder(LSP) .Four levels of sulfates contents in fine aggregate were investigated, these levels were ( 0.37, 0.5, 1.0, and 1.5)% which it is equal to(3.74, 3.99, 4.96 and 5.93)% by weight of cement for mixes contained limestone powder (LSP) and it is equal to (3.76, 4.01,4.98 and 5.96) % by weight of cement for mixes contains high reactivity metakaolin (HRM) Class N plus limestone powder(LSP). The experimental program is divided into two parts; the first part is devoted to produce self compacting concrete by using superplasticizers and fillers then determine the workability. Different test methods are adopted such as slump flow and T50 cm, V-funnel, VFunnel at T5 minutes, L-box and sieve segregation test. The second part is devoted to study the mechanical properties such as the compressive strength and splitting tensile strength. The results obtained from this work show that the optimum gypsum content was 0.5% by weight of fine aggregate for all mixes which gives increases in the compressive strength by a range(5.9 -10.1)% and in the splitting tensile strength by a range (1.2 – 8.5 )% for mixes of (SSC) with (LSP) and (LSP +HRM).

Abstract Reinforced concrete beams for high-strength concrete often exhibit structural and nonstructural cracking due to variety steel reinforcement. Four reinforced concrete beams with dimensions of (120*230*2550)mm were investigated. Beams (1&2) have tensile steel ratio (0.0099), while beams (3&4) have tensile steel ratio (0.018). Deflections were measured at first third, second third and mid span for original repaired beams using dial gauges with accuracy 0.01 mm. The repair strength achieved for risen epoxy injection high-strength reinforced concrete beams was shown similar that original beams, but a little deference. The failure load for repaired beams higher than original beams.

Abstract The present investigation was carried out to study the possibility of using waste glass of size up to 5mm as a fine aggregate in concrete and mortar. The waste glass was used as a partial weight replacement of sand with percentages of 10, 20, 30 and 40 %. The results have indicated that increasing the fractions of sand replacement by waste glass leads to reduce the compressive and tensile strength for both mortar and concrete. Up to 20 % replacement, the 28 days compressive strength of concrete and mortar is about 92 and 95 percent from the reference strengths, respectively. Also, it was found that the expansion of mortar specimens increase with increasing the waste glass content in the mix. At 20 % of sand replacement by waste glass, the expansion is slightly higher than that for the control specimens.

Abstract This research produces a new results about using of locally available reed fibers in concrete. The main parameter of this study was the volume fraction of fibers. The reed fibers were added to the mix in percentages of 1, 2, 3, 4,and 6%. The test program included: slump, compressive strength, splitting tensile strength and impact resistance. It was found that the presence of reed fibers leads to reduce workability, compressive, splitting tensile and impact strength. It was also found that, generally, this reduction increases as the volume percentage of fibers is increased.

Abstract This study had been conducted to investigate the influence of magnetized water on the properties of cement mortars such as initial and final setting time, consistency and compressive strength with various water/cement ratios at the ages of 1 and 7 day. Results of (50) specimens with different shapes had been adopted, which represented mortars specimens having compressive strength ranging from (5.5) to (32.5) MPa, initial setting time ranging from (4) to ( 32) minutes and final setting time ranging from (303) to (546) minutes, by using two types of mixing water , first one is tap water , and the other is magnetized water.The results showed that the use of magnetized water in producing cement mortars lead to increase in the compressive strength and decreasing in the initial and final setting time with compare to use of tap water. Results also showed that the optimum water/cement ratio give best compressive strength under the conditions of this study was (0.45).