Journal of Building Research

The wide range of structural problems resulting from the corrosion of rebar in the structural sections make it one of the important problems facing various countries of the world. The research aims to test the adequacy of the requirements contained in the Arab Code for the design and implementation of reinforced concrete structures, with regard to the requirements of reinforced concrete exposed to ambient or harmful conditions or to sea water, , and these requirements include the minimum cement content and the maximum ratio of water to cement to ensure sustainability, as well as studying the effect of partial replacement of pozzolanic materials (metacholine. silica dust ) of the weight of cement on increasing the protection of rebar from corrosion. Reference reinforced concrete was prepared with a cement content of 400 kg / m3, a maximum size of aggregates of 20 mm and a water-to-cement ratio of 0.4, as well as other reinforced concrete mixtures were prepared with partial compensation of the weight of cement with pozolanic materials (metacholine, silica dust) and the effectiveness of all these mixtures was tested to resist the corrosion of rebar in the partially submerged concrete in NaCl sodium chloride solution at a concentration of 4.5%. It was found that the use of pozzolanic materials reduces the corrosion current of rebar by more than 50% rather than in reference concrete.

Both the rutting and moisture in the asphalt mix are two major causes of the early failure of asphalt pavement, the current research includes a detailed study of the novolac test as an additive for the production of modified bitumen using polymers. Different ratios of this addition have been tested to determine the improvement in the rheological properties of the bitumen alone and the mechanical properties of the asphalt mixtures, the rheological properties of the bitumen were determined by the penetration test, the softining point, elongation test and bitumen thin layer, the mechanical properties of the asphalt mixture were evaluated by examining the Marshall stability of the model and the examination of the remaining stability and indirect tensile test and the examination of plastic distortions, the results of the tests showed that the novolac significantly improved the properties of cohesion of the bitumen as well as the property of adhesion to the bitumen with the aggregates in the asphalt mixture in addition to reducing the results showed that the addition of (4%) of the novolac to the asphalt is the optimal ratio of bitumen production modified using polymers where it showed, the results showed that the addition of this ratio to asphalt improves the stability of the Marshall model, which reached 14.6KN and the remaining stability strength of 92.4% and the value of the rutting resistance is about 5.2 mm at 14000 cycles, the very small percentage of these additives compared to the quantities of other components of the asphalt mixture and the moderate price of this additive makes it an excellent and practical solution For early failure problems in asphalt pavement.

Pervious paving concrete is considered one of the types of concrete with high performance in draining and permeating water through it due to the voids spread in it internally and externally, which requires conducting research to develop its properties in resisting external loads and maintaining its water-draining property. The research aims to study the effect of mineral and chemical additives and two types of fibers on the mechanical and hydraulic properties of porous paving concrete. The mechanical and hydraulic properties of five porous concrete pavement mixes were studied. The reference mix was prepared from cement, coarse aggregate and water only. In the second mix, superplasticizer and water reducer were added to a high degree with a reduction in the amount of water. In the third mix, silica fume and fine aggregate were added at rates of (3.3.4%) of the weight of the coarse aggregate, respectively, in addition to the plasticizer. In the fourth and fifth mixes, two types of fiberglass were added separately, type (PPF-300, PPM-12) at a rate of (0.43%) of the weight of the coarse aggregate, in addition to the rest of the components mentioned in the third mix. Mechanical and hydraulic tests were conducted for these concrete mixtures and the test results showed the possibility of improving the compressive strength properties when adding silica fume and fine aggregate with an increase rate of (110.158)% for ages (28.7) days respectively, but it contributed to reducing the size of the existing voids by (13.5)%, which led to a decrease in the amount of water permeability by (18.6)%. It was also clear that the use of glass fibers has a clear positive effect in improving the flexural resistance by (223)% and an improvement in the compressive strength by an increase rate of (160.183)% for ages (28.7) days respectively with a slight decrease in the size of the existing voids (14.9)% and in the amount of water permeability by (25.6)% compared to the reference mixture.

Regular cement mortar is one of the widely used building materials. Therefore, research continues in the field of improving its performance and specifications to reduce the problems it faces when used. In this research, the effect of adding metakaolin powder in certain ratio on the physical properties of cement mortar was studied. All the raw materials used to prepare the mortar mixtures in this research were local materials. Ordinary Portland cement was used. Raw kaolin was brought from the Husseiniya area and burned at a temperature of (750) °C to obtain metakaolin powder. Standard CEN sand was also used. Six types of mixtures were prepared, including the reference mixture and five mixtures containing the metakaolin additive with weight addition ratios of (5, 10, 15, 20, 25) % as a partial replacement of the weight of cement. The mixing ratios were prepared according to the requirements of Reference Guide No. 198/1 of 2021. The prepared samples were tested in dimensions (4*4*16) cm to determine the best mixtures and the best ratio for adding of metakaolin powder by conducting physical tests, which include (compressive strength, density, bending resistance, absorption, setting time, electron microscope examination, liner shrinkage). From the results of the tests, it was concluded that the mixture containing 20% of the metakaolin powder additive, indicated by the symbol (E), was the best mixture, as the compressive strength was improved to reach (52.11) N/mm2, with a density of (2.04) g/cm3, and the flexural resistance was also improved. Reducing the initial and final setting time of the mixture and reducing the liner shrinkage of the mortar with compared to the results of testing the reference mixture mortar. The results of the laboratory tests were conformed to the limits of Iraqi Standard No. (5) of 2019.

Refractory castable is one of the materials used in furnace manufacturing due to its high thermal tolerance and insulation. In this research, insulating refractory castable has been produced by mainly using local materials including alumina fire bricks waste which is used in most local factories with thermal insulation areas. Local additives such as white cement and fiberglass have also been used in the production. The results of physical and thermal tests were conformed to the limits of ASTM C401 rendering it suitable for use in thermal furnaces for temperatures up to (1300°C). Moderate alumina thermal insulating castable of (1.37g/cm3) bulk density has been produced in this research with the use of local additives consisting of (30%) white cement and (2.5%) fiberglass which can be used for temperatures up to (1200°C). While thermal insulating castable with high alumina aggregate is usually used for temperatures up to (1300°C). Batches from this product have been supplied to The General Company for Heavy Engineering Equipment one of The Ministry of Industry and Minerals companies, in addition to supplying various government companies including petroleum refineries and power plants. The supplied batches were successfully used and had been a successful supplement of the imported thermal insulating castable.

In order to estimate the chemical and physical properties of the soil, including its percentage of organic materials, laboratory experiments are used on soil samples that are taken from test pits during the excavation works in any project. This is considered as an essential process in construction because figuring out the percentage of organic materials which has no bearing on estimating the damages caused during construction and their effects on the physical and chemical properties of the soil as well as the evidence of soil plasticity. When the percentage of organic components in this kind of soil rises, the damage increases as well, leading to noticeable subsidence as the effective load rises. In the nation practices, common laboratory techniques are used to calculate the percentage of organic components, which are represented by the burning method, the chemical method, and other factors in the burning temperature according to different specifications. Fifty-five samples were collected from various locations close to Al-Bani College in Al-Jadriya, Al-Khulafa Mosque, Al-Ahmadiyya Mosque, and Sheikh Omar. The samples were then subjected to laboratory tests. In addition to the chemical method, laboratory experiments were carried out using various burning temperatures as these two approaches are among the most widely used in Iraq, particularly when investigating the site's soil. Since calculating the percentage of organic matter by the chemical method yields very small values compared to the burning method, it was observed that there is a significant difference between the percentage of organic matter content calculated by the burning method and that calculated by the chemical method. The percentage of organic matter content and the drying temperature were also found to have a linear correction connection, which was represented by two design equations (one for drying at 105 C0 and the other for drying at 45C0 in the case of gypsum contained soil).