This work intends to make structural lightweight aggregate concrete by using artificial expanded clay aggregate with different replacement levels from normal coarse aggregate and improve it with a high-performance superplasticizer to increase its strength. The mechanical characteristics covered in the present work were compressive strength, flexural strength, and splitting tensile strength in addition to freezing and thawing resistance. Different densities were found for all mixes ranging between normal and lightweight concrete and that depends on the replacement of normal aggregate with lightweight aggregates. Mixes with replacement exceeding 25% give compressive strength less than 17 MPa and cannot be regarded as structural lightweight concrete. Modified mixes give higher values of mechanical properties, and also some non-structural lightweight concrete mixes were improved to structural lightweight concrete by using PC-superplasticizer in this study. The research also includes freezing and thawing cycles on reference mixes and lightweight mixes. Lightweight mixes give high durability against freeze-thaw cycles where the reduction in compressive strength was 6.2, 4.6, and 5.5% for 10% rep, 15% rep, and 20% rep mixes, respectively, compared with 32.2% reduction for reference mix.

Background: This research focuses on the study of 40 K, 238 U, and 232 Th in a specific area at Kufa Cement Factory Sites in Najaf Governorate, Iraq using the γ-ray spectrometry scintillation detector NaI(Tl). Materials and Methods: Samples of soil were collected from locations around the Kufa cement factory in Najaf city of Iraq that are about 10 km 2 away from the center of Najaf city. They were analyzed to set the concentrations of natural radioactivity samples of 40 K, 238 U and 232 Th. Results: The specific activity values of 40 k, 238 U and 232 Th varied from (378.54±11.39 to 2404.27±26.13)Bq/kg, (15.51±5.88 to 106.08±7.35) Bq/kg and (1.80±3.41 to78.19±3.05) Bq/kg continually. Conclusions: Results demonstrate that the convergences of radiation and doses due to radionuclides in the overviewed area are higher than the safety field of the worldwide average (UNSCAER 2000). Almost all of the radiological parameters are inconsequential to cause any dangerous health problems to people living in the area.

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