The construction sector has embraced digitalization and industrialization to boost production, reduce material consumption, and improve workmanship. The 3D-printed concrete technology (3DPCT), more broadly recognized as the design of a 3D object via a computer-aided design (CAD) model or a digital 3D model, has accelerated considerable progress in these areas in other industries. Although 3DPCT has advanced remarkably in recent years, producing an appropriate 3D printing material that improves performance while reducing material consumption, which is really important for CO2 reduction, is urgently needed. The present 3DPCT faces many obstacles, one of which is the limited range of printable concretes. To tackle this limitation, extensive studies on developing creative approaches for formulating alkali-activated materials (AAMs) for 3DPCT for modern building applications have been conducted. AAMs are maintainable substitutive binders to ordinary Portland cement. Therefore, the need to undertake a comprehensive literature review on the current status of AAM performance on 3D-printable concretes for building applications is substantial. This article comprehensively reviews the quality requirements, advantages, disadvantages, common techniques, delivery, and placement of 3DCP. This literature also delivers indepth reviews on the behaviors and the properties of AAM-based concrete composites used in 3D-printed construction. Moreover, research trends are moving toward a wide-ranging understanding concerning the economic benefits and the environmental footprints of 3DCP for building applications with AAMs as suitable concrete materials for the emerging robust eco-friendly concrete composite for digital construction constructions nowadays. Given the merits of the study, several hotspot research topics for future investigations are also provided for facilitating the wide use of 3DPCT in real applications to address rapidly the gap between demand and supply for smart and cost-effective homes for upcoming generations.
Hakim S. Abdelgader(2-2022)

نتقدم بهذه الدراسة، التي تعالج مشكلة من أهم المشكلات الهندسية حيث أن الأساسات على القواعد المرنة تشكل مشكلة تقنية شائعة في مجال الهندسة المدنية وقد تم أقتراح العديد من الحلول لها في السنوات الأخيرة لقد بقى أعتبار مرونة التربة تحت الأساسات مهملاً لفترة طويلة، وذلك نظراً لصعوبة الحل الرياضي من جهة، بالإضافة إلى عدم وجود نظريات ثابتة ومحققة دوماً، وما ذلك الا بسبب عدم وجود خواص ثابتة لتربة القواعد، موضوع البحث ومع تقدم العلوم والهندسية منها بشكل خاص، ونتيجة للإبحاث والتجارب التي لاحصر لها، والتي أستند إليها العديد من الفرضيات والنظريات المتتابعة، وبفضل الوسائل التعليمية، التي مكنت من حل أعقد المسائل الرياضية، فقد تمكن التوصل إلى بعض الحلول المقبولة من الناحية النظرية، إلى جانب أنها أعطت نتائج عملية جيدة، كما سنرى في الدراسات والحلول المقدمة ضمن هذه الدراسة وبالنظر لأهمية الأساسات وخطورتها بالنسبة لكافة المنشآت الهندسية، فإننا نأمل أن يلقى الموضوع كل ما يستحقه من اهتمام ومتابعة.
زينب عمر القضقاض (2006)

Two-layered Grouted Aggregates Fibrous Concrete Composite (TGAFCC) is a new category concrete which became popular recently and attracted the attention of researchers globally. Recent studies indicated that TGAFCC has notable improvement in mechanical properties, which has been sufficiently documented. However, the impact behaviour of TGAFCC when combined with Glass Fibre Mesh (GFM) and Textile Fibre Mesh (TFM) is still unexplored. The research objective is to study the effect of GFM and TFM inser- tion in TGAFCC against the drop hammer impact. Twenty one TGAFCC mixtures were prepared and divided into two series; non-fibrous concrete and fibrous concrete. The combined action of GFM and TFM of various diameters were inserted between the two layers and tested experimentally against drop mass impact. Additionally, all fibrous specimens were reinforced with a constant 3% dosage of 5D hooked end fibre. All specimens were tested under repeated drop mass impact as per ACI Committee 544. The impacts number or number of blows till the first visible crack and failure, impact energy at the first vis- ible crack and failure, impact ductility index and cracking configuration were examined. Besides, Weibull distribution was used to examine the variations in the test results, where impact numbers were pre- sented using the reliability function. The research findings indicate that inserting GFM and TFM between the two layers combined with 5D hooked end steel fibres, provided high impact resistance, higher absorbed energy and prolonged failure duration. Increasing the diameters of the GFM and TFM insertions, in both non-fibrous and fibrous concrete resulted in increasing the impact numbers till the first visible crack and failure. The experimental findings confirm that the major contribution of impact resistance comes from the 5D hooked end steel fibres, while the share of the intermediate meshes was significantly lower. arabic 13 English 88
Hakim S. Abdelgader (12-2020)