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This investigation evaluates the influence of various curing conditions and slag inclusion on the fresh, mechanical, and durability properties of self-compacting geopolymer concrete (SCGC) based on fly ash (FA). Curing temperature and curing time have a vital role in the strength and microstructure of geopolymer concrete. Therefore, to begin the research, the impacts of different curing conditions (curing temperature and curing time) and slag content on the compressive strength of FA-based SCGC were examined to determine the optimum curing method. A series of four SCGC mixes with a fixed binder content (450 kg/m3) and an alkaline/binder ratio of 0.5 was designated to conduct a parametric study. FA was replaced with slag at four different substitution percentages, including 0%, 30%, 50%, and 100% of the total weight of the binder. The fresh properties of the produced SCGC specimens were investigated in terms of slump flow diameter, T50 flow time, and L-box height ratio. Additionally, the following mechanical properties of SCGC specimens were investigated: modulus of elasticity and fracture parameters. The water permeability and freezing–thawing resistance were studied to determine the durability behavior of SCGC. In this study, the optimum curing temperature was 85 °C for the duration of 24 h, which provided the maximum compressive strength. The results confirmed that adding slag affected the workability of SCGC mixtures. However, the mechanical characteristics, fracture parameters, and durability performance of SCGC were improved for slag-rich mixtures. When using 50% slag instead of FA, the percentage increase in compressive, flexural, elastic module, and fracture energy test values were about 100%, 43%, 58%, and 55%, respectively, whilst the percentage decrease in water permeability was 65% and the resistance to freeze–thaw test in terms of surface scaling was enhanced by 79%.

This work deals with the possible use of a renewable resource; the ash of walnut shell as partial replacement for cement to produce an economical and ecologically friendly cementinous binding material for cement, mortar and concrete. The agricultural waste; the walnut shell was processed and converted to ash in order to increase its pozzzolanic properties. The green ash is characterized and converted chemically to nanosilica to be incorporated later into cement contain the optimum content of the green pozzolanic admixture. A statistical method is used to narrow the number of experiments, followed by computational optimization to identify the optimal balance of the cementless additive and water/cement ratio on initial and final setting time, as well as modeling the influence of the variables on setting time. Reference samples of cement samples are prepared and evaluated for the purpose of comparison. The results obtained revealed that walnut shell ash act as green binder for partial replacement of cement, and the optimum content of walnut shell ash in cement which can retain the cement setting time is 22% wt. Also, the incorporation of nanosilica resulted in decrease of the setting time of (cement-walnut shell ash) fresh paste.

An investigational study is conducted to examine the effects of different amounts of binders and curing methods on the mechanical behavior and ductility of Ultra-High Performance Fiber Reinforced Concretes (UHPFRCs) that contain 2% of Micro Steel Fiber (MSF). The aim is to find an optimum binder content for the UHPFRC mixes. The same water-to-binder ratio (w/b) of 0.12 was used for both water curing (WC) and steam curing (SC). Based on the curing methods, two series of eight mixes of UHPFRCs containing different binder contents ranging from 850 to 1200 kg/m3 with an increment of 50 kg/m3 were produced. Mechanical properties such as compressive strength, splitting tensile strength, static elastic module, flexural tensile strength and the ductility behavior were investigated. This study revealed that the mixture of 1150 kg/m3 binder content exhibited the highest values of the experimental results such as a compressive strength greater than 190 MPa, a splitting tensile strength greater than 12.5 MPa, and a modulus of elasticity higher than 45 GPa. The results also show that all of the improvements began to slightly decrease at 1200 kg/m3 of the binder content. On the other hand, it was concluded that SC resulted in higher mechanical performance and ductility behavior than WC.

Expansive soils create challenges in civil engineering projects due to their tendency to significant volume changes with variation in moisture content. In this study, an experimental study was carried out to evaluate the influences of rock powder on the geotechnical properties of expansive soil. This paper presents the results of some index and engineering properties of expansive soil mixed with the rock powder, including Atterberg limits, compaction, free swelling, unconfined compressive strength (UCS), California bearing ratio (CBR), direct shear, and permeability at different percentages (0%, 8%, 16%, 24%, 32, and 40% by dry soil weight). The results reveal that the index properties, optimum moisture content, free swelling, cohesion, and coefficient of permeability decrease with the addition of rock powder up to 40%. Whereas, the maximum dry density, UCS, and CBR increase up to 24% of rock powder thereafter reversed. Furthermore, the internal friction angle increases by 95.32%, while the subbase thickness layer for a roadway could be reduced by 40% with the addition of 40% rock powder to the soil samples. Based on the test results, the optimum ratio of rock powder for the improvement of expansive soil is about 24%.

The waste generated by brick industries in many countries around the world is increasing significantly with the continuous expansion of urbanization and industrialization, and as a result, more environmental and financial problems are brought about. The waste material out of bricks production could be used as a stabilizing material for high-plasticity silt (MH) that has caused damage to different roads and buildings. This study aimed to investigate the effect of waste brick powder (WBP) on stabilizing high-plasticity silt and reduce the influence of WBP on the environment. An experimental study was performed to evaluate the effects of WBP on the geotechnical properties of MH soil. Atterberg limits, compaction characteristics, specific gravity, free swelling, unconfined compressive strength (UCS), California bearing ratio (CBR), and permeability were performed for natural and stabilized soil at different ratios (6%, 12%, 18%, 24%, and 30% by dry weight of the soil sample) of WBP. The test results showed that liquid limit, plastic limit, plasticity index, linear shrinkage, free swelling, and the coefficient of permeability are decreased by adding WBP, whereas specific gravity, maximum dry density, UCS, and CBR are increased by adding WBP.

This study examines the effects of high-volume micro-steel fibers (MSF) content on the mechanical properties, fracture parameters, and ductility of ultra-high performance fiber reinforced concrete (UHPFRCs). The MSFs used in this experiment had an aspect ratio of 37.5 with average length of 6 mm. The investigated parameters include very low water/binder (w/b) ratio and fiber content. Sixteen UHPFRC mixes were examined, eight mixes were made with w/b of 0.12 and eight fiber contents (0%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5, 4%) while the other eight mixes were made with the same fiber contents but with w/b of 0.14. The UHPFRC mixes were examined for various strengths (compressive, splitting tensile, flexural), elastic modulus, and fracture parameters. The experimental results showed that the mixture with 4% of MSFs content and 0.12 w/b ratio exhibited a compressive strength of more than 160 MPa, splitting tensile strength higher than 12 MPa, and modulus of elasticity greater than 43 GPa. Moreover, the results also demonstrated that with increasing MSFs content from 0 to 4% the load–displacement behavior, ductility, and all other fracture parameters were improved significantly.

The excavation of tunnels below the water table causes variations in the hydraulic level, pore pressure and effective stresses. In this regard, rapid drawdown is considered as a destructive phenomenon as to the change in the flow regime which has mostly been studied for the reservoirs of embankment dams. The rapid drawdown occurred at the upstream shell of the dam gives rise to increase in the pore pressure at the upstream shell. This is as a result of the incompliance between the water loss inside the shell and the reservoir water level. Hence, it would be more likely to have instability and sliding at the upstream slope on account of decrease in the effective stress. Lack of sufficient studies performed on this matter in tunnelling projects on the one hand and the knowledge on the most important parameter for decreasing the destructive effects of this phenomenon on the other hand necessitates performing further studies on this matter. To this end, the reasons for the occurrence as well as the affecting parameters were studied by modelling the large subsidence of the inlet portal of Heybat Sultan twin tunnels located in Kurdistan-Iraq making use of the variations of the groundwater boundary conditions under Phase2 code. The modelling results depict the importance of the drawdown rate and the permeability coefficient of the surrounding rock mass. In the interim, the rapid loss in the hydraulic gradient caused by the drainage of a considerable volume of precipitations into the tunnels led to the rapid decrease in the pore pressure and increase in the effective stresses up to total stress. This has resulted in the consolidation settlement in the tunnel portal.

Due to the urbanization and the need to develop the transportation services, it is inevitable to deal with ground characterized by undesirable geotechnical properties. The problematic soils are divided into swelling soils, collapsible and dispersive soils. The arid to semiarid climate of the Middle East has provided the conditions for the expansion of them. The presence of problematic soils in Iraqi Kurdistan has given rise to many damage to the construction projects of this region. The under-construction road of Gali Ali Bag designed in the vicinity of the Erbil-Haji Omeran highway in Iraqi Kurdistan was faced with pavement settlement and collapse of side slopes due to the passing through the collapsible soils. The presence of collapsible soils in the vicinity of the aforesaid international highway grew concerns about the occurrence of such settlements during its construction. Therefore, how to treat or reduce the collapsibility, especially by the use of practical methods on the site, was addressed as one of the major challenges. In this study, the behavior of treated host soil by four cementitious materials including cement, quicklime, gypsum and NaCl was determined by applying indirect and direct methods. The results show that the addition of 6% quicklime will have the greatest effect on the reduction in collapsibility. After implementing this plan on the site, the collapsibility index decreased by an average of 2.92%.

Municipal solid waste materials are growing worldwide due to human consumption. Nowadays, a different type of goods on large-scale is produced in the factories which is going to generate numerous amount of solid waste materials in the near future. Therefore, the management of these solid waste materials is a great concern around the world. Inadequate landfill, environmental pollution and its financial burden on relevant authorities, recycling and utilization of waste materials have a significant impact compared to disposing them. Studies have been done to reuse of waste materials as one of the elements of concrete composites. Each of the elements gives the concrete strength; however, the reuse of these wastes not only makes the concrete economical and sustainable, but also helps in decreasing environmental pollution. There are a number of different types of waste materials such as plastics, carpets, steels, tires, glass, and several types of ashes. In this paper, a comprehensive review was carried out on the influence of recycled plastic fibers (RPFs), recycled carpet fibers (RCFs) and recycled steel fibers (RSFs) on the fresh, mechanical and ductility properties of concrete. The previous studies were investigated to highlight the effects of these waste product fibers on the most important concrete properties such as slump, compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, ultrasonic pulse velocity, energy absorption, ductility, and toughness. In this regard, more than 200 published papers were collected, and then the methods of preparation and properties of these recycled fibers (RF) were reviewed and analyzed. Moreover, empirical models using mechanical properties were also developed. As a result, RPFs, RCFs and RSFs could be used safely in concrete composites due to it is satisfactory fresh, physical and mechanical properties.

Solid waste management can be regarded as one of the major environmental concerns across the globe. Annually, substantial quantities of plastics are produced. The utilization of this waste can result in a variety of huge problems such as health hazards, disposal, and environmental pollution. In this paper, the workability and rheological characteristics of self-compacting high strength concrete (SCHSC) made with recycled polypropylene plastic particles (RPPP) with fly ash (FA) and silica fume (SF) are investigated. The SCHSC was employed by replacing the medium-coarse aggregate (MCA) with five percentages of RPPP contents at 0%, 10%, 20%, 30%, and 40% by volume. The first group of mixtures contained 20% FA and 80% Portland cement (PC). On the other hand, the second group of the mixes made with 20% FA, 10% SF, and 70% PC. To investigate such workability-related properties as slump flow diameter (SFD), T50 slump flow time (SFT), V-funnel flow time (VFT), L-box height ratio (LHR), and L-box T200 and T400 flow times, 10 concrete mixtures were produced and tested. ICAR rheometer in the rheological testing of fresh SCHSCs was used to determine the rheological parameters. For all mixtures, the compressive strength was measured at 28 days. With respect to the experimental results of the current study, the Herschel-Bulkley and modified Bingham models can provide well defined rheological representations for SCHSC with RPPP. The mixtures containing a combination of FA, SF, and RPPP can have better fresh characteristics compared to those without SF. Moreover, all produced SCHSC mixtures can be at a satisfactory level with the limitations required for the fresh properties of SCC.

Given the frequent cost overruns and schedule delays associated with tunnel construction projects, it is imperative that a detailed estimation of both be developed and considered prior to starting construction. To this end, two artificial intelligence tools of Gaussian Process Regression (GPR) and Support Vector Regression (SVR) were used to forecast geology, construction time and construction costs of a road tunnel project. The initial training datasets applied in the prediction tools were accessed from the previously-constructed road tunnels and the pre-existing observations of the tunnel under consideration. Also, during the tunnel construction, more training datasets obtained in the constructed parts were added to the previous datasets and the pre-constructed predictions of the GPR and SVR tools were updated. Lastly, comparing the predictions made by the GPR and SVR tools with the actual mode of the tunnel, and comparing the pre-updating predictions with the post-updating ones, it was concluded that, the GPR and SVR tools have presented very good predictions and they have reduced the uncertainties regarding geology and construction time and costs to an acceptable level. But, the GPR tool has presented more accurate results than the SVR tool. Also, the updating procedure can significantly increase the predictions accuracy.

Due to manufacturing processes, municipal solid wastes and service industries, huge amount of waste materials are generated. Recently, a considerable growth in the plastic consumption across the globe can be observed. This has caused enormous quantities of plastic-related waste. Producing new materials such as mortar or concrete from recycling of plastic waste (PW) seems to be one of the best solution for disposing of PW since it is considered to be environmentally and economically advantageous. In modern constructions, self-compacting concrete (SCC) is employed as a main cementitious material, which functions complex formworks without mechanical vibrations with high segregation resistance and greater deformability. Reuse of recycled plastic (RP) in SCC mixes can provide an environmentally friendly and sustainable construction material. Therefore, it has been an ongoing topic for several researches, and a large number of studies investigating the properties of SCC comprising waste and RP materials have been conducted.- In this study, the current and most recent literatures considering plastic recycling method and the influence of plastic materials on the fresh and mechanical properties of SCC are summarized. So that a comprehensive review can be provided in which the reviewed studies are categorized into sub groups based on whether they dealt with SCC containing plastic aggregates (PAs) or plastic fibers (PFs). Furthermore, the effect of RP on the fresh and mechanical properties of various self-compacting composites like self-compacting mortar (SCM), self-compacting high strength concrete (SCHSC) and self-compacting light weight concrete (SCLC) have been reviewed to illustrate the differences with normal SCC. The empirical relationships among various mechanical properties were also developed. Based on the obtained results from previous studies, recycled plastic self-compacting concrete (RPSCC) can be used for structural applications due to its satisfactory fresh and mechanical properties. Moreover, this type of concrete is environmentally friendly and sustainable product due to replacing the natural aggregates (NA) with plastic materials.

Due to uncertainties in determining the geotechnical parameters, it is inevitable to change the supporting system and excavation method during the tunnel construction projects. Such changes will in many cases lead to an increase in the foreseen time and cost. Since the beginning of the 1960s, value engineering (V.E.) was raised based on three principles of safety, cost optimization and sustainable design. Iraqi Kurdistan has had an increasing trend in design and implementation of development projects since 2008, but high safety factors considered to compensate for uncertainties in geotechnical parameters has imposed high construction costs to these projects. The design of more than 70 km of tunnels, 212 dams and more than 500 km of highways under construction in this region necessitates performing applicable case studies on the implementation of V.E. in these development projects. The Heybat Sultan twin tunnels project is being constructed as a part of the Erbil–Koya–Sulaymaniyah highway in Iraqi Kurdistan. Preliminary studies showed that the outlet portals of these tunnels had been designed with a high factor of safety. Hence, the decision was made to make changes based on V.E. principles prior to the commencement of the excavations and at the time of site mobilization. For this purpose, the most optimal method statement was selected for the outlet portal, and then the slope stability was evaluated using numerical analysis. By implementing the optimized design, the factor of safety was increased from 1.27 to 2.48 and the corresponding construction costs was decreased for 2.4 million USD compared to the original plan.

The occurrence of karst phenomenon is one of the common problems in carbonate rocks in the presence of water. The rock masses constituting the ground surface are mostly of sedimentary types among which carbonate rocks are widely observed. It is therefore necessary to accept such a geological hazard in many projects. Some of the rehabilitation methods for karstic subsidence include grout injection, filling with concrete or shotcrete and making use of geosynthetic products. Few studies have been carried out on the application of the geosynthetic products. Limy rocks form the main lithology of a large part of the 72 km long access road tunnel designed for the Iraqi-Kurdistan. The occurrence of a karstic subsidence with a volume of about 2250 m3 in the portal of Heybat Sultan tunnels revealed the necessity of examining and selecting one of these rehabilitation methods. Concerns about the repetition of such collapses in other tunnels, especially in the 6740 m long Korek twin tunnels that is the longest tunnel of the Middle East located in the vicinity of the project, has doubled the importance of the issue. This paper aims to render an account of the use of shotcrete and geogrid to rehabilitate the subsidence of the portal of Heybat Sultan tunnels. The modeling results with the FLAC numerical finite difference code showed that the displacement amount of the host rock mass after implementing the second method would be 2.9 times less than the first method. Geogrid also reduces the axial forces exerted to the tunnel supporting system up to 43 tons.

Control and stabilization of swelling soils have been a basic challenge in geotechnical engineering since 1970s till now. Major stabilization methods applied for swelling soils lead to minimum one of the disadvantages of high construction cost, laboratory-scale application, implementation only in flat areas and diseases caused by the use of chemical materials. Several instabilities and collapses have happened in side slopes excavated in swelling soils of the under construction highways of Iraq-Kurdistan. This necessitates presenting a method statement to decrease and control swelling potentials. This study aims to describe the cement grouting method applied in Salaheddin side slope which is known as one of the most critical instabilities of Erbil–Haj Omran highway where the optimal grout content was first determined in the laboratory and then it was used in the project as the consolidation grouting. Results indicated that the soil swelling decreases for > 90% by injecting 6% of cement grout. The grouting also increases the uniaxial compressive strength of the soil for more than two times.

This study focuses on the mechanical, fracture and durability characteristics of self-compacting high-strength concrete (SCHSC) containing recycled polypropylene plastic particles (RPPP) with and without silica fume (SF). The designation of the two different sets of SCHSC containing plastic particles were used on the basis of a constant water–cementitious substance (w/cm) ratio of 0.32 and a total cementitious materials content of 550 kg/m3. The first set of mixtures included binary cementitious blends of 20% fly ash (FA) and 80% Portland cement (PC). However, the second series of the mixtures incorporated ternary cementitious blends of 20% FA, 10% SF and 70% PC. To produce the concretes, medium size aggregate was replaced with RPPP at five designated percentages of 0%, 10%, 20%, 30% and 40% by volume in both sets of concretes. Totally, 10 mixtures were produced and tested for mechanical, fracture and durability properties such as elastic modulus, compressive and splitting tensile strength, flexural strength, sorptivity, chloride ion permeability, gas permeability and fracture energy. The tests were carried out 28 and 90 days after casting. The test results showed that the use of RPPP significantly improved the fracture and ductility properties, whereas aggravated other measured properties of SCHSCs. However, with the addition of SF all mechanical and durability characteristics remarkably enhanced. The results also demonstrated that SCHSC with compressive strength higher than 70 MPa at 90 days was produced by using RPPP content up to 40% replacement level by total medium aggregate volume, and 10% SF.

Minimizing uncertainties is an important issue among the significant discussions pertaining to the project design and planning. Usually, the uncertainties in subsurface projects arise from the unknown ground conditions that may cause the designer to fail to consider all the potential issues prone to occur during the construction procedure. Total time and costs uncertainties can be considered as the most important uncertainties during the planning and excavation of a tunnel project that is directly connected with cognition of the subsurface conditions. This work presents an updating procedure and associated code, which allows one to refine predictions during construction. Updating does not only involve replacing the original prediction by actual data from the excavation but also includes a learning effect. The updating uses information from the actual excavation to arrive at an improved prediction for the unexcavated part. Updating the ground conditions and time-cost scatter-gram in tunnels during excavation is a tool, which helps the user refine input parameters by deriving relevant information from construction data and presenting it together with original input. In this paper, an example project shows that the updating result has a significant impact on the precision of the prediction and reduces the uncertainty about ground conditions and construction time and cost of the tunnel substantially. It facilitates both the owners and the contractors to be aware of the risk they should carry before construction of the unexcavated part, and it is useful for both tendering and bidding.