The delaying in the construction projects is one of the magnifying problems facing the construction industry in Egypt, and still a lot of researchers interest to find the main reasons for these problems and suggest the solution for mitigate or avoid the problem, a lot of contractors in Egypt suffer from the liquated damages due to the delaying problems, although there are a lot of researchers find out the delaying factors problems, but we need to get the root cause analysis of the delaying factors, in our research, the investigation find out the most critical delaying factors and categorized the factors in modeling by using factor analysis methodology into 7 factors modelling and hence using the root cause analysis to link the reasons with each other, Fault tree is one of a valuable tool can be used to link with the reasons of delaying which will be used in our research and help us to investigate deeply with the roots of the problems which is our target in the research and in the final the major problems leads to most of the problems are the delaying of the supplies ( Code of Factor DF5) with mean 4.2039 and RII = 0.84078, A lot of change Orders ( code of Factor DF 14) with mean 4.1845 and RII =0.8369, no of delaying factors in our research are 22 factors which considering as an important delaying factors in the construction industry in Egypt, the survey pilot contains no of 103 questionnaires to rank the delaying factors by statistical analysis.

The evaluation of the existing construction building is one of the urgent problems in the current era, different tests and methodologies can be used to get the required information about the properties of the structure so that the construction industry interests in applying the concrete test with the lowest time and cost, The purpose of this study is to present the combination between Nondestructive test (NDT) and Machine compression Test (MCT) to get the real results for the Schmidt hammer test method. All tests are created for different grade of RC concrete from medium to high grade with classes between Grade 200 to Grade 800, to study the Nondestructive test (NDT) and generate the comparison with the Machine compression Test (MCT), using different composition of the concrete with Varity in the proportion mix between ingredients of cement, water content, aggregate, all results have been represented tabular and graphically to notice any deviation between Destructive test (DT) and MCT test, Regression analysis was been used as a statistical method to get the variation between tests and establish as a linear mathematical relationship between compressive strength and rebound number and it can be illustrated that the variances between them in case of Low. the medium and semi-high grade is very low which means the null hypothesis is accepted according to the statistical analysis, and on another side, there are variances in case of very high grade according to statistical analysis.

At present, global waste tire generation considerably exceeds consumption. Moreover, waste rubber tires (WRTs) are a cause of concern, as huge volumes are being discarded and buried, thus causing serious environmental pollution. Rubberized waste concrete (RWC) is a type of environmentally friendly construction material. The main challenge encountered when manufacturing rubberized concrete is the low adhesive properties between the cement paste and rubber particles. This paper demonstrates the effects, through experiments, of using waste tire rubber instead of recycled coarse aggregate (RCA) on two types of cement, i.e., sulfate-resistant cement (SRC) and ordinary Portland cement (OPC), where SRC is a specially blended cement designed to improve concrete performance and workability in the most aggressive environments. All tested samples contained 10% silica fume (SF) and 0.2% fly ash (FA), and the substitution of recycled aggregate content with waste rubber tier (WRT) at different percentages of 100%, 75%, and 50% was evaluated .The research investigated the synergistic effect on the workability and mechanical properties of various cement types with different amounts of rubber aggregate . It was found that the sulfate-resistant (SRC)type can increase the compressive strength than OPC with a percentage of 25% with the same content of WRT at concrete mix. Moreover, ductility and cracking behavior are improved, and it appears that it is also possible to make lightweight rubber aggregate concrete with this type of mixture. Using this type of cement, it is possible to restore satisfactory ductility to the waste tires, thus facilitating a reduction in the formation of potential plastic cracks. Moreover, the indicative compressive strength development for SRC with recycled rubber in concrete positively contributes to a reduction in formed cracks. However, SEM microstructural analyses suggest a higher proportion of C–S–H intermixed with sulfate reaction phases of SRC rubberized mortar than those of OPC; thus, given that crystal growth results in a decreased percentage of air voids rather than decreased internal cracking, it is clearly shown that the average crack width increases in OPC mortar compared with SRC. Finally, t-testing was used as an inferential statistical tool to determine whether there is a sizeable distinction between the properties of the two categories of materials, OPC and SRC, by comparing the mean and standard deviation of the values for compressive and tensile strength.

Delays are a common problem in the global construction industry, affecting the development of the road construction industry, particularly in developing countries. Where, the construction industry faces a lot of risk factors that can contribute to project delays, particularly during COVID-19. The road projects risk management framework was used to identify potential risk categories that could impede the success of road construction in Egypt. On the other hand, road construction in Egypt faces numerous challenges with increasing unexpected parameters throughout the project life cycle. In other words, unanticipated risk factors have a significant impact on the success of project execution. As a result, the study’s primary goals are to investigate the majority of the risk factors that cause road construction delays in Egypt. The impact of numerous risk factors has changed the delays in road projects as the COVID-19 pandemic spread across the world. As a result, the study incorporates previously unstudied factors. As well, the research has sought to investigate the new severity of risk factors during coronavirus infection. Moreover, risk breakdown structures have classified the risk factors into several categories. They include consultant risk, design risk, equipment risk, material risk, owner risk, contract risk, contractor risk, labor risk, external risk [coronavirus effects and others] and operational risk. The strategy employed in the paper is to incorporate the DEMATEL technique and risk analysis into the statistical model. Whereas the risk analysis prioritizes risk based on the evaluation of each specific project risk. Additionally, this approach has been able to create connections between risks, which may make it easier to understand the likelihood and severity of project risk than if the risks were just considered isolated events. Furthermore, the pilot survey is divided into two stages, the first of which is based on risk analysis to identify the most significant risks. As a result, the identification of the high-risk for each category has been researched. The second survey was issued to risk management by evaluating the importance of risk factors and creating causal relationships among components using the decision-making trial and evaluation laboratory (DEMATEL) approach. Finally, it is noticed that operational risk and external risk caused by the effects of the coronavirus have the greatest impact on the delay of road projects.

The goal of this study is to work out different experiments for retarding concrete setting time, which needed to reach slump 15 cm after six hours from mixing of concrete having grade C700. Six hours comprise 1.5 hour for transporting and 4.5 hours needed for constructability method, this long time for casting concrete is owing to a long transporting time of the concrete from the plant to the site and also the time needing for casting the concrete by using the slide form of high ring concrete wall, for these reasons there are needs to retard the concrete setting time with increasing the workability for concrete, using super-plasticizers is one of the best methods to improve the properties of the concrete, from fundamental experimental investigations on retardation, setting time and the concrete mixture with high strength of 626 kg / cm2 after 7days and 755kg / cm2 after 28 days can be achievable by using super-plasticizers