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.

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 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

Many of reinforced concrete structures especially underground and undersea are subjected to aggressive environmental conditions throughout their exploitation. These conditions are represented by the aggressive sodium sulphate attack from surrounding soil or underground water. When based materials of cement are exposed to sodium sulphate attack produce gypsum and ettringite by its chemical reactions. Formation of gypsum plays a very important role within the damage of materials. According to that the actual compressive strength of concrete elements decreases accompanied with large deformations of concrete. Consequently, a higher reduction of the construction durability occurs, so using of effective and economic admixture for concrete elements protection against sulphate attack or the other environmental conditions is needed. The main purpose of this research is to study through an experiment the effect of the local admixture (BM2010) which contained in its composition wastes from petroleum industries, silica fume, Wastes of coke factory and its mechanism effect on the compressive strength of concrete specimens subjected to external sulphate attack. The experimental results showed that Compressive strength of concrete specimens modified with the organic admixtures (BM2010) at age of 128 days hardened in salt solution with concentration (9%NaCl + 12% Na2SO4) increased by about 15% compared to the control specimen with (Addicrete dm2) for sulphate resistance cement (S.R.C) & 3.6% compared to the control specimen (without admixture) for ordinary Portland cement (O.P.C). The absorption of concrete specimens modified with the organic admixture (BM2010) at age of 128 days hardened in salt solution with concentration (9%NaCl + 12% Na2SO4) is less than concrete specimens modified with (Addicrete dm2) by about 29%percent in case of (S.R.C) but in case of (O.P.C) it is more by about 16% percent. The experimental results showed that, the optimum composition of all components of the suggested admixture (BM 2010) was successfully and experimentally achieved.

Concrete permeability plays the main role in concrete durability because of the entry of harmful substances such as chlorides, sulfates, carbon dioxide (CO2), oxygen (O2). Concrete permeability is affected by factors such as size and proportion of aggregate, type, and quantity of cement, water-cement ratio, type and dose of admixture used, which help concrete have a high life. This research aims to investigate the effect of local admixture prepared to improve concrete properties, especially reducing the permeability of concrete using its proven effectiveness in salt attack. This research studies the effect of this admixture on concrete microstructure for several concrete specimens. This chemical admixture, which contains calcium oxide (CaO), chloride (Cl), and others, helps obtain a good performance of concrete. Adding calcium oxide (CaO) plays an important role in improving the physicochemical properties of concrete. An increase in the compressive strength was observed for all specimens. Incorporating additives without CaO to concrete has been shown to decrease its strength. In the present study, concrete showed higher compressive strength than other concrete, which has not contain this admixture which may be explained by the larger quantity of CaO in the cement.