Concrete structures suffer from the impact of many harmful attacking materials that affect theproperties of the main material in them, which is concrete. These structures are also, exposedto the negative impact of many hostile environments such as soils containing harmful salts andharmful acids. A number of precautions should be considered in order to protect the concreteused in such structures. Adding polymer to concrete components as a percentages weight ofcement is one of the methods for producing polymer-modified concrete, which has lowpermeability, better mechanical properties and is more resistant to the negative effects ofharmful environmental factors. The utilization of polymers could help in protecting structuresand enhancing concrete strength. In this study, concrete mixes were prepared with inclusion ofstyrene butadiene rubber (SBR) polymer at four percentages (0%, 5%, 7% and 10% by cementweight). Co-polymers of butidine with styrene (styrene-butadine rubber (SBR)), are a group oflarge-volume synthetic rubbers. High adhesion occurs between the polymer films that formand cement hydrates. This action gives improves the properties of concrete such as flexuraland compressive strength and gives also a higher durability. The investigation was extended toevaluate the compressive strength of the SBR concrete mixes immersed in three types ofwaters: tap, drainage and ground water, at three different ages. The results showed that SBRpolymer enhanced the compressive strength of concrete significantly. A comparison betweenreduction in strength of concretes immersed in these three types of waters was also presented.Moreover, the presence of SBR polymer led to reduced loss in strength of concrete specimensimmersed in drainage and ground water. A proposed model to determine the compressivestrength of concrete specimens immersed in drainage and ground waters was deduced. Thismodel could be a helpful tool for rapid and easy estimation of the strength of concretespecimens immersed in drainage and ground water at different contents of SBR polymer. Theresults showed the highest improve in compressive strength to be associated with 7% SBRmixes at the three tested ages. The increases in this strength at days 7, 28 and 56 with inclusionof 7% SBR polymer were 112.8%, 113.9% and 116%, respectively, compared to OPC mix.
The cash flow forecasting is beneficial for the project in both the tender stage and during the project construction progress, where the contractors want to make sure that their planned cash funds is sufficient to cover any possible financial deficit of the project. This research aims to find out minimum fund needed for highway projects in Iraq required by the contractor to maintain the progress of work under some circumstances and effects of the shortage of fund, particularly in case of payment delay, in addition to the implication of the payment delay. Data from record files of 9 highway projects in Iraq, of the unit price type contracts. It was found that the minimum fund required is 20.944 percent of the contract value of three months delay . The minimum fund required for those projects is directly proportional to the time of payment delay. The minimum fund required for projects is represented in a linear equation as a function of payment delay time, such equation would help the contractor to estimate the future amount of minimum fund required for any delay in months. Interim profit is calculated for the purpose of comparison with the expected profit for the purpose of exploring the consequences in case exceedance. Because of the use of unit price contracts in the implementation of highway projects in Iraq, it did not cause the appearance that the contractor receives large profit at early stages of the project. The delay in payment leads to negative results, including the delay in the project, reduces the level of performance of the contractor which is negatively affects project, reduce the quality of implementation and, increased cost of the project in case of the contractor to claim compensation for the damage, as well as the occurrence of a difference in currency and inflation due to the time difference between the payment date and the actual date.