The standard concrete mixing procedures indicate that during concrete mixing process, it is recommended to use fully saturated- dry surface course aggregates (FSDCA). It is clear that the exact application of this rule will produce a concrete of a good quality. But in practice, course aggregates are exposed to weather changes. This actual situation will lead to dry the course aggregates in summer and to over wet it during winter. To investigate the effect of using different moisture content course aggregates on concrete product in work site an experimental program had been done. This program consists of testing 54 concrete samples (27 cube +27 prism). The samples were divided into three groups (a, b, and c). The second group (b) was a concrete mix containing dry aggregates, while the third group (c) contained over wet aggregates and the first group (a) was the basic standard mix using (FSDCA). One third of the samples were tested in the age of 7 days, while the other third was tested in the age of 14 days and the rest after 28 days. Test results show that there are reduction in compression and flexural strengths of concrete due to the use of different moisture content course aggregates. Finally, new recommendations were concluded to be used in practice to overcome the mentioned repetitive error and to be more close to the theoretical recommendations in order to get better concrete properties.
The presented work investigates the effect of addition admixtures (superplasticizer and polymer) to Chopped Worn-Out Tire concrete as a partial replacement of cement weight. Superpasticizer was addition by 4% and polymer (SBR) by 15%. The Chopped Worn-Out Tire (Ch.W.T.) addition to reference concrete with the three proportions as a Partial Replacement Ratio (PRR) of (25,25),(20,30),and (30,20) by volume of (sand and gravel) respectively. Three mixes were selected with above PRR for each type of admixture in additional to three mixes for Ch.W.T. concrete without admixtures and three reference mixes with admixtures without Ch.W.T. Thus, twelve mixes could be used in this investigation. Compressive strength and modulus of elasticity (static and dynamic) were tested. The test results indicated that the use of admixture led to significant improvement in concrete properties in general. Superplasticizer gave best results comparative with polymer, for example at 28 day the compressive strength of superplasticizer Ch.W.T. concrete Csp25,25 was 32.5 MPa, while compressive strength of polymer modified Ch.W.T. concrete CB25,25 was 28 MPa and compressive strength of Ch.W.T. concrete C25,25 was 21.2 MPa.