Fine aggregate contaminated with interior sulfates is an important problem of concrete
manufacture in Iraq. It is difficult to obtain well graded fine aggregate with sulfates content within
standard specifications. The main objective of this study is to investigate the effect of internal
sulfates in sand on some properties of self compacting concrete (SCC) by adding natural gypsum to
fine aggregate as a partial replacement by weight. In this work, two basic categories of selfcompacting
concrete are used: (SCC) incorporating limestone powder (LSP) and SCC
incorporating 10% high reactivity metakaolin (HRM) Class N plus limestone powder(LSP) .Four
levels of sulfates contents in fine aggregate were investigated, these levels were ( 0.37, 0.5, 1.0,
and 1.5)% which it is equal to(3.74, 3.99, 4.96 and 5.93)% by weight of cement for mixes
contained limestone powder (LSP) and it is equal to (3.76, 4.01,4.98 and 5.96) % by weight of
cement for mixes contains high reactivity metakaolin (HRM) Class N plus limestone
powder(LSP). The experimental program is divided into two parts; the first part is devoted to
produce self compacting concrete by using superplasticizers and fillers then determine the
workability. Different test methods are adopted such as slump flow and T50 cm, V-funnel, VFunnel
at T5 minutes, L-box and sieve segregation test. The second part is devoted to study the
mechanical properties such as the compressive strength and splitting tensile strength. The results
obtained from this work show that the optimum gypsum content was 0.5% by weight of fine
aggregate for all mixes which gives increases in the compressive strength by a range(5.9 -10.1)%
and in the splitting tensile strength by a range (1.2 – 8.5 )% for mixes of (SSC) with (LSP) and
(LSP +HRM).