Strength Evaluation of Mortar by Inclusion of Stone Dust as a Cement and Sand Replacing Material

Mortar, a matrix of concrete which is a masonry product, composed of binder and fine aggregates. It is an essential associate in any reinforced structural construction. The strength of mortar is a special concern to the engineer because mortar is responsible to give protection in the outer part of the structure as well as at a brick joint in masonry wall system. The lack of mortar strength sometimes throws the whole structure in a great danger. Cement, sand and water are the key parameters of mortar which are dealing with the strength directly. The purpose of this research is to investigate the compressive and tensile strengths of mortar by replacing the cement and sand by stone dust. This research is focused on the comparison between fresh mortar and modified mortar. For sand replacement, the gradation and fineness modulus of stone dusts was kept similar to that of sand. Stone dusts passing by No. 200 sieve was used as cement replacing material. The portion of dusts which was retained on No. 100 sieve was separated to substitute sand and the remaining part of dusts was made finer by abrasion machine. Then the stone dusts were screened again by No. 200 sieve and the dusts passing by No. 200 was used as the cement. The compressive and tensile strengths of modified mortar were investigated by replacing of 20%, 30% and 40% of fine aggregates as well as replacing of 5% of cement by stone dusts. Several numbers of cube and briquette samples were cast with aforementioned proportions to investigate compressive and tensile strengths at 7 days and 28 days of curing. From tested results, it was found that the compressive strength of samples of 30% of sand replacing stone dust with 0% of cement replacing stone dust increases by 12% and 17% at 7 and 28 days while for the tensile strength it was increased by 8.7%. However, the mechanical properties of mortar with stone dusts as replacement of cement shows no satisfactory results.