Sand constitutes bulk of cement mortar. Meeting the demand for sand in the construction industry without exploiting the natural resources is becoming a challenging task. In search of an alternative material for natural sand, gold mine tailings are substituted partially for natural sand in the production of masonry mortars. Natural sand is reconstituted by replacing it with 10%, 20% and 30% gold mine tailings. The effect of replacement on the properties of masonry mortars such as water retentivity, drying shrinkage and compressive strength is investigated. Major findings of the study are (a) water retentivity increases with the increase in fineness of sand for all sand types (b) As the sand becomes finer, the drying shrinkage increases and compressive strength decreases
The quality of water plays a vital role on setting, strength development and durability of cement mortar or concrete. In the present study, the effect of strong alkaline substances like sodium carbonate (Na 2 CO 3 ) and sodium bicarbonate (NaHCO 3 ) on setting time, compressive strength, pH and durability of cement mortar is assessed under laboratory conditions. The results indicate that sodium carbonate (Na 2 CO 3 ) in mixing water accelerated the setting times of cement mortar and sodium bicarbonate (NaHCO 3 ) retarded the setting times. The presence of Na 2 CO 3 and NaHCO 3 in mixing water decreases the compressive strength, acid resistance and alkaline resistance of cement mortar. The rate of decrease in these continuous with increase in concentration of alkaline substances (Na 2 CO 3 and NaHCO 3 ) present in mixing water. The pH of cement mortar increases with increase of alkaline substances in mixing water. The present work analyses the hydration characteristics of cement mortar using SEM analysis. Keywords: Cement mortar, Setting Time, Compressive Strength, pH, Durability, Alkaline Substances
I.INTRODUCTION Since water actively reacts with cement, the quality of water plays an important role in the preparation of concrete or cement mortar. Thus water used for mixing in concrete or mortar should not contain any substance which affect the strength of cement mortar or concrete.Potable water is generally considered satisfactory for mixing concrete. The pH value of mixing water shall be not less than 6.The chemical substances present in water are generally classified into neutral salts, strong alkaline substances, slightly acidic substances and strong acids. The effects of strong alkaline substances on setting, hardening, strength, pH and durability of cement mortar or concrete are not known much. Hence, an investigation is carried out in order to study the effect of strong alkaline substances on setting times, strength, pH and durability of cement mortar under laboratory conditions.
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