Cement

e-ISSN: 2582-5208 International Research Journal of Modernization in Engineering Technology and Science

Volume:03/Issue:02/February-2021 Impact Factor- 5.354 www.irjmets.com

ALKALI-SILICA REACTIVITY OF AGGREGATES IN HYDERABADJAMSHORO REGION

Farhan Ahmed*1 , Aneel Kumar*2 , Samar Hussain Rizvi*3 , Shabir Ahmed*4 , Shahzeb*5

Department of civil engineering , Mehran UETJamshoro, Sindh, Pakistan.

ABSTRACT

Alkali-silica reaction is from one of the numerous chemical interactions thathave a major impact on concrete’s durability. In ASR reaction, silicon content of aggregates possessing highly reactive silica reacts with alkali content present with in the cement. This Forms hygroscopic gel, which on absorbing water from it’s surrounding, expands and cause damage to the concrete structures. The aim of this research paper is to check the alkali silica reactivity of crushed gravels selected from quarries in the vicinity of Hyderabad and Jamshoro. In the study crushed gravel from two quarries in the vicinity of Hyderabad and Jamshoro were used. ASTM C 1260 research methodology was followed to check the Alkali silica reactivity of Crushed gravels. The result showed that expansion after 14 days of both the crushed gravel sources with OPC cement did not exceed 0.2 % limit, by ASTM C1260 research methodology (testing specimen dimension 25×25×285mm). Both crushed gravel sources were found of innocuous behavior and are safe against ASR.

I. INTRODUCTION

Concrete is commonly used material in the constructionsector. It is the major material used in constructing the largest and most prominent structures around the world including buildings, roads, hydraulic structures, power plants and many more other numerous structures. It is presumed to last for long-term periods because of its good durability characteristics. Nowadays, deterioration of concrete is a common problem seen in most of the structures around the world. Environment hazards like weathering actions, alkanity, freezing and thawing, carbonation, chemical attack and abrasion have reduced the durability of concrete. Not only the environment hazards influences the durability of concrete members but also the chemical interaction among the constituents of concrete ingredients has sufficiently effect on the durability and in general the lifespan of concrete (1). Variation in mineralogical and textural properties of the rock aggregate has considerable effect on durability of concrete. Excessive reactivity and harmful properties of rock aggregate cause expansion and cracking which ultimately results in loss of concrete strength and durability. Silica-alkali reaction (SAR) which is considered as cancer for concreteis the one of the effects of excess reactivity and deleterious properties of rock aggregate. ASR occurs in concrete due toreaction of silicathat occur in concrete due to thedisintegrations of the (Si –O) bonds in poorly crystallized aggregates with the OH ions present within the pore fluid of the cement paste. Silica-Alkali reaction (SAR) often results into the degradation of concrete structures (2). Silica -Alkali reaction (SAR) has become one of the most daunting threats in construction sector around the world. In order to prevent the damage in future, the liability of aggregates to occur Silica-alkali reaction (SAR) must be checked. Numerous test mythologies have been developed to check the liability of aggregate to occur SAR in concrete. Various laboratory tests have been established including ASTM C227, ASTM C295, ASTM C1293 and ASTM C1260 to access the SAR. ASTM C1260 and ASTM C 1293 being most popularly used laboratory methods due to the similarity in the results of the test and field performance history of aggregates in concrete at site(3).

II. ALKALI-SILICA REACTION

Silica-Alkali reaction is a chemical interaction between the reactive silica that occurs in aggregates of certain forms with the alkali hydroxides present with in the concrete pore fluid. The alkalis present in concrete occur from certain amount of alkali content present within the cement and admixtures used in it. This reaction results in formation of gel which has characteristics to expand when it absorbs water from surroundings. Expansion of gel increases the internal stresses and results in the formation of cracks within the concrete structures. Whole process of alkali-silica reaction causes degradation of concrete and thus reduces the life of concrete structures. The severity of the deterioration depends on various reasons including the aggregate types and their chemical