The International Journal of Engineering and Science (IJES) || Volume || 7 || Issue || 7 Ver. II|| Pages || PP 01-07 || 2018 || ISSN (e): 2319 – 1813 ISSN (p): 23-19 – 1805 DOI:10.9790/1813-0707020107 www.theijes.com Page 1 Effect of Admixtures on Strength and Permeability of Concrete Ichebadu G. Amadi A and Kemejika I. Amadi-Oparaeli B a Department of Civil Engineering, Rivers State University, Port Harcourt, Nigeria b Department of Civil Engineering, Rivers State University, Port Harcourt, Nigeria CorrespondingAuthor: Ichebadu G. Amadi --------------------------------------------------------ABSTRACT---------------------------------------------------------------- This study investigates the effect of admixtures on the compressive strength and permeability of concrete. Five mixes comprising of a control mix and four modified mixes using the following admixtures: accelerator, water proofer, two superplasticizers namely- Sulphonated Naphthalene Formaldehyde condensates (SNF) and a Poly carboxylate Ether (PCE). The control mix was designed for a grade 30 concrete with a water cement ratio (w/c) of 0.55. To maintain constant slump, the w/c ratio was reduced on application of the admixtures. Compressive strength test was carried out at 3, 7 and 28 days; while Initial Surface Absorption Test ISAT and High Pressure Permeability Tests HPPT were both carried out after 28days. Results indicate that SNF and PCE superplasticizer can be used to enhance exceedingly the performance and durability of concrete. KEYWORDS:Compressive Strength, Durability, water cement ratio, admixtures. --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 04-07-2018 Date of acceptance: 19-07-2018 --------------------------------------------------------------------------------------------------------------------------------------- I. INTRODUCTION There are far more concrete structural problems associated with poor durability than there are due to low compressive strength[1] . As a result, it becomes imperative that concrete be designed for durability. However, this is not the case as compressive strength remains the primary criterion for concrete quality. [2]cited that mix designs have been tailored towards strength: this according to him can be seen in the selection of water/cement ratio which is related or converted to strength. The reason for this is not far-fetched as [3] argued that the concept of strength cuts across other properties of concrete, according to him, increase in strength generally increases- density, impermeability and durability. Strength gives an overall picture of concrete quality because of its direct relationship with the structure of cement paste [4]. Thus, compressive strength and durability to an extent, seem inseparable. Durability issues of concrete usually involve aggressive fluids moving from the surrounding environment into the concrete through the cover concrete and then acted upon by some physical and/or chemical reaction in its internal structure, thereby leading to deterioration[5] . The mechanisms of ingress of harmful materials involved are in fluid form or dissolved in water, thereby making water an agent of deterioration. Water is responsible for most physical and chemical degradation-cum-durability problems: both directly, eg freeze- thaw action and indirectly by permitting the ingress of aggressive ions[6]. It then follows that one of the most promising evaluation methods regarding concrete durability is water penetration based tests. To this end, it becomes imperative that concrete be made as impermeable as possible. From the first line of defence which is the cover-crete to the concrete core should be made waterproof or impermeable. The effect of admixtures in this regards cannot be overemphasized. Admixtures have increased both compressive strength and durability of concrete through their water/cement (w/c) reduction, hydrophobic effect, pore reduction/blocking, increased density etc. This has tremendously increased their use in the construction industry today. This work will be examining comparatively the effect of commonly used admixtures such as superplasticizers, accelerators and water proofers on the compressive strength and durability of concrete vis-à- vis its water permeation with and without pressure. II. SIGNIFICANCE OF STUDY Concrete durability issues could be broadly classified into two aspects: first is the force instigating damage and secondly is the material resistance/response to the damaging force[7] . As already pointed out, water remains the vehicle/force with which aggressive fluids and chemicals permeate concrete[5], [6]. Thus, water Permeability is often seen as the most important indices to measure concrete durability[8], [9]. A typical example is the corrosion of steel which is regarded as the leading cause of deterioration in concrete[10]. The rust from corroding steel occupies a greater volume than the steel. This causes expansion and creates tensile stresses in the concrete, which can eventually cause cracking, delamination and spalling.