Browsing Department of Mechanical Engineering & the Built Environment by Subjects
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Impact of vibration time on compressive strength of hardened sandcrete building blocksThe majority of the sandcrete blocks used in the Nigerian building industry fall short of the minimum specification standards. There is evidence to suggest a wide variation in compressive strength from one block manufacturer to another and also within block samples from a single source. This problem has been attributed to poor quality control and substandard constituent materials. Also very alarming is the ignorance surrounding the usage and engineering properties of some of the widely used fine aggregate deposits. As a way forward, this paper aims to re-establish the impact of vibration time in sandcrete block production using six fine aggregate deposits found within Benin City (Midwestern Nigeria) and their various pair combinations. Some of the basic properties like silt content, grading parameters—co-efficient of uniformity (Cu), curvature co-efficient (Cc) and the fineness modulus (Fm)—of these fine aggregates were established by laboratory means. In addition, the wet and dry compressive strength of these sandcrete blocks made from these sands were established. A total of 1,080 block samples produced under very controlled conditions were used in this investigation. It was revealed that the utility value of sand can be improved when the weaker and commonly used sands were combined with those that are better, more expensive and less frequently used at different vibration periods and ratios. Findings further revealed that sand types and the sand combination approach adopted were very significant to grading parameters and strength; at a much higher vibration time the compressive strength and durability properties were also considerably improved
The influence of fine aggregate combinations on particle size distribution, grading parameters, and compressive strength of sandcrete blocksThe current extensive use of low priced fine aggregate (sand) deposits in sandcrete block making in Nigeria is of concern because there appears to be a level of ignorance surrounding their existing properties and implications. To this end, silt contents and some grading parameters of the most commonly used fine aggregate deposits in parts of midwestern Nigeria (Benin City), the coefficient of uniformity (Cu), curvature coefficient (Cc), and the fineness modulus (Fm) were derived by laboratory experiments to ascertain these basic properties. In addition, the strength and durability properties of sandcrete blocks made from these sands were also established. It revealed that the low priced sands exhibited worse properties in comparison to the more expensive sand. As a way of improving the properties of these frequently used low priced sands, a combination approach was adopted that used the weaker and commonly used sands with those that are more expensive and less frequently used. Findings revealed that combining the two created significant improvement in compressive strength, durability, and grading parameters of low priced sands with only marginal impact on cost.Key words: fine aggregates, uniformity coefficient, curvature coefficient, fineness modulus, compressive strength, durability, silt contents, Nigeria.