Construction industries around the world are facing many difficulties in obtaining good-quality fine aggregates for concrete and mortar due to a shortage of river sand. This problem leads the researchers to find possible alternatives to replace river sand in construction. A brief review has been carried out to identify the alternatives suggested by researchers, merits and demerits of substitutions, availability of standards, and previous studies on the effects of replacing river sand with alternatives in concrete and mortar. Manufactured sand (M Sand), offshore sand, sea sand, quarry dust, and demolition waste have been identified as the most common substitutions for river sand. M Sand and quarry dust have more angularity, rougher surface, higher total specific surface, and lower presence of deleterious substances than river sand, offshore sand, and sea sand. These characteristics played a vital role in the fresh, hardened, and durability performance of cement-based mixes where studies revealed both positive and negative outcomes when comparing with river sand concrete and mortar. Intensely, the strengths of cement-based mixes were improved with angular and rough particles while the workability was declined. The void content and specific surface of alternatives manifested pivotal effects on water absorption of concrete and mortar.

The environment and ecological systems are suspected of serious drawbacks as a result of the over-extraction of river sand for construction activities. An attempt was made in this research on completely replacing river sand in lime-cement masonry mortars with blended sands comprised of manufactured sand and offshore sand. The S and N types (as defined in the standards) were selected for producing masonry mortars with different sand contents. For each type, five mortars were prepared to contain river sand alone (reference mortar), manufactured sand alone, and three blended sands (replacing manufactured sand by offshore sand at 25%, 50%, and 75%). Because of the dominant roles of particle angularity, surface roughness, and gradation of the alternatives, the performance of mortars was evaluated and compared based on these sand characteristics. Furthermore, the level of statistical significance of the experiment results was analyzed from a single factor one-way ANOVA test. Outcomes of this research revealed that the blended sands and manufactured sand declined the fresh state performance of mortars than the river sand mortars. However, most of the stiffened and durability properties of alternative mortars were significantly advanced than the reference mortars.

This study investigated how were correlates with the parental involvement and the achievement of students in the urban and semi-urban type 2 schools in mathematics and science. The descriptive survey research design was employed to carry out this study. One hundred and ninety two (192) students from 16 type 2 schools in Batticaloa educational zone, Sri Lanka were stratified randomly selected for this study. The type 2 school was selected for maintaining the homogenous values. From the results of this study, parental involvement accounts for 26.1% of the total variance in mathematics achievement of secondary schools (R² = 0.261; p< 0.05) and 19.4% of the total variance in science achievement of secondary schools (R² =0.194; p < 0.05). These percentages are significant at 0.05 level of confidence. It shows that parental involvement is an important predictor of mathematics and science achievement. There exists a significant difference in the parental involvement of urban and semi-urban type 2 school students (t =-8.12; p<0.05). Urban school students enjoy more parental involvement than their counterparts in the semi-urban school students. It shows that there is a correlation between parental involvement and male, female students in type 2 schools (t =-7.34; p <0.05), and also there is a significant difference in the academic achievement of male and female students in mathematics and science (t =-0.432 and, -0.512 respectively; p < 0.05). It also shows the finding reports that, there is a significant difference in the academic achievement of mathematics and science with urban, semi-urban schools students (t =-9.142 and, -8.314 respectively; p <0.05). Teachers and Counselors need to enlighten parents on the need to personality get involved in the academic activities of their children.