$($a$)$ When selecting a suitable building material for a project, in addition to the properties of the given material, briefly discuss the influence of economics and sustainability on the decision process.$[4$ Marks$]$

$($b$)$ From the following list of properties, select two properties that best describe each of the four stress$-$strain diagrams curves shown below.

$[4$ Marks$]$

Brittle

Hard

Soft

Strong

Tough

Figure $1$: Stress$-$strain curves of four different materials

$($c$)$ Draw a typical well$-$labelled stress$-$strain diagram illustrating the behaviour of $($i$)$ cement paste, $($ii$)$ aggregate and $($iii$)$ concrete.

$[3$ Marks$]$

Question $2(24$ marks$)$

$($a$)$ Briefly discuss how the shape and texture of aggregates affect the workability and strength of concrete?

$[2$ Marks$]$

$($b$)$ With respect to aggregate characterisation, briefly discuss the following:

i$.$ uniform grading

ii$.$ gap grading

iii. continuous grading

$[3$ Marks$]$

$($c$)$ What types of concrete admixtures would you recommend for the following situations and why?

i$.$ Mass concrete for a dam in hot weather conditions.

$[1$ Mark$]$

ii$.$ High performance concrete for use in a cold weather conditions.

$[1$ Mark$]$

$($d$)$ Describe the purpose of the slump test in concrete, how the results are reported and the meaning of the results.

$[3$ Marks$]$

$($e$)$ Describe the causes of bleeding and methods to reduce bleeding in fresh concrete.

$[2$ Marks$]$

$($f$)$ In a concrete production process where the correct water$/$binder $($w$/$b$)$ ratio is used and the mixing of the concrete ingredients is sufficiently carried out, briefly explain at least two factors that may lead to the target compression strength of concrete not being achieved.

$[4$ Marks$]$

$($g$)$ Even through precast concrete is relatively costly$,$ it has several advantages over in$-$situ concrete. However, it is rarely used due to various limitations$.$ Apart from cost, briefly discuss at least two other limitations to using pre$-$cast concrete. Give practical examples for each limitation$.$

$[4$ Marks$]$

$($h$)$ Briefly discuss two physical deterioration processes that affect concrete durability.

$[4$ Marks$]$