STRESS-STRAIN CHARACTERISTICS OF BRICK MASONRY PREPARED WITH POND ASH IN CEMENT MORTAR UNDER UNIAXIAL COMPRESSIVE STRENGTH

The waste from coal-based thermal power plants in the form of pond ash is utilized in making of environment-friendly cement mortar with using sand and cement. The mechanical properties like compressive strength under uniaxial stress of brick masonry and cement mortars prepared with the incorporation of pond ash into the cement mortar at various mixing ratios have been determined. The mathematical relationship of compressive stress values and the composition of brick, mortar and masonry have been developed. The compressive stress, strain and Young’s modulus values and their relationships have been determined. Using pond ash lead to an increase in the strength of the mortar and brick masonry prism prepared.


Introduction
The usefulness of ash in building materials and civil engineering application has been known for a long time. 1,2here are attempts to utilize pond ash in cement mortar in the brick masonry with replacement of cement and sand with various ratios as per IS 1905, 3 IS 2250, 4 Eurocode EC 6 and EN 1996-1-1. 54.The present work includes the results about compression tests for masonry prisms prepared using reference mortar and pond ash modified mortar and the evaluation of relationships between the values of Young's modulus of elasticity (E) and the compressive strength for mortars prepared with various curing methods.

Experimentals
The locally available burnt clay brick, cement mortar with 1:4 proportion (contained one par cement and four parts sand) and brick masonry prism specimen were prepared.The samples of clay brick, mortar cubes and brick masonry prism were cured at 3, 7 and 28 days period.For the preparation of modified mortars, ordinary Portland cement (53 grade), river sand (locally available) and pond ash (sample collected from Thermal Power Plant, Bhusawal, Dist Jalgaon, Maharashtra) were used.Pond ash samples were dried after collection from disposal sites.The ratio between binder and filler used in the experiments was 1:4.The filler means river sand is first replaced with pond ash with a percentage level of replacement from no replacement to fifty percentage (abbreviation used as: SR0-50).Replacement of cement at the same level named as CR0-50.The mortar sample was prepared and cured at 7 and 28 d periods before testing.The compression test set up with a capacity of 400 kN was used to determine compressive strength and value of strain for burnt clay brick, cement mortar cube and brick masonry prism prepared using pond ash partially replaced with cement and sand.The samples were tested for their ultimate load carrying capacity.Stress and strain values were obtained and recorded.Test set up for brick masonry prism and cement mortar specimen can be seen in the Electronic Supplementary Information (ESI Fig. 1.).

Result and discussion
Compressive strength values were measured and given in Table 1 and 2. The compressive strength values for pond ash modified products, the values decrease with increasing the replacement level for both CR5-40 and SR30-50 samples.The values of compressive strength for pond ash modified mortar exceeds the control in case of SR5-35 samples.These values can be used to determine the elasticity modulus (E).
The K, α and β values as constants for model Eqn. 1 were determined with fitting the experimental values.
where,  k = characteristic strength of masonry prism (N mm  The strength of brick prism is associated with the strengths of mortar and brick The relations between elasticity modulus and strength for reference mortar/prism and pond ash modified mortar/prisms can be used for further analysis of masonry structures.The equations for 7 and 28 d curing period for reference and pond ash modified mortar/ prism samples are shown in Table 3  If the strength of mortar prism is known, the values for elasticity modulus can be calculated by using these equations available in Tables 3 and 4.
The compressive strength for pond ash modified mortar is higher for SR5-40 than CR5-50.The relation between elasticity modulus and compressive strength is obtained for 7 and 28 days are curing periods for brick masonry and mortar for reference and pond ash modified mortar.The new mathematical model obtained in accordance with Eurocode EC 6 and EN 1996-1-1 related to pond ash modified mortars for brick masonry prism.

Table 1 .
Compressive strength values of prism, brick and mortar, along with a comparison of Fk (experimental and values obtained from Eqn. 2) for CR0-50

Table 3 .
The equation for the relation between elasticity modulus (E) and Compressive strength () for cement mortar

Table 4 .
The equation for the relation between elasticity modulus (E) and compressive strength (k) for brick masonry prisms